Host plant quality is a key determinant of the fecundity of herbivorous insects. Components of host plant quality (such as carbon, nitrogen, and defensive metabolites) directly affect potential and achieved herbivore fecundity. The responses of insect herbivores to changes in host plant quality vary within and between feeding guilds. Host plant quality also affects insect reproductive strategies: Egg size and quality, the allocation of resources to eggs, and the choice of oviposition sites may all be influenced by plant quality, as may egg or embryo resorption on poor-quality hosts. Many insect herbivores change the quality of their host plants, affecting both inter- and intraspecific interactions. Higher-trophic level interactions, such as the performance of predators and parasitoids, may also be affected by host plant quality. We conclude that host plant quality affects the fecundity of herbivorous insects at both the individual and the population scale.

Host plant quality and fecundity in herbivorous insects

Push-pull strategies involve the behavioral manipulation of insect pests and their natural enemies via the integration of stimuli that act to make the protected resource unattractive or unsuitable to the pests (push) while luring them toward an attractive source (pull) from where the pests are subsequently removed. The push and pull components are generally nontoxic. Therefore, the strategies are usually integrated with methods for population reduction, preferably biological control. Push-pull strategies maximize efficacy of behavior-manipulating stimuli through the additive and synergistic effects of integrating their use. By orchestrating a predictable distribution of pests, efficiency of population-reducing components can also be increased. The strategy is a useful tool for integrated pest management programs reducing pesticide input. We describe the principles of the strategy, list the potential components, and present case studies reviewing work on the development and use of push-pull strategies in each of the major areas of pest control.

The Use of Push-Pull Strategies in Integrated Pest Management

▪ Abstract This review covers selected literature from 1982 to the present on some of the ecological, behavioral, and biochemical aspects of hydrocarbon use by insects and other arthropods. Major ecological and behavioral topics are species- and gender-recognition, nestmate recognition, task-specific cues, dominance and fertility cues, chemical mimicry, and primer pheromones. Major biochemical topics include chain length regulation, mechanism of hydrocarbon formation, timing of hydrocarbon synthesis and transport, and biosynthesis of volatile hydrocarbon pheromones of Lepidoptera and Coleoptera. In addition, a section is devoted to future research needs in this rapidly growing area of science.

/pdf/ecological-behavioral-and-biochemical-aspects-of-insect-4bbi7ldpkx.pdf

Ecological, behavioral, and biochemical aspects of insect hydrocarbons*

Organic Chemistry By Dr. I. L. Finar. Vol. 2: Stereochemistry and the Chemistry of Natural Products. Pp. xi + 733. (London and New York: Longmans, Green and Co., Ltd., 1956.) 40s. net.

Advanced Organic Chemistry

https://www.fabinet.up.ac.za/publication/pdfs/2509-lacey_et_al_2001.pdf

Insect Pathogens as Biological Control Agents: Do They Have a Future?

Solid-phase microextraction (SPME) is a versatile new technique for collecting headspace volatiles prior to GC analysis. The commercial availability of uniform SPME fibers makes routine, practical quantitation of headspace concentrations possible, but straightforward information for relating GC peak areas from SPME analyses to headspace concentrations has not been available. The calibration factors (amount absorbed by the fiber divided by headspace concentration) were determined for 71 compounds using SPME fibers with a 100 μm poly(dimethylsiloxane) coating. The compounds ranged from 1 to 16 carbons in size and included a variety of functional groups. Calibration factors varied widely, being 7000 times higher for tetradecane than for acetaldehyde. Most compounds with a Kovats retention index of <1300 on a nonpolar GC column (DB-1) equilibrated with the fiber in 30 min or less. A regression model is presented for predicting the calibration factor from GC retention index, temperature, and analyte functional...

Calibration of a commercial solid-phase microextraction device for measuring headspace concentrations of organic volatiles.

