Mature `McIntosh'/MM.111 apple (Malus domestica, Borkh.) trees were treated to evaluate the response of root pruned trees to chemical thinning and to determine if reducing the crop load increased fruit size on root pruned trees. The trees were root pruned at full bloom in 1988 and 1989, by cutting on both sides of the row 1m from the trunk and 30cm deep. Water, 600mg/liter carbaryl, 5mg/liter napthaleneacetic acid (NAA), or NAA plus carbaryl were applied when fruit diameter was approximately 10mm. Trunk cross-sectional area (TCSA) was increased by thinning treatments in 1988, but root pruning had no effect. In 1989, root pruning reduced TCSA increment by 35%. Shoot length was reduced by root pruning both years. All treatments reduced percent fruit set in 1989, however root pruned trees and trees treated with NAA had the highest fruit numbers at harvest. Preharvest fruit drop was reduced by root pruning in both 1988 and 1989. Root pruning had no influence on the response of apple trees to chemical thinning. Removing a portion of the crop with chemical thinners was partially successful in counteracting the reduction in fruit size caused by root pruning.
The growth and fruiting of 10-year-old `Mcintosh'/M.7 apple trees were compared under the following weed management systems: 1)untreated control; 2) herbicide spray (paraquat + oryzalin); 3) rotary tilling applied in May, June and July; 4) rotary tilling plus herbicide (oryzalin); 5) rotary tilling plus oats sown in August. All weed control methods increased tree growth compared to the untreated control over three years. Yield and fruit size were increased by the herbicide and the rotary tilled treatment. Rotary tilling plus herbicide increased yield but fruit size was larger than controls in 1990 only. Rotary tilling plus oats produced yield and fruit size equivalent to the control. In 1989 and 1990 rotary tilling alone provided less weed control compared to the herbicide treatment, while in July 1991, the reverse was true. Rotary tilling with herbicide and with oats have demonstrated weed control comparable to or better than the herbicide treatment except for the rotary tilled plus oats treatment in 1990. There were no differences among treatments in fruit color, maturity and percent soluble solids.