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Cultural Practices Affecting the Abundance of Cotton Aphids and Beet Armyworms in Dryland Cotton

M. N. Parajulee, J. E. Slosser and D. G. Bordovsky


 
ABSTRACT

A study was conducted at the Texas Agricultural Experiment Station farm at Munday, Texas during the 1998 cotton growing season to quantify the effect of planting date and planting pattern on beet armyworm, Spodoptera exigua (Hübner), and cotton aphid, Aphis gossypii Glover, abundance. The 1998 growing season was the first full year of boll weevil eradication in the central Rolling Plains. ‘Sphinx' cotton was planted on April 29, May 19, and June 9, representing early, normal, and late planting dates in the Texas Rolling Plains. Within each planting date, planting pattern treatments included 1) solid-row stand, 2) two rows planted, one row skipped (Skip 2x1), and 3) two rows planted, two rows skipped (Skip 2x2). Abundance of beet armyworm was monitored weekly by visually inspecting all the plants in 13 row-ft per plot, whereas cotton aphid abundance was estimated by inspecting 10 leaves from the top half and 10 leaves from the lower half of plants from each plot. Percentage square damage by beet armyworm was also quantified. Analysis of variance showed that average beet armyworm abundance varied significantly with planting date and planting pattern. Late planted cotton was significantly most susceptible to beet armyworm infestation, followed by early planted and normal planted cotton. Solid-row pattern attracted fewest numbers of beet armyworms, followed by Skip 2x1 and Skip 2x2, with a strong positive relationship between the number of rows skipped and beet armyworm abundance. Cotton aphid abundance was not significantly affected by planting dates; however, average abundance was lower in normal planted cotton compared with early and late planted cotton. Planting pattern had a significant effect on aphid abundance, with a strong positive relationship between the number of rows skipped and cotton aphid abundance. Because normal planted cotton was least attractive to beet armyworms and cotton aphids during boll weevil eradication, the current recommended uniform planting date of mid-May for boll weevil management may continue to be the best planting date for insect pest management in the Rolling Plains during eradication.



Reprinted from Proceedings of the 1999 Beltwide Cotton Conferences pp. 1014 - 1016
©National Cotton Council, Memphis TN

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Document last modified Monday, Jun 21 1999