Author
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UMBLE, JOHN - OSU |
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FISHER, JIM - USDA-ARS |
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Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/1/2002 Publication Date: 10/1/2003 Citation: Umble, J., Fisher, J. Influence of below-ground feeding by garden symphylans (symphyla, scutigerellidae: scutigerella immaculata newport) on plant health. Environmental Entomology. 2003. 32 p. 1251-1261. Interpretive Summary: The effect of root-feeding by the garden symphylan (Scutigerella immaculata Newport) on crop health was measured in the laboratory and in the field. In the laboratory, sweet corn, potato, spinach and tomato in pots were exposed to either 0, 15 and 45 garden symphylans. As density of pests increased, root length and the above-ground dry weight of plant parts of week-old spinach and tomato seedlings were reduced from 85 to 98%. Corn root length was reduced by as much as 34% and potato and corn dry weight and potato root length were not reduced. We studied the pest-host plant association in the field by relating garden symphylan densities and two vegetational parameters: 1) crop health and 2) after tillage spring weed densities. Crop health in corn and potato was only slightly reduced with increasing garden symphylan populations. Squash and broccoli crop health decreased sharply as garden symphylan densities increased from 1 to 10. These findings will be used to help develop the sample size requirements needed by growers to accurately estimate garden symphylan populations, to help growers make informed pest (garden symphylan) management decisions, and to help reduce garden symphylan damage by avoiding the planting of highly susceptible crops at sites with high garden symphylan populations. Technical Abstract: The influence of garden symphylan (Scutigerella immaculata Newport) root feeding on crop health was measured in the laboratory and in the field. In the laboratory, the relative susceptibility of sweet corn (Zea mays L.), potato (Solanum tuberosum L.), spinach (Spinacia oleracea L.) and tomato (Lycopersicon esculentum L.) to S. immaculata feeding was investigated by subjecting each crop to 3 levels of pest pressure (0, 15 and 45 S. immaculata). As S. immaculata densities increased from 0 to 45, root length and dry weight of above-ground plant parts of week-old spinach and tomato seedlings were reduced from 85 to 98%, whereas, corn root length was reduced by 34% and potato and corn dry weight and potato root length were not reduced. The pest-host association was investigated in the field by examining the relationships between S. immaculata densities and two vegetational parameters: 1) crop health measured by the normalized difference vegetation index (NDVI) and 2) post tillage spring weed densities. S. immaculata densities were estimated using a baiting method. NDVI in corn and potato was only slightly reduced with increasing within-field S. immaculata densities after adjusting for spatial autocorrelation. Squash and broccoli showed sharp decreases in NDVI at densities from 1 to 10 S. immaculata. The nonlinear asymptotic form of the Bleasdale-Nelder curve was selected as the best curve to describe the damage/pest relationship for all crops using Akaike information criteria . The relative susceptibilities of direct seeded crop varieties to S. immaculata in western Oregon reported in 1937 by Morrison were reanalyzed to make comparisons with our data. In further analysis, seed size appeared to be linearly related with susceptibility of direct-seeded crops to S. immaculata. Stand count was predicted to increase by 0.24% for each 1 mg increase in seed size using linear regression. These findings will be used to help develop action thresholds and sample size requirements, and to help reduce S. immaculata damage by avoiding the planting of highly susceptible crops at sites with high S. immaculata populations. |
