Arthropod Populations Research Articles

The Design and In Vivo Evaluation of Engineered I-OnuI-Based Enzymes for HEG Gene Drive

The homing endonuclease gene (HEG) drive system, a promising genetic approach for controlling arthropod populations, utilises engineered nucleases to spread deleterious mutations that inactivate individual genes throughout a target population. Previous work with a naturally occurring LAGLIDADG homing endonuclease (I-SceI) demonstrated its feasibility in both Drosophila and Anopheles. Here we report on the next stage of this strategy: the redesign of HEGs with customized specificity in order to drive HEG-induced ‘homing’ in vivo via break-induced homologous recombination. Variants targeting a sequence within the Anopheles AGAP004734 gene were created from the recently characterized I-OnuI endonuclease, and tested for cleavage activity and frequency of homing using a model Drosophila HEG drive system. We observed cleavage and homing at an integrated reporter for all endonuclease variants tested, demonstrating for the first time that engineered HEGs can cleave their target site in insect germline cells, promoting targeted mutagenesis and homing. However, in comparison to our previously reported work with I-SceI, the engineered I-OnuI variants mediated homing with a reduced frequency, suggesting that site-specific cleavage activity is insufficient by itself to ensure efficient homing. Taken together, our experiments take a further step towards the development of a viable HEG-based population control strategy for insects.

Transcriptome profiling of Nasonia vitripennis testis reveals novel transcripts expressed from the selfish B chromosome, paternal sex ratio.

A widespread phenomenon in nature is sex ratio distortion of arthropod populations caused by microbial and genetic parasites. Currently little is known about how these agents alter host developmental processes to favor one sex or the other. The paternal sex ratio (PSR) chromosome is a nonessential, paternally transmitted centric fragment that segregates in natural populations of the jewel wasp, Nasonia vitripennis. To persist, PSR is thought to modify the hereditary material of the developing sperm, with the result that all nuclear DNA other than the PSR chromosome is destroyed shortly after fertilization. This results in the conversion of a fertilized embryo—normally a female—into a male, thereby insuring transmission of the “selfish” PSR chromosome, and simultaneously leading to wasp populations that are male-biased. To begin to understand this system at the mechanistic level, we carried out transcriptional profiling of testis from WT and PSR-carrying males. We identified a number of transcripts that are differentially expressed between these conditions. We also discovered nine transcripts that are uniquely expressed from the PSR chromosome. Four of these PSR-specific transcripts encode putative proteins, whereas the others have very short open reading frames and no homology to known proteins, suggesting that they are long noncoding RNAs. We propose several different models for how these transcripts could facilitate PSR-dependent effects. Our analyses also revealed 15.71 MB of novel transcribed regions in the N. vitripennis genome, thus increasing the current annotation of total transcribed regions by 53.4%. Finally, we detected expression of multiple meiosis-related genes in the wasp testis, despite the lack of conventional meiosis in the male sex.

Population dynamics of arthropods in a sunn-hemp zucchini interplanting system

Zucchini, Cucurbita pepo L., is often colonized by economically important insect pests such as the striped (Acalymma vittatum Fab.) and spotted (Diabrotica undecimpunctata howardi Barber) cucumber beetles. To evaluate the impact of an interplanted cover crop on arthropods associated with zucchini, field experiments were conducted in which sunn hemp (Crotalaria juncea L.) was interplanted with zucchini as a living mulch and compared with zucchini monoculture (bare-ground) during 2009, 2010 and 2011 growing seasons. The experiment consisted also of two types of fertilizer usage including the application of synthetic or organic fertilizer in the form of chicken manure. Foliar counts of arthropods conducted on zucchini plants showed significantly lower numbers of the striped cucumber beetle in sunn hemp interplanted plots compared to bare-ground treatment plots. Also, fewer spotted cucumber beetles were found on zucchini plants in sunn hemp plots. Aphid abundances were variable during the study and significantly lower in sunn hemp treatment plots at one study site in 2009. Among predators, spiders were significantly more abundant in sunn hemp treatment plots during 2009. Fertilizer type did not have a significant effect on arthropod numbers on zucchini plants. Potential causes of arthropod population differences among the two treatments are discussed.

