INTRODUCTION
The silverleaf whitefly (SL WF) and cotton aphid are not new insects to the SJV, but only in recent years have late-season populations of both of these pests become widespread. The silverleaf whitefly was first found in the SJV in 1992. The SL WF has continued to adapt to SJV conditions and cropping patterns and starting in 2001 SL WF populations expanded greatly both in severity and particularly in range. Populations in significant numbers occurred farther northward and westward into the SJV. This has pushed the whitefly into the primary cotton production area. The cotton aphid occurred sporadically in cotton throughout…
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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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