Re: [apple-crop] Late summer drop and fruit size
Hello Vincent, I usually am not an active participant in post but I thought that I might weigh in on your comment since I have been doing preharvest drop research for a number of years. Jim Krupa our technical assistant has been involved and he expressed an interest in doing an experiment to find out a little more about why fruit drop? The experiment was done on McIntosh and Delicious over two seasons. Briefly, 6 to 10 trees were selected. Half were designated to be drop trees and half were designated to be harvest trees. The experiment was carried out from the time the first fruit dropped until most of the fruit were on the ground. Each morning fruit under the drop tree were picked up and taken to the lab where they were weighed and internal ethylene was determined on each fruit. Red color, flesh firmness, soluble solids and starch rating were determined and seed number counted. This was repeated for fruit that dropped at 3:00 pm. Three times a week 10 fruit were harvested from the harvest trees and similarly processed. Seed number was not associated with fruit weight or drop although this has been documented in the literature. I suspect that this may be an issue when there are 0, 1 or 2 seeds per fruit but that was not the case here. The conclusion that we came to was all fruit that dropped were climacteric and showed signs of ripening (internal ethylene greater than 1 ppm, increased red color and reduced starch content). The appropriate question to ask then may be why did the fruit that drop ripen early? We know from research done here in the 1980s that fruit with very low seed number are also low in calcium. Fruit low in calcium may ripen earlier. I offer another explanation. Many of you know that recent reserach has indicated that a carbohydrate balance deficiency in trees druing June drop is a factor that infouences thinner response as well as the severity of June drop. This is based on the original work of Alan Lakso and taken to the field by Terence Robinson. The model is good and the practical application for thinning is important. However, if one looks at the carbon balance in Alan's model over the growing season you will note two things. First, there is likely to be a deficit during the June drop period and this has been highly publicized. A second period of deficit occurs at harvest time and this has been largely ingnored. It makes perfect sense since as fruit ripen there is a large increase in respiration (climacteric) which fuels the synthesis of enzymes involved with ripening. Vincent mentioned that were might be a shelf shedding mechanism in trees. When trees have a carbohydrate deficit they must respond. In some instances this response is shedding of fruit. Even with fruit it is survival of the fittest. This occurs at June drop, why not at harvest? Drop is frequently controlled by spurs. If spurs are shaded or leaf area is small then the fruit on these spurs are most likely to drop early. Mite damaged trees also show early drop. We have followed drop from McIntosh over the course of the season which often occurs over a 7 week period. Fruit increase in size about 1% per day they are on the tree. Consequently, it is not surprising that average fruit sized will increase over the harvest season. This is one of the attributes of using drop control compounds. I am not sure if I have helped in this discussion but drop can be precipitated by several events (seed number, heat, lack of light, reduced leaf area, damaged leaves, etc) but I do believe it comes right back to any factor that stimulates ripening will lead to increased drop. Duane On 1/13/2014 12:12 PM, Vincent Philion wrote: Hello, I'm analyzing some data and I have seemingly contradictory results. I'm hoping someone can comment and make sense of this: For a number of randomly selected trees, fruit drop was recorded starting late summer until harvest. For each tree, we recorded total fruit drop (and weight), harvested fruit (and weight) and the total (drop + harvest). As I was looking at the data, I noticed average harvested fruit size (weight/number) was related to Total fruits per tree... Nothing strange, until I realized harvested fruit size INCREASED with Total fruit number on tree. As if the fruit dropping left more energy for the remaining fruits to grow? I was expecting harvested fruit size to be smaller on trees that had more total fruit, not the other way around. I'm not sure this late natural fruit drop can be compared to very late hand thinning, but does anyone know if fruit size increase can be linked to late thinning (notwithstanding total yield that can go down)? Maybe this is normal? Any comment welcome! Vincent http://www.irda.qc.ca/assets/client/img/logo.png *Vincent Philion*,M.Sc. agr. Microbiologiste Phytopathologiste pomiculture *Institut de recherche et
