Searching for natural enemies of the goldspotted oak borer in Arizona

Searching for natural enemies of the goldspotted oak borer in Arizona

By CISR Team | May 29, 2013

Vanessa Lopez

Vanessa Lopez
University of California, Riverside


Written by:
Vanessa Lopez (Ph.D. Candidate, UC Riverside)
Mark Hoddle, Ph.D. (Biological Control Specialist and Principal Investigator)

Photos by:
Mike Lewis and Vanessa Lopez




The goldspotted oak borer (GSOB), (Agrilus auroguttatus) (Coleoptera: Buprestidae), is a recent pest of native oak trees in southern California.  This fairly small beetle (about 10 mm long and 2 mm wide) is native to the mountains of southern Arizona, and was likely introduced into the Cleveland National Forest in San Diego County, California through the unintentional movement of infested oak firewood.  GSOB was first collected in San Diego County in 2004, but was probably introduced into the area several years earlier.  This beetle has killed more than 22,000 native California oaks in a relatively short time period, and continues to spread into new areas within southern California.  In fall 2012, GSOB was found in Idyllwild, Riverside County, about 80 miles from the GSOB infestation epicenter, This find resulted in immediate eradication efforts by local government agencies including CAL Fire and the US Forest Service.  GSOB was also detected in 2010 in Marion Bear Memorial Park, San Diego County, about 65 miles from the GSOB epicenter and has likely established here. Movement of infested oak firewood out of the Cleveland National Forest probably moved GSOB into these new areas.

In southern California, GSOB aggressively attacks larger (more than 12 cm in diameter) coast live oak (Quercus agrifolia), California black oak (Q. kelloggii), and canyon live oak (Q. chrysolepis), and can even attack and kill healthy trees.  Trees infested with GSOB die from repeated larval feeding damage to the cambial layer, which is the water and nutrient transportation system of the tree.  Although adult GSOB feed on oak foliage, adult feeding does not result in tree injury.

In southern Arizona, where this beetle is native, GSOB is not a pest.  In its native habitat, this beetle infests stressed tress, and can actually be very difficult to find.  Since GSOB occurs at much lower population levels in Arizona, there may be natural enemies that have evolved to efficiently find and consume these beetles.

Developing a classical biological control program for GSOB in California

Since 2009, research towards the development of a classical biological control program for GSOB in California has been ongoing.  The goal of classical biological control is to restore balance to an ecosystem by reuniting an invasive pest with its host specific co-evolved natural enemies.  To find natural enemies that have co-evolved with and only attack GSOB, we’ve conducted several surveys throughout the home range of this beetle, and are continuing our search in summer, 2013.

Searching for egg parasitoids of GSOB

Surveys for egg parasitoids of GSOB were initiated in summer 2012 using field deployed GSOB egg masses to attract and potentially become parasitized by these tiny wasps.  For eight weeks, GSOB egg masses were set out and collected every seven days in the Santa Rita Mountains, Pima County, Arizona and in the Cleveland National Forest, San Diego County, California.  Surveys in Arizona resulted in the collection of the first known egg parasitoid of GSOB, a Trichogramma species that is a currently undescribed generalist parasitoid wasp which likely attacks eggs of a lot of different species.  No egg parasitoids were found in California.  Additional GSOB egg parasitoids surveys are planned for this summer (2013) in Arizona.

Continuing surveys in summer 2013

GSOB has been collected from several mountain ranges across southern Arizona including the Chiricahua, Dragoon, Huachuca, Santa Catalina, and Santa Rita Mountains.  To find field sites for the 2013 GSOB egg parasitoid surveys, we took a road trip through southern Arizona to search for active populations of GSOB.  GSOB densities in Arizona are naturally very low, so this beetle can be difficult to find in its native range.  Trees showing symptoms of decline (crown die-back, patches of pale and dry leaves, and bark staining) were ground checked for evidence of GSOB infestation (D-shaped exit holes, larval feeding galleries, and GSOB life stages), but the majority of death or decline in the oaks we encountered was due to fire damage.  However, we did encounter several sites with GSOB activity in the Chiricahua, Dragoon, Huachuca, and Santa Rita Mountains which we will use in summer 2013 to search for GSOB egg parasitoids by hanging GSOB eggs onto infested oak trees.

Ultimately, if we can find a host specific egg parasitoid of GSOB eggs it may be a candidate for eventual release in California to help control this invasive pest. So far our surveys suggest that GSOB eggs in California are not attacked by parasitoids and this could be one reason why populations of this pest are so high in the Cleveland National Forest when compared to forests in Arizona. Restoring an egg parasitoid from Arizona with GSOB in California may help reduce the densities of this pest and alleviate some of the damage it causes.


Topics: Goldspotted Oak Borer, Mark Hoddle | 3 Comments »

Has the Red Palm Weevil Gone Extinct in Laguna Beach?

By Mark Hoddle | March 28, 2013

The Situation: On 27 March 2013, a Canary Island palm on the Pacific Coast Highway that had been previously inspected and treated for red palm weevil (RPW) infestation in June 2011 was removed by MPA Landscape Services (Chuck Galanti). The palm was removed because it was causing structural problems to an adjacent building, and not because it was damaged by RPW.

The felling of this palm provided an excellent opportunity to examine the crown for evidence of RPW activity two years after the palm was treated with insecticides.

Careful inspection of every frond that was removed failed to find evidence of RPW tunneling, holes, or RPW cocoons wedged into cavities at the bases. This damage had been observed in June 2011.

Further, dissection of the meristematic bulb of the palm, the most preferred feeding site for RPW larvae, failed to detect any evidence of RPW feeding activity. No tunnels or feeding damage was observed, no larvae, pupal cocoons, or adults (in 2011 body parts of dead RPW adults were found in the crown of this tree) were found.

