Interaction of early-season herbicide injury, tobacco thrips injury, and cultivar on peanut

Peanut (Arachis hypogaea L.) can tolerate severe early-season injury by tobacco thrips [Frankliniella fusca (Hinds)], and controlling populations usually is not recommended in the southeastern USA. Field observations, however, indicated that injury from early-season thrips infestation may exacerbate injury caused to peanut by early postemergence herbicide application. Studies were conducted near Jay and Marianna, FL, during 1989 and 1990 to evaluate the interaction between peanut cultivar, preplant incorporated application of vernolate (S-propyl di-propylcarbamothioate), postemergence application of alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] plus paraquat (1,1'-dimethyl-4,4'-bipyridinium ion) and thrips suppression with foliar application of acephate (O,S-dimethyl acetylphosphoroamidothioate). 'Southern Runner' was more susceptible than 'Florunner' to early-season stress from insect and herbicide injury. Injury from preplant incorporated herbicide alone, postemergence herbicide alone, or thrips alone usually was not sufficient to cause long-term damage to peanut growth or to adversely affect peanut maturity or yield. When two or all of these factors impacted peanut simultaneously, however, delays in crop maturity and reduced yields (up to 11%) were often observed. Early-season suppression of tobacco thrips often alleviated the detrimental effects to peanut. Suppression of thrips populations should receive greater consideration in future integrated pest management programs of peanut to avoid interactions with early-season herbicide stress, especially when growing Southern Runner.