Apples Pears:Guidelines
GUIDELINES: APPLE AND PEAR PRODUCTION
Contents
- 1 STATISTICS
- 2 OUTLINE OF MANAGEMENT ACTIVITIES
- 3 DEVELOPMENT
- 4 GROWTH REQUIREMENTS
- 5 Establishing an Orchard
- 6 MANAGEMENT METHODS
- 7 ROOTSTOCK AND VARIETY SELECTION
- 8 PLANTING: New Orchard
- 9 FERTILIZING
- 10 IRRIGATION
- 11 REPLANTING
- 12 FROST PROTECTION
- 13 WATER MANAGEMENT
- 14 FRUIT THINNING AND PREHARVEST DROP
- 15 HARVESTING
- 16 PRUNING
- 17 SANITATION
- 18 BIOLOGICAL CONTROLS
- 19 PESTICIDES
STATISTICS
OUTLINE OF MANAGEMENT ACTIVITIES
Cultural Practices
_____ Prune dormant trees to improve spray penetration and air circulation. _____ Prune during summer on densely foliated trees. _____ Remove and destroy all prunings. _____ Use size controlling rootstocks for new or replantings.
Nutrient and Moisture Management
_____ Apply fertilizer based on leaf tissue analysis. _____ Use surface or subsurface drip irrigation systems.
Pesticide Management
_____ Use approved and registered pesticides according to label. _____ Maintain application records. _____ Minimize pesticide drift. _____ Develop and implement a resistance management plan. _____ Calculate for each block, tree-row volumes. _____ Select pesticides which will preserve natural enemies of pests.
Biological Pesticides or Strategies
_____ Select disease resistant varieties when introducing new stock. _____ Select materials for insect mating disruption. _____ Remove non-cultivated trees within 100 yards of the orchard.
Insect Pest Management
_____ Scout "SUSPECT INSECTS" .. Apple Maggot .. Apple Pandemis .. Codling Moth .. European Red Mite .. Fruit tree Leafroller .. Green Apple Aphid .. Green Fruitworms .. Italian Pear Scale .. Leafhoppers .. Lygus Bugs .. Obliquebanded Leafroller .. Omnivorous Leafroller .. Orange Tortrix .. Rosy Apple Aphid .. San Jose Scale .. Stink Bugs .. Webspinning Spider Mites .. Western Tussock Moth .. Woolly Apple Aphid _____ Keep a scouting record. _____ Identify control measures and implement according to thresholds.
Disease Pest Management
_____ Identify major disease pests. _____ Keep a scouting record. _____ Identify control measures and implement according to thresholds.
Weed Pest Management
_____ Identify major weed pests. _____ Keep a scouting record. _____ Identify control measures and implement according to thresholds.
Vertebrate Pest Management
_____ Identify major weed pests. _____ Keep a scouting record. _____ Identify control measures and implement according to thresholds. _____ Use bait stations for rodent management, instead of broadcast treatments.
Weather and Crop Monitoring
_____ Monitor weather and crop parameters _____ Keep daily records.
Date: - Min/max temperatures: - Rainfall - Hours of leaf wetness - Stage of tree development (by cultivar, weekly)
DEVELOPMENT
The Nonbearing Years
The first year of growth is important for root growth and development and stresses should be avoided that may hinder the root development such as disease, nematodes, weed competition, or unbalanced soil moisture. During the first and second years, the tree experiences one, two, or three growth flushes a year depending on the interaction the tree has with its environment. By mid-July, most of the top growth has slowed down, but the roots will have another growth spurt in the fall, and again in late spring.
The Seasonal Cycle of Bearing Trees
Deciduous fruit trees must go through a period of dormancy and a period of growth. During dormancy the tree rests and during the growth period, the tree blooms and sets fruit. Shoot growth, bud initiation and differentiation also occur during the growth period.
Dormancy
During the fall, the tree begins to decrease its total moisture content and stores sugar as starch to be used in the next growth flush. Dormancy ends when the chilling requirements are satisfied for the tree, which is different for all varieties and is often not recognized.
