Responses of High-Oil and Hybrid Corn to Rootworm Beetles during Pollination
2001
Strachan, Stephen D. | Kaplan, Stuart L.
High-oil corn (Zea mays L.) may be produced as a physical mixture consisting of 91% male-sterile hybrid plants and 9% pollinator plants. Two field studies were conducted to determine if corn blends consisting of only 9% pollinator plants are more sensitive to high populations of rootworms (Diabrotica spp.) feeding on silks during pollination than hybrid blends consisting of 50 to 100% male-fertile plants. In one study, silks of hybrid corn and silks of the male-sterile hybrid within the high-oil corn blend were clipped daily during pollination to simulate silk clipping caused by rootworms. In a separate study, 165 locations of high-oil corn and 134 locations of hybrid corn were monitored for rootworm population and severity of silk clipping during pollination. Grain yield was significantly reduced (P ≤ 0.05) if average lengths of exserted silks were <37 mm for high-oil blends with 9% pollinator plants and <25 mm for hybrid corn. Oil, protein, and starch concentrations of the high-oil grain were not significantly different from those of the untreated check if exserted silks were at least 25 mm during pollination. Severity of beetle infestation correlated poorly with daily average silk length (r = −0.06) and with grain yield (r = −0.01). Economic thresholds for grain yield were crossed, and appropriate pest control measures should be considered when rootworm beetles consistently clip exserted silks to <37 mm for high-oil blends with 9% pollinator plants or <25 mm for hybrid corn.
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