Effects of integrated control measures on earthworms, leaf litter and Venturia inaequalis infection in two European apple orchards

Two-, three-year studies were conducted to determine the effect of combining chemical (fungicide and urea) and non-chemical (leaf shredding) sanitation treatments on earthworm populations, leaf litter density (LLD), and leaf and fruit infections caused by Venturia inaequalis in Dutch and Hungarian integrated apple orchards from 2000 to 2002 and 2001 to 2003, respectively. The combined sanitation treatment included urea and captan sprays applied to the tree and to the orchard floor and the shredding of fallen leaves in the previous autumn and winter. The earthworm numbers were significantly higher in the sanitation treatment compared to the treatment without sanitation in 2001 and 2002 (P < 0.05) at Randwijk (The Netherlands) and in 2002 and 2003 (P < 0.05) at Derecske (Hungary). LLD decreased continuously from leaf fall in late autumn to mid-May the following spring at Randwijk, which was explained well by a linear function fitted to the LLD data, with R2 values ranging from 0.82 to 0.99. Model coefficients for the sanitation plots were significantly different (P < 0.05) from those of the non-sanitized plots in 2001 and 2002. At Derecske, LLD started to clearly decrease in both treatments from February 2001 and 2002 and from March 2003 to late spring, and this was explained well by an exponential function fitted to the LLD data, with R2 values ranging from 0.80 to 0.97. Model coefficients for the sanitation plots were significantly different (P < 0.05) from those of the non-sanitized plots only in 2002. In most years and at both sites, the sanitation treatment resulted in significantly lower (P < 0.05) scab incidence on spur-leaf clusters compared to the treatment without sanitation. However, the sanitation effect on scab levels on older leaves and fruits was low and varied by year and location. The results are discussed in connection with the environmental conditions in the two countries.