Growing season
Most apple varieties need to be exposed to temperatures below 45° F (7° C) for about 1,200 to 1,500 hours and pears between 1,000 and 1,200 hours. If the chilling requirement is at least minimally met during winter, buds begin to expand and the trees will bloom earlier than normal. However, the time to bloom varies greatly between all varieties and the growing areas.
Apple, dormant to silver tip (S. Savage; Colorado State University)
Apple, bud development, 1/2 green tip stage (S. Savage; Colorado State University)
Jonathan apple, green tip (S. Savage; Colorado State University)
Bloom
Apples and pears form two kinds of buds: mixed and vegetative. Mixed buds contain both flowers and leaves. Each has its own blooming procedures. For apples, shoot growth begins before bloom, and it follows bloom in pears. Apples have 5-6 flowers in a whorl with the terminal bloom producing the largest, best-shaped fruit. Pears have 7-8 flowers in the bud and the side blooms open first. A second bloom can occur in some Bartlett pears, but is not desirable because it can lead to fire blight. Pear trees usually will need some protection to prevent fire blight infection.
Apple (20% bloom), cluster (N. S. Luepschen; Colorado State University)
Apple (full bloom), cluster (N. S. Luepschen; Colorado State University)
Apple (pink stage) (N. S. Luepschen; Colorado State University)
Apple (pink stage) (N. S. Luepschen; Colorado State University)
Apple blossoms (full bloom) (N. S. Luepschen; Colorado State University)
Bartlett pear (early bloom) (C. R. Ure; Colorado State University)
Bartlett pear (full bloom) + return stack heater (C. R. Ure; Colorado State University)
d' Anjou pear, full bloom (J. Sexton; Colorado State University)
Fruit set
Simply because apple and pear trees bloom so abundantly, only about 5 to 10 percent of the blossoms produced are needed to result in a full crop. Some varieties are parthenocarpic, but most are pollinated and fertilized. Pollination occurs when one or more grains of pollen are transferred from the anthers to the stigma of a flower and this is accomplished mainly by honeybees. Weather is an important factor in the pollination process because honeybees are not effective if the temperature is below 55° F (13° C), if the weather is rainy, or when winds exceed 15 miles per hour.
Fruit development
Apples and pears are pome fruits, which means that the fruit is formed from the fusion of the ovaries, calyx cup, and floral tube. Usually two periods of flower or fruit drop occur. The first drop occurs after petal fall and is a result of the flower not getting pollinated or fertilized. The second drop is often called June drop and is probably a result of competition among fruit for the tree's resources. During the first few weeks after bloom, the fruit growth undergoes a rapid period of cell division and shoots grow quickly for several weeks. From this time until harvest, the fruit grows at a fairly constant rate unless interrupted by environmental stresses. Beginning in late fall, the buds will rest for a period. Much of this rest occurs in January and February when the buds cannot be forced into growth by warm temperatures. A certain amount of chilling is required during dormancy and then the tree will flower normally.
GROWTH REQUIREMENTS
All trees need sufficient light, water, nutrients, and adequate temperatures. Light is important in the process of photosynthesis, which is when sugars are made and supply the energy needed for tree and fruit growth. The tree requires a great amount of water, but only a small amount is used by the tree roots for growth. The majority of the water is taken up through the tree and transpired through the leaves. This is the way that the leaves and fruit receive nourishment and get cooled off when the temperatures are high. Sunshine, humidity, heat and wind all influence how much water the tree will transpire. Trees also need nutrients for growth. Nitrogen has to be replenished frequently through fertilization, but many other important nutrients are available in sufficient amounts in the soil. Apple and pear trees are most successful when they are grown in deep, well-drained, medium textured soils.
