Stability of Cacopsylla pyricola (Hemiptera: Psyllidae) Populations in Pacific Northwest Pear Orchards Managed with Long-Term Mating Disruption for Cydia pomonella (Lepidoptera: Tortricidae)

This study focused on conservation biological control of pear psylla, Cacopsylla pyricola, in the Pacific Northwest, USA. We hypothesized that insecticides applied against the primary insect pest, codling moth Cydia pomonella, negatively impact natural enemies of pear psylla, thus causing outbreaks of this secondary pest. Hence, the objective of this study was to understand how codling moth management influences the abundance of pear psylla and its natural enemy complex in pear orchards managed under long-term codling moth mating disruption programs. We conducted this study within a pear orchard that had previously been under seasonal mating disruption for codling moth for eight years. We replicated two treatments, “natural enemy disrupt” (application of two combination sprays of spinetoram plus chlorantraniliprole timed against first-generation codling moth) and “natural enemy non-disrupt” four times in the orchard. Field sampling of psylla and natural enemies (i.e., lacewings, coccinellids, spiders, Campylomma verbasci, syrphid flies, earwigs) revealed that pear psylla populations remained well below treatment thresholds all season despite the reduced abundance of key pear psylla natural enemies in the natural enemy disrupt plots compared with the non-disrupt treatment. We speculate that pear psylla are difficult to disrupt when pear orchards are under long-term codling moth disruption

Peach Extrafloral Nectar Impacts Life Span and Reproduction of Adult Grapholita molesta (Busck) (Lepidoptera: Tortricidae) 1

ABSTRACT This study evaluated the longevity and fecundity of a laboratory strain of Grapholita molesta (Busck) (Lepidoptera: Tortricidae) when provided peach, Prunus persica L., extrafloral nectar for nourishment. Moths lived longer and females had a greater reproductive output when presented with extrafloral nectar and a source of water compared with moths provisioned only with water. Adult male G. molesta presented with nectar and water lived an average of 28.7 days, whereas, males provided only water lived about 17.8 days. Adult female G. molesta provided nectar and water lived 33.7 days and produced an average 255.9 fertile and 10.9 infertile eggs, whereas, females provided only water lived 14.4 days and produced an average 117.2 fertile and 2.1 infertile eggs. The higher number of infertile eggs laid by nectar fed females is attributed to an extended oviposition period of 29.4 days compared with 10.0 days for females provided only water. Peach extrafloral nectar did not affect the duration of preoviposition and postoviposition periods. It is quite possible that orchards planted with extrafloral nectar bearing varieties of peaches and nectarines may contribute to the longevity and reproductive potential of G. molesta in the field

Comparative analysis of pesticide effects on natural enemies in western orchards: A synthesis of laboratory bioassay data

Pesticides are commonly used for pest management in apple, pear and walnut orchards in the western U.S. and may disrupt biological control of secondary pests in these crops. A comparative analysis was made of results obtained from a series of laboratory bioassays of acute mortality and life table response experiments to estimate lethal and sublethal effects of eight pesticides on seven natural enemy species through use of stage-structured population models. Even though a number of the pesticides tested were reduced-risk products, all of them with the exception of copper plus mancozeb and chlorantraniliprole, caused more than 80% acute mortality of at least one life stage of at least one of the natural enemy species at a full field-rate concentration and could thus be considered moderately harmful according to the International Organization for Biological Control classification for laboratory bioassays. Important sublethal effects included reductions in daily fecundity and egg fertility. From integration of the lethal and sublethal effects in matrix models, the mean of the estimated intrinsic rates of increase for natural enemy species was negative for exposure to cyantraniliprole, lambda-cyhalothrin and spinetoram, but positive and not significantly different from the control for exposure to chlorantraniliprole, copper plus mancozeb, novaluron, and sulfur. For comparisons among pesticides, there appears to be considerable variation in response among natural enemy species that can only be represented effectively from a full life table response experiment and a population-level endpoint, whereas among natural enemy species, their population-level response to the range of pesticides tested could frequently be represented by acute adult mortality alone

Seasonal cues induce phenotypic plasticity of Drosophila suzukii to enhance winter survival