Has RPW Gone Extinct in Laguna Beach? The last live RPW to be captured in Laguna Beach was January 2012 when a single adult was trapped in a CDFA bucket trap baited with aggregation pheromone, ethyl acetate synergist, and fruit. Enhanced trapping trials run over June-July and October-November 2012 using stacks of cut date palm logs and pheromone baited bucket traps failed to capture RPW.

Given the lack of RPW captures and no recent signs of RPW feeding damage to Canary Island palms in Laguna Beach it is possible that RPW has either gone extinct or populations are so low as not to be noticeable.

International monitoring protocols suggest that before a pest can be considered eradicated monitoring programs must fail to detect the pest for three consecutive years.

Why Would RPW Go Extinct in Laguna Beach? There are several potential reasons why RPW populations may have gone extinct in Laguna Beach. The first impediment to successful invasion could be a lack of genetic diversity. DNA analyses of RPW collected from Laguna show very little genetic variation suggesting that the founder population was small. Consequently, inbreeding may have resulted in an unhealthy and weak population that was susceptible to environmental events that cause extinction (e.g., climate or pesticides). Second, the climate in Laguna Beach is cool, much cooler year round than the tropical climates of southeast Asia where this weevil is native. Low temperatures may not be favorable for year round RPW breeding, development, and dispersal. This would affect population growth and stability. Third, the variety of RPW in Laguna (black with a red stripe) may not perform well on Canary Island palms. Its preferred host in southeast Asia is coconut palm. There are no coconuts in Laguna Beach as it is too cool for this palm to grow well. Fourth, targeted pesticide treatments of RPW-infested palms may have been very successful at exterminating small RPW populations before they could grow large enough to spread into more favorable areas.

Are California’s Palms Safe from Palm Killing Weevils? No! There is another palm killing weevil invading southern California from Mexico. This is the South American palm weevil, Rhynchophorus palmarum. This pest has killed Canary Island palms in Tijuana and adult weevils have been trapped in San Diego County and southern Texas. It may only be a matter of time before this pest establishes in southern California and starts killing palms.

The Back Story: Red palm weevil (RPW) was first discovered in Laguna Beach in October 2010 following the inspection of a Canary Island palm that had died on a residential property. The infested palm was removed and destroyed.

RPW is native to southeast Asia and has been moved internationally through trade in live palms. This beetle is a highly destructive palm pest that has invaded many countries and killed hundreds of thousands of palm trees.

It is possible that RPW was intentionally introduced into California for food as the larvae are edible either cooked or raw.

The Response to Detecting RPW: In response to this RPW find in Laguna Beach, a red palm weevil Technical Working Group (TWG) was formed to develop a management plan for this highly destructive invasive pest.

A pheromone trapping program was initiated to delineate the infestation zone in Laguna Beach and a series of town hall style meetings were conducted in Laguna Beach and Coachella Valley by the California Department of Food and Agriculture (CDFA) to alert the public and stakeholders (e.g., date and ornamental palm producers) to this problem.

Additionally, a surveillance program was initiated and this was a joint effort between the University of California Cooperative Extension (John Kabashima [Orange County] and Mark Hoddle [UC Riverside]), the Orange County Agricultural Commissioner’s Office (Nick Nisson), and the CDFA (Mohammed Alzubaidy).

The surveillance program had two objectives: (1) to find RPW infested palms in Laguna Beach and treat them with pesticides,and (2) to run enhanced trapping trials using CDFA’s RPW pheromone traps and stacks of cut date palm logs to lure flying RPW adults to traps.

Date palm logs were acquired for these trials via cooperative efforts with Cocopah Nurseries (Duane Young) and Hadley Dates (Albert Keck) in the Coachella Valley.

This enhanced trapping trial design was motivated by RPW research that was completed in the Philippines.

Two enhanced trapping trials replicated across three different sites were conducted for four-five weeks in Laguna Beach over June-July 2012 and again in October-December 2012. These super-trapping-trials failed to capture any RPW adults (adult weevils are attracted to pheromone traps and fermenting palm logs to mate and feed and are often captured in bucket traps as a result.)

There is now mounting evidence that RPW may be extinct in Laguna Beach or populations are too low to be detected with currently available tools.

Topics: Mark Hoddle, Red Palm Weevil | 3 Comments »

Update from Israel on the Polyphagous Shot Hole Borer and its Fusarium fungal symbiont

By CISR Team | March 25, 2013

Update from Israel on the Polyphagous Shot Hole Borer and its Fusarium fungal symbiont


Mary Lu Arpaia
University of California, Riverside

Written by:
Mary Lu Arpaia (Extension Specialist, UC Riverside) David Obenland (Plant Physiologist, USDA-ARS)

Photos by:
Mary Lu Arpaia

We recently had the opportunity to visit Israel and spend several days looking at avocados including a visit with Zvi Mendel and Stanley Freeman, the lead researchers in Israel on the Polyphagous Shot Hole Borer (PSHB) and its Fusarium fungal symbiont. (The authors would like to thank them for their editorial comments on this report.)
So far the beetle is still largely confined to the central coastal region of Israel and the northern Negev. The beetle has also been found in the Upper Galilee at Kibbutz Hagoshrim in avocado and on ornamental trees in other locations in this region which is quite far from the primary infested area. The infested avocado trees have been destroyed but the beetle population already spread outside of the site of the initial infestation. Interestingly, this find was with a grower who packs their avocados in the coastal area. It is assumed that the beetles arrived in the bins originating from the infested area. This is a reminder to California growers and packers that to minimize the spread of pests clean bins are essential. The spread of avocado thrips and persea mite in California is also assumed to have been by bins containing vegetative material.

The Israeli researchers have continued searching for materials that will either control the beetle or the fungus. They have had reasonable success in the lab when they test materials under controlled conditions but application out in the field is not effective. There are no chemical treatments on the horizon that growers can use.