Establishing an Orchard
When establishing a new orchard, it should not be planted where an old orchard has been or on an old vineyard site. These areas tend to host nematode populations that are difficult to control. The best sites for new orchards are in areas that have not had woody crops grown for several years. The soil should be tested for nematodes since they pose such a threat to orchard crops. The testing can be done at any time of the year and should be to a depth of 36 inches. Take the soil to a laboratory and ask them to identify problems associated with root lesions, root knot, and dagger nematodes. The selection of rootstock is also important in a new orchard to avoid unnecessary disease problems. Select rootstock that is tolerant to nematode attack although no rootstock is available that is completely resistant to root lesions, root knot, or dagger nematodes. However, it is possible to reduce the risk of major disease problems if the soil is properly prepared. A schedule, such as the one that follows, is one method of reducing nematode infestations. During the first summer or fall, remove all trees and vines, destroy all existing residues, and sample for nematodes. In the winter or spring, plant grains that can be used for ground cover unless nematodes are present, otherwise leave it fallow and weed free. During the second spring or summer, level, cultivate and make other preparations for planting. In the fall or winter, rip the soil and fumigate in September or October. Apples usually benefit from preplant fumigation, but pears do not unless lesion nematodes are a serious problem. Proper fumigation can give up to 6 years of nematode protection and allows the tree to develop a healthy root system. It is important to have proper soil moisture, soil texture, and soil temperature before fumigating because poor soil conditions cause a rapid return of nematodes. Soil moisture is probably the single factor that determines if fumigation is successful. If the soil moisture is too low, the fumigant adsorbs onto the soil particles and if there is too much moisture present, the fumigant will not effectively seep into the soil. Sandy soils are certainly easier to control because liquids move through them so easily. Clay and other fine textured soils hold onto high percentages of water and often cause the fumigants to be diluted as they are moving through the soil. Fumigants do not penetrate clods of soil or roots that are larger than 1/2 inch (1.25 cm) in diameter if they are within 6 inches (15 cm) of the soil surface. The best time to fumigate is in the fall before the soil gets wet and cold. Sometimes fumigants are difficult to apply evenly because they can volatilize easily in the top several inches before being incorporated into the soil. Follow the directions of the fumigant label because some fumigants are toxic to plants and must be applied several weeks or months before the trees are planted. Finally, to help control the moisture levels and dust, most crops have a ground cover. Cover crops need to be chosen carefully and often rotated on a 2 or 3 year basis so that they do not introduce more nematode diseases. Grasses are a good choice because they are not conducive to root knot nematodes.
MANAGEMENT METHODS
There are several factors that should be considered when managing a successful orchard. Soil texture, soil depth, drainage, climate, rainfall patterns, potential for frost damage, frequency of high winds, winter chilling and summer heat are all important aspects of orchard planning and management. Many site problems can be prevented before planting if they are known. Apple and pear trees should be grown in deep, well-drained soils. To avoid the presence of troublesome weeds, good weed control should begin a full year before the orchard is planted. Planting sites should be avoided if they have a history of oak root fungus because it is nearly impossible to control. After a site has been selected, fall is the best time for preparing the soil for planting while the soil is dry. Not only is proper land preparation important for optimum root growth, it is also important for maximum effectiveness of fumigants and herbicides used in the orchard.
ROOTSTOCK AND VARIETY SELECTION
When selecting rootstock, choose varieties that are well adapted to the area and have some tolerance of local diseases and insects. If there is significant pest damage on the trees, they will require an excess amount of management, which will in turn reduce the economic outcome.
Apple rootstocks
Rootstocks are labeled with a number, preceded by M. If the number is less than 100, it is considered to be a standard rootstock, and if the number is greater than 100, it has developed some resistance to the woolly apple aphid. The most commonly used rootstocks used today are M7, M9, M26 M106 and M111. Standard rootstock will develop into trees that are 20 feet or more tall, but they are slow to come into production and the rootstock suckers abundantly. M111 is also a slow bearing tree but has a greater tolerance to varying soil conditions, provides good anchorage, and is reportedly resistant to woolly apple aphid. M106 produces early bearing trees, is easily propagated, resistant to woolly apple aphid, but can easily be infected by Phytophthora root rot. M7a performs well when being replanted, but suckers profusely and usually needs support. Trees on rootstock smaller than M7a have not been very successful because they are easily stunted, not well anchored, and are subject to sun damage.
