Issue link: http://winesandvines.uberflip.com/i/122527
grapegrowing normally 6 to 12 inches long during the period of rapid cluster elongation.) Foliar applications of gibberellin during the cluster elongation period accentuate the internal gibberellin supply and have negligible effects on yield.8,19 There is no effect on wine quality.19 It is too late to apply gibberellin after cluster stems have elongated so far that flowers on lateral braches have separated, due to the risk of excessive flower abscission and yield reduction (Figure 4).19 With very late applications, gibberellin causes very little cluster elongation.3 Late gibberellin applications may also induce primary bud death.4 Gibberellin application concentration The quantity applied is as important as timing of application. For gibberellin, grape clusters respond to the concentration of active ingredient in the solution rather than the active ingredient per acre.2 Varieties differ in their sensitivity to gibberellin, and as a result the appropriate application concentration varies accordingly. Due to the presence of seeds, all wine grape varieties are highly sensitive to gibberellin, especially compared with some other crops like seedless table grapes, citrus and cherries. BreAK tHroUGH tHe PowderY MILdew BArrIer PM has left the building Get M-Powered Of all the powdery mildew fungicides on the market, only one offers the Enhanced Systemic ProtectionTM of tetraconazole, a powerful and proven active ingredient found in Mettle® 125 ME fungicide. With strong preventive and post-infection action; Mettle aggressively attacks and controls powdery mildew longer, breaking the barrier to improved fruit quality and yield, with no adverse crop effect. Only Mettle contains a "tetrafluoroethoxy" chemical structure giving it optimized systemic movement throughout the plant, including new and emerging tissues. This enhanced systemic protection is delivered in a state-of-the art formulation, helping provide superior and consistent mildew control and longevity compared to other fungicide brands. And, it's tank mix-flexible for broader disease control programs. This season, M-power your crop with the breakthrough protection of Mettle fungicide. You'll feel M-powered too. www.isagro-usa.com ©2013 Isagro USA. All Rights Reserved. Always read and follow label directions. Mettle is a registered trademark of Isagro USA. Gibberellin must be applied at the proper time and in the proper concentration to avoid undesirable side effects related to fruit yield, both during the year of application and the following year. At low concentrations (2.5 to 20 ppm depending on variety), gibberellin induces moderate cluster elongation and minimizes bunch rot in wine grapes. At high concentrations, however, gibberellin causes clusters to stretch excessively and creates cluster deformation including twisting.3 They also decrease bud fruitfulness of seeded grape varieties.13,21 At very high concentrations (50 ppm), gibberellin will prematurely defoliate grapevines.3 Other gibberellin considerations Gibberellin is registered with the Organic Materials Review Institute (OMRI) and therefore is suitable for organic-manpr actica l win ery & vin e ya rd MAY 20 13 73