Good Fruit Grower

May 15

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GOOD TO KNOW A research report from Rachel Elkins, Kitren Glozer, and Michael Devencenzi, California. Using AVG to reduce VG is a substituted amino acid derived via fermenting the naturally occurring antibiotic rhizobitoxine. After its activity was discovered in 1972, it received a federal Experimental Use Permit in 1995 and a Section 2C label in 1997. It is formulated by Valent BioSciences as a 15% active ingredient wettable powder under the trade name ReTain. AVG is approved for organic use, but check acceptability with individual certifiers. AVG temporarily inhibits ethylene biosynthesis by blocking the vital enzyme ACC syn- thase, required in the ethylene synthesis pathway. This contrasts with NAA, which acts strictly as an abscission control agent, and often hastens ripening. Since AVG delays ripening, fruit can hang an extra five to ten days or more to size. This may also enable a more orderly harvest using fewer workers, especially in blocks and cultivars that mature rapidly, such as Red Clapp's Favorite, Bartlett, and perhaps Bosc in some years. AVG timing—AVG has shown more consistent effects on apple than on pear, partially because pears produce much less ethylene on the tree than apples, making spray timing more difficult. Timing is critical because once ethylene autocatalysis (ethylene synthesis is promoted by the presence of ethylene) begins, AVG will be less or not effective. Timing will vary with fruit maturity, especially in years with extended bloom. AVG should be applied prior to the onset of the preclimacteric rise of ethylene in the fruit. Late-season fruit with high internal ACC synthase and ethylene levels will overcome some or all of the effect of AVG. Label timing for pears is one to two weeks prior to first anticipated normal harvest period of untreated fruit. Table 1 NAA and AVG compared A comparison of NAA and AVG for control of preharvest fruit drop in pome fruit. Parameter What is blocked NAA Stem loosening Fruit softening Rescue option? Days to "take effect" Split sprays helpful? Reentry interval Preharvest interval Advanced No effect Advanced Yes ~2-4 AVG Ethylene production Drop delay (approximate) 10-14 days (5-7 some apples) 14 days or more Fruit ripening Fruit color Slowed Delayed Delayed Applied (relative to drop) 5-10 days 4 weeks apples/ 2 weeks pears No ~7 (can be 10-14 in apples) No (pears) Yes (apples) No 24 hours 2 days SOURCE: Jim Schupp, Pennsylvania State University 12 hours 7 days preharvest drop This is the second part of an article comparing NAA and AVG (aminoethoxyvinylglycine hydrochloride) for delaying preharvest drop in pears. Available (some restrictions apply) Delivery We MANUFACTURE metal stakes, posts, crossarms & braces Your Source for All Vineyard & Orchard Trellising Products Anchors Crossarms ! 509.781.0898 LOCAL 36 MAY 15, 2012 GOOD FRUIT GROWER

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