Apple varieties
The most common apple varieties are Red Delicious, Granny Smith, Yellow Newtown, Gravenstein, Rome Beauty, Golden Delicious, Jonathan and Fuji. Many apple varieties have "spur-type" strains, which produce smaller, compact trees with more spurs and less shoot growth than standard strains.
Red delicious apple, normal fruit (H. J. Larsen; Colorado State University)
Golden Delicious apple tree with mature fruit (H. J. Larsen; Colorado State University)
Pear rootstocks
Successful pear rootstock is determined by its resistance to fire blight and pear decline, its strong vigor, its compatibility to several varieties, and its ability to be grown in a range of soil conditions. Pyrus communis is the most commonly used European pear and is known as Bartlett and Winter Nelis. Other common rootstocks that are used include Pyrus betulaefolia, Pyrus calleryana, and quince. Pyrus betulaefolia produces a large vigorous tree that grows well in poor soil and is highly resistant to fire blight. Pyrus calleryana is not as vigorous as Pyrus betulaefolia and is subject to the toxin produced by pear psylla and can reduce its vigor drastically when populations of this pest are heavy. Dwarfing rootstocks are not recommended for European pears because they rely too heavily on environmental conditions that easily influence its success.
Pear varieties
The most popular European pears are Bartlett, Bosc, Comice, Butirra Precoce Morettini (BPM), and Winter Nelis. Bartlett trees are prolific, bear regularly, and will grow in a wide variety of soil and climatic conditions. Bosc trees grow upright and are quite susceptible to fire blight. Comice pears are easily bruised and require special care to avoid a damaged crop. The trees are less vigorous than other varieties and are often grown in very small orchards. BPM is a flavorful, early maturing pear that is grown in large clusters, and is easily damaged by leafrollers. Winter Nelis is used mostly as a pollinizer variety for Bartletts and is difficult to train. D'Anjou pears are not grown in summer heat and can be easily infected with corkspot disease. Asian pears are more susceptible to codling moth infestations and fire blight disease than are European pears. Most Asian pears are from Japan or China, Japanese pear varieties are round and Chinese are elongated.
Pollinizer varieties
Most apple and pear varieties require cross pollination. Bartlett pears, however, set fruit parthenocarpically which is when fruit develops without fertilization and is seedless. For varieties that require cross pollination, choose a pollinator with a bloom period that overlaps that of the variety to be pollinized.
Apples
When planting apples, they should be in patterns where the pollinator varieties can be close to the varieties that cannot pollinize themselves. Since bees are the greatest pollinators, they perform best when they do not have to fly long distances. Sometimes, alternating pollinizing trees with those that do not pollinize themselves in rows will provide the best results.
Pears
Of the most common pear varieties, Bartlett pears generally do not need to be pollinated because of parthenocarpy if the weather is warm enough. Japanese and Chinese varieties can pollinate themselves, but most European varieties need to be pollinated by bees. Most pear varieties that require cross pollination should be planted with four, six, or eight rows of one variety, followed by an equal number of the pollinizer variety.
PLANTING: New Orchard
All young trees in a newly established orchard require special irrigation, fertilization, pruning (training), and pest management practices.
Storing new trees=
When receiving new trees, they must be handled properly to establish a strong root system to support the tree. It is critical that the roots not dry out and if the tree will not be planted immediately, heal the trees in damp soil that is free of herbicides and in a sufficient amount of shade. If the trees will not be planted for 2-3 weeks, place the trees in storage, but not in the same room as stored fruit.
