SPATIAL-DISTRIBUTION OF PHYLLOPHAGA-IMPLICITA (HORN) (COLEOPTERA, SCARABAEIDAE) LARVAE IN RELATION TO DISTANCE FROM THE ADULT FOOD SOURCE

The spatial distribution of the Phyllophaga implicita (Horn) larval po pulation in relation to the distance from the adult food source was in vestigated. Commercial soybean fields with 1 of 4 different shelterbel t arrangements were sampled in the fall of 1993, 1994, and 1995 to ass ess P. implicita distribution and density. Larvae were found only in f ields with bordering shelterbelts. Ninety percent or more of the speci mens were collected within 55 m of the shelterbelts. Exponential model s indicated a significant relationship between larval density and dist ance from the shelterbelts, with densities declining as distance incre ased. Logistic regression analyses were performed to assess models for predicting the probability of finding larval infestations. A positive association between the probability of finding larvae (pi(x)) and the distance from the shelterbelt was found. With P. implicita having a 3 -yr life cycle, the 1993 season was the night year for the largest of the 3 broods. Sampling guidelines based on higher densities of larvae nearer the shelterbelts are discussed.