Identification and Synthesis of Leptotriene, a Unique Sesquiterpene Hydrocarbon from Males of the Leaffooted Bugs Leptoglossus zonatus and L. occidentalis.

The leaffooted bugs Leptoglossus zonatus and L. occidentalis (Hemiptera: Coreidae) cause substantial damage in tree nut crops in North America and pine seed orchards in North America and Europe, respectively. Sexually mature males of both species produce a number of aldehydes, esters, and sesquiterpenes, which are hypothesized to constitute an aggregation pheromone attractive to both sexes. Among the volatiles produced by males of both species, we identified a unique sesquiterpene hydrocarbon, given the common name "leptotriene" (5), which elicited strong responses from antennae of both sexes in electroantennogram assays. Here, we report its structure and its synthesis from (-)-(E)-ß-caryophyllene (1).

Spatial Associations of Vines Infected With Grapevine Red Blotch Virus in Oregon Vineyards.

Spread and in-field spatial patterns of vines infected with grapevine red blotch virus (GRBV) were documented in Oregon vineyards using field sampling, molecular diagnostics, and spatial analysis. Grapevine petiole tissue collected from 2013 to 2016 was tested using quantitative polymerase chain reaction for GRBV. At Jacksonville in southern Oregon, 3.1% of vines were infected with GRBV in 2014, and GRBV incidence reached 58.5% of study vines by 2016. GRBV-infected plants and GRBV-uninfected plants were spatially aggregated at this site in 2015, and infected plants were spatially associated between years 2015 and 2016. In a southern Oregon vineyard near Talent, 10.4% of vines were infected with GRBV in 2014, and infection increased annually to 21.5% in 2016. At Talent, distribution of the infected vines was spatially associated across all years. GRBV infection was highest at Yamhill, in the Willamette Valley, where 31.7% of the tested vines had GRBV infection in 2014. By 2016, 59.2% of the vines tested positive for GRBV. Areas of aggregation increased and were spatially associated across all years. From 2013 to 2015, GRBV was not detected at Milton-Freewater in eastern Oregon. Spatial patterns of GRBV infection support evidence of spread by a mobile insect vector. GRBV is a significant threat to Oregon wine grape production because of its drastic year-over-year spread in affected vineyards.

Entomological Opportunities and Challenges for Sustainable Viticulture in a Global Market.

Viticulture has experienced dramatic global growth in acreage and value. As the international exchange of goods has increased, so too has the market demand for sustainably produced products. Both elements redefine the entomological challenges posed to viticulture and have stimulated significant advances in arthropod pest control programs. Vineyard managers on all continents are increasingly combating invasive species, resulting in the adoption of novel insecticides, semiochemicals, and molecular tools to support sustainable viticulture. At the local level, vineyard management practices consider factors such as the surrounding natural ecosystem, risk to fish populations, and air quality. Coordinated multinational responses to pest invasion have been highly effective and have, for example, resulted in eradication of the moth Lobesia botrana from California vineyards, a pest found in 2009 and eradicated by 2016. At the global level, the shared pests and solutions for their suppression will play an increasing role in delivering internationally sensitive pest management programs that respond to invasive pests, climate change, novel vector and pathogen relationships, and pesticide restrictions.

Phenyl Propionate and Sex Pheromone for Monitoring Navel Orangeworm (Lepidoptera: Pyralidae) in the Presence of Mating Disruption.

The recent availability of sex pheromone lures for the navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), improves options for monitoring this key pest in conventionally managed almonds. These lures are, however, minimally effective in the presence of mating disruption. Experiments were conducted to determine if phenyl propionate (PPO), an attractant for the navel orangeworm, acts in an additive or synergistic manner when presented together with the pheromone. In the absence of mating disruption, traps baited with PPO captured significantly fewer adults than traps baited with a sex pheromone lure. There was no difference in the number of adults captured in traps with both attractants when mating disruption was not used. In the presence of mating disruption, pheromone traps were completely suppressed, yet traps with both pheromone and PPO captured significantly more adults than traps baited with only PPO. Traps with only PPO captured equal numbers of both sexes, whereas traps with both attractants had significantly more males. These findings demonstrate that PPO is likely to be useful for monitoring navel orangeworm in fields treated with mating disruption.

Crop Loss Relationships and Economic Injury Levels for Ferrisia gilli (Hemiptera: Pseudococcidae) Infesting Pistachio in California.