Planting on berms or mounds
If the soil is not well drained, then plant the trees on berms or mounds to avoid the risk of crown rot. Berms should be about 2-3 feet wide and 4-8 inches higher than the surrounding soil. Mounds should be about 3 feet square and 6 inches high.
Planting
When planting apple or pear trees, make sure that the soil is moist, but not wet. It is recommended to dig the hole a day or so before planting. Make sure that the hole is large enough to accommodate the tree roots and trim off any roots that are smashed or broken. The tree should be planted so that after the soil settles it will be at about the same depth that it was in the nursery. After planting, head the trees back 24 to 32 inches and paint the trunks with an interior water-based paint to act as a tree protector from rodents and the sun.
FERTILIZING
Fertilizing a new orchard
Newly planted trees frequently benefit from light applications of nitrogen but they should not be exposed to nitrogen at the time of planting. The nitrogen applications should be split into either two or three applications during the growing season. The fertilizer can be applied either through furrow, sprinkler, or flood irrigation but should not come closer than 18 inches from the trunk. It is necessary to protect young trees from pests and hazardous environmental conditions. Protect the trees from sunburn by either painting the trunk with a white interior latex paint or wrap the trunks with a protective tree wrap. Watch for and predict pest infestations, especially if they have been a problem in the past. Oil treatments can be used on trees that are one year old to control aphids, psylla, scale, and mite eggs. Check trees weekly as soon as blossoms appear for fire blight infections and remove any strikes immediately.
Fertilizer Application
Apples generally require a little less nitrogen than pears. Smaller amounts of nitrogen are used on red variety apples because too much nitrogen can cause poor color, soft fruit, and reduced storage and shelf life. Higher levels are used mostly for yellow or green apple varieties, especially those that will be used for processing. If legume crops are planted as a ground cover, after two years additional fertilizer may not be necessary because of the amount the cover crop puts back into the soil. Nitrogen should be applied in split applications and immediately incorporated into the soil to reduce loss due to volatilization. Other nutrients that may be deficient in orchards are zinc, potassium, phosphorus, magnesium, boron, copper, iron, and calcium. Phosphorus, magnesium, and boron deficiencies mostly occur in hilly regions and boron deficiencies are common in shallow soils. Iron deficiency may occur in alkaline soils or in areas of excess soil water. Have the soil tested on a regular basis for nutrient levels, but also observe the plants because many nutrient deficiencies produce characteristic leaf symptoms. Ground covers can improve water penetration and aeration of difficult soils, but also require more management because of their requirements for water and nutrients. Be aware of the different parasites and predators that ground covers may encourage. Depending on the other pests that may be present in the orchard, it would be beneficial to choose a ground cover that would not worsen this condition. Finally, mow the ground cover frequently to minimize its competition for water and nutrients.
IRRIGATION
Irrigating a new orchard
When planting new trees make sure that the soil is moist 4-5 feet deep at planting time and avoid irrigating the soil again until after the tree has grown 4-6 inches. Adequate soil moisture is the single factor that affects good tree growth and future production in the nonbearing years. Trees that are stressed for water may be weakened, sunburned, or attacked by wood borers. Young trees irrigated by drip or microsprinklers generally grow faster and survive better than young trees irrigated by furrow, but it is important to keep the emitters away from the tree trunk. Pruning is done to develop a sturdy tree during the first 2 or 3 years after planting. The primary tree training systems used for high density apple plantings are the central leader system and trellising. Pear trees perform better with a multiple leader system. Check with a local farm advisor for the proper techniques in pruning a successful apple or pear orchard.
Irrigation methods
Several methods of irrigation can be used in orchards, which include flood, furrow, sprinkler, and drip, low-volume sprinklers. The system used should be determined by the soil texture, slope of the land, frost hazard, installation and operation costs. The cost, source, and availability of water are also factors to consider.
=Surface irrigation
Surface irrigation (flood or furrow) is a good method of irrigation if extremely hot weather has been present and the trees rapidly need water. It is most successful in level orchards so the water can be evenly distributed across the orchard. However, if the soil texture varies in the orchard, the water may not infiltrate uniformly. Be aware or the potential pest problems that can be found in surface water, such as unwanted seeds and pathogens.
