Species composition and seasonal abundance of stink bugs in cotton in the Lower Texas Gulf Coast and the virulence of Euschistus species to cotton
Hopkins, Bradley Wayne
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Stink bugs are beginning to emerge as important pests of cotton that often require management in the Lower Texas Gulf Coast. As eradication of the boll weevil progresses and producers increasingly adopt transgenic cotton varieties resulting in reduced broad spectrum pesticide use, stink bugs will likely become key cotton pests in this area. The Lower Texas Gulf Coast has a stink bug complex that differs somewhat from other areas of the Cotton Belt. Euschistus servus and lesser brown stink bugs, including E. quadrator, E. obscurus, E. crassus, and E. ictericus, make up the largest portion of this pest complex, and green/southern green stink bugs play less important roles than in other areas. Using evidence of internal feeding as a sampling criterion detected stink bug infestations more frequently that when using visual or drop cloth sampling methods. The main drawback to using this method is that species composition may still need to be determined when an economic threshold is reached in order to select the most effective control. Euschistus servus and E. quadrator both caused significant reductions in yield and fiber quality in cotton bolls, but E. servus was able to reduce yield and quality in small (1.8 cm), medium (2.8 cm), and large (3.2 cm) bolls, whereas E. quadrator reduced yield in only small bolls and reduced quality in only small and medium bolls. In general, E. servus caused more damage to bolls than E. quadrator and was able to damage a wider range of boll sizes. Dicrotophos was the most effective insecticide for stink bug control. Exposure to pyrethroids caused high mortality in N. viridula similar to that of dicrotophos, but pyrethroid activity was more variable when E. servus were exposed. In general, E. quadrator was more susceptible to insecticide treatments than E. servus, but both had similar mortalities when exposed to organophosphates, pyrethroids, and carbamates. Dynamic evidence of internal feeding thresholds may potentially be the best method for determining the need for stink bug control in cotton, but further research is necessary to refine these thresholds and make them applicable to the Lower Texas Gulf Coast.