MAYSIN CONTENT AND GROWTH OF CORN-EARWORM LARVAE (LEPIDOPTERA, NOCTUIDAE) ON SILKS FROM 1ST AND 2ND EARS OF CORN

Silks of selected corn, Zea mays L., genotypes from the first or second ears and silks regrown for 1 or 2 d after cutting were evaluated for maysin content and for antibiosis responses from the corn earworm, Helicoverpa zea (Boddie). Corn earworm neonates that were fed diets of silks from the first ears weighed significantly less than larvae that were fed diets of silks from the second ears. Maysin concentration was generally higher in silks from the first ears than in silks from the second ears. In general, silks regrown for 1 or 2 d after an initial cutting produced larger larvae at 8 d than those fed on silk diets from the initial cutting. Maysin contents also were lower in silks regrown for 1 or 2 d after cutting than were maysin concentrations in silks from the initial emergence. Relative weights of larvae and maysin content were consistent among genotypes, whether the silks were from the first or second ears. This was especially true for silks of the genotypes such as 'PI340856', which has a high level of antibiosis. 'PI340856' followed the pattern described above by producing significantly larger larvae and a lower maysin content from regrown silks than from silks from the initial cutting. However, larvae were still quite small, and the maysin concentration was high for regrown silks of 'PI340856' compared with regrown silks of other resistant materials. Larvae were especially small when compared with weight of larvae that were fed on regrown silks of more susceptible genotypes. These results suggest that silks for bioassay or breeding purposes could be used from first and second ears or regrown silks of genotypes with high levels of antibiosis.