Sprinkler irrigation
There are different sprinkler systems that can be used in orchards. Solid set sprinklers are commonly used because they are easy to operate, they can distribute the water evenly, it is possible to apply fertilizers with the water, and they are less expensive than other systems. However, when the orchard is planted in hedgerows, overtree sprinklers are more effective.
Localized irrigation
Localized irrigation includes drip or other low-volume sprinkler systems. With these systems, water is applied to the orchard floor on a frequent basis, replacing the water that is used by the tree. The root zone for these trees are much smaller than those trees that receive surface water simply because they receive less water volume. These systems can save a lot of water because less is drained out of the soil and timers can be set to apply water at specific intervals. Factors to consider are the high cost and high maintenance of these systems. In addition, they are labor intensive if emitters get clogged or if pipes break.
Scheduling irrigations
Water budgeting is a method used primarily in the spring to determine when to irrigate and how much water to apply. In order to use a water budget efficiently, it must first be determined how much water is used per day at different temperatures and with varying environmental conditions. In addition, it is necessary to know the field capacity and texture of the soil. The efficiency of irrigation is determined by the water that is actually available for use by the trees. A rough estimate of efficiency is as follows: surface irrigation is normally 60 to 80% efficient, sprinkler irrigation around 65 to 75% efficient, and localized irrigation about 80 to 85% efficient. To avoid disease problems, the irrigation should be absorbed within 48 hours after application. Tensiometers, soil tubes, soil augers, and gypsum blocks are other instruments that can be used to determine the amount of moisture in the soil.
REPLANTING
Before replacing lost trees in an established orchard, determine why the trees died and correct the problem. In most situations it is not feasible to replace each and every tree that is lost, especially if they are scattered throughout the orchard. However, if a large area has been lost, then it would be necessary to replant. It is recommended to remove all the old tree stumps and as many large roots as possible in the fall to allow the soil to settle before planting new trees in the spring. Fumigating the soil may not be necessary but is advised if the root lesion nematode, Pratylenchus vulnus, is present. Fumigation gives the new tree a start in an area relatively free of nematodes and disease organisms and kills roots of older trees that have grown into the new planting location. This reduces the competition for nutrients and water and improves the chances of the tree performing well. Special considerations must be made for replants. They do not grow well when surrounded by other trees that shade the young tree and it may be necessary to cut the tops off of surrounding trees. They also will require extra irrigations and small amounts of nitrogen fertilizer once or twice during the summer to overcome competition. Finally, do not allow weeds or other vegetation to grow around a replant as they can severely compete for water and nutrients.
FROST PROTECTION
Orchards must be able to protect against frost due to the serious potential fruit damage. The risk of frost damage is greater in semi-dwarf trees than in standard-sized trees because the bearing surface is closer to the ground. Frost occuring during bloom can kill blossoms and can cause internal freezing of the fruit and seeds when the fruits are 1/3 inch in diameter. It may be difficult to monitor external symptoms but as the fruit matures it becomes flattened or distorted in shape. The following are some possible methods of protecting against frost damage. Keep the cover crop closely mowed to conserve heat in the orchard and use sprinklers or wind machines to protect the crop against injury. Keep in mind that as long as both ice and water are present in a mixture on a surface, the surface cannot get any colder than 32° F (0° C). However, keeping the plants wet increases the chance of possible limb breakage due to the weight of the ice buildup. In addition, if not enough water is applied because of high winds or the system fails and turns off too soon, significant damage can occur.
WATER MANAGEMENT
The amount of water the trees receive should be closely monitored because trees stressed for water can have slow fruit development and a reduction in fruit size and yield. Trees that receive too much water are oxygen deprived and will not perform at potential levels.
