The impact of western corn rootworm (Coleoptera: Chrysomelidae) on pollination success in seed corn production fields
Abstract
Field studies were conducted during 1983-1986 to determine damage thresholds for western corn rootworm (WCR) adults feeding on silks of inbred corn grown under seed production field conditions. Three inbred genotypes were used as pollen sources and three others as female plant material to assess beetle impacts. Damage was observed with beetle densities of 1.0 to 3.0 beetles/ear for all genotypes tested. These levels reduced kernels per acre, kernels per pound and test weight while increasing round kernel fractions and decreasing flat fractions. Effects due to silk length as regulated by scissor cuts to simulate WCR adult feeding damage were investigated from 1984-1986. Two inbred genotypes were used as male pollen sources and three different genotypes were used as female plants. Silk lengths shorter than 2.54 cm (1.0 in) were found to reduce kernels per acre significantly under seed field conditions. Silk removal to lengths of 0.635 cm (0.25 in) did not affect yields under conditions of open pollination. Effects due to distance between male pollen source and receptive female ears were observed in studies simulating seed production field conditions. Reductions in kernels per acre and kernels per pound and increases in round and decreases in flat kernel fractions were observed with greater separation of pollen and silk. Environment and plant genotype were found to influence impacts of beetle density, silk length and distance between male pollinator and receptive ear. Conditions of moisture and heat stress during pollination were observed to magnify effects of other factors. Pollen level was also found to influence impacts with greater treatment effects observed when pollen was not limited. Regression equations for prediction of kernels per acre yield as influenced by beetle density, silk length and distance between pollen source and receptive ear were calculated. The threshold proposed was dependent upon both beetle density and silk length and suggested the need for consideration of plant stress and corn growth stages.
Degree
Ph.D.
Advisors
Edwards, Purdue University.
Subject Area
Entomology
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