We visited infested avocado orchards in the Hefer Valley and the region southwest of the Carmel mountains (south of Haifa). We visited a Reed orchard which is believed to have been infested approximately 5 to 6 years. Three years ago this grove showed heavy infestation in the entire grove. What we saw on our visit was severe limb dieback, many broken branches scattered on the orchard floor, dropped mature fruit and smaller than normal fruit size for the fruit remaining on the trees. Signs of the beetle boring as evidenced by sugar exudates were easy to find wherever we looked. Dr. Mendel told us that the grower is giving up on this orchard and plans to bulldoze the orchard after harvest. We went on to see several other groves; in all except a 2-year-old orchard it was easy to find limb dieback, fallen fruit and sugar exudate up and down branches. We were told that they do not often find infestation of young groves but when they do, it is usually on the base of the trunk (either rootstock or scion).

We visited a plot with some growers along with Leo Winer (an extension officer) and Udi Gafni (head of the research and development unit of GRANOT) where insecticide applications to infested trees had been made last fall (2012). Unfortunately, signs of continued beetle activity were relatively easy to find. The growers told us about seeing fruit shriveling as the branch dies back. Since substantial fruit drop occurs of both mature and developing there is also an overall drop in productivity as an infestation spreads throughout a grove. Growers are extremely concerned and frustrated that there are no control measures for the beetle. Similar to California, Israel has historically used minimal pesticide sprays. The growers know that in areas already infested that spray applications are key to their continued orchard viability.

Avocado growers in Israel are also seeing problems with Botryosphaeria fungal infections. We visited the northern Negev Desert area where avocados are grown. We went to a large Hass orchard the grower is attempting to control this problem using phosphite injections. We were able to see upper limb dieback and staining on the upper branches.
In the meantime, Drs. Mendel and Freeman are continuing to study beetle biology and the behavior of the Fusarium fungal component. Dr. Mendel is developing a method to raise the beetle in the laboratory. This will be a important breakthrough since it will allow for a better understanding of the beetle life cycle. They know that the female beetle once it flies and seeks a place to burrow has about a 48 hour window to successfully establish itself in the host plant since this is the time period it can survive without feeding. We also learned that the beetle carries the Fusarium spores in its mycangium (a specialized structure at the back of its jaw), rather than hyphae. The larvae and pupa do not have mycangium, only the adults. While the larvae pupate, the Fusarium in the galleries sporulates and the emerging adult as it feeds picks up the Fusarium spores. On a side note, Drs. Mendel and Freeman do not necessarily agree with our use of the name PHSB. They argue that the beetle is monophagous (eats only one kind of food, Fusarium) but uses several tree species as hosts. We will have to see how the final name for the beetle is ultimately settled among the insect taxonomists.
Finally, Dr. Mendel is very worried about the spread of the beetle to native tree species in Israel, especially oaks which are found in many areas throughout the country. The box elder (which also occurs as a landscape tree in California) has been decimated by the PHSB. This is a warning flag for all California residents to take action to safeguard our native oaks, other native species and landscape trees.
These visits reinforced the extreme importance that the California industry must be diligent looking for tree infestation. The industry must work with the landscape industry and forestry service in southern California to understand how fast the infestation is spreading and what hosts are most susceptible. The industry needs to continue funding both applied (surveys, control measures and understanding of the beetle and fungal biology) as well as more basic work such as the origin of the beetle. This latter piece of information may lead to better ideas concerning control measures. Finally California researchers and industry leaders would be well advised to collaborate closely with our Israeli colleagues. They are facing this crisis head on since the PSHB has already spread into commercial groves. From their advanced experience, the California industry can learn much.

A conference on the PSHB and its Fusarium fungal symbiont was held in August 2012 in Riverside. The talks from this meeting are available for review on the website www.avocadosource.com. Video of the conference presentations from the public meeting are available for viewing on YouTube. The science portion of the meeting will be posted on YouTube in the forthcoming weeks.

Topics: Polyphagous Shot Hole Borer | No Comments »

Has the Asian Citrus Psyllid Parasitoid, Tamarixia radiata, Established in California?

By Mark Hoddle | July 19, 2012

Tamarixia radiata (female)

The Problem: Tamarixia radiata, a tiny parasitic wasp has been imported into California from the Punjab of Pakistan to attack nymphs of Asian citrus psyllid (ACP), a serious citrus pest that has established wide spread populations in the counties of Los Angeles, San Bernardino, and Riverside (significantly smaller populations are known in Imperial and San Diego Counties too). Releases of Tamarixia commenced in December 2011 after USDA-APHIS cleared this natural enemy for release from the Quarantine Facility at the University of California Riverside. Since these initial releases in December, approximately 8,500 parasitoids have been released at about 50 different sites in Southern California by July 2012.

The Biocontrol Release Program: Parasitoid releases have been made in the cities of Azusa, Bell Gardens, Chino, Duarte, Fontana, Los Angeles, Mira Loma, Montclair, Ontario, Pico Rivera, Pomona, Rialto, Riverside, San Bernardino and Whittier. In these areas, citrus in residential gardens with ACP infestations were selected for parasitoid releases. Ideally release sites had lemons or limes, and other types of citrus too (e.g., oranges or grapefruit.) Lemons and limes are good hosts for ACP because they tend to produce a lot of flush growth that is favored by ACP females for egg laying, and lemons in particular, tend to produce flush growth more frequently when compared to other types of citrus (e.g., oranges.)

A mixture of different citrus types in gardens is desirable for a release site because it increases the possibility that there will be flush present on different citrus types at different times of the year that will be available for ACP can infest. We’ve also noticed that semi-regular pruning of citrus, good fertilization, and decent watering schedules can also help garden citrus produce strong flush.

