Abundance of Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) neonates falling to the soil under tree canopies in Florida citrus groves.

Abstract

The purpose of these experiments was to estimate the number and distribution of Diaprepes abbreviatus (L.) neonate larvae dropping from the canopy of infested citrus trees. The number of neonates was monitored in the field using passive funnel traps in two simultaneous experiments and a separate experiment for an additional year. In one experiment, traps were placed from trunk to dripline in the cardinal directions under each of five trees (132 traps total). In a second experiment, eight traps were placed under each tree in the cardinal directions, one trap 30 cm from the trunk and one trap 30 cm from the dripline/direction for 25 trees (200 traps total). Larvae were collected weekly for 50 wk in conical tubes containing ethylene glycol as a preservative. Traps closer to the tree trunk captured more larvae than traps nearer the dripline. The area under the tree canopy was positively correlated with the total estimated number of larvae captured per tree. The estimated number of total larvae/tree over the course of our experiments ranged from 955 to 7,290. The highest number of neonate larvae observed in 1 wk was 67 +/- 6/m2. There was an inverse relationship between the number of traps beneath a tree and the number of trees that needed to be sampled to estimate mean population density with a given precision. However, there was a direct relationship between number of traps/tree and the total number of traps needed for a given precision. This passive technique could be used to quantify the destructive larval stage and to assess D. abbreviatus management strategies.