Armoured scale (Hemiptera: Diaspididae) aerial invasion into kiwifruit orchards from adjacent host plants

Abstract

The aerial dispersal and settlement of armoured scale into kiwifruit Actinidia deliciosa (A. Chev.) orchards was assessed using scale-free kiwifruit trap plants. Greedy scale Hemiberlesia rapax (Comstock) invasion was monitored over five seasons from 1985 to 1990 in an orchard adjacent to taraire trees Beilschmiedia taraire Benth. and Hook. f. Two major periods of invasion occurred in summer and autumn corresponding to the two scale generations on taraire. The intensity of invasion varied between generations and seasons with a peak rate of 8.7 scale/ 100 leaves per day in January 1987. Scale invasion was highest in kiwifruit blocks immediately adjacent to the taraire trees and declined in blocks further away. A survey of 25 kiwifruit orchards identified clear gradients in both greedy scale and latania scale H. lataniae (Signoret) settlement, with higher levels closest to host plants. Scale invasion was reduced where host plants were removed or when host plants were regularly sprayed with insecticides after trimming to ensure full coverage of the sprays. An assessment of the risk of scale invasion into kiwifruit orchards is considered important in determining both the frequency and timing of insecticide applications in order to obtain a scale-free crop.

Keywords:

• armoured scale
• Hemiberlesia rapax
• Hemiberlesia lataniae
• kiwifruit
• invasion
• host plants