Seed-borne microorganisms stimulate seedcorn maggot egg laying

Abstract

LARVAE of the seedcorn maggot, Hylemya platura (Meigen) may damage or kill young plants of many crop species by feeding on the cotyledons and plumules (Fig. 1). Damage may be caused by larvae already present in the soil before the seeds are planted¹ or by larvae that hatch from eggs laid near germinating seeds^2,3. It has been assumed that the stimulus for oviposition is provided by the germinating seeds themselves but we suspected that seed-borne microoiganisms growing on seed exudates could produce metabolites that promote oviposition. Many metabolic processes begin at the onset of seed germination, and concurrently organic substances are leached from the seeds which provide substrates for microorganisms. We now report that microorganisms growing on substrates from seeds produce metabolites which simulate egg laying in H. platura, and that germinating microorganism-free seeds are not stimulatory. This is an excellent example of a complex ecological interaction between an insect pest, the host plant and organisms of the microenvironment.