Introduction to Apple fruit drop causes, control methods: Apple (Malus pumila) is an important fruit. Apples are consumed fresh but a small part of the production is processed into juices, jellies, canned slices, and other items. The apple is a temperate fruit crop. One of the greatest problems that apple growers face is the fruits drop before it can be harvested. Some cultivars, such as ‘McIntosh’, are mainly prone to this problem. Drop on several cultivars can exceed 20%, but on the drop-prone cultivars, it is not uncommon to have losses exceed 50%. In this article we also discussed below topics;
- Causes of premature apple fruit drop
- Fruit drop causes and control
- What makes apples fall from trees
- Apple premature fruit drop
- Why do apples fall off the tree prematurely
- Why does apple tree drop fruit
A step by step guide to Apple fruit drop causes, control methods
Fruit drop is the detachment or separation of the fruit from a branch of a tree, caused by the formation of separation of a layer of cells on the fruit stalk due to a series of physiological events. There are many reasons why apples prematurely drop; some are a part of the normal life cycle, others indicate a pest infestation and environmental effect. It is very important to determine the cause in each case before rushing to treat a potential problem. One must know the controlling process of Apple fruit drop by learing the causes and factors behind it.
Fruit drop in apples
First drop in apples
The first drop begins just after the petals fall from the tree and may continue for the next 2 or 3 weeks. At this period the apples are not much bigger than a pea when they start to drop. Inadequate pollination is the main cause of apples dropping at this stage. Most apple tree varieties produce little or no fruit when pollinated by their pollen. They want to cross-pollinate with a different apple variety.
Reasons for apple trees dropping fruit
Apples could have a couple of periods when fruit drop occurs. The first is often after the flower petals fall off and may last 2 to 3 weeks. The small dropping fruits are the ones that were not pollinated, so they will not develop further. Many fruit species want to be pollinated by bees. Lack of pollination can be the result of cold or wet weather during the bloom period, or by a lack of honey bees. And, if there is freezing weather just before the flower buds open, more fruit drop may occur.
In case if you miss this: Post Harvesting Technology of Fruits.
Lack of water can also cause premature fruit fall of apples, so be sure to keep a watering schedule and mulch to retain moisture and regulate soil temps. Other reasons for apple fruit fall are a bit more sinister. Attack by pests or disease can result in fruit drop. For this reason, adherence to a pesticide spray schedule is very important. Be sure to follow the manufacturer’s instructions and don’t spray when pollination is taking place while you don’t want to kill off the bees and other pollinators or you really won’t get any apples. Because of pollinators, another reason an apple tree might shed fruit is if there is inadequate pollination during bloom time. Keep pollinators within 50 feet of the tree, encourage beneficial insects and bees by companion planting other flowering plants nearby, and avoid using pest control sprays when the apple tree is in bloom.
The second drop more commonly known as the June drop and seems to cause gardeners the most concern. By this time, the apple fruits are between one-half inches to one inch in diameter. The most accepted explanation for the June drop in apple trees is the temporary lack of adequate carbohydrates in the plant. Trees need plenty of carbohydrates to produce fruits. Cloudy weather and low temperatures reduce the rate of photosynthesis, which causes a carbohydrate shortage. On the other hand, high nighttime temperatures stimulate a higher respiration rate, which further lowers carbohydrate reserves.
Environmental Factors of Apple fruit drop causes
Honeybees are the important pollinator of apple trees. Cold, rainy weather prevents bees from flying and then collecting pollen. If rainy weather persists throughout the flowering period, honeybees will not get the chance to pollinate the apple blossoms or flowers of an apple tree. When apple blossom buds begin to open, and they become vulnerable to freezing temperatures. The further along they are in the opening, and the more susceptible to the cold they become. Freezing temperatures during flower bud development or blossoming is a main environmental cause of early apple drop.
Reasons for Apple trees drop their fruit early
Some Apple fruit trees will naturally thin themselves by dropping excess fruit prematurely. Often, a period of stress (a long, hot summer with very little rain) will cause an apple tree to abort its fruit to conserve energy. Apple trees need deep watering during drought. Lack of pollination can effect in pea-size fruit that falls off prematurely.