Ferrisia gilli Gullan (Hemiptera: Pseudococcidae) is a new pest in California pistachios, Pistacea vera L. We conducted a 3-yr field study to determine the type and amount of damage caused by F. gilli. Using pesticides, we established gradients of F. gilli densities in a commercial pistachio orchard near Tipton, CA, from 2005 to 2007. Each year, mealybug densities on pistachio clusters were recorded from May through September and cumulative mealybug-days were determined. At harvest time, nut yield per tree (5% dried weight) was determined, and subsamples of nuts were evaluated for market quality. Linear regression analysis of cumulative mealybug-days against fruit yield and nut quality measurements showed no relationships in 2005 and 2006, when mealybug densities were moderate. However, in 2007, when mealybug densities were very high, there was a negative correlation with yield (for every 1,000 mealybug-days, there was a decrease in total dry weight per tree of 0.105 kg) and percentage of split unstained nuts (for every 1,000 mealybug-days, there was a decrease in the percentage of split unstained of 0.560%), and a positive correlation between the percentage of closed kernel and closed blank nuts (for every 1,000 mealybug-days, there is an increase in the percentage of closed kernel and closed blank of 0.176 and 0.283%, respectively). The data were used to determine economic injury levels, showing that for each mealybug per cluster in May there was a 4.73% reduction in crop value associated with quality and a 0.866 kg reduction in yield per tree (4.75%).

Estimation of stage duration distributions and mortality under repeated cohort censuses.

Many processes in nature can be viewed as arising from subjects progressing through sequential stages and may be described by multistage models. Examples include disease development and the physiological development of plants and animals. We develop a multistage model for sampling designs where a small set of subjects is followed and the number of subjects in each stage is assessed repeatedly for a sequence of time points, but for which the subjects cannot be identified. The motivating problem is the laboratory study of developing arthropods through stage frequency data. Our model assumes that the same individuals are censused at each time, introducing among sample dependencies. This type of data often occur in laboratory studies of small arthropods but their detailed analysis has received little attention. The likelihood of the model is derived from a stochastic model of the development and mortality of the individuals in the cohort. We present an MCMC scheme targeting the posterior distribution of the times of development and times of death of individuals. This is a novel type of MCMC that uses customized proposals to explore a posterior with disconnected support arising from the fact that individual identities are unknown. The MCMC algorithm may be used for inference about parameters governing stage duration distributions and mortality rates. The method is demonstrated by fitting the development model to stage frequency data of a mealybug cohort placed on a grape vine.

Life history parameters of Chinavia hilaris (Hemiptera: Pentatomidae), a stink bug injurious to pistachios in California.

Life history parameters were established under controlled laboratory conditions for the green stink bug, Chinavia hilaris (Say) (= Acrosternum hilare), to improve pest control in pistachios in California. Parameters measured and calculated included survival and development at seven constant temperatures (ranging from 15 to 35 degrees C), development time, upper and lower development thresholds, thermal constants, fecundity, generation time, net reproductive rate, and intrinsic rate of increase. C. hilaris did not complete development at 15 and 35 degrees C. Within the range of 20-27.5 degrees C, development time decreased linearly with temperature; it increased again at 30 degrees C. The lower threshold was calculated by linear methods to be 12.3 degrees C, and the thermal constant was calculated to be 588 degree days. Fastest development was recorded at 27.5 degrees C, whereas greatest survival was observed at 22.5 degrees C. At 27.5 degrees C, mean fecundity was 53.5 eggs per female, mean generation time was 74.4 d, net reproductive rate was 20.09, and intrinsic rate of increase was 0.04. Use of a nonlinear model yielded estimates of 13.2, 28.4, and 33.4 degrees C, for the lower threshold, optimum temperature, and upper threshold, respectively. Results were compared with similar studies and interpreted in the light of pest management needs in pistachio. Increased emphasis on monitoring and management ofoverwintering sites and early-season migration are recommended.

Factors Limiting Peach as a Potential Host for Drosophila suzukii (Diptera: Drosophilidae).

