Author
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Charlet, Laurence |
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Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings Publication Acceptance Date: 3/26/2002 Publication Date: N/A Citation: N/A Interpretive Summary: The presence of kernel brown spot on confection sunflower in the past several years has increased the need for understanding the underlying causes and means to alleviate the problem for growers and processors. The quality issue is significant because processors are allowed only 0.5% damage in the finished product and in 2000 damage ranged between 1-7% in some areas in the northern Plains. Damage to the sunflower kernel is caused by lygus bugs feeding on the developing seed. Tissue destruction causes the brown spot on the sunflower kernel and can also result in a bitter taste to the seeds. Studies were conducted in 2001 to determine economic injury levels, susceptible plant stages, incidence of lygus bugs on cultivated and native sunflower, and the potential for control of seed damage with insecticides. A survey of sunflower fields in North and South Dakota conducted by the National Sunflower Association included the determination of kernel brown spot damage in confection fields. Results from a number of studies conducted on lygus bug and its impact on sunflower showed that all stages were present in both confection and oilseed sunflower and in just one of 5 species of native sunflowers in North Dakota. Damage was present in cultivated confection fields in both North and South Dakota. Damage averaged about 4% in North Dakota. Greenhouse studies showed that 10 to 20 seeds were damaged per adult lygus bug and that all reproductive growth stages were vulnerable to attack. Insecticide treatments with two pyrethroids reduced feeding damage by lygus bugs from the 1.7% occurring in the untreated controls, but 2 sprays of FMC F0570 were needed to lower damage below 0.5% needed to prevent dockage in confection sunflower. Technical Abstract: The presence of kernel brown spot on confection sunflower in the past several years has increased the need for understanding the underlying causes and means to alleviate the problem for growers and processors. The quality issue is significant because processors are allowed only 0.5% damage in the finished product and in 2000 damage ranged between 1-7% in some areas in the northern Plains. Damage to the sunflower kernel is caused by lygus bugs feeding on the developing seed. Tissue destruction causes the brown spot on the sunflower kernel and can also result in a bitter taste to the seeds. Studies were conducted in 2001 to determine economic injury levels, susceptible plant stages, incidence of lygus bugs on cultivated and native sunflower, and the potential for control of seed damage with insecticides. A survey of sunflower fields in North and South Dakota conducted by the National Sunflower Association included the determination of kernel brown spot damage in confection fields. Results from a number of studies conducted on lygus bug and its impact on sunflower showed that all stages were present in both confection and oilseed sunflower and in just one of 5 species of native sunflowers in North Dakota. Damage was present in cultivated confection fields in both North and South Dakota. Damage averaged about 4% in North Dakota. Greenhouse studies showed that 10 to 20 seeds were damaged per adult lygus bug and that all reproductive growth stages were vulnerable to attack. Insecticide treatments with two pyrethroids reduced feeding damage by lygus bugs from the 1.7% occurring in the untreated controls, but 2 sprays of FMC F0570 were needed to lower damage below 0.5% needed to prevent dockage in confection sunflower. |