The objectives of these studies with Acala and Pima varieties are to evaluate approved Acala varieties and Pima varieties submitted for testing under different environmental conditions and management across the San Joaquin Valley region of California. In order to provide a reasonable limit on the number of varieties in the tests, the entries include newly-approved varieties (approved by the San Joaquin Valley Cotton Board) for the current year, varieties released last year that are in their second year of testing, plus the top 4 or 5 previously-approved varieties (in terms of planted acreage). The new varieties are the focus of tests, but only remain in tests for a minimum of two years following release unless that variety moves into the top 4 or 5 varieties in planted acreage. Released varieties also may not show up in tests if companies request that the variety is for a special market and don’t want it in multiple location testing, or when seed supplies are inadequate. The Pima tests focus on approved varieties, but in the past two years have also included a non-approved hybrid that has been of interest due to yield…
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Preventing sticky cotton is crucial in producing quality cotton. Late-season populations of cotton aphid and Silverleaf whitefly can produce significant amounts of honeydew when populations build. These pests are of most concern from mid-boll filling through harvest, when insect populations build and threaten exposed lint. Pest management guidelines for cotton aphid and silverleaf whitefly focus on strategies to use once threshold pest populations are reached, with the approach varying with the composition of the developing population (nymphs, adults), crop growth stage, and with the presence of exposed lint. Current pest management guidelines for whitefly and aphid can be interpreted as meaning defoliation is the final event of the season. This is based on the assumption…
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Introduction:
During the last 10 years, the cotton aphid (Aphis gossypii) has developed from a non-pest to one of the most significant insect pests of California cotton. For instance,in1997, cotton aphid outbreaks were severe and an estimated 3.5% yield loss occurred despite -$40/acre control costs which were incurred. Cotton aphid infestations during the mid-season (July to mid-August) reduce cotton lint yields since the aphids act as a significant sink, competing with the bolls, for energy. The late-season infestations (mid-Aug.to Sept.) are problematic because the aphids deposit honeydew on the exposed cotton lint, which reduces the lint value. Reasons for this change in pest status of cotton aphid are unclear; however, one of the most noticeable changes in cotton production over the last 10 years is the use of a plant growth regulator instead of irrigation and nitrogen deficits to limit early-season cotton vegetative growth. This has allowed cotton production practices in the SJV to evolve to higher nitrogen fertilization and irrigation inputs.
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