The spotted wing drosophila, Drosophila suzukii Matsumura, has widely established in North America and become an economic concern for a variety of fruit crops. To better understand fruit susceptibility, we evaluated peach surface characteristics on the pest's oviposition success. The number of D. suzukii eggs laid into the fruit flesh was tested on 1) peaches with or without indumenta (commonly referred to as peach fuzz), 2) peaches physically damaged by harvest operations, 3) peaches damaged by the peach twig borer Anarsia lineatella Zeller or the forktailed bush katydid, Scudderia furcata Brunner von Wattenwyl, and 4) peaches with punctures that simulated stink bug damage. Female D. suzukii did not lay eggs in intact fuzzy sections of the fruit or into small punctures (0.3 or 0.5 mm), but readily laid eggs in sections without fuzz, with insect damage, and with large punctures (1 mm). The number of eggs per treatment was positively related to the area of the damaged section; the overall fruit firmness and sugar content was not related to the number of eggs laid in treated or damaged spots. Direct observations of D. suzukii oviposition confirmed that peach fuzz appeared to be an obstacle for the fly's oviposition success, and female flies ceased ovipositional attempts on fuzzy peach sections after a short period of time. Successful oviposition times were associated with substrate firmness, with shorter oviposition time in damaged spots than in cherry fruit or shaved spots of the peach. The results indicate that intact, preharvest peach fruit are unlikely to be infested by the fly, but any surface damage could render the fruit susceptible to the fly.

Floral resources enhance fitness of the parasitoid Hadronotus pennsylvanicus (Hymenoptera: Scelionidae) but not biological control of its host Leptoglossus zonatus (Heteroptera: Coreidae).

The diet of adult parasitoid wasps is vital for their survival and reproduction. However, the availability of food resources, such as plant nectar, can vary widely in cropping systems, potentially affecting parasitoid fitness and thereby biological control of pests. The egg parasitoid Hadronotus pennsylvanicus (Ashmead) (Hymenoptera: Scelionidae) is a potential biological control agent of the pistachio pest Leptoglossus zonatus (Dallas) (Heteroptera: Coreidae). While H. pennsylvanicus is known to attack L. zonatus eggs in California, USA, parasitism rates in orchards are highly variable. Floral resource provisioning has the potential to enhance parasitoid longevity and thus improve parasitism rates, leading to reduced pest densities. Here, a combination of field and laboratory studies was used to assess the influence of flowering groundcovers on the reproductive fitness of H. pennsylvanicus and the abundance of L. zonatus. Evaluated groundcovers included oat (Avena sativa L.), cowpea (Vigna unguiculata L.), white mustard (Sinapis alba L.), and buckwheat (Fagopyrum esculentum Moench). Under laboratory conditions, buckwheat and mustard provided the greatest benefit to female H. pennsylvanicus longevity. However, females provided a buckwheat diet produced the greatest number of offspring over the course of their lifetime. In field trials, flowering groundcovers did not influence the abundance of H. pennsylvanicus nor parasitism rates on L. zonatus. While the availability of floral resources can improve the reproductive fitness of H. pennsylvanicus, the use of groundcovers in pistachio did not enhance biological control of L. zonatus.

Genome divergence and reproductive incompatibility among populations of Ganaspis near brasiliensis.

During the last decade, the spotted wing drosophila, Drosophila suzukii, has spread from eastern Asia to the Americas, Europe, and Africa. This fly attacks many species of cultivated and wild fruits with soft, thin skins, where its serrated ovipositor allows it to lay eggs in undamaged fruit. Parasitoids from the native range of D. suzukii may provide sustainable management of this polyphagous pest. Among these parasitoids, host-specificity testing has revealed a lineage of Ganaspis near brasiliensis, referred to in this paper as G1, that appears to be a cryptic species more host-specific to D. suzukii than other parasitoids. Differentiation among cryptic species is critical for introduction and subsequent evaluation of their impact on D. suzukii. Here, we present results on divergence in genomic sequences and architecture and reproductive isolation between lineages of Ganaspis near brasiliensis that appear to be cryptic species. We studied five populations, two from China, two from Japan, and one from Canada, identified as the G1 vs G3 lineages based on differences in cytochrome oxidase l sequences. We assembled and annotated the genomes of these populations and analyzed divergences in sequence and genome architecture between them. We also report results from crosses to test reproductive compatibility between the G3 lineage from China and the G1 lineage from Japan. The combined results on sequence divergence, differences in genome architectures, ortholog divergence, reproductive incompatibility, differences in host ranges and microhabitat preferences, and differences in morphology show that these lineages are different species. Thus, the decision to evaluate the lineages separately and only import and introduce the more host-specific lineage to North America and Europe was appropriate.

Seasonal biology of Ferrisia gilli (Hemiptera: Pseudococcidae) in California Sierra foothill vineyards.