Additional file 7: Table S6. Table of differentially expressed genes in bodies of winter morphs of D. suzukii relative to those of summer morphs. Fold change represents the ratio of expression levels of winter to summer morphs

Large-plot field studies to assess impacts of newer insecticides on non-target arthropods in Western U.S. orchards

The non-target impacts of two reduced risk insecticides, chlorantraniliprole and spinetoram, were evaluated for two years in Oregon pear and California walnut orchards. Experiments were conducted in large replicated plots (approximately 0.25–0.4ha) to assess the impact of these two insecticides on natural enemies of secondary pests when applied against codling moth, Cydia pomonella. Cumulative insect days (CID) of secondary pests and natural enemies were calculated from leaf samples, plant volatile traps, beat trays or cardboard trunk bands. Ratios of natural enemies and prey were also calculated. Results from these field studies demonstrate that applications of chlorantraniliprole can reduce abundance of predatory Neuroptera and that spinetoram negatively impacts parasitic Hymenoptera. However, these trends did not always occur each year. As a percentage among all trials within a crop, there were more treatment differences for natural enemy/prey ratios (50 and 33% for pears and walnut plots, respectively) than for natural enemy CIDs (25 and 13% for pears and walnut plots, respectively). It is likely that unseasonably cool weather during the two years of this study impacted both pest and natural enemy abundance. The intrinsic value of large-plot field studies is discussed

Using plant volatile traps to develop phenology models for natural enemies: An example using Chrysopa nigricornis (Burmeister) (Neuroptera: Chrysopidae)

A model predicting phenology of adult Chrysopa nigricornis (Burmeister) (Neuroptera: Chrysopidae) in orchards was developed from field (trapping) data supplemented with development data collected under laboratory conditions. Lower and upper thresholds of 10.1°C and 29.9°C, respectively, were estimated from published and unpublished laboratory observations, and were used to develop a phenology model. Season-long field data were collected using white delta traps that had been baited with squalene, a volatile shown previously to be highly attractive to C. nigricornis. The model was developed from data collected in three Washington apple orchards, and was validated using independent data sets collected from apple, sweet cherry, pear, and walnut orchards over a 2–4year period across a much wider geographic region. We found that the mean absolute deviation across all crops and years was 39.7±1.2day-degrees (DD), or 4.4±0.14days. Populations of C. nigricornis from walnut orchards in California emerged 105DD later than those in Oregon and Washington, thus requiring correction of average time of first trap catch in California to synchronize models. The ability to use a single model across multiple crops, different prey species and abundances, and different pesticide regimes demonstrates that phenology models for generalist predators may have broader application to IPM programs in other cropping systems

Using plant volatile traps to estimate the diversity of natural enemy communities in orchard ecosystems

In this study we used sticky traps baited with plant volatile lures to monitor the biodiversity of natural enemies in orchard ecosystems in the western U.S. We compared the diversity of predator genera from season total trap catches in 37 different orchards (apple, cherry, pear and walnut) over a two-year period (2010−2011) using standardized Hill number biodiversity indices and community similarity profiles. For a subset of 23 of these orchards we were also able to monitor the change in biodiversity of predator genera over the full growing season in the different orchard crops. A total of 37,854 individuals from 31 different genera of foliage-active generalist predators were collected from all orchards combined. Mean sample coverage was high (0.98) and richness, diversity and evenness differed between crops in 2010, but not in 2011. There was more than 90% similarity in the richness of predator genera among crops and among orchards within crops, but a greater level of differentiation was observed among orchards when variation in their relative abundance and dominance in the communities was taken into account. There was a consistent rise in predator generic richness and diversity through the season in both years for apple, cherry and pear orchards, but in walnut orchards, a steep rise from March to May was followed by a decline through the rest of the season. In an additional component of the study, the species level similarity of predator and parasitoid communities was analyzed for total season trap catch data from six walnut orchards. The rarefied species richness of parasitoids was much greater than that for predators, although the diversity, evenness and dominance of the parasitoid species varied considerably among orchards. The results from this study highlight the fact that natural enemy communities in orchard ecosystems can be effectively monitored using plant volatile traps, and that these communities are surprisingly diverse despite frequent disturbance from pest management intervention