Volatile and Non-Volatile Organic Compounds Stimulate Oviposition by Aphidophagous Predators.

Abstract

Simple SummaryEvidence that volatile and non-volatile organic compounds stimulate aphid-eating predators to lay eggs is scattered throughout the scientific literature. The objectives of this review are to compile records indicating that organic compounds stimulate egg laying, calculate an egg production ratio for stimulated predators, and determine if the egg production ratio is correlated with vapor pressure and molecular weight of active compounds. Results indicated that both volatile and non-volatile compounds stimulated egg laying behavior by coccinellid beetles and syrphid flies, but not chrysopid lacewings. The egg production ratio was greatest for syrphid flies. Regardless of predator taxa, the egg production ratio was negatively and positively correlated with molecular weight and vapor pressure, respectively. In conclusion, volatile organic compounds stimulate syrphid flies to lay more eggs than coccinellid beetles and chrysopid lacewings. Volatile organic compounds could be used to manipulate predators to lay more eggs in mass rearing systems or on aphid-infested plants in greenhouses or high tunnels. Introduction: Evidence that volatile organic compounds (VOCs) and non-VOCs stimulate oviposition by aphidophagous predators is scattered throughout the literature. The objectives of this review are to (1) compile records indicating that VOCs and non-VOCs are responsible for oviposition stimulation, (2) calculate an egg production ratio (EPR) for stimulated predators, and (3) determine if EPR is correlated with vapor pressure and molecular weight of active compounds. Methods: The USDA (United States Department of Agriculture), National Agricultural Library, online digital catalog system was used to retrieve abstracts, then the full text of manuscripts on oviposition stimulants for predators. Oviposition-stimulating VOCs and non-VOCS were tabulated with molecular weights and vapor pressure estimates. EPRs were calculated for stimulated coccinellids, syrphids, and chrysopids. Results: Both VOCs and non-VOCs stimulated oviposition behavior by coccinellids and syrphids, but not chrysopids. EPR was greatest for syrphids. Two VOCs, (E)-β-farnesene and 3-methyl-2-butenal, stimulated very high EPR values by the syrphid Episyrphus balteatus. Regardless of predator taxa, EPR was negatively and positively correlated with molecular weight and vapor pressure, respectively. Conclusions: Syrphids (rather than coccinellids or chrysopids) produce more eggs in response to VOCs. Organic compounds with low-to-moderate molecular weights and moderate-to-high vapor pressures might be most effective oviposition stimulants for aphidophagous predators.