Effect of soil moisture on development of Diaprepes abbreviatus (Coleoptera : Curculionidae)

We conducted trials to determine conditions of soil moisture required to op timize production of adults of Diaprepes abbreviatus (L.) in a laboratory c olony. Larvae of D. abbreviatus were reared on a commercially available art ificial diet and then placed in soil with water content ranging from 20 to 80%. Optimal moisture content of soil for pupation was determined to be 60 +/- 10% by weight. When 68-d-old larvae were transferred from artificial di et to soil with these moisture levels and constant temperature (25 degrees C), mean (+/- SEM) development time of D. abbreviatus from neonate to pupa was 126 +/- 2.3 d (n = 47). For all pupae, the time required for pupation d id nut vary with soil moisture. When 68-d-old larvae were taken from diet a nd placed in soil, the proportion that pupated varied with moisture content . Low (20-40%) and high (80%) moisture content resulted in increased mortal ity, and fewest larvae pupated within the low range. The mean +/- SEM numbe r of days to pupation of 68-d-old larvae was 58.2 +/- 2.3 (n = 47). Older ( 180 d) larvae reared on diet pupated over a greater range of moisture treat ments (30-70%) and were adversely affected only by the highest (80%) and lo west (20%) treatments. Mean +/- SEM time to pupation (38.4 +/- 1.9 d, n = 5 4) did not vary for 180-d-old larvae kept at 30-70% moisture content.