Microencapsulated Spodoptera frugiperda nucleopolyhedrovirus: insecticidal activity and effect on arthropod populations in maize

Excessive use of chemical insecticides to control Spodoptera frugiperda in maize (Zea mays L.) crops in Colombia has resulted in pest resistance and environmental contamination. A Colombian multicapsid nucleopolyhedrovirus (SfMNPV) was produced in laboratory reared larvae and formulated as a wettable powder by microencapsulating the viral occlusion bodies (OBs) with a methacrylic acid polymer. Microencapsulated OBs were tested for insecticidal activity in laboratory, greenhouse and field bioassays, and were then sprayed onto a commercial crop where their effect on arthropod populations was estimated. In laboratory bioassay, microencapsulated and non-microencapsulated OBs caused a larval mortality of 98 and 96%, respectively. The percent of plants showing recent feeding damage in a greenhouse experiment oscillated between 2.5 and 7.5% when OBs were applied compared to 70% observed in the control. In two field trials, the highest dose of 1.5×1012 OBs/ha (1500 g/ha) was selected as the recommended rate for field application in maize crops, with efficacies higher than 70%. Total arthropod populations were negatively affected by chemical pesticides; whereas the OBs formulation did not affect the diversity of these organisms. Our results indicate that microencapsulated SfMNPV has the potential to be commercialised as an alternative to substitute or complement chemical insecticides in fall armyworm integrated management programmes.

Which insect species numerically respond to allochthonous inputs?

Herons (Ardeidae) frequently breed in inland forests and provide organic material in the form of carcasses of prey (that they drop) and chicks (that die) to the forest floor. Such allochthonous inputs of organic materials are known to increase arthropod populations in forests. However, the exact species that show numerical responses to allochthonous inputs in heron breeding colonies remains unclear. Very few studies have clarified which factors determine numerical responses in individual species. We used pitfall and baited traps to compare the densities of arthropods between forest patches in heron breeding colonies (five sites) and areas outside of colonies (five sites) in central Japan. The density of all arthropods was not significantly different between colonies and non-colony areas. However, significant differences between colonies and non-colony areas were found in four arthropod groups. Earwigs (Dermaptera: Anisolabididae), hister beetles (Coleoptera: Histeridae), and carrion beetles (Coleoptera: Silphidae) were more abundant in colonies, while ants (Hymenoptera: Formicidae) were less abundant in colonies. We detected numerical responses to heron breeding in two earwig, one histerid, five silphid, and one ant species. Chick and prey carcasses from herons may have directly led to increases in consumer populations such as earwigs, histerids, and silphids in colonies, while microenvironmental changes caused by heron breeding may have reduced ant abundance. In the Silphidae, five species showed numerical responses to allochthonous inputs, and the other two species did not. Numerical responses in individual species may have been determined by life history traits such as reproductive behaviour.

Arthropod survey on soybean crops in Cambodia: a comparison of the sweep netting and beat sheeting collection methods for estimating arthropod diversity and species richness

AbstractThis is the first assessment of insect assemblages on soybean crops in Cambodia. Sweep netting and beat sheeting collection methods were used to evaluate the effectiveness of sampling arthropods and their collection efficiency in soybean crops and to determine soybean insect diversity and composition at two sites. Overall, arthropod populations sampled by sweep netting were substantially different compared to populations collected by beat sheeting. The sweep netting caught significantly higher numbers of most Orders; however, the beat sheeting caught a significantly higher number of Acari. Beat sheeting was also effective for sampling Nezara viridula which is a major invertebrate pest of soybean. There was a significant interaction between location and collection methods for both Hemiptera and Hymenoptera assemblages. Selection of insect sampling method depends on many factors such as plant type, plant structure, field conditions, ease of use, cost of use and target insect species. However, the sweep netting was best for fast flying insects such as hymenopteran wasps and those located in upper parts of the plant canopy. The use of different sampling methods to assess pest, predator/parasitoid and general community structure in crops is crucial for assessing Integrated Pest Management strategies.

