Damage and grain yield losses caused by European corn borer (Lepidoptera :Pyralidae) in early maturing European maize hybrids

The European corn borer, Ostrinia nubilalis (Hubner), is a major pest of ma ize, Zen mays L., in Central Europe. The resistance of 8 early maturing com mercial maize hybrids and 6 experimental hybrids against European corn bore r was assessed during 1996 and 1997 in Germany. Resistance was evaluated by yield reduction and damage ratings under natural and manual infestation in 11 or 6 environments, respectively. The infestation level of European corn borer was assessed by the percentage of damaged plants and number of larva e per plant in each environment. Average grain yield of the commercial hybr ids was reduced by 0.28% for each 1% of damaged plants and by 6.05% for eac h European corn borer larvae per plant. All commercial and experimental hyb rids were susceptible to European corn borer attack. The commercial hybrids showed little variation in their resistance to European corn borer. The ex perimental hybrids derived from crosses between resistant inbreds were more resistant than crosses between intermediate and susceptible inbreds. The e valuation of yield reduction required manual infestation because of the low natural infestation level in most environments. However, a comparison of e rror variances and repeatabilities revealed that they were of similar magni tude for environments with a high level of natural and manual infestation. Yield reduction and damage ratings were highly correlated (r(p) less than o r equal to 0.85) under both infestation regimes. Consequently, the latter t rait should be useful for indirect selection to improve European corn borer resistance in maize.