Strengths and limitations of Bacillus thuringiensis galleriae for managing Japanese beetle (Popillia japonica) adults and grubs with caveats for cross-order activity to monarch butterfly (Danaus plexippus) larvae.

BACKGROUND: Target-selective biopesticides are needed to facilitate integrated pest and pollinator management in urban landscapes and gardens. Bacillus thuringiensis galleriae, strain SDS-502 (Btg), recently registered in the USA and Canada, produces Cry8Da protein active against scarab beetles. We evaluated Btg formulations for managing the Japanese beetle [Popillia japonica Newman (JB)], a polyphagous invasive pest, including residual spray effectiveness for reducing adult feeding on Rosa and Tilia spp., and granular formulations for early- or late-curative control of root-feeding grubs in turfgrass. We also tested for cross-order activity to monarch butterfly (Danaus plexippus L.) larvae and other non-target insects. RESULTS: Field-weathered Btg residues reduced JB feeding on foliage for 3-14 days. Most beetles were still flight-capable after 24 h confinement with Btg-treated leaves. Granular Btg failed to control early- or late-instar JB grubs in soils under several turfgrass species at multiple field sites. In three trials, feeding on Btg-sprayed milkweed resulted in 97-100% mortality of early instar monarchs, with symptoms of B. thuringiensis pathogenesis. Fall armyworms (Spodoptera frugiperda (J.E. Smith)) fed Btg-treated grass had reduced body mass, but there were no adverse effects on lady beetle larvae preying on Btg-sprayed aphids or on the aphids themselves. CONCLUSION: This study supports efficacy of Btg strain SDS-502 for reducing defoliation by adult JB in urban landscape settings. Granular formulations, however, failed to control JB grubs in turfgrass soils. Btg should not be used in gardens with larval host plants of the monarch butterfly or other non-pest Lepidoptera, especially species of conservation concern. © 2019 Society of Chemical Industry.

Fungicides affect Japanese beetle Popillia japonica (Coleoptera: Scarabaeidae) egg hatch, larval survival and detoxification enzymes.

BACKGROUND: Larvae of the Japanese beetle, Popillia japonica (Coleoptera: Scarabaeidae), have a patchy distribution in soils, which complicates detection and management of this insect pest. Managed turf systems are frequently under pest pressure from fungal pathogens, necessitating frequent fungicide applications. It is possible that certain turfgrass fungicides may have lethal or sublethal adverse effects on eggs and larvae of P. japonica that inhabit managed turf systems. In this study, eggs and first-, second- and third-instar larvae were treated with the fungicides chlorothalonil and propiconazole, and survival was compared with that of untreated controls as well as positive controls treated with the insecticide trichlorfon. RESULTS: Chlorothalonil reduced survival of first-instar larvae treated directly and hatched from treated eggs. Propiconazole delayed egg hatch, reduced the proportion of eggs that successfully hatched and reduced survival of first-instar larvae treated directly and hatched from treated eggs. Sublethal doses of the fungicides lowered the activities of certain detoxification enzymes in third-instar grubs. CONCLUSIONS: Fungicide applications to turfgrass that coincide with oviposition and egg hatch of white grubs may have sublethal effects. This work is applicable both to high-maintenance turfgrass such as golf courses, where applications of pesticides are more frequent, and to home lawn services, where mixtures of multiple pesticides are commonly used.

Suitability of Creeping Bentgrass and Bermudagrass Cultivars for Black Cutworms and Fall Armyworms (Lepidoptera: Noctuidae).

The black cutworm, Agrotis ipsilon Hufnagel, and fall armyworm, Spodoptera frugiperda Smith (Lepidoptera: Noctuidae), are common turfgrass pests of golf courses in the southeastern United States. Heat-tolerant bentgrass (Agrostis stolonifera L.) cultivars are expanding the range of bentgrass further south, but these cultivars have not been studied for their potential host plant resistance to black cutworm or fall armyworm. The goals of the study were to investigate feeding response of black cutworm and fall armyworm to these newer heat-tolerant creeping bentgrass cultivars, as well as commonly used cultivars of bermudagrass [Cynodon dactylon (Loppers.)]. Choice and no-choice feeding assays and fecundity tests were conducted in the laboratory and greenhouse to evaluate performance and preference of the two insects. When given a choice, neither black cutworm nor fall armyworm showed a preference for the majority of new cultivars tested. There were no differences in leaf area consumption or insect development for either pest in no-choice feeding assays. Black cutworm females preferred laying eggs in bentgrass compared with bermudagrass, but will oviposit onto bermudagrass, suggesting that both turf species are suitable hosts of this pest. The broad host ranges of generalist caterpillar pests of turfgrass hinder the application of host plant resistance in integrated pest management on golf courses.

Evaluation of a nonconventional insecticide and appropriate application timing for destruction of gypsy moth (Lepidoptera: Lymantriidae) egg masses.

Two field studies were conducted in 2001-2002 and 2003 to evaluate the effectiveness and appropriate application timing of Golden Pest Spray Oil (GPSO) for destruction of gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), egg masses in Wisconsin. GPSO is a commercially available, registered pesticide that is predominantly comprised of a soybean-oil base (93%); its primary mode of action is by means of suffocation. Because gypsy moth spends the majority (>75%) of its life cycle in the egg stage (August-April), the potential utility of this product by arborists, city foresters, landscapers, and homeowners is high, especially because GPSO is a United States Environmental Protection Agency registered, nonconventional pesticide that is considered relatively nontoxic. When GPSO was applied at a 1:1 ratio with water, >96% control of gypsy moth egg masses was achieved, regardless of application timing (October, 3 d before egg hatch).