Apple leaf shredding as a non-chemical tool to manage apple scab and spotted tentiform leafminer

Abstract

The effect of leaf-shredding on Venturia inaequalis , and Phyllonorycter blancardella and its parasitoids was studied under orchard conditions, respectively, during four and three overwintering periods. Naturally scab-infected leaves were collected in the fall. Five treatments were compared in 1995 and 1996, i.e. shredded leaves, urea (5%), Microsphaeropsis ochracea , Athelia bombacina and untreated leaves (control). In 1997 and 1998, two more treatments were added, i.e. shredded leaves treated with 5% urea and shredded leaves treated with M. ochracea . The ascospore production from a sample corresponding to the average area of nine leaves was evaluated for each spore ejection period from late April to early July. All treatments applied in fall 1995 and 1996 significantly reduced ascospore production in 1996 and 1997, and there was no significant difference among treatments. The most efficient treatment was urea followed by leaf shredding, M. ochracea , and A. bombacina , with reduction in ascospore production of 92.1, 85.2, 84.8, and 80.6%, respectively. In 1998 and 1999, highest reduction in ascospore production was obtained for combined treatments, i.e. shredding and M. ochracea or shredding and urea, with 93.9 and 90.5% reduction in ascospore production, respectively. Apple leaf-shredding in the fall of 1994, 1995 and 1996 significantly reduced emergence of both adult P. blancardella and adult parasitoids associated with the leafminer . Leaf-shredding is a sanitation practice that should be systematically done as a long-term tactic as part of a sustainable integrated pest management program in apple orchards.