The mealybug Ferrisia gilli Gullan is an emerging pest of wine grapes grown in California's Sierra foothills. A relatively new species, it had previously been recorded as a pest of pistachio, almond, and ornamentals. It was first reported on grape in El Dorado County in 2003 and has since established and spread. Nondestructive monitoring of grape vine sections was conducted in untreated vineyard plots and compared with destructive sampling conducted in grower-treated plots in 2008 and 2009 to determine F. gilli life stage seasonal presence, number of generations, location on the vine during the season, and damage potential to fruit clusters. Two generations were observed to be completed during the season. F. gilli overwintered under the bark at the base of the trunk, trunk, and cordon as second and third instars. Adults were found at the base of emerging shoots (spring) or on and under bark of old and new spurs. Live crawlers were born in June (first generation) and late August to September (second generation), and migrated to leaves to feed before moving to protected locations under bark or into fruit clusters. Lower mealybug densities and fruit damage were recorded on vines with than without insecticide treatment(s). Parasitized mealybugs were collected in low numbers and an Acerophagus sp. was the dominant parasitoid.

Reproductive biology of overwintering leaffooted bug Leptoglossus zonatus (Hemiptera: Coreidae) in California.

Leptoglossus zonatus (Dallas) (Hemiptera: Coreidae) is a polyphagous insect pest attacking a wide variety of crops. In California's Central Valley, it is now the dominant leaffooted bug on almonds, pistachios, and pomegranates. Leptoglossus zonatus pest status depends largely on overwintering adult survival and reproductive potential, which determines its population size in spring and early summer when nut crops are particularly susceptible to bug damage. Here, we investigated the overwintering reproductive biology of L. zonatus in laboratory and field experiments to gain information about its ovary development, time of mating, and the impact of low temperatures on egg hatch. With dissections of laboratory-reared L. zonatus, we established a baseline for ovarian development and determined that the size of the spermathecal reservoir is larger in mated than in unmated females. Dissections and behavioral experiments of field-collected material provided evidence of mating events before dispersal from overwintering sites. Laboratory trials showed that temperature significantly impacted L. zonatus egg hatch. Leptoglossus zonatus reproductive biology presented provides valuable information on its population dynamics and dispersal from overwintering sites, and will contribute to the development of monitoring and management tools.

Alterations in Ferrisia gilli (Hemiptera: Pseudococcidae) phenology in California pistachios and potential impacts on controls.

The mealybug, Ferrisia gilli Gullan, attacks important crops such as almonds, grapes, and pistachios in California. In pistachios, F. gilli has 3 generations per year, and a single insecticide application timed to the presence of first instars of the first or second generation provided sufficient control. This strategy has, recently, become less effective, and here we tested the possible explanation that F. gilli life stages are smeared, with different life stages present concurrently, reducing the efficacy of a single pesticide application. We monitored F. gilli populations and their natural enemies in central California pistachio orchards from 2021 through 2022. We found the first generation of F. gilli was synchronous, but occurred 3 wk earlier than previously reported. Subsequent generations were smeared. Increased yearly temperatures are a likely explanation for the changes observed in phenology. Almost all natural enemies found were lacewings (n > 10,000). Parasitoids were recovered from pistachios in 2021 (n = 4) and 2022 (n = 164), most were hyperparasitoids. Based on these studies, recommendations are made to monitor F. gilli in early May rather than late May to better target insecticide applications for the first instars.

Closer view of antennal sensory organs of two Leptoglossus species (Insecta, Hemiptera, Coreidae).

Detailed description of antennal sensory organs of Leptoglossus occidentalis Heidemann, 1910 (Insecta: Hemiptera: Heteroptera: Coreidae) and a comparison with L. zonatus (Dallas, 1852) are presented. A novel approach that combines the advantages of field emission scanning electron microscopy (FE-SEM) and atomic force microscope (AFM) was used to detail micromorphological structures. A simplified classification system for sensilla that eliminates the subjective aspects of morphology, such as their shape, is proposed. Fourteen sensory organs have been classified into three main groups: (a) aporous sensilla with a flexible socket, (b) porous sensilla with a flexible socket and (c) porous sensilla with an inflexible socket. A large variety of sensory organs (nine types) with olfactory functions are described. The antennal sensory organs have been recognized as one of the factors responsible for the evolutionary success of Leptoglossus spp. and their status as important pests and invasive species.

A comparison of candidate banker plants for management of pests in lettuce.

