Author
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CHARLET, LAURENCE |
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Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings Publication Acceptance Date: 2/15/1997 Publication Date: N/A Citation: N/A Interpretive Summary: The sunflower beetle occurs from Texas to Manitoba, Canada, and is the major defoliating pest of sunflower. Both the adult and larval stages of the sunflower beetle cause damage to the plant. The sunflower beetle overwinters as an adult, emerging from late May to early June. After mating, eggs are deposited on wild or volunteer sunflower until cultivated plants become available. The objectives of this study were to investigate the overwintering biology of the sunflower beetle adult to determine their location in the sunflower field and the depth in the soil where they overwintered in both the fall and spring. Overwintering adult survival and the pattern of emergence the following year were compared in untilled soil and in soil disked in the fall and spring. Sunflower beetle adults move into the soil directly under the sunflower plants to overwinter. Evacuation of soil in the sunflower field in the fall showed that adults were located 5-10 cm below the surface. However in the spring, adults were present 0-10 cm below the soil surface with the majority at the 0-5 cm level. It appears that the sunflower beetle adults move closer to the soil surface prior to emergence. Although preliminary trials showed that neither fall nor spring tillage reduced survival of overwintering sunflower beetle adults, the emergence period was affected. Both fall and spring tillage lengthened the time it took for adults to emerge compared to beetles in untilled soil. Increasing the emerge period may provide some protection to the sunflower plants by reducing the populations when plants are small. In addition, the densities of eggs and larvae might also be reduced on young plants. Technical Abstract: The sunflower beetle occurs from Texas to Manitoba, Canada, and is the major defoliating pest of sunflower. Both the adult and larval stages of the sunflower beetle cause damage to the plant. The sunflower beetle overwinters as an adult, emerging from late May to early June. After mating, eggs are deposited on wild or volunteer sunflower until cultivated plants become available. The objectives of this study were to investigate the overwintering biology of the sunflower beetle adult to determine their location in the sunflower field and the depth in the soil where they overwintered in both the fall and spring. Overwintering adult survival and the pattern of emergence the following year were compared in untilled soil and in soil disked in the fall and spring. Sunflower beetle adults move into the soil directly under the sunflower plants to overwinter. Evacuation of soil in the sunflower field in the fall showed that adults were located 5-10 cm below the surface. However in the spring, adults were present 0-10 cm below the soil surface with the majority at the 0-5 cm level. It appears that the sunflower beetle adults move closer to the soil surface prior to emergence. Although preliminary trials showed that neither fall nor spring tillage reduced survival of overwintering sunflower beetle adults, the emergence period was affected. Both fall and spring tillage lengthened the time it took for adults to emerge compared to beetles in untilled soil. Increasing the emerge period may provide some protection to the sunflower plants by reducing the populations when plants are small. In addition, the densities of eggs and larvae might also be reduced on young plants. |
