Stop-Drop Sprays for Apples
Fruit drop at harvest time can result in heavy losses. The use of a stop-drop spray(s) may lessen fruit drop considerably. Although the use of stop-drop sprays can be fairly expensive, if preharves drop can be reduced substantially, the sprays are a good investment.
The traditional recommendation for the use of NAA as a stop-drop is to apply one spray at about 10 to 20 ppm when the first sound fruit of a variety begin to fall. Up to 7 to 10 days stop-drop activity may be achieed. An additional application may be made about 6 to 7 days after the first to get an additional 6 to 7 days of stop-drop activity. In many years, relatively poor control has been achieved with this spray, possibly because it was applied too late.
Preloading trees with NAA has given better stop-drop activity than a single application,. Preloading involves applying 5 ppm NAA each week for 4 weeks immediately precediing harvest. If harvest is delayed beyind the noral date, 2 additional weekly applications of 5 ppm NAA may be applied.
ReTain has given good stop-drop control when applied at the proper time. Use one application 4 weeks prior to anticipated harvest. Silwet L-77 or Sylgard surfactant should be used with the ReTain. ReTain will delay maturity which can result in improved fruit size and color for red varieties. However, if delayed maturity is not desired for the anticipated market, ReTain wll not be the best choice.