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ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #121947
Title: ADULT DIABROTICA SPP. (COLEOPTERA:CHRYSOMELIDAE) INFECTION AT EMERGENCE WITH INDIGENOUS BEAUVERIA BASSIANA (DEUTEROMYCOTINA:HYPHOMYCETES)

Author
item Bruck, Denny
item Lewis, Leslie

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: The western and northern corn rootworm (soil dwellers in the immature stages) are the most damaging insect pests of corn, in the major corn-producing states of the north central United States and Canada. Beauveria bassiana is a naturally occurring fungus which invades and kills pest insects including corn rootworms. This study was conducted to determine the number of corn rootworm infected with this fungus when the adults emerge from the soil. The percentage of adults infected with B. bassiana at emergence from untreated continuous cornfields was determined using emergence cages modified for live beetle capture. This trapping system allowed us to determine whether the level of beetle infection increased with increasing beetle populations. Cages were placed in tilled and no-tilled cornfields in central Iowa in 1999 and 2000. Levels of B. bassiana infection were low in 1999 and ranged from 0 to 0.7% whereas the level of infection was slightly higher in 2000 with levels ranging from 0 to 3.2%. Tillage did not have a significant impact on the percentage of beetle infection. There was a positive relationship between the size of the beetle population and the resulting percentage of beetles infected with B. bassiana. The percentage of beetles infected with B. bassiana at emergence is fairly low, but beetles were infected in five of the seven fields surveyed. This research demonstrates that naturally occurring B. bassiana is active against corn rootworm beetles. This research also indicates that if the fungus could be added to the soil during tillage/planting practices, more beetles would be infected with B. bassiana. This technique would be a nonchemical approach to beetle management.

Technical Abstract: The western (Diabrotica virgifera virgifera)(Coleoptera: Chrysomelidae) and northern corn rootworm (Diabrotica barberi)(Coleoptera: Chrysomelidae) are the most damaging insect pests of corn (Zea mays), in the major corn-producing states of the north central United States and Canada. This study was conducted to determine the level of adult Diabrotica spp. infection at emergence with indigenous Beauveria bassiana (Balsamo) Vuillemin (Hyphomycetes: Moniliaceae). The percentage of adult Diabrotica spp. infected with B. bassiana at emergence from untreated continuous cornfields was quantified using emergence cages modified for live beetle capture. The trapping system used allowed us to determine whether levels of beetle infection were density-dependent. Cages were placed in tilled and no-tilled cornfields in central Iowa in 1999 and 2000. Levels of B. bassiana infection were low in 1999 and ranged from 0 to 0.7% whereas the level of infection was slightly higher in 2000 with levels ranging from 0 to 3.2%. Tillage did not have a significant impact on the percentage of infection. There was a positive relationship between the size of the beetle population per hectare and the resulting percentage of adults infected with B. bassiana. A regression analysis of the percentage of beetles infected on the beetle emergence per hectare accounted for 42% of the total variation. The percentage of beetles infected with B. bassiana at emergence was fairly low, but beetles were infected in five of the seven fields surveyed, indicating that natural inocula of B. bassiana active against Diabrotica spp. are widely spread.