Succession and Significance of Several Hemipterans Attacking a Pistachio Orchard

Abstract

Two insecticides (carbaryl and permethrin) failed to control epicarp lesion (EL) in a pistachio orchard at Winters, Calif., because several hemipterous insect species continually invaded the orchard. Beating-tray and sweep-net samples revealed high adult populations of Psallus vaccinicola (Knight), Psallus ancorifer (Feiber), and Liorhyssus hyalinus (F.). Nymphs and adults of a Neurocolpus sp., Calocoris norvegicus (Gmelin), Thyanta pallidovirens (Stål),Lygus hesperus (Knight), and Leptoglossus clypealis (Heidemann) also were collected. A Phytocoris sp. (Miridae) was captured in a sticky trap placed in the orchard. Psallus vaccinicola, Neurocolpus sp., C. norvegicus, Phytocoris sp., and the rhopalid L. hyalinus induced EL on young pistachio fruits from early April to late May, while the pericarp firmness was ≤1.8 kg force. In contrast, nymphs and adults of T. pallidovirens and L. clypealis were able to cause EL until late June (pericarp firmness, 4.0 kg force), and kernel necrosis (KN) thereafter (pericarp firmness, 5.5–6.0 kg force). All insect species appeared to prefer feeding in or near the base of the fruit, which lignified later than the fruit apex. Also, significantly less KN (19–34%) developed in clusters protected with net bags compared with uncaged controls (48–65% KN).