Substantial evidence indicates that drought stress promotes outbreaks of plant-eating (phytophagous) fungi and insects. Observations and experiments show that colonization success and pervalence of such fungi as root and stalk rots, stem cankers, and sometimes wilts and foliar diseases are much higher on water-stressed plants than on normal plants (Schoeneweiss 1986). The evidence associating insects and drought is more circumstantial, consisting largely of observations that outbreaks around the world of such insects as bark beetles and leaf feeders (see Table 1) are typically preceded by unusually warm, dry weather. There is also a consistent, positive correlation between insect oubreaks and dry, nutrient-poor sites (Mattson and Haack 1987).

The Role of Drought in Outbreaks of Plant-eating Insects

The fall‐webworm (FWW), Hyphantria cunea, is a highly polyphagous insect pest that is native to North America and distributed in different countries around the world To manage this insect pest, various control methods have been independently evaluated in the invaded areas Some of the control methods have been limited to the laboratory and need further study to verify their effectiveness in the field On the other hand, currently, integrated pest management (IPM) has become a promising ecofriendly insect pest management option to reduce the adverse effect of insecticides on the environment The development of an IPM for an insect pest must combine different management options in a compatible and applicable manner In the native areas of the insect pests, there are some recommended management options However, to date, there is no IPM for the management of the FWW in the newly invaded areas Therefore, to develop an IPM for this insect pest, compilation of effective management option information is the first step Thus, believing in the contribution of an IPM to the established management strategies, the chemical, biological, natural enemy, sex pheromone, and molecular studies regarding this insect were reviewed and potential future research areas were delineated in this review study Therefore, using the currently existing management options, IPM development for this insect pest should be the subject of future research in the newly invaded areas

Current status of the management of fall webworm, Hyphantria cunea: Towards the integrated pest management development

1. Hyphantria cunea is a problematic invasive species that has caused considerable damage to agricultural and forestry ecosystems in China.

Potential range expansion and niche shift of the invasive Hyphantria cunea between native and invasive countries

In China, the fall webworm, Hyphantria cunea, causes enormous losses. The potential of entomopathogenic fungi (EPF) to control pest insects has been demonstrated in the laboratory and the field. In this study, we isolated and identified EPF from the surfaces of H. cunea larvae cadavers, and we investigated their efficacy against fall webworm larvae under bioassay conditions in the laboratory. Isaria javanica BE01 conidial suspensions with concentrations between 1 × 104 and 1 × 108 conidia ml−1 were shown to have marked effects on the larval mortality (the 3rd, 4th, and 5th instar larvae) over a 15 days period. However, the effect of the instar on the mortality was not always significant, except during the late stages (10–14 days) at low concentrations (1 × 104–1 × 106 conidia ml−1) or the early stages (1–5 days) at high concentrations (1 × 107–1 × 108 conidia ml−1). Otherwise, the mortality of the 3rd and 4th instar larvae exceeded 85% at 1 × 108 conidia ml−1. The present study suggests that I. javanica BE01 is a potential biological control agent of H. cunea.

Isolation and identification of entomopathogenic fungi and an evaluation of their actions against the larvae of the fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae)

Host-plant volatiles play vital roles for insects to locate foraging, mating, and oviposition sites in the environment. As one of the devastating invasive forestry pests, Hyphantria cunea causes a great annual loss in China, and understanding its chemical ecology is an important task. The current research was done in terms of chemical analysis, electrophysiology, and behavioral assays on H. cunea to assess its olfactory reception toward host-plant volatiles. A screen of possible common host volatiles was done, targeting on five favored hosts of H. cunea, harvesting six potential bioactive compounds from a total of 78 odorant components. Six types of antennal sensilla were investigated on their distributions on the antennae, and sexual dimorphism was described. H. cunea showed responses to all selected host-related volatiles in electroantennogram tests, and linalyl butyrate elicited the strongest responses. Furthermore, mating rates in adult pairs that are exposed to dibutyl phthalate and phytol have been significantly increased, while oviposition rates and female fecundity were not influenced. The results of the current study provide initial evidence showing that universal host-derived volatile cues are essential for H. cunea moth in terms of mating, which can also provide insights into the development of botanical attractants.

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Botanical Volatiles Selection in Mediating Electrophysiological Responses and Reproductive Behaviors for the Fall Webworm Moth Hyphantria cunea.

The fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Erebidae), is a widespread defoliator that is native throughout the continental United States, as well as southern Canada and northern Mexico. It has been introduced accidentally into many parts of Europe and Asia. Larvae have been recorded from >400 species of forest and shade trees, primarily hardwoods, but also several conifer species in the southern United States. This species is of minor importance in forests, but can cause serious losses in pecan and fruit tree orchards and is a major nuisance in urban parks and homelots where it often completely defoliates ornamental and shade trees. Fall webworm larvae construct conspicuous webs that start at the ends of branches and expand as the larvae grow to incorporate multiple branches. Foliage within webs is completely consumed. Two color races occur throughout the range of this moth, but pure white adults and black-headed larvae predominate in northern regions, whereas spotted adults and red-headed larvae predominate in southern regions. Populations of fall webworm are regulated naturally in its native range by host quality and abundance and by at least 50 species of dipteran and hymenopteran parasitoids and 36 species of predators and parasites. Physical removal, biocontrol, and insecticides are available for management of this moth.

D. R. Ring

Papers

Biology and Management of the Fall Webworm, Hyphantria cunea (Lepidoptera: Erebidae)