Improvement of biological control agents : laboratory selection for fast larval development in the convergent lady beetle, Hippodamia convergens guerin-Méneville (Coleoptera: Coccinellidae)

Hippodamia convergens Guerin-Meneville was selected for rapid development through five generations at four constant temperatures (18, 22, 26, and 30°C). Two levels of selection were used: intense and moderate. Differences in developmental rate, survivorship, live adult weight, aphid consumption, adult longevity, and fecundity were measured for both groups and an unselected line. The two selected lines exhibited significant differences in developmental rate after the first generation of selection. The differences increased by the fifth generation of selection. Average differences between selected lines at 18, 22, 26, and 30°C in development from egg to adult were 4.9, 3.0, 1.0, and 1.5 days, respectively. Individuals from the intense selected line had a lower developmental threshold (11.3°C) than the moderate selected line (12.0°C). Also, degree-day requirements from egg to adult were lower in the intense (266 DD°) than moderate (277 DD°) line. Wild type beetles accumulated 231 degree-days above a threshold of 13.6°C. Survivorship at cold temperatures significantly increased with selection for fast development. In addition, no significant differences occurred in either live adult weight, total larval consumption of prey, fecundity, or adult longevity. Larvae selected for fast growth consumed higher numbers of aphids per day and were more efficient metabolically in converting prey mass into body mass than slow growing larvae. Because of a lower developmental threshold and lower degree-day requirements, for complete development, beetles from the intense selected line may accumulate more degree-days throughout a year compared to a moderate selected line. Predictions of population growth, based on an equation for intrinsic growth rate, showed that beetles from the intense selected line would produce 1.6 and 1.4 times more individuals in a 60-day period than beetles from the moderate selected and unselected lines, respectively. The results suggest that intense selected beetles would develop faster earlier in the season and would produce higher population numbers under optimum conditions. Thus, selection of H. convergens produced superior beetles for future introductions in biological control

Cranberry Toad bugs: What are they?

Abstract: In recent years, there has been an increased concern among New Jersey cranberry growers for the potential increase in secondary pests, such as the cranberry toad bug Phylloscelis atra (Hemiptera: Dictyopharidae), because of changes in pest management strategies (e.g., adoption of new reduced-risk products and decreased applications of broad-spectrum insecticides). In 2013, we observed damage in cranberry bogs caused by the cranberry toad bug in New Jersey. Here we report results from studies being conducted to: 1) determine the life cycle of cranberry toad bugs in New Jersey cranberries; 2) determine the impact of toad bug feeding damage on cranberries, and 3) assess the efficacy of various insecticides against toad bugs. Our results from 2016 show that 1st instar nymphs start to appear by the end of June, and develop throughout July and August until early September. Adults are active from the end of July through October (harvest), and eggs are laid from end of August through October. To determine the impact of toad bugs on cranberry vine health and fruit quality, we conducted studies to characterize their feeding damage to cranberries at various densities. Treatments consisted of 0 (control), 10, 25, or 50 toad bug nymphs, replicated 5 times. Nymphs were used as they are the main target of insecticide applications and the cause of most of the early damage to the vines. Toad bug damage to uprights differed among treatments. Although there were no differences in number of damaged uprights between the control and 10 toad bugs, damage to uprights was three times higher at densities equal or greater than 25 toad bugs. No differences were found on number of damaged fruit or fruit weight. In 2016, we evaluated the efficacy of a late season application of nine insecticides (plus an untreated control) against toad bugs. A cranberry bog (var. ‘Early Black’) located at the Rutgers P.E. Marucci Center was divided into 40 (4.5 m x 6 m) plots for a total of 10 treatments replicated four times. Plots were sprayed on 5 August using a customized 2.4 m boom sprayer, and insecticide treatments were applied in 20 gal water per ha. Vacuumed samples were taken on 3 August (pre-treatment) and on 12 August (post-treatment) from 1 m2 sections in each plot with a 2‐cycle backpack aspirator. Lorsban, Sevin, Diazinon, Brigade, Agri-Mek, and Assail were effective at controlling toad bugs, whereas Beleaf, Exirel, and Closer were not effective. These studies are being repeated in 2017

Balancing Disturbance and Conservation in Agroecosystems to Improve Biological Control

Disturbances associated with agricultural intensification reduce our ability to achieve sustainable crop production. These disturbances stem from crop-management tactics and can leave crop fields more vulnerable to insect outbreaks, in part because natural-enemy communities often tend to be more susceptible to disturbance than herbivorous pests. Recent research has explored practices that conserve natural-enemy communities and reduce pest outbreaks, revealing that different components of agroecosystems can influence natural-enemy populations. In this review, we consider a range of disturbances that influence pest control provided by natural enemies and how conservation practices can mitigate or counteract disturbance. We use four case studies to illustrate how conservation and disturbance mitigation increase the potential for biological 2 control and provide co-benefits for the broader agroecosystem. To facilitate the adoption of conservation practices that improve top-down control across significant areas of the landscape, they will need to provide multifunctional benefits, but should be implemented with natural enemies explicitly in mind

Phytoplasma Infection Influences Gene Expression in American Cranberry

Cranberry false blossom disease (CFBD) is caused by a leafhopper-vectored phytoplasma infection. CFBD results in distinctive branching of the upright shoots (witches' broom) and the formation of deformed flowers that fail to produce fruit. This disease is reemerging and poses a serious threat to the cranberry industry. To determine the impact of the disease on host gene expression, we compared transcriptome profiles between plants with CFBD and uninfected cranberry plants. We found that phytoplasma infection induced expression of 132 genes, and suppressed 225 genes, compared to uninfected cranberry plants. Differentially expressed genes between uninfected and infected plants were largely associated with primary and secondary metabolic, defensive, and developmental pathways. Phytoplasma infection increased the expression of genes associated with nutrient metabolism, while suppressing genes associated with defensive pathways. This expression profile change supports the “host manipulation hypothesis,” whereby CFBD enhances host quality for insect vectors, thus promoting phytoplasma transmission

