Graduate Thesis Or Dissertation
 

Sampling and management of garden symphylans (Scutigerella immaculata Newport) in western Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/m613n152s

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  • Garden symphylans (Scutigerella immaculata Newport) are increasingly important pests of below-ground parts of over 100 crops in Oregon. The focus of our work was to improve S. immaculata management through 1) development of a bait sampling method, 2) examination of the susceptibility of selected crops to S. immaculata feeding in the field and laboratory and a reanalysis of previously published results, and 3) investigation of the suitability of selected crops and soil for the development of S. immaculata populations in the field and laboratory. Sample size requirements were developed for the bait and soil sampling methods. Estimating densities of 1 to 20 S. immaculata at fixed precision levels required 1.5 times more sample units for the baiting method than the soil method. Sampling recommendations for the baiting method performed well when validated by resampling a large independent data set. The bait sampling method provides an effective reliable alternative to the standard soil sampling method. In the laboratory, as S. immaculata densities increased, dry weight of spinach (Spinacia oleracea L.) and tomato (Lycopersicon esculentum L.) seedlings were significantly reduced from 85 to 89%, whereas corn (Zea mays L.) and potato (Solanum tuberosum L.) dry weight were not reduced. As S. immaculata densities increased in the field, the normalized difference vegetation index (NDVI) of squash (Cucurbita pepo L.) and broccoli (Brassica oleracea L.) crops sharply decreased, while the NDVI of corn and potato crops was only slightly reduced. In reanalysis of previously published data, the stand counts of crops seeded into S. immaculata infested soil appeared to increase as seed size increased. These findings will be used to help develop action thresholds and sample size requirements, and reduce S. immaculata damage. In the laboratory, S. immaculata population growth was significantly greater on spinach than on tomato, sweet corn, potato, or soil alone, and significantly lower on potato than on spinach, corn, tomato, or soil alone. In the field, greater S. immaculata population decreases were observed in potatoes than in sweet corn or clean fallow. These results provide strong evidence that crop rotation may significantly influence S. immaculata population levels.
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