You should not miss this: Medicinal Plants Cultivation, Farming Guide, Training.
To encourage fruit trees to yield the maximum amount of healthy fruit, then you can use dormant oil as well as insecticide and fungicide treatments. Whether you select to use synthetic chemical products or the less toxic, more environmentally friendly ones, adherence to a strict schedule is very important. The first treatment, applied in early March, contains dormant oil sprayed thoroughly over the tree’s trunk and branches. Dormant oils are often used on other deciduous trees as they are quite effective in controlling overwintering insects and their eggs.
Factors affect pre-harvest drop in Apple trees
The pre-harvest drop in Apple is related to several factors including tree mineral nutrition, summer pruning, and insect or disease severity, and water availability.
Some factors that affect pre-harvest drop
Mineral Nutrition – Pre-harvest fruit drop is frequently more severe in orchards with low fertility soils, and orchards with low magnesium (Mg), high potassium (K), and high boron (B). To counteract the negative effect of high potassium on apple fruit drop we recommend that McIntosh orchards receive yearly maintenance sprays of Mg (Epsom salts) at 1st and 3rd cover sprays to reduce preharvest drop.
Summer pruning – Pre-harvest fruit drop is frequently severe in orchards which are heavily pruned during summer. This problem is likely associated with a limitation in carbohydrate supply when too many of the leaves are cut off leaving older less functional plant leaves. If summer pruning reduces leaf-fruit ratio below 20: 1 then fruit drop will be increased. It is recommended that moderate summer pruning must be performed if needed where only a small fraction of the functional leaves are cut off.
Insects and Mites – Pre-harvest drop severity can be increased by heavy infestations of mites, tentiform leaf miners, and other insects or diseases that significantly reduce the photosynthate produced by the plant leaves. Severe mite and tentiform leaf miner infestations have been shown to reduce the photosynthetic capacity of plant leaves resulting in a limitation of carbohydrate supply to the fruits late in the season. Therefore, strict adherence to these thresholds will not normally result in an increased risk of the drop. Though, if substantial insect or mite damage is combined with summer pruning or low Mg or drought stress the combine effects of each stress can increase the severity of the pre-harvest drop.
Water availability – Pre-harvest drop will be severe in dry seasons than in seasons with adequate or more-than-adequate rainfall. In dry years irrigation becomes a necessary management tool to control pre-harvest drop.
Premature fruit drop causes in apple trees
Fruits of all kinds should be harvested on time, at the proper stage of maturity to maintain their nutrients, quality, and freshness. Apple trees can be somewhat tricky to find when they are at their peak and ready to harvest. At this time of year, trees begin fruit dropping prematurely. There are many reasons for this occurrence. Apples infested with codling moths will have rotten areas within the developing fruit and they will drop from the tree.
Pests and diseases contribute to the problem of premature fruit drop. Cool wet weather during the bloom period of walnuts results in infections of walnut blight, a bacterial disease that damages catkins, leaves, and newly-pollinated nuts. Infected nuts may drop prematurely. Premature ripening and fruit drop occurs in apples that are infested with codling moth larvae. It is very important to remove the fallen fruit (even small apples) as soon as they fall so that the codling moth larvae are removed from the vicinity of the tree. Failure to do so allows the codling moths population to increase and overwinter to reinfect fruit next year. Codling moths will have at least two generations per year, so be sure to replenish traps with fresh pheromone attractant now. Another cause of the premature drop in an apple tree is a heavy fruit set. Apples that grow in clusters will “push off” each other close to fruit harvest time. Early season thinning to reduce fruits to one or two per cluster will help prevent this type of fruit drop.
You may also like the Ecological Farming Benefits, Principles, Objectives.
Certain tree varieties are more prone to early drop that others. Gravenstein, Honeycrisp, Golden Delicious, Liberty and Red Delicious are the most varieties prone to pre-harvest drop. Watch for full-sized and healthy apples dropping to the ground. Healthy apples typically begin falling when the fruit is ripe. Apples ripen at various times depending on the variety. Gravensteins apple ripens in August but Granny Smiths won’t be ready until November. A given fruit variety will ripen earlier or later in different climates. And it is best to keep a record for your trees as they will ripen at pretty much the same time each year. If the season is right and the apple fruits are full-sized, cut an apple open and check the color of the seeds. The seeds of apples normally turn dark brown when they are nearing maturity. When an apple is ripe and ready to pick, and you can lift it off the tree without pulling hard or twisting. Just lift the apple upward and it must come loose from the tree.