Tamarixia Recoveries: Parasitoids have been recovered at about 4-6 release sites in Azusa and Bell Gardens, and some of these sites have not received parasitoid releases for 2-3 months suggesting that Tamarixia has likely established and is breeding on its own (the life cycle of the parasitoid is about 12-14 days depending on the temperature). DNA analyses suggest that the parasitoids that have been recovered from release sites have a unique genetic signature that is very similar to the parasitoids imported from Pakistan for the biological control of ACP in southern California. This result tentatively suggests that the parasitoids recovered from release sites are most likely those that were mass reared and released by the

Tamarixia radiata parasitizing an Asian citrus psyllid nymph in Bell Gardens Los Angeles County

University of California Riverside. Further, at one site in Azusa, it appears that Tamarixia has self-dispersed about 65 m from where it was released on citrus and it established new populations on ACP infested curry plants (curry plants are really good hosts for ACP too.) Additionally, the genetic signal from captured parasitoids is reasonably diverse which suggests that the foreign exploration, rearing, and release program at UCR has preserved a lot of genetic variation which could be very important for local adaptation by parasitoids to citrus growing areas from the coast to the inland valleys.

How Does Tamarixia Kill ACP? Tamarixia can kill ACP nymphs in two different ways. First is parasitism, and in this instance a female parasitoid lays an egg underneath a fourth or fifth instar (instar refers to the developmental stage of the nymph, so a fifth instar is the fifth nymphal stage before the nymph becomes an adult) nymph. These larger nymphs are most preferred by Tamarixia for parasitism. When the egg hatches, the parasitoid larva begins to feed on the under surface of the ACP nymph. Eventually the Tamarixia larva will completely excavate the body cavity of the ACP nymph, and it will pupate inside the empty shell of its host. Often you will see beige colored silk strands radiating out from the edge of a mummified ACP nymph. The parasitoid larva spins this silk to hold the ACP shell onto to the twig that the nymph was feeding on. This ensures that the husk of the host won’t fall off the twig prematurely exposing the parasitoid pupa to predators or inclement climatic conditions. Once the parasitoid has finished pupating, the adult wasp chews a perfectly circular hole near the head of the mummified ACP husk and the parasitoid emerges. After emergence it will mate and if it is a female, it will hunt for more ACP nymphs to attack. The presence of these emergence holes near the head of dried up ACP nymphs is very strong evidence that Tamarixia emerged from that host.

The second way Tamarixia can kill ACP nymphs is by host feeding. When Tamarixia host feeds, the female uses her ovipositor or egg laying tube at the posterior end of her abdomen to stab and mutilate the ACP nymph. This physical injury causes hemolymph (the equivalent of insect blood) to leak from the body and the parasitoid feeds on this fluid. Hemolymph is an important source of protein for female parasitoids, and the trauma of being stabbed then feed upon is sufficient to kill ACP nymphs. Only females can attack ACP nymphs in this manner because males lack an ovipositor because they don’t lay eggs.
Laboratory studies on the biology of Tamarixia suggest that through the combined actions of parasitism and host feeding, individual female parasitoids have the capacity to kill several hundred ACP nymphs during their life time.

Argentine ants tending an infestation of Asian citrus psyllid nymphs. Ants may hamper biological control of ACP by Tamarixia

Ants and ACP Biocontrol: At some release sites, ants, in particular the invasive Argentine ant, may have the potential to interfere with the biological control of ACP. Field observations strongly suggest that ants tend ACP nymphs and as a reward for guarding them, the ACP provide the ants honeydew, a sweet waste product that they excrete. We’ve also seen ants capture and eat Tamarixia parasitoids foraging in clumps or patches of ACP nymphs, and in some instances the ants have chased Tamarixia off the patch if they could not catch it. It is possible that when ACP infestations are heavily tended by ants, some sort of ant control may be needed if the natural enemies are to attack the pests. This problem is not unique to ACP, honeydew producing scales and mealybugs, for example, are also tended by ants, which in turn hampers effective biological control of these pests too.

Future Plans: Monitoring and release programs are ongoing, and UC Riverside is now ramping up the mass production of Tamarixia for expanded releases throughout ACP infested zones. It is hoped that as more Pakistani Tamarixia are released in southern California greater establishment rates will occur and natural spread will begin to fill in areas between release sites.

Topics: Asian Citrus Psyllid, Mark Hoddle, Tamarixia radiata | 4 Comments »

Testing a New Trapping Program for Red Palm Weevil in Laguna Beach California

By CISR Team | June 28, 2012

Since the first official detection of red palm weevil (RPW) in September 2010, the California Department of Food and Agriculture has been running a pheromone trapping program for this pest in Laguna Beach. As part of this trapping program, CDFA is monitoring 153 traps that are set up in two different patterns. The core area around the initial RPW finds is being trapped at a rate of 50 traps per square mile. Outside of this intensive trapping area the remaining traps are deployed at 25 per square mile. Traps were monitored weekly until March 2012, after this time, servicing has been reduced to once every two weeks. The first RPW adult caught as part of this monitoring program was collected from a trap on 18 January 2012 that was last serviced 9 January 2012. The trap that caught the single RPW was on a Washingtonia palm close to the Pacific Coast Highway in Laguna Beach.

It is surprising that despite the intensive and long-term trapping effort by the CDFA that so few RPW have been trapped. In overseas countries were RPW is either native (e.g., India) or invasive (e.g., the Mediterranean and Saudi Arabia) the pheromone traps are very effective at luring and trapping RPW. However, it should be noted that the color form of the RPW caught in these trapping programs is the orange and black form, and not the red stripe form that is present in Laguna Beach.

Orange and red stripe on the Red Palm Weevil.

There could be several reasons for the lack of RPW captures in Laguna Beach using the pheromone bucket traps:

  1. The RPW pheromone that is being used in the trapping program, while very attractive to the orange and black form RPW, is not particularly attractive to the red stripe form in Laguna Beach. May be it is not even the correct aggregation pheromone.
  2. Densities of RPW in Laguna Beach are simply too low to be captured in the bucket traps with the pheromone.
  3. The pheromone trap set up being used is not very attractive to the red stripe form of RPW in Laguna and dispersing RPW simply ignore it because they find infested palm trees more attractive and they tend to aggregate here with other RPW instead of going to the traps.

To address these potential issues a couple of research projects were executed overseas with funding from the CDFA’s Specialty Crops Program. This program was designed to investigate possible factors affecting the success of the trapping program in Laguna Beach, and if possible, to figure out ways to make it more effective.

