The obliquebanded leafroller (OBLR), Choristoneura rosaceana (Harris), is a moth pest of pistachio and other crops (e.g., apple, cherry, prune, peach). In most infested crops, the larvae damage fruit and result in 1-4% fruit damage. In pistachio, while the larvae can feed on both pistachio leaves and nut clusters. High OBLR population densities can cause extensive defoliation. We hypothesize that leaves are preferred and there is little damage to the nuts. To study, OBLR population dynamics were followed in six pistachio blocks. The number of damaged clusters and leaves (OBLR strikes) were monitored. The results of bi-weekly counts showed a steady rise in damaged leaves from late April to August (1.25 damaged leaves/sec. of observation). After mid August, there was a reduction in OBLR density, with most “strikes” with <10% live larvae. On average, <2% of the nuts showed “signs” of OBLR feeding, and there was no relation between OBLR leaf and cluster damage. To evaluate larval feeding damage, 2nd instars were exposed to clusters with or without leaves (touching the cluster or free from the cluster). Results showed when leaves were present, an average of 72.5% had feeding damage. Significantly fewer nuts had external damage (10.5%) and the slight external feeding typically did not affect nut development. Internal nut damage was infrequently (3%). The results confirm that OBLR larvae fed mostly on the pistachio leaves rather than clusters. However, without the access to leaf, they survived feeding on the nut skin causing small external damage.
Species 1: Lepidoptera Tortricidae Choristoneura rosaceana (obliquebanded Leafroller)
Keywords: larval feeding, damage rating
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