In-transit temperature extremes could have negative effects on ladybird (Coleomegilla maculata) hatch rate

Authors: Riddick, Eric; Morales Ramos, Juan

Submitted to: Trends in Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2017
Publication Date: 8/1/2017
Publication URL: https://handle.nal.usda.gov/10113/5801862
Citation: Riddick, E.W., Morales Ramos, J.A. 2017. In-transit temperature extremes could have negative effects on ladybird (Coleomegilla maculata) hatch rate. Trends in Entomology. 13:1-11.

Interpretive Summary: The shipment of mass-propagated beneficial insects for eventual release on pest-infested crop plants (in greenhouses, glasshouses, and nurseries) is a standard procedure in the biocontrol industry. The change in temperature (and relative humidity) inside shipping containers, during transit, is poorly documented in the scientific literature. Extreme temperatures inside containers could have negative effects on the health and effectiveness of beneficial insects as they arrive at release sites. Using data loggers to record environmental conditions inside shipping containers, we discovered that much temperature variation occurred in-transit, with temperatures occasionally reaching a high of 35 degrees Celsius and a low of 4 degrees Celsius. Simulating the exposure of a beneficial insect (egg clutches of the pink-spotted ladybird beetle) to high and low temperatures for 24 h in the laboratory showed that these temperature extremes negatively affected the health (survival/hatch rate) of this ladybird beetle. We conclude that shipping containers must be re-designed to limit temperature extremes to fragile, developing stages of beneficial insects prior to release on pest-infested plants.

Technical Abstract: 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 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 24 h exposure to extreme temperature reduced egg hatch. We measured temperature (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 indicated that temperature fluctuated considerably in transit, reaching high and low temperatures 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, 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.