Current Research Projects
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Sterile Insect Technique for Navel Orangeworm (Lepidoptera: Pyralidae: Amyelois transitella)
Navel orangeworm (Pyralidae: Amyelois transitella) (NOW) is a key pest of tree nuts in California. There are 3-5 generations per year, adults oviposit onto nuts and larval feeding reduces nut yield, quality and can introduce aflatoxin, which is strictly regulated in key export markets. The CA pistachio industry and USDA recently invested in sterile insect technology (SIT) for NOW, but it is unclear how to most effectively use this technique in California tree nuts. I’m a member of the Technical Advisory Committee for this program and my lab is carrying out much of the initial research to evaluate the quality of irradiated NOW, including mating competition, dispersal capacity, and determining appropriate overflooding ratios. This work is in collaboration with Charles Burks (USDA-ARS), Joel Siegel (USDA-ARS), Raman Bansal (USDA-ARS) and Ron Haff (USDA-ARS).
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New Traps and Pheromones for Monitoring Leaffooted Bug (Hemiptera: Coreidae: Leptoglossus zonatus)
Aggregation of LFB on pomegranate Leaffooted bugs (Coreidae: Leptoglossus zonatus, L. clypealis) (LFB) are key pests of almonds, pistachios and pomegranates. There are 2-4 generations per year, adults lay eggs on tree branches and feeding of nymphs/adults can lead to nut abortion, necrosis and transmission of pathogens. IPM of LFB is weak due to the lack of an effective monitoring program, and so growers apply insecticides at will. My lab works with Dr. Jocelyn Millar (UC Riverside) to develop the use of pheromones for trapping LFB. The first goal of this program was to identify an effective LFB trap – which my lab successfully did in fall 2017 – and we are now conducting further studies to refine trap efficacy and evaluate candidate LFB lures under field conditions.
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Carpophilus Beetle
In the fall of 2023, our lab discovered the invasive beetle Carpophilus truncatus (Nitidulidae) infesting nuts in almond and pistachio orchards in Fresno and Madera counties. A subsequent regional survey confirmed that the carpophilus beetle was present throughout the entirety of the San Joaquin Valley. We are now leading a collaborative team of research and extension personnel to develop monitoring and management strategies for this pest, as well as to better understand the seasonal phenology and ecology of this insect. Our "Team Carpophilus" includes David Haviland (UCCE Kern Co.), Jhalendra Rijal (UC IPM North San Joaquin Valley), Sudan Gyawaly (UC IPM Sacramento Valley) and Raman Bansal (USDA-ARS). Currently, our efforts are focused on expanded survey efforts throughout the Central Valley, improving mass-rearing protocols, evaluating chemical controls, and characterizing the seasonal phenology of this pest in orchards throughout the San Joaquin and Sacramento valleys. The carpophilus beetle has been a major pest of almonds in Australia for the past ten years, so we are now also working closely with colleagues there to develop additional research and extension activities. More recently the carpophilus beetle has also been reported in Argentina and Italy. You can read more about this pest here.
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Pistachio Hull Integrity
Navel orangeworm (Pyralidae: Amyelois transitella) (NOW) is the primary insect pest of pistachios. Adults deposit eggs on the developing nuts, and larvae damage to the nut kernel reduces crop yield and quality. NOW infestation is also associated with increased incidence of aflatoxin, a known human carcinogen that is heavily regulated in key markets. The ability of NOW larvae to access and damage pistachio kernels is mediated by the integrity of the pistachio hull, which typically degrades over the course of the growing season. That said, hull integrity does not equally degrade every season, and in years with high hull integrity NOW damage to pistachios is relatively low. So, what drives these inter-annual changes in hull integrity? Since 2019, we have been conducting research to better understand the environmental factors that drive the annual timing and extent of hull degradation in pistachios. At the same time, we are characterizing the specific physical and chemical changes in the pistachio itself that are associated with decreased hull integrity, which may allow us to better understand the cues that NOW utilize to determine hull integrity. This is a collaborative project with Dr. Barbara Blanco-Ulate, Dr. Giulia Marino, Dr. Selena Wang, and Dr. Charles Burks.
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Orchard Grazing Project
Navel orangeworm (Pyralidae: Amyelois transitella) (NOW) overwinter as larvae/pupae on remnant/mummy nuts left behind after harvest. Not only do these remnant nuts help carryover the NOW population into the following season, but they also provide host material for the first flight of NOW adults in the spring. As such, removal and destruction (i.e. crop sanitation) of these remnant/mummy nuts is critical for NOW management. While almost all growers are aware of the importance of crop sanitation, it can be challenging to complete due to the high cost and limited availability of labor and equipment to carry this out. Even when a grower does have these on hand, inclement orchard conditions (i.e. wet/muddy soils) can impede orchard access by field crews and/or heavy equipment. As an alternative, we are now evaluating the use of sheep grazing for crop sanitation. Initial pilot studies have demonstrated that sheep can access orchards under a wider range of conditions and will readily consume remnant/mummy nuts in both almond and pistachio orchards. Given these promising initial findings, we are now conducting studies to determine the optimal timing, density and frequency of sheep grazing, not only for crop sanitation but also for weed control. We are also collaborating with a larger team of researchers to evaluate the influence of this practice on soil quality and food safety, which includes Alda Pires (School of Vet. Med., UC Davis), Amelie Gaudin (Dept. Plant Science, UC Davis), Bart Weimer (School of Vet. Med., UC Davis), Richard Pereira (School of Vet. Med., UC Davis), Rosie Busch (School of Vet. Med., UC Davis), Brittney Goodrich (Dept. Ag. and Resource Economics, UC Davis) and Amber Sciligo (The Organic Center). You can learn more about this project here: https://organic-center.org/site/impacts-orchard-grazing-soil-health-food-safety-and-pest-control
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Cover Crops in Almond Orchards
Multiple labs at UC Davis (Dr. Neal Williams, Dr. Amelie Gaudin, Dr. Brad Hanson, Dr. Brittney Goodrich) are exploring the influence of cover crops and hedgerows on pollinators, soil quality, weed control and pest management in almond orchards. The role of my lab in these projects is to evaluate the effects of winter cover crops on overwintering NOW mortality and spring egg deposition on remnant 'mummy' nuts in the orchard. This entomology component is an effort in collaboration with Dr. Kent Daane.