Three key research questions were addressed with research projects that were run in the Philippines and Indonesia: (1) can the commercially-available RPW pheromone that is being used in Laguna Beach attract the red stripe form of RPW in countries where this color form is native? We had to do the work in these overseas countries because there are no other areas in the world which have the red stripe form of RPW. (2) Is there a more attractive trap set up that could increase the chances of capturing the red stripe form of RPW? (3) Does the pheromone for the red stripe form of RPW have the same chemical make up as the commercial RPW pheromone used for trapping the orange form of RPW?

Assessing the Attractiveness of the RPW Trapping Program Used in Laguna Beach to the Red Stripe Form of RPW. Two large field experiments were conducted in the Philippines and Sumatra Indonesia to assess the attractiveness of the CDFA’s bucket trap to the red stripe form of RPW. Three different trap set ups were tried: (A) cut coconut logs only (coconuts are a highly preferred host palm for RPW in countries where it is native and volatiles released from cut coconut palms are very attractive to RPW), (B) pheromone traps only, and (C) pheromone traps with freshly cut coconut logs.

The daily RPW harvest from the field trials in Indonesia

The results of these trials in the Philippines and Indonesia were crystal clear – RPW was highly attracted to stacks of cut coconut palm logs that had the pheromone traps sitting on the log stack. This suggested to us that perhaps the missing element in Laguna was a lack of freshly cut palm material to help attract RPW to the pheromone traps that the CDFA is using to monitor for this pest.

The results of this study also indicated that the commercially-available pheromone seemed to be quite important for attracting the red stripe form of RPW to stacks of cut coconut logs. But did this mean that the pheromone was actually the correct one used by the red stripe form, or did these RPW simply find it O.K., but not as attractive as the pheromone that they produce themselves (assuming the red stripe RPW have a similar but different pheromone to that used by the orange and black forms)? To answer this question we collected aggregation pheromone for red stripe RPW captured in the field in an oil palm plantation in Sumatra Indonesia.

Cut coconut palm trunks and a RPW pheromone trap set up in Indonesia to test the efficacy of the commercially-available RPW aggregation pheromone

Collecting Aggregation Pheromone from the Red Stripe Form of RPW in Sumatra Indonesia. Adult red striped RPW collected from oil palm trees that had collapsed in a commercial oil palm plantation were used for the pheromone collection experiments. The process was quite simple in concept, but a little challenging to execute in an outdoor shed in an oil plantation! Field collected RPW (all red stripe forms) were set up in oven bags that had hoses hooked up to an aquarium pump. The aquarium pump pulled air through a special set of filters to remove any potential volatile contaminants before it passed into the oven bags and over the contents of the bags. The RPW were contained in mesh cages inside the oven bags so they couldn’t chew holes in the bags and escape. Four oven bags were set up each time pheromone aeration trials were run. The bags contained either an empty sterilized mesh cage (to capture the chemical signature of the mesh cage), RPW food only in a mesh cage.

RPW set up in oven bags and being aerated for pheromone capture in Sumatra Indonesia

Sugar cane or oil palm hearts were the food used for the RPW – it really likes to eat both types, but we didn’t know whether sugar cane or oil palm would be needed to stimulate RPW to release aggregation pheromone, so we tried both. RPW in a mesh cage only, or RPW with food inside a mesh cage. Aerations were made for these different treatments continuously for about 3-4 days. The volatiles released were trapped on ultra-pure charcoal filters as purified air was pulled through the oven bags containing the treatments. After this exposure time the charcoal filters were removed, new treatments were set up again, and then randomly assigned to a new set of oven bags. The process was repeated three or four times over a 14 day period.

The RPW field crew who assisted daily with the field experiments in Indonesia

The charcoal filters with aeration product were air expressed from Sumatra to Riverside, California. Jocelyn Millar at UC Riverside analyzed the aggregation pheromone captured on the charcoal filters that had been released from the red stripe RPW inside the oven bags. Millar’s analyses clearly showed that the aggregation pheromone released by the red stripe form in Sumatra was exactly the same as the commercially-available pheromone used to trap the orange and black form of RPW. We concluded from this work that we were using the correct aggregation pheromone to attract the red stripe form of RPW in Laguna Beach.

A New Trapping Plan for the Red Striped RPW in Laguna Beach. So after the completion of these studies in the Philippines and Indonesia, the pieces were now in place to consider a modified trapping program for the red stripe RPW in Laguna. We know that the aggregation pheromone released by the red stripe RPW is exactly the same as the commercially-available pheromone used to trap the orange and black form of RPW, so there is no problem in using this pheromone. We also learned that red stripe RPW are strongly attracted to stacks of freshly cut palm logs that have aggregation pheromone sitting on top of these log stacks. The challenge after figuring this out is to replicate this set up in Laguna Beach.

Setting up the RPW pheromone aeration experiment in Sumatra Indonesia

The CDFA gave permission to set up a new trapping plan in May 2012 using freshly cut date palm logs and pheromone traps. This program was a replication of the successful trapping programs that had been tested in the Philippines and Indonesia. In June 2012, three stacks of cut date palm logs with RPW pheromone traps were deployed at three different sites in Laguna Beach. This project was a major collaboration between UC Riverside with date palm producers in the Coachella Valley, in particular Duane Young with Cocopah Nurseries in Indio California, and Albert Keck with Hadley Dates in Vista Santa Rosa (both businesses operate out of the Coachella Valley.)

Cocopah Nurseries donated 3 date palms that were felled, and from which the top most third was removed from the trunk and cut with a chainsaw into sections for deployment at Laguna Beach. These palm sections were transported to Laguna Beach and set up at three different sites with pheromone traps. These sites were selected based on their close proximity to previous find sites for RPW and to palms which have had evidence of recent RPW attacks. The log stacks and pheromone buckets are checked daily and trap checking is a cooperative effort between CDFA (Mohammed Alzubaidy), the Orange County Agricultural Commissioner’s Office (Nick Nisson), UC Cooperative Extension (John Kabashima), and UC Riverside (Mark and Christina Hoddle). At the time this blog was written, this new trapping program had been out for one week and no RPW had been caught.