Field efficacy of neem (Azadirachta indica A. Juss) for managing soil arthropods and Cercospora leaf spots damage for increased yield in peanut

Field efficacy of neem (Azadirachta indica A. Juss) for managing soil arthropods and Cercospora leaf spots damage to peanut was studied in Ghana from 2008 to 2010. Treatments consisted of neem kernel water extract (NKWE) and neem kernel powder (NKP) applied separately as soil drench at the rates of 10.5 and 21.0 kg/ha at either planting or pegging. Untreated control and chlorpyrifos treatment at pegging were included as checks. Results showed generally that the neem products at the concentrations tested were efficacious and comparable to chlorpyrifos in lowering populations of soil arthropods and severity of leaf spot diseases, leaf defoliation, and scarified and bored pod damage, resulting in increased pod yield in 2008 and 2009.

Plant pathogens structure arthropod communities across multiple spatial and temporal scales

Summary Plant pathogens and herbivores frequently co‐occur on the same host plants. Despite this, little is known about the impact of their interactions on the structure of plant‐based ecological communities. Here, we synthesize evidence that indicates that plant pathogens may profoundly impact arthropod performance, preference, population dynamics and community structure across multiple spatial and temporal scales. Intriguingly, the effects of plant–pathogen–herbivore interactions frequently cascade up and down multiple trophic levels and explain variation in the arthropod community at spatial scales ranging from patterns within single host plants to entire landscapes. This review indicates that knowledge on pathogen–herbivore interactions may be crucial for understanding the dynamics of terrestrial communities.

Terrestrial arthropod abundance and phenology in the Canadian Arctic: modelling resource availability for Arctic-nesting insectivorous birds

AbstractArctic arthropods are essential prey for many vertebrates, including birds, but arthropod populations and phenology are susceptible to climate change. The objective of this research was to model the relationship between seasonal changes in arthropod abundance and weather variables using data from a collaborative pan-Canadian (Southampton, Herschel, Bylot, and Ellesmere Islands) study on terrestrial arthropods. Arthropods were captured with passive traps that provided a combined measure of abundance and activity (a proxy for arthropod availability to foraging birds). We found that 70% of the deviance in daily arthropod availability was explained by three temperature covariates: mean daily temperature, thaw degree-day, and thaw degree-day2. Models had an adjustedR2of 0.29–0.95 with an average among sites and arthropod families of 0.67. This indicates a moderate to strong fit to the raw data. The models for arthropod families with synchronous emergence, such as Tipulidae (Diptera), had a better fit (average adjustedR2of 0.80) than less synchronous taxa, such as Araneae (R2= 0.60). Arthropod abundance was typically higher in wet than in mesic habitats. Our models will serve as tools for researchers who want to correlate insectivorous bird breeding data to arthropod availability in the Canadian Arctic.

The Demographic of Brontispa longissima variety of celebensis Gestro (Coleoptera: Chrysomelidae) on Mapanget Tall Coconut and Brown Dwarf Coconut

Brontispa longissima variety of celebensisis considered an important pest on coconut trees. Basic information such as the biology and the life table of the species is extremely important in the effort to control its attack. The life table of B. longissima variety of celebensis on Mapanget Tall Coconut (MTC) and Brown Dwarf Coconut (BDC) can be examined in laboratory. The study aimed at examining the biology and the life table of B. longissima variety of celebensis on MTC and BDC. The study was conducted at Entomology Laboratory of Indonesia Palmae Research Institute, Manado, from June to November 2012. The parameters examined during the study consisted of the followings: 1) the development period from larvae of each instar into adult, 2) the longevity of adult, and 3) the number of eggs laid. The results of the study show that the young leaves of DMT are more suitable to support the life of B. longissima variety of celebensis compared to the young leaves of GRA, and this could be seen from the shorter immature development periods, the higher number of eggs laid, and the longevity of adult. B. longissima variety of celebensisis more suitable to live and grow on the young leaves of DMT than on the young leaves of GRA. This could be seen from the average rm value which was higher on DMT leaves, that was 0.123 individual per adult per day, and mean generation time (T) which was 35.28 days, as compared to the rm value on GRA leaves, that was 0.108 individual per adult per day, and mean generation time (T) which was 39.61. The rm value shows the suitability of the host plants to increase the population of arthropods by considering the development periods, fecundity, longevity, survivorship, and sex ratio.