Agricultural systems are often lacking in resources for natural enemies. Providing alternative prey can help natural enemies persist through periods of low pest abundance, although this approach has been rarely commercially implemented in open field crops. In this study, we tested the potential of eight plant species to provide alternative prey to natural enemies in lettuce fields over a 2-yr period. Results showed that the tested plants would not act as sources of the lettuce aphid Nasonovia ribisnigri Mosley (Hemiptera: Aphididae), the primary lettuce pest. Of the banker plants tested, barley contained high numbers of non-lettuce aphids and appeared to provide reliable habitat for hoverfly larvae. However, lettuce aphids were present on lettuce early in the season, and may have dwarfed any effects of nonlettuce aphids on natural enemy populations. Numbers of hoverfly larvae were also high in lettuce, but did not appear to track numbers of non-lettuce aphids on banker plants. In contrast, numbers of lacewing larvae were highest on plants containing high numbers of non-lettuce aphids, and predatory hemipterans appeared to be associated with numbers of thrips on banker plants. Although barley showed promise as a source of alternative aphids, it did not appear to improve pest control in the adjacent crop.

Management of Almond Leaf Scorch Disease: Long-Term Data on Yield, Tree Vitality, and Disease Progress.

Almond leaf scorch disease (ALSD) has been a chronic problem for California almond growers. This disease is caused by the bacterial pathogen Xylella fastidiosa and is transmitted by xylem-feeding insects. Previous research suggested that retaining, rather than roguing, ALSD-affected trees may be more economically beneficial because ALSD-affected trees produced a reasonable yield and did not die over a 3-year period. Because almond orchards are kept in production for approximately 25 years, longer-term data are needed to fully evaluate the merits of retaining ALSD-affected trees. Extension of yield evaluations from 3 to 5 years demonstrated that yield loss due to ALSD was consistent over 5 years, with yields of ALSD-affected trees reduced by 20 and 40% compared with unaffected trees for 'Nonpareil' and 'Sonora', respectively. To assess risk of ALSD-affected trees serving as a source of inocula for secondary (tree-to-tree) spread and to evaluate vitality of ALSD-affected trees, previous surveys of two orchards were extended from 3 to 6 or 7 years. The relationship between disease incidence (percentage of trees infected) and survey year was linear for all cultivars examined at both orchards. Furthermore, at each orchard, the spatial location of infections detected after the first survey was random with respect to the spatial location of infections identified during the first survey, suggesting that ALSD-affected trees retained in orchards did not serve as a source for secondary spread. Over the 6- to 7-year study period, death of ALSD-affected trees was rare, with only 9% of ALSD-affected trees dying. Because orchards used in this study had relatively high disease incidence, 61 orchards containing Sonora were surveyed to determine typical levels of ALSD incidence. ALSD was widespread, with at least one infected tree in 56% of orchards surveyed, but incidence was typically low (mean incidence = 0.47%). Collectively, the results suggest that retaining ALSD-affected trees may be economically beneficial in older orchards.

Seasonal phenology of Ferrisia gilli (Hemiptera: Pseudococcidae) in commercial pistachios.

The mealybug Ferrisia gilli Gullan is a serious new pest of pistachios in California. It was first found near the town of Tulare in the late 1990s and has since spread to orchards in most pistachio-producing regions of the state. The seasonal phenology of F. gilli was evaluated in a commercial pistachio orchard in Tulare County during 2005 and 2006. During both seasons E gilli overwintered as small nymphs and had three complete generations per year. Mealybug population densities were low and remained as immatures in March and April; by late May adult females formed and averaged (+/- SE) 1.3 +/- 0.3 and 1.2 +/- 0.3 per 0.75 m of sample branch in 2005 and 2006, respectively. The first in-season generation occurred from early June through mid-July, with mealybug densities ranging from 17.6 +/- 5.6-26.4 +/- 6.2 mealybugs per 0.75 m sample branch. The second in-season generation occurred from late July through September and had peak densities of 408.6 +/- 93.9 and 182.0 +/- 34.2 mealybugs per branch. In March and April mealybugs were located primarily on the buds and branch wood; in May the population was on branch wood as well as the rachis; from June through September the population was located primarily in the pistachio cluster. F. gilli's seasonal phenology described herein was used to develop a management program.

