Response of determinate and indeterminate corn hybrids to simulated early-season black cutworm injury
Abstract
Black cutworm larvae (Lepidoptera: Noctuidae, Agrotis ipsilon (Hufnagel)) are a pest of corn (Zea mays L.) during early stages of plant development. Larvae feed on developing corn seedlings until pupation. Feeding on or near the growing point results in plant injury or death and results in significant grain yield losses. Current thresholds indicate significant economic losses can occur when 3% of the plant population shows signs of black cutworm (BCW) feeding but do not differentiate between indeterminate (flex) and determinate (fixed) hybrids. This study was conducted to determine if flex and fixed corn hybrids differ in their response to simulated BCW injury. The effects of BCW injury at three corn growth stages (i.e., VE, V2, and V4) and three feeding positions (below-surface, surface, and above-surface) were investigated on a fixed (i.e., LHE136 x LH82) and a flex hybrid (Pioneer brand 3377). Whole-plot grain yields decreased significantly when simulated feeding positions were near plant growing points and when plants were injured at advanced (V4) growth stages. Below-surface injury at V4 caused greater yield losses (11.3%) than below-surface injury at VE but did not differ from below-surface injury at V2. Grain yield of uninjured plants (in adjacent 30-in rows) significantly increased when injured plants were damaged below the soil surface at V4 (12.3% greater than controls) and V2 (5.6% greater than controls) but were not affected when injured plants were damaged at VE. Nearby uninjured plants ('C' plant position within the 30-in row) had significantly greater grain yields when injured plants were damaged at V4 and V2 growth stage (17.8 and 7.8%, respectively) when compared to plants damaged at VE. Fixed and flex hybrids did not differ for whole-plot grain yields or for their ability to compensate for nearby injured plants. Grain yield losses were directly related to the position of the plant's growing point at the time of injury. Nearby uninjured plants contributed significantly to grain yield but economic thresholds appeared not to differ between fixed and flex hybrids.
Degree
Ph.D.
Advisors
Edwards, Purdue University.
Subject Area
Agronomy|Entomology
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