Grape Scale (Homoptera: Diaspididae) Biology and Management on Grapes

Abstract

Grape scale, Diaspidiotus uvae (Comstock), is a pest of grapes, Vitus spp., in the south-central United States. This study compared Julian days and cumulative degree-days (DD at base 10°C accumulated after 1 April) to grape scale biology and control in Arkansas. On the average, first generation crawlers began emerging 14 May (274 DD) and peaked on 20 May (356 DD). First generation winged males began emerging on 26 June (794 DD) and peaked 13 July (1,108 DD). Second generation crawlers began emerging on 20 July (1,166 DD) and peaked on 12 August (1,549 DD). Second generation wingless males began emerging on 31 August (1,857 DD) and peaked on 18 September (2,026 DD). Relative to untreated vines, vines treated with chlorpyrifos at bud swell (early April) or as late as early May (near grape bloom) realized at least an eight-fold reduction in the number of crawlers and adult males per sticky tape trap. Vines receiving the second application near grape bloom had significantly fewer crawlers in May, August and September than vines sprayed once in late April. A chlorpyrifos treatment in early April provided at least a 30-d lethal residual on grape against grape scale crawlers that emerged during May.