Potential uses of kairomones for behavioral manipulation ofCotesia marginiventris (Cresson)

The effects of kairomone pattern and preconditioning on parasitization rates of fall armyworm larvae,Spodoptera frugiperda (J.E. Smith) byCotesia (=Apanteles)marginiventris (Cresson) were investigated in the laboratory and greenhouse using a hexane extract of frass and actual fall armyworm frass. Parasitization rates increased 55 and 26% in Petri dishes and on corn seedlings, respectively, when the entire experimental area was sprayed with the frass extract. Applying the extract in spots resulted in a 20-30% reduction in parasitization compared to treating the entire area. However, spot application produced significantly better parasitization rates compared to the control treatment. Exposing the parasitoids to actual fall armyworm frass resulted in ca. 50% greater retention in the release area and an increase of ca. 60-75% in the number of parasitoids searching.C. marginiventris parasitized factitious hosts topically treated with an extract of fall armyworm frass.

Behavioral and biological responses ofCotesia marginiventris to kairomones of the fall armyworm,Spodoptera frugiperda

Potential kairomone sources of the fall armyworm (FAW),Spodoptera frugiperda (J.E. Smith), were bioassayed with females ofCotesia marginiventris (Cresson) in Petri dishes (10 cm diam). MatedC. marginiventris females, ranging in age from 1 to 3 days exhibited the most intense bioassay responses to potential sources of kairomone. Contacting a FAW-damaged corn leaf modified the pattern of movement inC. marginiventris from random to one exhibiting a significant increase in klinokinesis. No significant differences were present in kairomone responses of nonconditioned and conditioned parasitoids and parasitoid response to kairomones did not change throughout the photophase (0800-1800 hr). Removal of one, both, or the first eight antennal segments reduced or eliminated the response of the parasitoid to kairomones. Female parasitoids did not exhibit a preference for corn leaves damaged by a particular fall armyworm instar and parasitization rates were highest in larvae 48 hr old.

Sources of fall armyworm,Spodoptera frugiperda (Lepidoptera: Noctuidae), kairomones eliciting host-finding behavior inCotesia (=Apanteles) marginivenitris (Hymenoptera: Braconidae)

Bioassay responses inCotesia marginiventris (Cresson) females to materials derived from fall armyworm (FAW) larvae,Spodoptera frugiperda (J. E. Smith), were most intense for frass and somewhat less intense for larval and pupal cutical materials, scales, exuviae, silk, and oral secretion, with FAW larval hemolymph eliciting only a slight response. The highest percentage of ovipositor probing was caused by frass (100%) and moth scales (90%). Various types of corn-leaf damage when assayed alone did not produce responses as intense as when assayed in combination with frass, cuticle material, and oral secretion. Parasitoid response was somewhat better to frass derived from FAW larvae feeding on corn and peanut leaves than from larvae feeding on the foliage of soybeans, Bermuda grass, cowpeas, or laboratory diet. Hexane and chloroform were better than methanol and water for extracting active material from FAW frass, and chloroform was the best of these solvents for extracting corn leaves. Serial dilutions of frass extracts resulted in a reduction in parasitoid response.