FRUIT THINNING AND PREHARVEST DROP
Thinning is necessary to maintain a balance between vegetative growth and fruiting. Thin apples within one month of blooming, leaving fruit clusters 4-6 inches apart with one fruit per cluster. For pears, leave two fruits per cluster. Hand thinning is more successful and effective than chemical thinning, but must be done after the natural drop so that the crop is not overthinned. Asian pears are thinned twice a season, once just after bloom and then again 30-60 days later to obtain larger sized fruit.
HARVESTING
Apple and pear maturity depends on the intended use of the fruit. For apples, the number of days from full bloom to harvest is one index of apple maturity. Apples grown for fresh market consumption are hand harvested and moved to a cooler soon after harvest to avoid bruising or internal deterioration. European pears reach maturity based on a pressure test for firmness. Bartlett pears are picked twice: when they are still green and hard for packing and fresh market, and a second pick mostly for canning. Maturity for Asian pears is based on the base color of the skin and sugar content (12.5 to 13 percent). They must be carefully packaged to avoid bruising the skin, which readily shows dark marks when injured.
PRUNING
Pruning is done to maintain a proper balance between vegetative growth and fruit production, permit light penetration, remove weak or diseased wood and water sprouts, renew fruiting wood, and maintain the desired tree height.
Apple, high density, Hy-Tek trellis system (A. R. Renquist; Colorado State University)
Apple, high density, Hy-Tek trellis system (A. R. Renquist; Colorado State University)
Apple, high density, vertical axis trellis system (A. R. Renquist; Colorado State University)
Apple, high density orchard with modified tatura trellis system (A. R. Renquist; Colorado State University)
Apple, low central leader (A. R. Renquist; Colorado State University)
Golden Delicious, central leader (A. R. Renquist; Colorado State University)
Golden Delicious apple, central leader (A. R. Renquist; Colorado State University)
Apple training with concrete weight (A. R. Renquist; Colorado State University)
Apple trees, standard central leader training (H. J. Larsen; Colorado State University)
Bartlett pear, multiple leaders (A. R. Renquist; Colorado State University)
Granny Smith, training with twine (A. R. Renquist; Colorado State University)
Wind wires to prevent wind rocking (A. R. Renquist; Colorado State University)
SANITATION
The following is several methods of improving the necessary sanitation in successful orchards: remove shoots infected with powdery mildew, always clean the equipment between orchards, keep the tree crown areas free of weeds, spot-treat infestations of perennial weeds, control drainage from fields infected with nematodes, destroy all weeds along the orchard's borders, remove nesting or resting areas of crop destroying birds, and finally remove all debris to prevent pest infestations.
BIOLOGICAL CONTROLS
Biological controls are frequently used to control pest populations in orchards. The control agents can be native or introduced from other areas and are most successful in controlling mites. They are also very effective in controlling scales, aphids, pear psylla, leafminers, plant bugs, and certain caterpillars. When placing biological controls in an orchard, it is necessary to understand how they will interact with other control measures to determine if they will be beneficial.
PESTICIDES
Pesticides, including insecticides, herbicides, fungicides, nematicides, and rodenticides, belong to a variety of chemical groups with different properties. Carefully choose pesticides because it may be possible to select one chemical to control several pests at the same time or to use compatible materials together. The choice depends on the degree of control needed, the effect on other pests and beneficial species, and on economic and legal restrictions. Pesticides can be applied either through air blast sprayers or aerially. As with the application of all chemicals, the machinery must be properly calibrated and used by an experienced operator to receive maximum control. Nozzles must frequently be replaced to emit the proper droplet size. The trees must be completely covered with pesticide so adjustments must be made when tree sizes vary. Pesticides are applied either in concentrate sprays or in dilute sprays. Concentrates require greater precision in application but use less chemical than dilute sprays. Be aware of the dangers involved when using chemicals. They may pose a hazard for pollinating bees, pests may not respond accordingly and a different method of control must be used, and they can be potentially hazardous to human and wildlife. Always follow the safety guidelines that are outlined on each pesticide label.
