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4. INTEGRATION OF THE FLEA BEETLE, APHTHONA NIGRISCUTIS FOUDRAS, AND HERBICIDES FOR CONTROL OF LEAF SPURGE, EUPHORBIA ESULA L.  Jeff A. Nelson, Rodney G. Lym, and Robert Carlson, Graduate Student and Professors, North Dakota State University, Fargo, ND 58105.

Abstract. The combined treatment of the biological control agent, A. nigriscutis plus the herbicide treatment picloram plus 2,4-D generally provided better leafy spurge control compared to either method used alone. Leafy spurge control from the combined treatment averaged 44% 12 months after application. Leafy spurge with A. nigriscutis was oversprayed with picloram plus 2,4-D with a minimal negative impact to the A. nigriscutis population. The number of A. nigriscutis adults collected in the field was similar regardless of herbicide application date. Leafy spurge root nutrient content was not affected by picloram plus 2,4-D applied in the fall. Soluble and insoluble carbohydrate and soluble protein concentrations in herbicide treated plants were similar to concentrations in the untreated control. Leafy spurge plants harvested within an insect confining screened cage had root nutrient concentrations similar to roots harvested outside the screened cage.

Uptake and translocation of 14C-picloram and 14C-2,4-D was similar in plants damaged or unaffected by A. nigriscutis larvae. Therefore, the observed increase in leafy spurge control from the combined treatment was likely from the combined effect of herbicide toxicity to root tissue plus A. nigriscutis larval feeding on leafy spurge root buds.

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