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Three experiments were conducted on 'Empire∑apple (Malus ×domestica Borkh.) to evaluate the effects of hard water, calcium chloride (CaCl 2), water condition- ers, surfactants, and captan fungicide on the growth reduction and fruit cracking caused by prohexadione-calcium (PC). Two applications of 63 mg·L-1 PC provided season-long growth control in two studies. Adding a water conditioner to PC reduced shoot growth more than an application of PC in hard or soft water in one New York study. Ammonium sulfate (AMS) and Choice were equally effective water conditioners. PC provided no growth control of water sprouts and had no effect on fruit set or yield. PC applied at 250 mg·L-1 reduced fruit size. 'Empire∑ fruit cracking and corking was severe, despite the use of only 63 mg·L-1 PC in two of the three experiments. This damage was exacerbated by the addition of a water conditioner, however AMS applied with a surfactant but with- out PC had little or no effect on either the severity or extent of fruit injury. In a third experiment, the addition of surfactants, CaCl 2, or captan to 250 mg·L -1 PC plus a water conditioner had no effect on the severity of fruit damage. Fruit cracking caused by PC increased preharvest drop in two of three experiments, and increased postharvest rot in the Geneva, N.Y., experiment where fruit were stored prior to grading. Application of PC plus a water conditioner reduced estimated gross return per hectare for 'Empire∑ . We conclude that the fruit injury is caused by the formulated PC product itself under certain environmental conditions, and that this product should not be used on 'Empire∑ . Chemical name used: calcium 3-oxido-4-proprionyl-5-oxo-3-cyclohexine-carboxylate (prohexadione-calcium (PC)). applied at excessive concentrations, under poor drying conditions, or when applied with pesticides (Stiles and Reid, 1991). In large scale, unreplicated trials, 'Empire∑ cracking was worse when AMS was added to the PC spray mixture than when it was omitted (Butch Palmer, ACDS Research, Williamson, N.Y., unpublished data). A similar 'Empire∑ fruit injury has been attributed to a tank mix of captan fungicide with CaCl 2 or surfactants under slow drying conditions (Rosenberger, 1999). The captan label cautions that necrotic spotting of newly formed foliage can occur on sensitive cultivars when this fungicide is applied at high rates under slow drying conditions, but makes no mention of fruit damage. Users are cautioned against the use of spreader-stickers, and are advised to avoid tank-mixing captan with sulfur, oil, or "solvent formulations" of other pesticides. 'Empire∑is widely planted throughout eastern North America, and there are many instances when it would be desirable to man- age tree vigor using PC. The objectives of this study were 1) to evaluate the effect of hard water, with and without water conditioners, on the efficacy of vegetative growth reduc- tion and incidence of 'Empire∑ fruit cracking caused by PC; and 2) to evaluate the effect of surfactants, captan, and CaCl 2 on the efficacy of growth reduction and incidence of 'Empire∑ fruit cracking caused by PC.

Effect of Water Conditioners and Surfactants on Vegetative Growth Control and Fruit Cracking of `Empire' Apple Caused by Prohexadione-calcium