Symptoms and characteristics premature fruit drop in apples
Premature fruit drop is related to unfavorable environmental conditions, for example, late frosts, excessive heat or cold and abrupt changes in humidity. Fruit drop symptoms can be soil-related, resulting from irregular watering and improper nutrition. Nutrient deficiency is a major problem. Boron-deficient green peppers will even exhibit a certain amount of fruit drop in the Apple tree. Deficiency diagnosis is more complicated if more than one nutrient is deficient in the soil. In Manitoba, only nitrogen, phosphorus, potassium and sulfur are of particular concern for apple production. Herbicide drift can lead to premature fruit drop.
Control or preventions of premature fruit drop in apples
Thin fruit to reduce competition and encourage the plant to put more energy into producing fewer numbers of larger, higher-quality apple fruit. The removal of fruit beyond what is lost during the early season drop could even be necessary. Some horticulturists even suggest thinning the blossoms, but flowers are usually an attractive feature for most homeowners. Avoid unfavorable environmental conditions that cause a plant to drop its fruit. This involves water management and a balanced fertilizer program, according to individual plant specifications. Soil testing can be required to confirm nutrient deficiency or toxicity. Supplement with fertilizer where necessary. Avoid herbicide drift. And never apply herbicides in windy or dead calm conditions. Contrary to popular belief, dead calm conditions are associated with a phenomenon known as temperature inversions. Spraying under such conditions can increase drift distance. If additional symptoms are observed on fruit, leaves or stems, proceed to identify the causal agent and administer control measures.
Preharvest fruit drop in Apple trees
Preharvest fruit drop (PFD) is an important cause of fruit loss in the apple industry and recognized as a severe problem in apple production for many years. Preharvest fruit drop (PFD) in which fruits are shed from the tree before the ripening phase before horticultural maturity could occur in several apple cultivars. The severity of drop is cultivar specific and cultivars have been categorized according to a propensity to drop that is less prone, intermediate and more prone.
After fruit setting in apple, there is a period of fruitlet (immature fruits during the cell division phase) drop that occurs 5 to 6 weeks after full bloom; this is referred to as ‘June drop’. A second period, called preharvest fruit drop (PFD) begins approximately 4 weeks before harvesting.
Preharvest fruit drop control by NAA
Application details for Naphthalene Acetic Acid (NAA) (Fruitone-L, Refine 3.5 WSG, Refine 3.5L) rates of 10 ppm are effective, however, up to 20 ppm can be used good coverage at dilute application is preferred to apply just as apples start to loosen; apply too early and drop control will be limited; apply too late, and drop will have already started drop control can last for 7 to 10 days; sometimes two applications (at 5 to 7 days apart) can extend that to 14 days NAA can result in accelerated fruit maturity and fruit softening
Apple fruit harvesting
The fruits mature within 130 to 150 days after the full bloom stage depending upon the variety grown. The ripening of fruits is associated with the change in color, texture, quality and the development of the characteristic flavor. The apple fruits at the time of harvest should be uniform, firm and crisp. The color of the fruit skin at maturity ranges from yellow-red depending on the variety. Though, the optimum time of harvest depends on fruit quality and intended period of storage.
Frequently asked questions about Apple fruit drop causes
Why are apples dropping early?
Apples start dropping off the tree before they are ripe. Often the flesh has softened and less tasty than normal. Several factors can trigger early fruit drop, for example, excessive fruit load, excessive summer pruning, insect damage, diseases and extremes in weather.
How long can you leave apples on the tree?
A good late keeping variety, stored well in a dark cool place, can keep for 6 months or longer. When grown with early varieties, you can be eating home-harvested apples for the majority of the year.
Do apples continue to ripen after being picked?
Apple fruits continue to ripen after they leave the tree. When fully ripe they become mealy. Some apples will begin drying out immediately after picking and some may lose their quality in just days.
You may also like the Growing Ginger Hydroponically.