Issue link: http://read.dmtmag.com/i/64944
THE SPIDER POLE Cherry Cultivar—Most use in pears will likely be on early ripening cultivars that produce more ethylene on the tree, i.e., Red Clapp's Favorite, Bartlett, and perhaps Bosc in some years. AVG application considerations—The label calls for the addition of 0.05 to 0.1% organosilicone surfactant. Check the spreader type and rate, then spray a small area and allow it to dry to check for fruit spotting. Unlike NAA, which can be applied by air, AVG is always applied by ground in California. AVG postharvest effects—AVG-treated fruit may be handled differently by packers, processors, and marketers compared to NAA-treated or untreated fruit. For exam- ple, about 30% of Bartlett pears are destined for cannery use in California. Since AVG delays maturity, plan care- fully to ensure fruit quality is satisfactory to the possible range of buyers. AVG-treated apples have been shown to stay firmer, store longer, and develop less watercore than NAA-treated fruit, but, in some instances, AVG-treated fruit had slightly less sugar and color. Studies on pear have produced promising but inconsistent results, and research is ongoing in California. Inconsistencies might be due, in part, to the trial locations—both the need for a stop-drop and the uptake and action of a stop-drop may be influenced by environment. In addition to reduced firmness loss, better green color retention and reduced internal browning have been reported. Importantly, while research areas Future pear Some questions for future research are: • Can the initiation of internal ethylene develop- ment in pear be predicted to better time applica- tions? Ethylene curves have been developed for pear once harvested, but not for fruit on the tree. A • What active ingredient concentration is needed for different cultivars, tree size, and crop loads? Large trees may require more material per tree to achieve desired results. • How do growing season and weather affect matu- rity and enhance or impede results? Drop control in apples is better during cool versus warm years. Results in pear may differ in cool (premature ripening) versus warm years. • NAA costs about $45 versus about $265 per acre for AVG. One potential cost-saving strategy is to utilize lower rates of both NAA and AVG to control drop while allowing extended harvest. Data thus far in pears in California suggest that NAA alone gener- ally controls drop better than AVG alone, and NAA plus AVG controls drop better than either alone. Can these materials be used synergistically to allow for a more orderly harvest of larger fruit using less labor, while improving fruit quality as well? More research is needed under varying conditions. • Could preharvest applications of Harvista (sprayable 1-methylcyclopropene) be used as a potential stop-drop? www.goodfruit.com GOOD FRUIT GROWER MAY 15, 2012 37 VG could be a valuable new tool, along with NAA, for preventing premature fruit drop in pears. the AVG treatment is generally thought to result in more uniformly mature fruit than no treatment, AVG cannot "even out" the ripening of variably mature fruit going into storage. Once applied properly, AVG requires about seven days to diffuse into fruit cells, compared to one to four days for NAA. If effective, drop control lasts five to ten days, or more, depending on application timing. Effectiveness for 15 days has been reported for one pear cultivar. • Acknowledgements The authors wish to thank the following individuals for their invaluable contributions to this article: Wes Autio, Don Elfving, Duane Greene, Andrew Macnish, Tory Schmidt, Jim Schupp, David Sugar, and Broc Zoller. Rachel Elkins is with University of California Cooperative Extension, Lake and Mendocino Counties; Kitren Glozer, Department of Plant Sciences, University of California, Davis; and Michael Devencenzi, Ag Pest Management and Research, Woodbridge, California. Thinner NNO MORE LS! NEW Call Foothills Toda Foothills Today! Call