Abundance and diversity of soil arthropods and fungi in shelterbelts integrated with pastures in the central tablelands of New South Wales, Australia

Shelterbelts are important for the sustainability of agriculture because they provide a variety of benefits to farmers and the society. Several published papers demonstrate that integration of shelterbelts with agroecosystems offers positive outcomes, such as better yield, more congenial microclimate, and greater organic matter levels. Nonetheless, soil biological diversity, the driver of greater organic matter levels, has not been convincingly tested and verified yet. In addressing this gap, we measured abundance and diversity of populations of arthropods and fungi in three<br />11-year old shelterbelts integrated with pasture to determine whether a correlation exists between the abundance of and diversity in populations of arthropods and fungi in two seasons: late autumn-early winter (May–June 2011) and late winter-early spring (August–September 2011). Litter from the soil surface and soil from two depths were sampled at increasing distance from the midpoint of shelterbelts for the extraction of arthropods and isolation culturing of fungi. The relationship among distance, depth and biodiversity of different groups of arthropods and fungi was analysed using linear regression. We found that over both seasons arthropod abundance in the litter and soil declined with increasing distance from the midpoint of the shelterbelts, and with soil depth. However, fungi abundance in either season was not affected by proximity to the shelterbelt but increased with greater soil depth. Distance from the shelterbelt midpoints did not bear an impact on the diversity richness of both arthropods and fungi.

The cropping systems mosaic: How does the hidden heterogeneity of agricultural landscapes drive arthropod populations?

Landscape ecology has emphasized the key role of spatial heterogeneity as a driver of ecological processes, which has led to a shift from a patch-matrix to a landscape mosaic representation of landscapes. However, in agricultural landscapes, the role of heterogeneity for biodiversity is often studied by considering (semi-) natural elements regardless of the functional heterogeneity of the cultivated mosaic. This mosaic, which emerges from the organization of cropping systems by farmers, is not just heterogeneous in space but also strongly dynamic (i.e. temporally heterogeneous) due to crop phenology, management and sequence. In this paper, based on agronomic and ecological literature we highlight the heterogeneous properties of the cropping system mosaics in space and time, and the implications of this “hidden” heterogeneity for controlling of arthropod population dynamics and persistence. An illustration is then given to propose different methodological approaches to map the hidden heterogeneity of agricultural landscapes. This conceptual and methodological framework concerns various species in agro-ecosystems, including crop and multi-habitat species, as well as species that only disperse through the crop mosaic. This paper suggests that the design of the cropping system mosaics could be complementary to the design of natural areas to manage populations, notably for species of economic interest (pests, natural enemies or pollinators). More empirical work on this topic is crucial, which will require new methodological approaches.

Evaluation of methyl salicylate lures on populations of Typhlodromus pyri (Acari: Phytoseiidae) and other natural enemies in western Oregon vineyards

Methyl salicylate (MeSA), a herbivore-induced plant volatile, can elicit control of pests through attraction of beneficial arthropods. This study evaluates the effect of synthetic MeSA lures (PredaLure) on arthropod populations during the 2009 and 2010 seasons in two Oregon vineyards (Dayton and Salem). MeSA lures were deployed at a low (4/plot or 260 lures/ha) and high (8/plot or 520 lures/ha) rate in ∼152m2 plots while control plots contained no lure. The predatory mite Typhlodromus pyri Scheuten is considered to be a key biological control agent of the grapevine rust mite, Calepitrimerus vitis Nalepa in Oregon vineyards. Leaf samples were collected to assess T. pyri, C. vitis, spider mite (Tetranychidae) and thrips (Thripidae) population densities in MeSA treated plots compared to control plots. Yellow sticky traps were used to monitor other key predator groups including Anthocoridae, Araneae, Coccinellidae and Syrphidae. Our data did not display consistent trends in T. pyri response to MeSA between treatments at the two field sites over two seasons. Mean seasonal coccinellid counts were significantly higher in MeSA treatments in both years at Dayton. No differences in C. vitis population densities were found between treatments in both years. In 2009 at Salem, significantly lower pest thrips densities occurred in low rate MeSA treatments in the latter part of the season although no trend of decreased seasonal abundance was evident.