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Black Fig Fly
The black fig fly, Silba adipata McAlpine (Diptera: Lonchaeidae), is a Mediterranean insect that exclusively reproduces on figs (Moraceae: Ficus carica L.). Widely considered a pest of figs throughout southern Europe, north Africa, and the Middle East, S. adipata was recently discovered infesting figs throughout southern California, representing the first report of this pest in the United States. Here, we provide background information on the distribution, biology, ecology, monitoring, and management of this pest, as well as outline research and extension efforts that have been catalyzed by this recent invasion. California accounts for a majority of both fresh and dried fig production in the United States. To date, S. adipata infestations have been limited to orchards in coastal and southern California, whereas most commercial fig production takes place in the inland Central Valley region. Better knowledge of temperature thresholds is currently needed to estimate potential range expansion to these more inland regions of the state.
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Cannabis and Hemp IPM
Cannabis Project Website: http://treecrops.ucr.edu/cannabis/
As a “new” commodity in the CA agricultural landscape, cannabis production will become subject to the same regulatory pressures as other specialty crops like almonds, grapes and citrus. Improper pesticide use, amongst other production practices, is likely leading to negative environmental impacts. As such, the development of IPM programs and non-chemical strategies will be a research priority. My lab recently led an effort to survey cannabis growers across the state to characterize production practices in CA. This research will soon be featured in a special edition of California Agriculture. This project is a collaboration that I organized with UC Berkeley faculty (Dr. Van Butsic, Dr. Ted Grantham, Dr. Christy Getz, Dr. Kent Daane) and The Nature Conservancy (Dr. Jennifer Carah).
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Vineyard IPM
I remain involved in research and extension efforts to improve biological control of the invasive Virginia creeper leafhopper (Cicadellidae: Erythroneura ziczac) as well as evaluate the ecology and transmission efficiency of insect vectors of grape vine red blotch-associated virus (GRBaV).Virginia Creeper Leafhopper Area-wide IPM Project: https://ucanr.edu/sites/vclh/
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Trap Crops to Control Large Plant Bugs in Pistachio
A pistachio grower with significant organic acreage expressed interest in the use of trap crops to monitor and control large plant bugs, such as LFB and various pentatomids (Thyanta pallidovirens, Chinavia uhleri, Chlorochroa hilare). These pests are all known to feed on various weedy vegetation that in some cases may be more attractive than pistachios, and my lab is currently evaluating the ability of a mustard, radish and alfalfa trap crop to reduce large bug populations and crop damage. This is in collaboration with Dr. Kent Daane (UC Berkeley, Kearney Ag. Center) and is part of the dissertation for PhD student Rob Straser.
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Aggregation Pheromones to Monitor Driedfruit Beetle (Coleoptera: Nitildulidae: Carpophilus hemipterus) in Figs
Driedfruit beetle (Nitidulidae: Carpophilus hemipterus) (DFB) is a primary pest of figs. This polyphagous beetle has 10-12 generations per year. Feeding causes direct damage to figs and can introduce bacteria and fungi that spoil fruit. My lab is evaluating the efficacy of experimental DFB aggregation pheromones to improve monitoring and possibly develop an attract-and-kill program.
- Mating Disruption of Navel Orangeworm in Figs
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Overwintering Biology of Walnut Husk Fly (Diptera: Tephritidae: Rhagoletis completa)
Walnut husk fly (Tephritidae: Rhagoletis completa) (WHF) is a key pest of walnuts. This univoltine fly overwinters as a pupa in the soil. Adults emerge in the summer, oviposit into walnut husks and larval feeding reduces crop quality and yield. In the fall, larvae drop from the nuts and pupate in the soil. My lab is leading a project to identify key factors that lead to increased mortality of WHF larvae and overwintering pupae, with the goal of developing practices to reduce overwintering success. This is a collaborative project that involves Statewide Area IPM Advisor Jhalendra Rijal (North San Joaquin Valley).
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Smart Traps for Regional Monitoring of Navel Orangeworm
Traditionally, wing- and delta-traps with a sticky liner and pheromone or ovibait lure are used to monitor populations of navel orangeworm (Pyralidae: Amyelois transitella) (NOW). Growers and pest control advisors (PCAs) can typically check on these traps 1-2x/week, but it requires a lot of time and effort, especially if many traps are being used across multiple orchard sites. NOW has a high dispersal capacity and is known to move between orchards. As such, local management efforts can be undermined by colonization from adjacent orchards, and in this way regional monitoring of NOW populations may provide better information to growers relative to more localized on-farm monitoring. In this project, we are evaluating the accuracy of five commercial automated "smart traps" for NOW. At the same time, we are developing a new online platform that will allow growers and PCAs to estimate NOW phenology and display real-time counts from automated traps.