Topics: Mark Hoddle, Red Palm Weevil, UC Riverside | No Comments »

Huanglongbing Detected in Hacienda Heights, Los Angeles County

By Mark Hoddle | April 13, 2012

The Situation: On Thursday April 5 2012, after about a week of testing, the California Department of Food and Agriculture (CDFA) removed a pumelo tree with a lemon graft from Hacienda Heights in Los Angeles County after the tree and an Asian citrus psyllid found on the tree both tested positive for a lethal citrus disease, Huanglongbing (pronounced Wong-Long-Bing [HLB]). HLB is caused by a bacterium, and HLB-causing bacteria kill citrus by affecting the food transportation systems of infected trees. There is no known cure for the disease, and the HLB-bacterium does not pose a threat to humans, pets, or other plants.

Asian Citrus Psyllid

The Problem: Huanglongbing, also known as yellow shoot disease, yellow dragon disease (these are English translations from the Chinese Huanglongbing indicating that the leaves of infected citrus appear an irregular mottled yellow color) or citrus greening (because fruit don’t ripen properly and remain green in areas) is spread from tree-to-tree by the Asian citrus psyllid (ACP), This small insect acts as a flying syringe carrying bacteria in its needle-like mouthparts and when infected psyllids feed on citrus they inject bacteria into trees. The disease can also spread by grafting infected branches onto healthy trees. The possibility that an infected branch was brought into California and used for a graft is being investigated.

Infected trees typically die within 5-8 years after being infected, but disease symptoms may take as long as 2 years to become obvious. This long latency period provides ample time and opportunities for ACP to visit infected plants, feed on them, acquire the bacteria and fly onto healthy trees to feed which puts these trees at risk of becoming infected with bacteria.

HLB has been a particularly devastating disease problem in Florida. In 2005, HLB was first detected and it was estimated that 10% or 60,000 acres of citrus was destroyed by HLB by 2009, just four years after the first find. This reduction of citrus acreage in Florida corresponded with an estimated loss of 6,600 jobs, $1.3 billion in lost revenues to growers, and $3.6 billion in lost economic activity associated with the citrus industry in Florida.

The commercial citrus industry is worth about $1.2 billion in California and about 300,000 acres are farmed.

Where are ACP and HLB in the USA? ACP and HLB are present in Florida, Texas, Louisiana, Georgia, and South Carolina. ACP is present in Arizona, Mississippi, and Alabama, but HLB has not yet been found. In California, ACP was first found in San Diego and Imperial Counties in 2008. Since this initial detection ACP has been found in Ventura, Orange, Santa Barbara, Los Angeles, Riverside, and San Bernardino Counties. ACP populations at this time are heaviest in Los Angeles County.

The quarantine for HLB in Los Angeles and Orange Counties

The Response: On April 5 2012, the CDFA held an open house meeting at Industry Hills Expo Center in the City of Industry. The purpose of the meeting was to provide the public with information on HLB and ACP and to respond to requests to examine citrus with disease symptoms that look suspiciously like HLB. Additionally, all citrus within an 800 meter (about 2,400 feet) radius of the infected tree have been treated with insecticides by the CDFA to kill any Asian citrus psyllids that may be carrying bacteria that cause HLB. A 93 square mile quarantine has been established in Hacienda Heights in Los Angeles County and part of northern Orange County. This quarantine prohibits the movement of all citrus nursery stock out of this area in case they are infected with HLB and these plants, if infected, could start new disease infestations in different areas of California. Any fruit from residential properties must not be moved to other areas in case ACP or HLB accidentally hitch-hike into new areas on this fruit.

A description of the Quarantine has been prepared by CDFA and maps of the Quarantine Zone are available.

What is the Future for Citrus in California? Following the find of HLB in Hacienda Heights there has been concern that a massive citrus die off in gardens is now imminent. This is unlikely because surveys have failed so far to find more than one tree infected with HLB. Further, it is unlikely that trees dying from HLB be initially widespread, it is probable that if there are other HLB infected trees in California, they are uncommon and widespread. The difficult problem facing the CDFA and USDA is finding these infected trees (should they exist) and eradicating them before ACP finds them, feeds, acquires HLB bacteria, and spreads them to healthy citrus. Because the disease is slow in killing trees, the loss of trees will be slow, and probably patchily distributed in the early stages of the spread.

What Can you Do to Help? The CDFA has set up a Pest Hotline 1-800-491-1899 and a Report-a-Pest website http://www.cdfa.ca.gov/plant/reportapest/ to help in the fight against invasive species coming into California.

Recent News Articles
Los Angeles Times: Gardeners’ Common Bond May Have Introduced Deadly Disease. 
Los Angeles Times: San Gabriel Valley Homeowners Swarm to Meeting about Citrus Disease

Topics: Asian Citrus Psyllid, Huanglongbing, Invasive Species, Mark Hoddle, News, UC Riverside | No Comments »

Entomophagy: Collecting and Eating Red Palm Weevil Larvae from Nipa Palms in Sumatra, Indonesia

By Mark Hoddle | March 9, 2012

The red stripe form of red palm weevil (referred to here as Rhynchophorus vulneratus) is harvested for food from nipa palm trunks in parts of Sumatra by rural and semi-rural agrarians. Nipa palms (Nypah fruticans; known as buah atap in Indonesia) typically grow in swampy muddy areas (in either fresh or brackish water conditions) and the fronds are used as thatch roofing, or basket making. Most of the trunk of the nipa palm grows underground and the leaves and flower stalks grow above ground. The sap and flowers are sweet, rich in sugars, and can be fermented. The trunk is high in starch and can be harvested, pounded, and dried to form a type of sweet “sago” flour.