Attraction to microbial volatiles was examined for the sap beetle, Carpophilus humeralis, which is a pest of maize. Using 54 pure yeast and bacterial cultures, we evaluated differences in volatile emissions among species of microorganisms and whether these differences were associated with insect attraction. On a sterile corn-based medium, both yeasts and bacteria generally multiplied well and produced detectable volatile metabolites. The yeasts ranged from inactive to highly attractive, but no bacterial cultures attracted beetles above control levels. A variety of alcohols, esters, ketones, acids, and phenolic compounds were identified from the headspace above yeast cultures. Growth, volatile production, and, ultimately, attractiveness to beetles depend strongly on the ability of the yeasts to assimilate and/or ferment the carbohydrates present. Abundant volatile production on sweet corn was observed only with yeasts that are able to ferment sucrose and/or maltrose. Saccharomyces cerevisiae (ferments glucose, sucrose, and maltose) and Candida shehatae (ferments glucose and maltose) produced considerably more attractive volatiles than Candida guilliermondii, which only ferments glucose. Yeast volatiles important for beetle attraction included typical fermentation-associated substances (ethanol, acetaldehyde, 2-methyl-1-propanol, 1-propanol, ethyl acetate, 3-methyl-1-butanol and 2-methyl-1-butanol), and also 3-hydroxy-2-butanone, whose presence was not correlated with the occurrence of fermentation. Using aqueous mixtures of synthetic components that produced headspace compositions simulating those of attractive yeasts, it was shown that the typical fermentation volatiles are attractive but not essential for attractiveness. 3-Hydroxyl-2-butanone is sufficient but not necessary, although its attractiveness is enhanced by the presence of fermentation volatiles such as ethanol and 2-methyl-1-proponol. In nature, the beetles could take advantage of a variety of different microbial metabolic processes to locate hosts. The laboratory bioaasays in this study involved flight and therefore were particularly relevant to host-finding behavior in the field.

Attraction of a Flying Nitidulid (Carpophilus humeralis) to Volatiles Produced by Yeasts Grown on Sweet Corn and a Corn-Based Medium

Adult Cosmopepla bimaculata discharge a volatile secretion from paired ventral metathoracic glands (MTG) when disturbed. Collected volatiles were similar in both sexes and consisted of n-tridecane (67%), (E)-2-decenal (12%), (E)-2-decenyl acetate (12%), (E)-2-hexenal (3%), hexyl acetate (2%), n-dodecane (2%), a tridecene isomer (1%), and n-undecane, n-tetradecane, and n-pentadecane (all <1%). In addition, undisturbed males produced a novel insect compound, (E)-8-heneicosene, whose function is unknown. The MTG secretion emerges as an enlarging droplet, which is held in place by a cuticular projection and a pleural scent area consisting of specialized rough cuticle surrounding the gland opening. Insects can selectively discharge from either the right or left gland or both glands simultaneously, can control the amount of fluid ejected, and can resorb the ejected secretion droplet back into the gland reservoir. In feeding trials, killdeer (Charadrius vociferous), starlings (Sturnus vulgaris), robins (Turdus migratorius), and anole lizards (Anolis carolinensis) rejected or demonstrated aversion to feeding on the bugs. Furthermore, bugs that lacked the secretion were more susceptible to predation than bugs with secretion, suggesting that the secretion functions in defense against predators.

Chemical Defense in the Stink Bug Cosmopepla bimaculata

Assay of tall fescue seed extracts, fractions, and alkaloids using the large milkweed bug

Headspace above tryptic soy broth culture filtrates of Klebsiella pneumoniae contained greater amounts of ammonia, methylamine, 3-methylbutanamine, 1-pyrroline, 2,3,4,5-tetrahydropyridine, and two pyrazines than were found above tryptic soy broth. It also contained chemicals not found above tryptic soy broth, including dimethyldisulfide and several alcohols and ketones. Headspace above tryptic soy broth culture filtrates of Citrobacter freundii contained greater amounts of ammonia, 1-pyrroline, and several pyrazines than were found above tryptic soy broth. It also contained chemicals not found above tryptic soy broth including dimethyldisulfide, some of the same alcohols as above K. pneumoniae filtrates, a different ketone, and phenol. Additional chemicals were detected above filtrates that were saturated with sodium chloride or had their pH adjusted up or down. In laboratory bioassays with protein-starved, sugar-fed Mexican fruit flies, chemicals that did not contain protonizable nitrogen were not attractive. All chemicals containing protonizable nitrogen, except 2-methylpyrazine, were attractive. Synthetic mixtures of ammonia, trimethylamine, 1-pyrroline, 3-methylbutanamine, pyrazine, 2,3,4,5-tetrahydropyridine, 2,5-dimethylpyrazine, and trimethylpyrazine in concentrations similar to those in filtrates of the two bacteria were 73–87% as attractive as bacterial filtrates.

Robert J. Bartelt

Papers

Calibration of a commercial solid-phase microextraction device for measuring headspace concentrations of organic volatiles.

Attraction of a Flying Nitidulid (Carpophilus humeralis) to Volatiles Produced by Yeasts Grown on Sweet Corn and a Corn-Based Medium

Chemical Defense in the Stink Bug Cosmopepla bimaculata

Assay of tall fescue seed extracts, fractions, and alkaloids using the large milkweed bug

Chemicals Attractive to Mexican Fruit Fly from Klebsiella pneumoniae and Citrobacter freundii. Cultures Sampled by Solid-Phase Microextraction