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United States Department of Agriculture

Agricultural Research Service

Title: Impact of combining planting date and chemical control to reduce larval densities of stem-infesting pests of sunflower in the Central Plains

Authors
item Charlet, Laurence
item Aiken, Robert - KANSAS STATE UNIV EXT CTR
item Meyer, Ron - COLORADO STATE UNIV EXT
item Gebre-Amlak, Assefa - COLORADO STATE UNIV EXT

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 17, 2007
Publication Date: August 1, 2007
Citation: Charlet, L.D., Aiken, R.M., Meyer, R.F., Gebre-Amlak, A. 2007. Impact of combining planting date and chemical control to reduce larval densities of stem-infesting pests of sunflower in the Central Plains. Journal of Economic Entomology. 100(4):1248-1257.

Interpretive Summary: Stem-infesting insect pests of sunflower in the central Plains are a concern to producers chiefly due to losses caused by plant lodging from the sunflower stem weevil and a longhorned beetle, Dectes texanus. The incidence of a root boring moth, Pelochrista womonana also has increased. Experiments were conducted in three locations in Colorado and Kansas during 2001-2003 to investigate the potential of pest management tactics including a combination of planting date and foliar and seed treatment insecticide applications to lower insect stalk densities. The impact of these strategies on weevil larval parasitoids was studied. A total of 8 sunflower stem weevil larval parasitoid species were identified. The density of sunflower stem weevil larvae within sunflower stalks over all environments declined as planting date was delayed. Chemical control often reduced pest numbers and application timing was not critical. Overall, delayed planting was the most reliable and effective management tool for producers to lower sunflower stem-infesting pest numbers. Chemical control and planting date were compatible with natural mortality contributed by stem weevil larval parasitoids.

Technical Abstract: The guild of stem-infesting insect pests of sunflower, Helianthus annuus L., within the central Plains is a concern to producers chiefly due to losses caused by plant lodging from the sunflower stem weevil, Cylindrocopturus adspersus (LeConte) (Coleoptera: Curculionidae) and Dectes texanus texanus LeConte (Coleoptera: Cerambycidae). The incidence of a root boring moth, Pelochrista womonana (Kearfott) (Lepidoptera: Tortricidae), also has increased. Experiments were conducted in three locations in Colorado and Kansas during 2001-2003 to investigate the potential of combining planting date and foliar and seed treatment insecticide applications to lower insect stalk densities of these three pests. The impact of these strategies on weevil larval parasitoids also was studied. Eight sunflower stem weevil larval parasitoid species were identified. All were Hymenoptera and included [relative composition in brackets]: Nealiolus curculionis (Fitch) [42.6%], N. collaris (Brues) [3.2%] (Braconidae); Quadrastichus ainsliei Gahan [4.2%] (Eulophidae); Eurytoma tylodermatis Ashmead [13.1%] (Eurytomidae); Neocatolaccus tylodermae (Ashmead) [33.7%], Chlorocytus sp. [1.6%], Pteromalus sp. [0.5%] (Pteromalidae); and Eupelmus sp. [1.0%] (Eupelmidae). The results from this three-year study revealed that chemical control was often reliable in protecting the sunflower crop from stem pests and was relatively insensitive to application timing. Although results in some cases were mixed, overall, delayed planting can be a reliable and effective management tool for growers in the central Plains to utilize in reducing stem-infesting pest densities in sunflower stalks. Chemical control and planting date were compatible with natural mortality contributed by C. adspersus larval parasitoids.

Last Modified: 12/27/2014
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