Behavioral and electrophysiological responses of Arhopalus tristis to burnt pine and other stimuli

The exotic longhorn beetle Arhopalus tristis is a pest of pines, particular ly those damaged by fire, and a major export quarantine issue in New Zealan d. Actinograph recordings of caged individuals showed that males and female s were most active from dusk to midnight. Olfactometer experiments indicate d that females moved upwind toward odors from burnt pine (80%, N = 75), com pared to unburnt pine (20%). Oviposition choice tests showed that eggs were predominantly laid on burnt logs (79%, N = 20), compared to unburnt logs. Beetles were trapped by funnel traps baited with burnt (mean catch per trap 7.8) and unburnt (mean catch 4.1 per trap) pine bark from inside a screen cage (4 x 3 m), while unbaited traps had a mean catch 0.1 beetles (N = 8 re plicates). The treatment of burnt pine bark with a 1:1:2 mixture of green l eaf volatiles (E)-2-hexen-1-ol and (E)-2-hexenal) in mineral oil as a repel lent reduced trap catch by fivefold in a similar experiment (mean catches o f 1.2 beetles per trap to burnt pine bark plus repellent treatment and 6.2 beetles per trap to burnt pine bark alone). The treatment of burnt pine bar k with this solution also reduced oviposition by 98.5% (mean eggs per log o f 11.1 on burnt pine and 0.3 on burnt pine plus repellent), indicating that oviposition cues have the potential to be significantly disrupted. The ele ctrophysiological responses of adult beetles were recorded to a range of od orants. Normalized responses to monoterpenes known to occur in Pinus radiat a ranged from about 20 to about 150, with alpha -terpineol giving the great est responses in both sexes. Green leaf volatiles also gave high responses. The potential exists to improve the management of this insect using chemic al cues in various ways.