Another use of the palm is for the deliberate rearing of R. vulneratus larvae for harvesting and eating. Adult weevils are attracted to exposed damaged trunks and in some instances salt may be applied to the cut area which reportedly increases the attractiveness to breeding weevils. Adult weevils attracted to the palm trunk release an aggregation pheromone which further amplifies the attractiveness of the palm for breeding and feeding. Female weevils use their long rostrum or snout to chew holes into the trunk and eggs are laid (oviposited) into these holes. After several days, the eggs hatch and the small first instar weevil larvae burrow into the trunk to feed.

Palm trunks prepared for weevil attack are opened with an axe and machete after about six weeks. If the trunk is infested with weevil larvae a distinctive fermenting odor emanates from the trunk when it is opened, the internal tissue has oxidized and taken on a brownish color with interspersed ginger-colored gelatinous globs. This fed upon and fermenting material has the consistency of sloppy oatmeal (porridge). Weevil larvae feeding inside the palm trunk are easy to find because they make large diameter tunnels, and disturbance and probing of tunnels causes the legless larvae to wriggle vigorously and once they start to move they are easy to pick out of the tunnels.

The larvae are very high in protein and are considered by FAO to be an insect food that has potential to be commercialized because it requires low inputs for the quantity and quality of nutrition provided. About 1,700 species of insects are eaten by humans, mainly in the tropics because they are available year round, diversity is high, and the harvest and sale of insects for human food is a good income supplement. Human consumption of insects is called entomophagy.

Large R. vulneratus larvae harvested from nipa logs in Sumatra can sell for as much as 1000 rupiah (~ $0.11 US) each while smaller larvae fetch around 500 rupiah. Larvae can be cooked before being eaten. To prepare larvae, the large head capsule is removed, larvae may be blanched quickly in boiling water before being battered and deep fried or prepared as a type of curry. When prepared this way weevil larvae are reminiscent of cooked shrimp or squid. Another selling point for these larvae is their apparent potency as an aphrodisiac (something I can’t confirm or deny after eating many). One of our field assistants refused to eat the larvae because he was working away from his village and wouldn’t see his wife for the next two weeks. This may be a powerful testimony to the power of this aphrodisiac.

Alternatively, larvae can be eaten raw straight from the nipa trunk. Smaller larvae are preferred because they are easier to chew and swallow. However, large larvae are no problem to eat alive. The best way to eat palm weevil larvae raw is to hold them by the head capsule between your thumb and forefinger, place the larva’s body in your mouth, and bite behind the head severing it from the body and leaving the head capsule between your fingertips. Palm weevil larvae from nipa palms are surprisingly sweet, the texture internal body contents is smooth and agreeable, and they don’t have a foul or weird taste (you’d expect them to taste like rotting wood but they don’t!) The larva cuticle or skin is very chewy and can be spat out or easily swallowed.

I was very surprised at how easy these larvae were to eat straight from the nipa palm trunk in the jungle. We washed the larvae with some drinking water to remove the fermenting palm mush prior to eating them. Our guides indicated that the most preferred weevil larvae are taken from nipa palms while those harvested from the crowns of coconuts have a less agreeable taste and texture.

For more info:
Red Palm Weevil on CISR
Edible Forest Insects – Humans Bite Back!!
Beastly Bugs or Edible Delicacies?
Time for a ‘Bug Mac’? The Dutch Aim to Make Insects More Palatable
Entomophagy: Edible forest insects
Could you please pass me the bug kabobs? 


Topics: Entomophagy, Invasive Species, Mark Hoddle, Red Palm Weevil | 4 Comments »

Tamarixia radiata release video

By CISR Team | January 12, 2012

Christina Hoddle explains the release of Tamarixia radiata at UC Riverside. Video recorded on December 20, 2011 at University California Riverside.

For more information about Tamarixia radiata and Asian Citrus Psyllid, visit the CISR website: http://cisr.ucr.edu/asian_citrus_psyllid.html

Topics: Asian Citrus Psyllid, Christina Hoddle, Invasive Species, Mark Hoddle, News, Tamarixia radiata, UC Riverside | 5 Comments »

First Release of Tamarixia radiata in California for the Biological Control of Asian Citrus Psyllid

By Mark Hoddle | December 20, 2011

Provost and Executive Vice Chancellor of UC Riverside Dallas Rabenstein (left) and Mark Hoddle (right) made the first release of Tamarixia in Southern California.

At 11:00 am on the 20 December 2011, approximately 30-40 people assembled at the UC Riverside Biological Control Grove to participate in the first release in California of the Asian citrus psyllid natural enemy, Tamarixia radiata. Representatives from the University of California, California Department of Food and Agriculture, Citrus Research Board, and Citrus Pest and Disease Prevention Committee were in attendance. The event was covered by local media including Riverside’s Press Enterprise. After a brief introduction and description of the problem California faces with Asian citrus psyllid, and a quick review of the approximately two year process to reach this point, Mark Hoddle invited Provost and Executive Vice Chancellor Dallas Rabenstein to make the first release of Tamarixia in Southern California.

The Issue: In 2008, Asian citrus psyllid (ACP) was first found in California. This insect feeds on citrus and close relatives of citrus. The major problem with ACP is that is spreads a bacterium that causes a lethal disease in citrus known as Huanglongbing (HLB) . There is no cure for this disease. HLB is NOT in California.
ACP is widely established in LA County and pest populations are increasing and spreading in Riverside and San Bernardino Counties. This pest is almost exclusively restricted to backyard citrus. Spray programs to control ACP are difficult and expensive, and not every infested tree can be found and treated. Additional tools are needed for controlling ACP in California and biocontrol is one of these additional control options for ACP.

An adult Asian Citrus Psyllid on a citrus leaf.