How do sheep affect plant communities and arthropod populations in temperate grasslands?

Grasslands being used in sheep farming systems are managed under a variety of agricultural production, recreational and conservational objectives. Although sheep grazing is rarely considered the best method for delivering conservation objectives in seminatural temperate grasslands, the literature does not provide unequivocal evidence on the impact of sheep grazing on pasture biodiversity. Our aim was therefore to review evidence of the impacts of stocking rate, grazing period and soil fertility on plant communities and arthropod populations in both mesotrophic grasslands typical of agriculturally improved areas and in native plant communities. We therefore conducted a literature search of articles published up to the end of the year 2010 using ‘sheep’ and ‘grazing’ as keywords, together with variables describing grassland management, plant community structure or arthropod taxa. The filtering process led to the selection of 48 articles, with 42 included in the stocking rate dataset, 9 in the grazing period dataset and 10 in the soil fertility dataset. The meta-analysis did not reveal any significant trends for plant species richness or plant community evenness along a wide stocking rate gradient. However, we found frequent shifts in functional groups or plant species abundance that could be explained by the functional properties of the plants in the community. The meta-analysis confirmed that increasing soil fertility decreased plant species richness. Despite the very limited dataset, plant species richness was significantly greater in autumn-grazed pastures than in ungrazed areas, which suggests that choosing an appropriate grazing period would be a promising option for preserving biodiversity in sheep farming systems. Qualitative review indicated that low grazing intensity had positive effects on Orthoptera, Hemiptera (especially phytophagous Auchenorrhyncha) and, despite a diverse range of feeding strategies, for the species richness of Coleoptera. Lepidoptera, which were favoured by more abundant flowering plants, also benefited from low grazing intensities. Spider abundance and species richness were higher in ungrazed than in grazed pastures. In contrast, there are insufficient published studies to draw any firm conclusions on the benefits of late grazing or stopping fertilization on insect diversity, and no grounds for including any of this information in decision support tools at this stage.

Condensed Tannins Inhibit House Fly (Diptera: Muscidae) Development in Livestock Manure

Reducing chemical use for suppressing internal and external parasites of livestock is essential for protecting environmental health. Although plant condensed tannins are known to suppress gastro-intestinal parasites in small ruminants, no research on the effects of tannins on external arthropod populations such as the house fly, Musca domestica L., have been conducted. We examined the impact of plant material containing condensed tannins on house fly development. Prairie acacia (Acacia angustissima (Mill.), Kuntze variety hirta (Nutt.) B.L. Rob.) herbage, panicled tick-clover (Desmodium paniculatum (L.) DC.) herbage, and quebracho (Shinopsis balansae Engl.) extracts were introduced at rates of 1, 3 or 5% condensed tannins/kg beef cattle, dairy cattle, and goat manure, respectively. In a second experiment, we also introduce purified catechin at 1 or 3% of dairy manure dry matter and measured its impact on house fly development. For the house flies used in these experiments, the following was recorded: percent fly emergence (PFE), average daily gain (ADG), and average fly weight (AFW). No effects (P>0.05) in house fly development were measured in the caprine manure. Prairie acacia (20.9% condensed tannins) had no effect on house flies developing in either bovine manures. Tick clover (4.9% condensed tannins) had a negative effect on all three quantifiable variables of house fly development in the bovine manures, whereas quebracho extract (64.0% condensed tannins) at the 3 and 5% rate reduced fly emergence in beef manure and average daily gain in dairy manure. The application of purified catechin at 3%, but not 1%, reduced fly PFE, ADG, and AFW.

