Abstract
Rhyacionia spp. and Retinia metallica (Busck) annually caused conelet losses (x ± SD) of 8.2 ± 3.0% and 5.4 ± 4.9%, respectively. Abortion and disappearance of conelets caused by Leptoglossus occidentalis Heidemann or physiological dysfunction averaged 65.7 ± 8.2% and were reduced by 13% when conelets were protected with screen cages. Survival of conelets averaged 19.5 ± 9.4%. Of those remaining, 76.8 ± 14.3% appeared healthy after the second growing season. Dioryctria spp. annually damaged an average of 14.2 ± 7.2% of the second-year cones. Mean annual seed potentials ranged from 77.4 to 127.1 seeds per cone, but mean annual seed yields ranged from only 0.4 to 8.1 filled seeds per cone. Caging cones to exclude L. occidentalis increased seed yield and efficiency and decreased damaged and empty seed. Feeding by L. occidentalis damaged an estimated 41% of initial ovules in cones harvested in 1985. Thus, insects can significantly reduce cone production and seed yield of ponderosa pine in southeastern Nebraska.
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