Pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), is the most economically important pest of pears grown in Washington State. Standard conventional management programs involve season-long broad-spectrum insecticide sprays. Although the industry uses some tools that are not disruptive to biological control, such as kaolin clay and selective insecticides, they are additions to broad-spectrum insecticides instead of replacements. Conventional sprays suppress pear psylla through the spring and early summer; however, disruption of biological control leads to pear psylla outbreaks near harvest. In 2018 and 2019, we tested two season-long programs that used only selective approaches. The programs began with either kaolin clay or reflective plastic mulch and were followed by identical spray programs using only selective insecticides. Programs were compared with an industry standard conventional program that used numerous broad-spectrum insecticides throughout the season, and a check program with no insecticides for pear psylla. Experiments were conducted using replicated 40-tree plots in a research orchard near Wenatchee, WA with high pear psylla pressure. In both years, selective programs had similar pear psylla densities to the industry standard program and all had lower pear psylla densities and fruit injury than the check. Both selective programs had lower fruit injury than the industry standard in the first year, and similar injury to the industry standard in the second year. Our results suggest kaolin clay and reflective mulch can effectively suppress pear psylla populations and injury in the early season and support season-long selective management programs without the use of broad-spectrum insecticides.

Pear psylla, Cacopsylla pyricola (Förster), is the most economically challenging pest of commercial pears in Washington and Oregon, the top producers of pears in the United States. The objective of this study was to quantify economic injury levels and thresholds for pear psylla. We used the relationship between pear psylla adult and nymph densities, and fruit downgraded due to psylla honeydew marking to identify injury levels. We calculated economic injury levels using the cost of downgraded fruit and average management costs (spray materials and labor). Using economic injury levels, we determined economic thresholds for pear psylla, which include predicted pest population growth, natural enemy predation, and anticipated delays between when pest populations are measured and when managers apply interventions. Economic thresholds generated by this study were 0.1–0.3 second-generation nymphs per leaf and 0.2–0.8 third-generation nymphs per leaf depending on predicted price and yield for insecticide applications at 1,300 pear psylla degree days in the second generation and 2,600 pear psylla degree days in the third generation. Natural enemy inaction thresholds identified by this study were 6 Deraeocoris brevis or 3 Campylomma verbasci immatures per 30 trays or 2 earwigs per trap for third-generation optional insecticide applications.

The European earwig Forficula auricularia (L.) (Dermaptera: Forficulidae) is an omnivorous insect that is considered a minor pest of stone fruit and a key predator of pests in pome fruit orchards. In many pome fruit orchards, earwigs are absent or in low abundance due to broad-spectrum spray programs and the slow recolonization rate of earwigs. Orchards in transition to organic or “selective” conventional programs often struggle to achieve effective levels of biological control, and thus, may benefit from inoculating earwigs to expedite their re-establishment. In a two-year study, we evaluated the potential for mass trapping earwigs from stone fruit using rolled cardboard traps to reduce fruit damage and provide earwigs for augmentation in pome fruit. We also tested whether a single mass release or five releases (on alternating weeks) of the same total number of earwigs in apples and pears reduced pests relative to plots where no releases occurred. Mass trapping did not decrease earwig abundance or substantially reduce fruit damage in stone fruit orchards. However, trapping was an efficient method for providing earwigs for augmentation. Earwig abundances were only increased in orchards where earwigs were previously low or absent; however, multiple orchards with varying prior levels of earwigs exhibited reductions in key pests (woolly apple aphid and pear psylla). For some other pests evaluated, plots with mass releases of earwigs had a slight trend in overall lower pest density when compared with control plots. A strategy for moving earwigs out of stone fruit orchards and into pome fruit orchards could be an effective method for augmenting orchard predator populations.

To evaluate how the Cry1Ac Bacillus thuringiensis (Bt) toxin and the ratio of dietary protein to carbohydrate (P:C) independently and jointly affect Helicoverpa zea (Boddie) larval feeding performance and behavior, we conducted no-choice and binary choice experiments using chemically defined diets. We tested two related strains of this polyphagous pest: a strain selected for resistance to Cry1Ac in the laboratory (GA-R), and its field-derived parent strain (GA). In no-choice tests, feeding performance in GA and GA-R was superior on a non-Cry1Ac 80P:20C diet compared to a non-Cry1Ac 35P:65C diet or an 80P:20C diet containing Cry1Ac. Based on consumption and position measurements in binary choice tests, larvae preferred the non-Cry1Ac 80P:20C diet over the other two diets mentioned above. However, the association between preference and performance was weaker when comparing the Cry1Ac 80P:20C diet versus a Cry1Ac 35P:65C diet, and when comparing the Cry1Ac 80P:20C diet versus the non-Cry1Ac 35P:65C diet. In all choice situations, consumption preference occurred mainly by the percentage of larvae that fed almost entirely from one or the other diet, rather than from variation in the extent of diet mixing by individuals. Resistance to Cry1Ac affected the balance between toxin avoidance and nutrient intake: larvae from the more resistant GA-R strain consumed significantly more of the Cry1Ac 80P:20C diet when paired with non-Cry1Ac 35P:65C diet, while GA larvae consumed more of the latter, though not significantly. The results show that dietary P:C ratio, Cry1Ac, and resistance to Cry1Ac affected feeding behavior and performance of H. zea larvae.