Behavioral and Antennal Responses of \u3ci\u3eDrosophila suzukii\u3c/i\u3e (Diptera: Drosophilidae) to Volatiles From Fruit Extracts

Native to Southeast Asia, the spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), has become a serious pest of soft-skinned fruit crops since its introduction into North America and Europe in 2008. Current monitoring strategies use baits based on fermentation products; however, to date, no fruit-based volatile blends attractive to this fly have been identified. This is particularly important because females are able to cut into the epicarp of ripening fruit for oviposition. Thus, we conducted studies to: 1) investigate the behavioral responses of adult D. suzukii to volatiles from blueberry, cherry, raspberry, and strawberry fruit extracts; 2) identify the antennally active compounds from the most attractive among the tested extracts (raspberry) using gas chromatography (GC)– mass spectrometry and coupled gas chromatography –electroantennographic detection (GC-EAD); and 3) test a synthetic blend containing the EAD-active compounds identified from raspberry extract on adult attraction. In olfactometer studies, both female and male D. suzukii were attracted to all four fruit extracts. The attractiveness of the fruit extracts ranks as: raspberry \u3e/= strawberry \u3e blueberry \u3e/= cherry. GC analyses showed that the fruit extracts emit distinct volatile compounds. In GC-EAD experiments, 11 raspberry extract volatiles consistently elicited antennal responses in D. suzukii. In choice test bioassays, a synthetic EAD-active blend attracted more D. suzukii than a blank control, but was not as attractive as the raspberry extract. To our knowledge, this is the first report of a behaviorally and antennally active blend of host fruit volatiles attractive to D. suzukii, offering promising opportunities for the development of improved monitoring and behaviourally based management tools

Sucrose Improves Insecticide Activity Against Drosophila suzukii (Diptera: Drosophilidae)

The addition of sucrose to insecticides targeting spotted wing drosophila, Drosophila suzukii (Matsumura), enhanced lethality in laboratory, semifield, and field tests. In the laboratory, 0.1% sucrose added to a spray solution enhanced spotted wing drosophila feeding. Flies died 120 min earlier when exposed to spinosad residues at label rates enhanced with sucrose. Added sucrose reduced the LC50 for dried acetamiprid residues from 82 to 41 ppm in the spray solution. Laboratory bioassays of spotted wing drosophila mortality followed exposure to grape and blueberry foliage and/or fruit sprayed and aged in the field. On grape foliage, the addition of 2.4 g/liter of sugar with insecticide sprays resulted in an 11 and 6% increase of spotted wing drosophila mortality at 1 and 2 d exposures to residues, respectively, averaged over seven insecticides with three concentrations. In a separate experiment, spinetoram and cyantraniliprole reduced by 95-100% the larval infestation of blueberries, relative to the untreated control, 7 d after application at labeled rates when applied with 1.2 g/liter sucrose in a spray mixture, irrespective of rainfall; without sucrose infestation was reduced by 46-91%. Adding sugar to the organically acceptable spinosyn, Entrust, reduced larval infestation of strawberries by >50% relative to without sugar for five of the six sample dates during a season-long field trial. In a small-plot field test with blueberries, weekly applications in alternating sprays of sucrose plus reduced-risk insecticides, spinetoram or acetamiprid, reduced larval infestation relative to the untreated control by 76%; alternating bifenthrin and phosmet (without sucrose) reduced infestation by 65

Phytoplasma Infection of Cranberries Benefits Non-vector Phytophagous Insects

Despite increasing knowledge about the impacts of pathogens on the interactions between plants and insect vectors, relatively little is known about their effects on other, non-vector, organisms. In cranberries, phytoplasma infection causes false blossom disease, which is transmitted by leafhoppers. We hypothesized that changes in plant chemistry induced by phytoplasma infection might affect the performance and feeding behavior not only of vectors but also of other phytophagous insects. To test this, we measured growth, survival, and the number of leaves damaged by larvae of three common non-vector herbivores: spotted fireworm (Choristoneura parallela Robinson), Sparganothis fruitworm (Sparganothis sulfureana Clemens), and gypsy moth (Lymantria dispar L.) on phytoplasma-infected and uninfected cranberries (Vaccinium macrocarpon Ait.). We also assessed the effects of phytoplasma infection on nutrients and phytochemistry related to defenses. In general, larvae of all three herbivore species grew 2–3 times bigger, and damaged 1.5–3.5 times more leaves, while feeding on infected vs. uninfected plants. Survival of Sparganothis fruitworm larvae was also ~1.5 times higher on infected plants, while spotted fireworm and gypsy moth larval survival was not affected. In a long-term (5-week) assay, gypsy moth larval survival and mass were enhanced when feeding on phytoplasma-infected leaves. Levels of important plant nutrients (e.g., N, P, K, Ca, S, Mn, Fe, B, Al, and Na) were higher in infected plants, while levels of defensive proanthocyanidins were reduced by 20–40% compared to uninfected plants. In contrast, levels of Mg were lower in infected plants, while concentrations of Cu, Zn, and defensive flavonols were not affected. Taken together, these findings suggest that phytoplasma infection enhances plant nutritional quality, while reducing plant defenses in cranberries. These effects, in turn, may explain the observed enhancement of non-vector herbivore performance, as well as the higher number of damaged leaves, on infected plants. Improved understanding of the ecology of pathogen-plant-herbivore interactions could aid efforts to enhance plant resistance and suppress disease transmission in agricultural settings