The Influence of Transgenic cry1Ab/cry1Ac, cry1C and cry2A Rice on Non-Target Planthoppers and Their Main Predators Under Field Conditions

Abstract Transgenic Bt rice has been shown to be an effective means of controlling Lepidoptera pests of rice. However, the potential roles of transgenic rice on planthoppers and their predators need to be investigated before its commercialization. Population density, species dominance and population dynamics are important parameters of arthropods populations in field. So the impacts of three transgenic Bt rice strains expressing cry1Ab/cry1Ac, cry1C and cry2A on population density, species dominance and population dynamics of three species of planthoppers ( Nilaparvata lugens, Sogatella furcifera and Laodelphax striatellus) and their three main predators ( Cyrtorhinus lividipennis, Pirata subpiraticus and Theridium octomaculatum) were evaluated at three sites in Hubei Province, China, in the current study. The results showed that among three species of planthoppers, both in transgenic and non-transgenic rice field, the predominant species of planthoppers within phytophagous guild was S. furcifera at any site either growing season (46–50%). Significantly higher population density of N. lugens was observed in T2A-1 field relative to Minghui 63 field at Wuxue in 2010. The species dominance of predator, P. subpiraticus, in TT51 field was significantly higher than that in T1C-19 and T2A-1 fields in 2009 at Xiaogan site. Sampling date significantly influenced six arthropods except for P. subpiraticus in 2010. The interaction between rice strain×sampling date had no significant adverse effects on the population dynamics of three species of planthoppers and their predators, except for several individual species in 2009. The interaction among rice strain×sampling date×sampling site also had no significant effect on six arthropods except for S. furcifera in 2009. The results indicated that transgenic Bt rice expressing cry1Ab/cry1Ac, cry2A and cry1C had no significant adverse effects on the population dynamics of three planthoppers and their predators in most investigated data and sampling site.

Qualitative and Quantitative Components of The Evaluating System of the Arthropods Biodiversity Populations Impact in the Blackcurrant Crops from the South Part of Romania (I)

The present paper is reffer to the original research carried out for the first time in Romania in the period spring-autumn 2009 and had the proposed objective the development of an ecological based pest management experimental model on the blackcurrant crops.
 In the first stage of the research the collecting of biological material using specific methods from different structural components (stratifications) of biotopes of the ecosystem upon which follows the identification and the species classifications in pest and useful for the management system proposed.The monitoring performed is referring so to the surveillance of arthropods populations dynamics correlated with the command factors and with share of those factors in the research area.
 The research activities of the stage are including:
 The biological material collecting;
 The present arthropod species identification;
 The arthropods fauna structure and biodiversity highlighting (number of individuals, number of species, density and relative abundance, dominant populations);
 The biodiversity of blackcurrant crops investigated by qualitative and quantitative methods was divided on a preliminary analysis (which will be thorough by the route of testing/experimentation of the ecological management system by specific statistical methods) in the frame of the structure highlight by the vegetation period of the crop.
 The arthropods identified are including:
 Characteristic species of the fauna of the soil level, on the soil or on the low plants (phytophagous, predators, coprophagous, necrophagous and detritophagous);
 Specific pest species;
 Polyphagous species (phytophagous, predators);
 Species without any trophyc correlations with blackcurrant crop, characteristic of surrounding crop with the accidentally presence.
 In the study two experimental surfaces of blackcurrant in which EBPM is applied (plot I and II) in comparison with one check plot with intensive crop management will be investigated.The arthropod populations identified belongs to 5 classes, 15 taxonomic orders, 35 families, 61 genuses and 67 species (plot I) and 5 classes, 17 taxonomic orders, 40 families, 60 genuses and 65 species (plot II).

