Damage caused by Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae) on Pinus pinea L. cones varies with feeding season

Abstract

1. The commercialization of pine nuts generates major economic benefits for the Mediterranean basin. This has been reduced due to an increase in cone and seed damage associated with the spread of the western conifer seed bug (WCSB) throughout the Mediterranean region and the Dry Cone Syndrome appearing on pine cones. Studies on several conifer species have associated cone and seed damage with WCSB feeding. 2. To relate cone and seed damage of stone pine to WCSB feeding, one exposure and exclusion trial of cones to the feeding of the natural WCSB population was carried out. To determine the seasonality of cone and seed damage caused by this pest, another trial consisting of bagging cones with insects was performed with first-, second- and third-year cones at different stages of cone development. 3. The natural WCSB population was associated with cone abortion in second-year cones (unprotected: 43.6% vs. protected: 2.7%), a decreased number of seeds per cone (82.0 vs. 105.3), kernel yield (1.8% vs. 3.8%) and proportion of sound kernels (35.6% vs. 73.6%), and numerous types of kernel damage. 4. Cone mortality in first- and third-year cones bagged with insects decreased as the bagging date advanced. A temporal sequence of kernel damage in third-year cones (aborted, dry embryo without endosperm, and totally or partially damaged endosperm) was reported for seed development and the timing of WCSB feeding. 5. Our findings may be useful in the management of WCSB populations to prevent significant damage to the stone pine nut crop.