The shipment of mass-produced natural enemies for augmentative release is a standard procedure used by the biological control industry. Yet there has been insufficient research on the effects of temperature change experienced during shipment, on the quality of the predators as they arrive at release sites. In this study, we monitored the in-transit environmental conditions inside polystyrene foam (Styrofoam) shipping containers and simulated the effect of low and high temperatures on egg hatch of the ladybird Coleomegilla maculata, a predator of small arthropods (e.g., aphids). We tested the prediction that a 24-h exposure to extreme temperatures reduces the rate of egg hatch. We measured the temperatures (and percent relative humidity) by placing data loggers inside containers, enclosed inside single-walled cardboard boxes, then shipping the boxes roundtrip from Mississippi to Georgia, Oregon, and California in August, October, December 2012, and March 2013. Our results indicate that the temperature fluctuated considerably in transit, reaching high and low values of 35 °C in October 2012 (California shipment) and 4 °C in March 2013 (Oregon shipment). Relative humidity sometimes correlated positively with temperature in the same containers. Relative humidity was lowest in the March 2013 shipments, averaging from 33% (Georgia shipment) to 43% (California shipment). In laboratory bioassays, a 24-h exposure to 36 °C and 6 °C significantly reduced C. maculata egg hatch when compared with the control, 25 °C. Egg hatch rate was 13% and 50% at 36 °C and 6 °C, respectively, in comparison to 64% at 25 °C. This suggests that brief exposure to high (rather than low) temperatures are more harmful to egg hatch. In summary, redesigning containers to limit temperature extremes (especially high temperatures) is necessary to facilitate shipment of fragile, developing stages (i.e., eggs) of predators intended as biocontrol agents.
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