Re: [apple-crop] Late summer drop and fruit size
Hello! Thank you all for your input! I did not explain why I was looking at drop and fruit size: it was an experiment on the use of ReTain. In the end I’m not sure I can pinpoint the reason this increased fruit size on trees with more apples (notwithstanding ReTain), but your input underlined that a number of variables can be involved! I liked Duane’s idea. If you’re curious, the report will read: ReTain Treatments significantly increased harvested McIntosh yield as compared to the control (p0.0001). Average fruit size at harvest was proportional to the total number of fruits on the trees present at the start of the experiment (p=0.01) and fruits treated with ReTain were larger than in the control (p=0.02). The effect of ReTain on harvest was expected (drop prevention) but the effect on fruit size was undetectable if the model was not adjusted to the initial crop load (thus my question) So the next question is now: why are ReTain treated fruits bigger than untreated fruit at harvest? bye for now, Vincent On 14janv., 2014, at 10:06, Duane Greene dgre...@pssci.umass.edumailto:dgre...@pssci.umass.edu wrote: Hello Vincent, I usually am not an active participant in post but I thought that I might weigh in on your comment since I have been doing preharvest drop research for a number of years. Jim Krupa our technical assistant has been involved and he expressed an interest in doing an experiment to find out a little more about why fruit drop? The experiment was done on McIntosh and Delicious over two seasons. Briefly, 6 to 10 trees were selected. Half were designated to be drop trees and half were designated to be harvest trees. The experiment was carried out from the time the first fruit dropped until most of the fruit were on the ground. Each morning fruit under the drop tree were picked up and taken to the lab where they were weighed and internal ethylene was determined on each fruit. Red color, flesh firmness, soluble solids and starch rating were determined and seed number counted. This was repeated for fruit that dropped at 3:00 pm. Three times a week 10 fruit were harvested from the harvest trees and similarly processed. Seed number was not associated with fruit weight or drop although this has been documented in the literature. I suspect that this may be an issue when there are 0, 1 or 2 seeds per fruit but that was not the case here. The conclusion that we came to was all fruit that dropped were climacteric and showed signs of ripening (internal ethylene greater than 1 ppm, increased red color and reduced starch content). The appropriate question to ask then may be why did the fruit that drop ripen early? We know from research done here in the 1980s that fruit with very low seed number are also low in calcium. Fruit low in calcium may ripen earlier. I offer another explanation. Many of you know that recent reserach has indicated that a carbohydrate balance deficiency in trees druing June drop is a factor that infouences thinner response as well as the severity of June drop. This is based on the original work of Alan Lakso and taken to the field by Terence Robinson. The model is good and the practical application for thinning is important. However, if one looks at the carbon balance in Alan's model over the growing season you will note two things. First, there is likely to be a deficit during the June drop period and this has been highly publicized. A second period of deficit occurs at harvest time and this has been largely ingnored. It makes perfect sense since as fruit ripen there is a large increase in respiration (climacteric) which fuels the synthesis of enzymes involved with ripening. Vincent mentioned that were might be a shelf shedding mechanism in trees. When trees have a carbohydrate deficit they must respond. In some instances this response is shedding of fruit. Even with fruit it is survival of the fittest. This occurs at June drop, why not at harvest? Drop is frequently controlled by spurs. If spurs are shaded or leaf area is small then the fruit on these spurs are most likely to drop early. Mite damaged trees also show early drop. We have followed drop from McIntosh over the course of the season which often occurs over a 7 week period. Fruit increase in size about 1% per day they are on the tree. Consequently, it is not surprising that average fruit sized will increase over the harvest season. This is one of the attributes of using drop control compounds. I am not sure if I have helped in this discussion but drop can be precipitated by several events (seed number, heat, lack of light, reduced leaf area, damaged leaves, etc) but I do believe it comes right back to any factor that stimulates ripening will lead to increased drop. Duane On 1/13/2014 12:12 PM, Vincent Philion wrote: Hello, I’m analyzing some data and I have seemingly contradictory results. I’m hoping
