Influence of maize row spacing on infestation and damage of intercropped beans by the bean aphid (Aphis fabae Scop.). I. Incidence of aphids

Publication Type

Journal Article

Journal Name

Journal of Economic Entomology

Publication Date

4-1-2002

Abstract

With the widespread introduction of the nitrogen-pxing legume sesbania, Sesbania sesban (L.) Merril, in agroforestry systems, the defoliating beetle Mesoplatys ochroptera Stal has become a serious pest of the trees in Africa. To determine within-Peld and within-plant spatial distribution of M. ochroptera on both seedlings and trees of sesbania, distribution statistics were computed using Iwao's mean crowding regression model. In 1-to 3-mo-old seedlings, the model accounted for 29.8, 32.2, and 61.0% of the variation observed in mean crowding to mean relationships in egg masses, larvae and adults, respectively. The model slopes of the regression were greater than unity for all stages indicating aggregated spatial distribution. Values of the intercept were greater than zero for egg masses, larvae and adults indicating that the basic components of the population are groups of individuals. The highest density (>80%) of mating and feeding adults was found in the upper third of 1-to 2-mo-old seedlings, while most of the egg masses were found in the lower half of seedlings. In trees, >60% of the individuals of all stages were found in the lower third of the foliage canopy, while <10% were found in the upper third. Sampling adults was found to be easier and gave better density estimates of M. ochroptera population than egg masses and larvae. Therefore, sampling plans useful for population studies and decision-making in pest management were developed for adults.

Keywords

Mesoplatys ochroptera, Sampling, Sesbania sesban, Spatial distribution

PubMed ID

12020033

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