Resistance of corn populations ot larvae of the corn earworm (Lepidoptera: Noctuidae)
1992
Wiseman, B.R. | Widstrom, N.W.
The corn earworm, Helicoverpa zea (Boddie), is the most important pest of corn, Zea mays L., in the southeastern United States. This study was conducted to determine whether tolerance or antibiosis mechanisms (or both) of resistance function in 18 populations of corn that are being developed for resistance to ear and leaf damage in the field to the corn earworm and fall armyworm, Spodoptera frugiperda (J. E. Smith). The populations and resistant and susceptible checks were evaluated in the field for corn earworm injury and husk tightness and in the laboratory for feeding responses of neonate corn earworm larvae on fresh silks or oven-dried silks mixed in a meridic diet. Several populations approached the resistance level of the resistant cheek, 'Zapalote Chico', to ear damage in the field, but none equaled 'Zapalote Chico' in husk tightness. In 1987, the growth reduction of corn earworm larvae that were fed silk-diets of five populations was similar to the growth reduction of larvae that were fed a silk diet of 'Zapalote Chico'. In 1988, only one population showed a growth reduction similar to that of 'Zapalote Chico'. However, none of the populations approached the level of resistance exhibited by 'Zapalote Chico' when other antibiotic measurements such as development time and weight of pupae were considered. Based on data from both the field and laboratory, the resistance of recently released populations, 'DDSA(C5)' and 'DDSB(C5)', is primarily tolerance. Tolerance to ear damage in the field is also present in the 18 populations evaluated, although a few populations also possess a minor level of antibiosis.
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