Northern Corn Rootworm Egg Sampling1

Seasonal Oviposition of a Western Corn Rootworm, <I>Diabrotica virgifera virgifera</I> LeConte (Coleoptera: Chrysomelidae), Variant in East Central Illinois Commercial Maize and Soybean Fields

“…Our research suggests that by only sampling to a depth of 10 cm for D. v. virgifera in maize or soybean, future investigators would miss as many as 40% of potential eggs that occur in the upper 20 cm of the soil proÞle. Egg laying after a drought may be considerably deeper because of the formation of soil cracks in which egg-laying females use as ovipositional sites (Foster et al 1979). Based on the results of our study, we hypothesize that overwintering survival of D. v. virgifera eggs may be comparable in maize and soybean Þelds based on the similarity in egg numbers for each soil depth that we sampled.…”

“…A number of environmental and agronomic factors were reported to affect the vertical distribution of corn rootworm eggs such as soil cracking (Foster et al 1979), tillage Apple 1966, Pruess et al 1968), soil moisture (Gustin 1979), and plant lodging (Sisson and Chiang 1964). Most research to date regarding the oviposition of D. v. virgifera has focused on maize (Hein et al 1988).…”

“…Many other investigators also have studied the oviposition of both D. v. virgifera and D. barberi in maize. Foster et al (1979) reported that 95% of D. barberi eggs may be found in the upper 10 cm of the soil. For this reason, they concluded that sampling to a depth of 10 cm was appropriate for this species.…”

“…Egg sampling programs for corn rootworms have been used in an effort to predict economically damaging densities of corn rootworm larvae (Lawson 1968, Foster et al 1979, Apple et al 1977; however, these methods are too labor intensive and time-consuming for producers or crop consultants (Foster et al 1979). In contrast to absolute sampling methods (Hein and Tollefson 1985), relative egg sampling techniques have been used most often for corn rootworms (Gunderson 1964, Howe and Shaw 1972, Foster et al 1979.…”

“…In contrast to absolute sampling methods (Hein and Tollefson 1985), relative egg sampling techniques have been used most often for corn rootworms (Gunderson 1964, Howe and Shaw 1972, Foster et al 1979.…”