The Biocontrol Program: ACP is native to Asia and the Punjab of Pakistan and India and this area is thought to be part of the native range where this insect evolved. People have accidently moved this pest and HLB around the world through the accidental movement of infested citrus plants.
Over the last two years Mark and Christina Hoddle (Department of Entomology, University of California, Riverside) have worked in Faisalabad Pakistan looking for natural enemies of ACP. Faisalabad Pakistan was chosen for this research effort because this part of Pakistan has a very good climate match (~70-75%) with the major citrus producing areas of California which will mean the natural enemies released in California will be pre-adapted to very hot dry summers and cold foggy winters.

An ACP Natural Enemy from Pakistan: One parasitoid found attacking ACP in the Punjab of Paksitan is Tamarixia radiata. This is a very small insect that kills ACP nymphs either by parasitizing them (i.e., females eggs laid underneath ACP nymphs and the parasitoid larvae burrow into the nymph to feed which kills the pest) or by host feeding (i.e., female parasitoids stab the nymph with their ovipositor, a tube that they use to lay eggs, and they feed on the body juices that leak from these wounds. This kills the nymph too.)

An adult female Tamarixia (left) and a dead Asian Citrus Psyllid nymph with an exit hole (right) from which an adult Tamarixia emerged after successfully parasitizing it.

Quarantine Studies: Safety tests conducted by Dr. Raju Pandey in Quarantine at UC Riverside clearly demonstrated that this parasitoid posed no undue risk to California’s environment, other species of insects, or humans. A 60 page Environment Assessment Report on Tamarixia that summarized the results of these studies was prepared by Mark Hoddle and Raju Pandey for review by USDA-APHIS. On 7 December 2012, APHIS issued a permit (P526P-11-04159) authorizing the release of Tamarixia from Quarantine for establishment in California for the biological control of ACP.

The Release Event: On 20 December 2011 at 11:00am, 12 glass vials containing 186 female Tamarixia and 95 male Tamarixia (total 281 parasitoids) were opened to release the parasitoids in the Biocontrol Grove at UC Riverside. The eight colonies in Quarantine from which these parasitoids were sourced for release were tested using DNA analyses to ensure that they were free of the bacterium that causes HLB. All tests were negative for HLB indicating that the parasitoids were free of this bacterium.
The Biocontrol Grove is a repository for natural enemies that have been imported for the biological control of citrus pests (e.g., scales, mealybugs, whiteflies, etc) in California over the last 50+ years. With the releases of Tamarixia in the Biocontrol Grove, one more natural enemy is being established here to combat an invasive pest that threatens California’s agricultural prosperity.

Expected Outcomes: This release of 281 Tamarixia is the first salvo against ACP in California. Over the next year or so it is anticipated that thousands of these parasitoids from Pakistan will be mass reared and released throughout LA, Riverside, and San Bernardino Counties and other areas as the pest continues to spread. Once Tamarixia establishes it will move by itself to find new populations of ACP to attack and kill. The parasitoids will have the ability to enter areas to kill ACP that may be difficult or impossible to reach for pesticide applications.

Tamarixia will *NOT* eradicate ACP from California but this natural enemy should reduce the populations of ACP in California. Every ACP killed by Tamarixia will be one less pest for homeowners and commercial citrus growers to worry about.

For More Information: These websites have more information on ACP and the work in Pakistan looking for natural enemies of ACP.

Topics: Asian Citrus Psyllid, Christina Hoddle, Mark Hoddle, News, Tamarixia radiata | 12 Comments »

Looking for the Asian Tiger Mosquito in Southern California

By CISR Team | December 9, 2011

In September 2011, Asian Tiger Mosquito (Aedes albopictus) was found in Southern California. Small pockets of communities were reporting extremely aggressive, daytime biting mosquitoes – a telltale sign of the Asian Tiger Mosquito. The Asian Tiger Mosquito was first found in isolated pockets of California in the early 1970’s. It was eradicated, but showed up again in the late 80’s and again in the early 2000’s. This time, the potential vector-carrying mosquito was reported in the city of El Monte, about 10 miles East of Los Angeles.

In response, two LA based agencies worked together to inform the public about its new mosquito resident and to determine the extent of its establishment in the area. The Greater Los Angeles County Vector Control District (GLACVCD) and the San Gabriel Valley Mosquito & Vector Control District (SGVMVCD) cooperatively began surveying a 20 square mile grid of homes in El Monte. Officials knocked on doors to inform residents of the new pest, and asked for permission to check each property for potential breeding grounds around their homes.

Truc Dever, Director of Community Affairs and Steven Vetrone, Assistant Vector Ecologist are two officials from GLACVD who participated in the sweep in El Monte.

“If the Asian tiger mosquito becomes established here in LA County, it would be a game changer for all of us. Residents would need to be concerned about disease-transmitting mosquitoes biting them during the day,” Dever said.
Dever and Vetrone participated in a 20 square mile grid by knocking on doors in a South El Monte neighborhood. They had two primary goals: help increase the public’s awareness of the Asian Tiger Mosquito and check for areas that could provide a breeding ground. They walked around with the home owners to point out potential problems. Each pool of standing water was carefully examined for larva and eggs, and a few samples were taken back to the lab for further examinations.

The Asian Tiger Mosquito differs from other mosquito’s in that it is an aggressive day time biter. It can also carry a number of vectors like dengue, yellow fever and west nile virus. Breeding grounds can include anything that holds standing water. Trash can lids turned upside down proved a popular culprit, as well as water trays under garden pots. Even some unsuspecting plants that hold water on their leaves were potential candidates for mosquito eggs.

“We need the public’s help in order to control and eradicate this dangerous pest. We are asking everyone to call us if they are getting bitten by mosquitoes during the day.” Dever said.

For more information on the Asian Tiger Mosquito, visit the CISR page

Los Angeles officials are asking residents to call and report if they see any black and white mosquitoes that bit during the day. Please contact the Greater Los Angeles County Vector Control District at (562) 944-9656 (www.glacvcd.org) or the San Gabriel Valley Mosquito & Vector Control District at (626) 814-9466 (www.SGVmosquito.org)

Topics: Asian Tiger Mosquito, Invasive Species, News | 3 Comments »

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