Discrimination Abilities and Parasitism Success of Pupal Parasitoids Towards Spotted-Wing Drosophila Pupae Previously Parasitized by the Larval Parasitoid Ganaspis brasiliensis (Hymenoptera: Figitidae).

Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) and Trichopria drosophilae (Perkins) (Hymenoptera: Diapriidae) are two cosmopolitan and generalist pupal parasitoids that are among a few of the resident parasitoids in North America capable of attacking Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), an invasive pest of small and soft fruit crops worldwide. Ganaspis brasiliensis (Ihering) is a specialist larval parasitoid of D. suzukii that was recently approved for biological control introduction against D. suzukii in the USA. As a solitary koinobiont species, G. brasiliensis oviposits in the host larva but emerges as an adult from the host puparium. This study investigated the discrimination ability and parasitism success by the pupal parasitoids towards D. suzukii pupae previously parasitized by G. brasiliensis, to examine whether interactions with resident parasitoids will affect G. brasiliensis after it is released in the USA. We found preliminary evidence that neither pupal parasitoid could discriminate towards D. suzukii pupae parasitized by early instars of G. brasiliensis. Pachycrepoideus vindemiae was able to successfully develop on D. suzukii pupae containing all preimaginal stages of G. brasiliensis, although parasitism success was significantly higher on those bearing later rather than early stages of G. brasiliensis. Trichopria drosophilae was only able to successfully develop on D. suzukii puparia containing early instars of G. brasiliensis. These results suggest that D. suzukii parasitized by the larval parasitoid could be subsequently attacked by the pupal parasitoids, possibly affecting the success of G. brasiliensis releases.

Comparative Life History Parameters of Three Stink Bug Pest Species.

California pistachios are threatened by several stink bug species (Hemiptera: Pentatomidae), including the native Thyanta pallidovirens (Stål) and Chlorochroa uhleri (Stål), as well as the invasive Nezara viridula (L.). In pistachio, control tactics often target specific life stages, which makes knowledge about life histories fundamental to successful IPM programs. For that purpose, life history parameters of these stink bug species were assessed. Nymphal development and survivorship at seven constant temperatures, upper and lower development thresholds, thermal constants, adult longevity and fecundity, and life table parameters were evaluated. No species completed development at 15°C or 35°C. For N. viridula, egg to adult development was fastest at 30°C, whereas for T. pallidovirens there was no significant difference between 27.5 and 30°C and C. uhleri development was similar between 25 and 30°C. Egg to adult survival was highest at 22.5°C and 27.5°C. The thermal requirements as degree-days (DD) to complete immature development were estimated to be 714.3, 370.4, and 434.8 for C. uhleri, T. pallidovirens, and N. viridula, respectively. For C. uhleri, life table calculations produced a value of 56.7 d for mean generation time (To), 24.89 for net reproductive rate (Ro) and 0.057 for the intrinsic rate of increase (r). Thyanta pallidovirens had a To of 39.9 d, a Ro of 81.10 and a r of 0.11. The results are discussed with respect to the improvement of IPM in California pistachios, and the information presented may contribute to the control of these pest species in other ecosystems.

Winter Cover Crops Reduce Spring Emergence and Egg Deposition of Overwintering Navel Orangeworm (Lepidoptera: Pyralidae) in Almonds.

Habitat diversification has been shown to positively influence a variety of ecosystem services to agriculture, including biological control of arthropod pests. The impact of increased biodiversity tends to be species specific though, and practices therefore need to be developed on a case-by-case basis for each cropping system. In perennial systems, numerous studies have demonstrated that cover crops can have positive impacts on soil quality and other ecosystem services, such as pollination and pest management. However, few studies have focused on the use of cover crops to enhance pest control in almond orchards, especially winter cover crops. The primary pest of almonds in North America is navel orangeworm, Amyelois transitella Walker, which overwinter as larva or pupa on remnant nuts, many of which remain on the orchard soil surface. In the spring, first flight adults subsequently use these remnant nuts as reproductive substrate. An experiment was conducted to evaluate the influence of two distinct winter cover crop mixtures on overwintering mortality and spring egg deposition of A. transitella. Remnant nuts placed into cover crop plots produced fewer adult A. transitella in the spring, suggesting increased overwintering mortality. Additionally, spring egg deposition was reduced on remnant nuts in the cover crops, possibly due to the ground covers interfering with host location and access. In this way, winter cover crops appear to contribute to the reduction of A. transitella populations in the orchard by altering abiotic and physical conditions, although studies to document specific mechanisms are still needed.