| dc.description.abstract | North Dakota is the top sunflower producing state in the United States, annually harvesting about 405,000 ha (1 million acres). Up to 63% of this crop is grown in central North Dakota in an area known as the Prairie Pothole Region (PPR). Since the early 2000s, com also has become a major crop in the PPR due to the development of hybrids for northern crop areas and increases in com prices. Blackbirds (Icteridae) can cause significant damage to both ripening com and sunflower. It has been three decades since a comprehensive sunflower damage survey was conducted in the PPR. I assessed blackbird damage to ripening sunflower and com in 120 randomly-selected plots during three growing seasons,
2008-2010. Damage was analyzed across four strata (Northeast Drift Plains, Northwest Drift Plains, Southern Drift Plains and Missouri Coteau) within the PPR. Landcover was analyzed to determine possible variables (pasture, com, sunflower, open water, wetland, small grains, developed, wooded, beans and other) related to blackbird damage. Stepwise logistic regressions were performed along with AIC model selection to determine significant (p<0.1) independent variables related to sunflower and com damage. Average damage to sunflower (2.14%) was higher than damage to com (0.33%), with sunflower in the Southern Drift Plains having the greatest levels of damage (11.11 %). Beans and wetland showed the greatest significance in relation to sunflower damage (p=<0.001, p=0.035), according to the selected AIC model. The most significant landcover variables surrounding damaged corn fields was open water (p=0.022), showing an increase in damage, and pasture (p=0.056), showing a decrease in damage. The results of this study provide data to help producers make informed decisions about crop selection and location. | en_US |
