Ecological Studies on the Population of the Pear Leaf Miner, Bucculatrix pyrivorella KUROKO (Lepidoptera : Lyonetiidae) : VI. Effects of Injury by the Pear Leaf Miner on Leaf Fall and Photosynthesis of the Pear Tree

Abstract

Japanese pear trees infested with the pear leaf miner began to shed leaves late in August while in an uninfested orchard leaf fall began late in September. The following relationships were detected between cumulative density of leaf miners (N₂ for the 1st to 2nd generations; N₃ for the 1st to 3rd generations) and the period (D₅₀) from August 15 to the date of 50% leaf fall : log D₅₀=1.885-0.285 log(N₂+1) r²=0.66 log D₅₀=1.893-0.172 log(N₃+1) r²=0.82 Net photosynthesis was negatively correlated with cumulative density late in August. Tolerable pest densities were determined to be 0.5 and 1.0 per leaf for N₂ and N₃, respectively.