Diatomaceous earth structural treatment against Oryzaephilus surinamensis (L.)(Coleoptera : Silvanidae) under fluctuating UK conditions

摘要

The first UK trial to assess diatomaceous earth (DE) structural treatment was carried out during February 2002 . A bin containing 20 t of "heating" insect-infested wheat resulted in migration of large numbers of Oryzaephilus surinamensis into the storage structure and surrounding area. The DE "Silico-Sec'" was applied at ca. 10 g/m~2 to the outsides, undersides and concrete floor beneath a nest of six, galvanised steel 3 X 3 X 4 m bins. Hand-operated, electric and gaspowered dusters were compared for ease of treatment. I-SPy Insect Indicators, incorporating multi-species lures, were placed before and after treatment. These showed an immediate reduction in insects trapped of 86-100 percent from an initial average of 406 per trap. Before treatment,a sample of the population was used to set up bioassays in Petri dishes containing 100 insects each. Paired bioassays, one uncovered, the other closed, were placed in 10 floor positions to give treated and untreated controls. Mean mortality increased from 52 percent at 7 days to 99 percent after 14 days and 100 percent after 21 days. The mean temperature for this period was 6 deg C with relative humidity at 80 percent. The low temperature and high humidity allowed testing under the most challenging environmental conditions for the DE dust. Photographed tracks gave an indication of insect movement after treatment, and hypotheses are put forward to explain this activity. Trap and bioassay assessments were continued for 5 weeks after treatment when the dust was removed by vacuuming and the store further monitored to measure the success of the treatment.