Large-scale diversity patterns of parasitoid insects

Parasitoids, which mainly include taxa belonging to the Hymenoptera, play an important role in the maintenance of other arthropod populations, acting as regulators of host densities. However, the large-scale patterns of these insects and the factors that shape them are still not well established. In this review we focus on several aspects of the biology and macroecological patterns of parasitoids that have received some attention in the past, including recent studies on island parasitoid faunas. Parasitoid latitudinal gradients have been widely analyzed, with most studies apparently showing the anomalous pattern of species richness decreasing towards the tropics, particularly in the Ichneumonidae. This pattern has been proposed to be related to host feeding niche and parasitoid attack strategy. However, it is quite possible that these latitudinal gradients might be artifacts of sampling or description biases. Island parasitoid faunas also show latitudinal gradients in species richness, with the proportion of generalist species increasing towards the tropics. Island communities are in fact biased towards generalist species, being highly influenced by the communities of the surrounding territories and by the existence of rainforests. We conclude by briefly discussing the need for the development of future studies on parasitoid large scale diversity patterns, and proposing new research lines.

Impact of <I>Lygus</I> spp. (Hemiptera: Miridae) on Damage, Yield and Quality of Lesquerella (Physaria fendleri), a Potential New Oil-Seed Crop

Lesquerella, Physaria fendleri (A. Gray) S. Watson, is a mustard native to the western United States and is currently being developed as a commercial source of valuable hydroxy fatty acids that can be used in a number of industrial applications, including biolubricants, biofuel additives, motor oils, resins, waxes, nylons, plastics, corrosion inhibitors, cosmetics, and coatings. The plant is cultivated as a winter-spring annual and in the desert southwest it harbors large populations of arthropods, several of which could be significant pests once production expands. Lygus spp. (Hemiptera: Miridae) are common in lesquerella and are known pests of a number of agronomic and horticultural crops where they feed primarily on reproductive tissues. A 4-yr replicated plot study was undertaken to evaluate the probable impact of Lygus spp. on production of this potential new crop. Plant damage and subsequent seed yield and quality were examined relative to variable and representative densities of Lygus spp. (0.3-4.9 insects per sweep net) resulting from variable frequency and timing of insecticide applications. Increasing damage to various fruiting structures (flowers [0.9-13.9%], buds [1.2-7.1%], and seed pods [19.4-42.5%]) was significantly associated with increasing pest abundance, particularly the abundance of nymphs, in all years. This damage, however, did not consistently translate into reductions in seed yield (481-1,336 kg/ha), individual seed weight (0.5-0.7 g per 1,000 seed), or seed oil content (21.8-30.4%), and pest abundance generally explained relatively little of the variation in crop yield and quality. Negative effects on yield were not sensitive to the timing of pest damage (early versus late season) but were more pronounced during years when potential yields were lower due to weed competition and other agronomic factors. Results suggest that if the crop is established and managed in a more optimal fashion, Lygus spp. may not significantly limit yield. Nonetheless, additional work will be needed once more uniform cultivars become available and yield effects can be more precisely measured. Densities of Lygus spp. in unsprayed lesquerella are on par with those in other known agroecosystem level sources of this pest (e.g., forage and seed alfalfa, Medicago sativa L.). Thus, lesquerella production may introduce new challenges to pest management in crops such as cotton.

Olfactory response of Typhlodromus pyri (Acari: Phytoseiidae) to synthetic methyl salicylate in laboratory bioassays

The herbivore-induced plant volatile (HIPV) methyl salicylate (MeSA) is widely present in the chemical profile of several plant species and is known to attract natural enemies, including predatory mites. In this study, the response of Typhlodromus pyri, a key predator of pest mites in west coast vineyards, to synthetically produced MeSA was tested using a Y-tube olfactometer in laboratory bioassays. Six doses ranging from 0.002 to 200 μg of MeSA diluted in 0.1 ml hexane were tested. Significantly higher proportions of T. pyri preferred MeSA at doses 0.02, 0.2 and 20 μg. No differences in response to MeSA were detected at the highest (200 μg), intermediate (2 μg) and lowest (0.002 μg) doses. Mite response to MeSA was a function of dose when fitting polynomial and logistic regression models using dose and square of the log dose prediction factors. Results indicate that synthetic MeSA may be applied to attract predatory arthropod populations in vineyards to enhance biological control of pest mites.