Issue link: http://read.dmtmag.com/i/117824
20 10 2013 2011 2009 2007 2005 2003 0 2001 Millions of bushels 30 Yield Predicted SOURCE: NASS Data MaxCel recommendations Thinning difficulty crisis occurs with carbohydrate levels. Reserves are used up, and photosynthesis Thinning difficulty, by variety may not provide adequate levels of carbohydrates. In this competition, leaves and Easy Intermediate Difficult shoots win, and fruit loses. Fruit fails to Ginger Gold McIntosh Spur Delicious grow and falls off.��� Temperature and light conditions Empire Paulared Gala add to or reduce stress, making thinning easier or harder. Cortland Honeycrisp Fuji On bright days when light conditions Idared Rome are good, there is an increased supply of carbohydrates from photosynthesis, and Mutsu Spartan Golden Delicious fruit is hard to thin. Under low light Jonagold conditions, fruit is easier to thin. Low temperatures create low demand Nonspur Rome Stayman Cameo for carbohydrates, so fruit is hard to thin when it���s colder. High temperatures create Jonathan high demand for carbohydrates, and fruit is easier to thin. The best conditions for thinning are when light is low and temperature is warm (low supply and high demand for carbohydrates), and the worst conditions are when there is lots of light, but it���s cool (high supply, low demand). As leaves and fruits get larger, leaves produce more energy and fruit becomes harder to thin. The best time to thin is when a warming trend is forecast and temperature is rising. Varieties Michigan apple production history, 2001������2012 Desired thinning strength Aggressive Moderate Slight Hard 150 ppm + Sevin 100 ppm + Sevin 100 ppm Moderate 100 ppm + Sevin 75 ppm + Sevin 75 ppm Easy 75 ppm + Sevin 75 ppm 50 ppm SOURCE: Phillip Schwallier ���About the time fruitlets reach ten millimeters in size, a crisis occurs with carbohydrate levels.��� ���Phil Schwallier Orchard Proven, University Tested Bee-Scent���s natural, non-toxic pheromone ingredient induces the foraging behavior in honey bees, increasing the number of bee-to-blossom visits at each tree. The result is a higher percentage of blossom set and increased fruit yields. ��� Increase Fruit Set on Pears, Cherries and Braeburn Apples! ��� Increase Size Potential of Gala Apples by Increasing the Seed Complement! ��� Conforms to National Organic Program Standards ��� WSDA Organic Certified 610 Central Avenue Billings, MT 59102 (406) 248-5856 1-800-735-5323 www.scentry.com For more information, call 1-800-735-5323 or visit www.scentry.com. Bee-Scent research data obtained from Dr. Dan Mayer, Washington State University Help with thinning Over the last few years, researchers have put thinning theories into advice that can help growers as they go through the season. Researchers at Cornell University, especially Dr. Alan Lakso and Dr. Terence Robinson, have led the effort to create a carbohydrate model, called MaluSim, that has been integrated into grower advisory services. In Michigan, where Schwallier cooperated in validating the model, that information is part of the EnviroWeather network. Similar networks are in New York and in Pennsylvania, where work on the model was also done. Schwallier advised that growers apply their thinners, wait four or five days to see results, then thin again if necessary. Another tool they can use to see how thinning is progressing was developed by Dr. Duane Greene at the University of Massachusetts. Realizing that growers are reluctant to make repeated thinner applications without knowing how effective their treatments have been, he developed his ���fruitlet model.��� This involves marking and measuring apples before thinning and again seven to ten days after applying the thinner. Those apples growing at less than half the rate of the fastest growing fruitlets will fall off at some point, probably during June drop. The method was described in the April 15, 2010, issue of Good Fruit Grower magazine and can be accessed in the archives at www.goodfruit.com. ���Thinning predictions from 13 experiments over four years confirmed that a prediction can be made within seven to ten days with near 95 percent accuracy if 130 to 140 heating degree units (using a base of 50��F) have been accumulated after the thinner application,��� he said then. ���We followed the growth rate of thousands of fruit, and slow fruit growth is highly correlated with fruit abscission. Rapid fruit growth is highly correlated with fruit set.��� When thinning, growers need a target. Schwallier suggests that target should be eight apples per square centimeter of trunk cross-sectional area for most varieties; five apples for Honeycrisp. That can be calculated on a limb-by-limb basis for mature trees, but on younger trees, it can be done from the trunk, especially if the trees are being pruned on a renewal pruning system. Alternatively, growers can calculate backward by dividing expected yield in bushels per acre by number of trees per acre. Figure 100 apples per bushel, multiply by bushels, and divide by trees per acre to get apples per tree. ��� 10 April 1, 2013 GOOD FRUIT GROWER www.goodfruit.com