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ARS Home » Plains Area » Brookings, South Dakota » Integrated Cropping Systems Research » Research » Publications at this Location » Publication #130116
Title: SUPERCOOLING AND COLD-HARDINESS IN EGGS OF WESTERN AND NORTHERN CORN ROOTWORM

Author
item Ellsbury, Michael
item LEE, JR., R. - MIAMI UNIVERSITY, OHIO

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2004
Publication Date: 5/28/2004
Citation: Ellsbury, M.M., Lee, Jr., R.E. 2004. Supercooling and cold-hardiness in eggs of western and northern corn rootworm. Entomologia Experimentalis et Applicata 111: 159-163.

Interpretive Summary: Corn rootworms overwinter as eggs in the soil and are exposed to very cold winter soil temperature. Animals that pass the winter in exposed conditions often can withstand very low subfreezing temperature. Although freezing is thought to cause some mortality to corn rootworm eggs when soil temperature reaches about 10 C, it is not known whether eggs can withstand temperatures lower than this. The influence of moisture on egg mortality at very cold temperatures also is not known. This research was done to determine how moisture and cold temperature interact to produce corn rootworm egg mortality. Western corn rootworm eggs were withstood supercooling under dry conditions to greater extent than did northern corn rootworms. Hatching of northern corn rootworms was higher following brief cold exposure in the presence of moisture than similar cold exposure under drier conditions Hatchability of western corn rootworm eggs was less affected by varying the moisture conditions during brief exposure to cold temperature. Effects of cold temperature exposure under differing moisture levels may explain some of the variability seen in distribution of corn rootworms within fields.

Technical Abstract: Northern corn rootworms, Diabrotica barberi Smith and Lawrence, and western corn rootworms, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), are key pests of corn in the Great Plains of the United States. Oviposition by both species occurs in the soil during late summer. Overwintering eggs are exposed to variable soil moisture and temperature below -5 C. Overwinter mortality of eggs in the soil is a primary factor that determines the potential for larval injury to corn the following spring. The objectives of our studies were to determine the comparative super-cooling capacities of northern and western corn rootworm eggs and to assess egg mortality following brief exposure to extreme cold temperature, ranging from 12.0 to - 21.5 C, under three moisture regimes. Eggs of northern corn rootworm supercooled to a temperature as low as -27 C and survived supercooling to a greater extent than did western corn rootworm eggs. Moisture treatment prior to supercooling had little effect on northern corn rootworm eggs. Western corn rootworm eggs were more resistant than northern corn rootworm eggs to effects of desiccation followed by supercooling. Survival of northern corn rootworm eggs was better than that of western corn rootworms under dry conditions followed by exposure to temperatures of 12.0 and -17.5 C, but was very low at - 21.5 C, regardless of moisture regime. Results suggest that moisture and temperature interact in the soil environment to determine overwintering survival of corn rootworms.