Controlling Problems

Fruit and nut crops are susceptible to a variety of different insects, diseases and weeds. Some of these problems damage the plants themselves, while others attack the fruits or nuts, leaving them unattractive and inedible. Successful control of these problems requires careful monitoring of your plants and a program combining management practices and chemical controls.

Insects

More than 100 species of insects attack the home garden and orchard. Most are only occasional pests, but many are commonly found feeding on vegetables and fruit.

Many insect pests attack the foliage; others may feed on plant roots or on the fruit. Many pests can build up high numbers rapidly, causing extensive damage quickly. If not controlled, some insects can destroy an entire crop, while others can destroy the trees. Learn to identify which bugs require treatment and which are "good bugs."

Scale Insects. White peach scale and San Jose scale are two serious pests of trees. These pests attach themselves to the limbs and suck out plant sap. Heavy infestations may kill limbs or even entire trees in the dormant season.

Plum Curculio. The plum curculio is a devastating pest of peaches and plums. The adult is a weevil. The female weevils lay eggs in the fruit, and the larvae feed on the developing fruit. Small fruit will fall off the tree, and larger fruit will be ruined by the feeding of larvae inside. To control this pest, apply insecticides first when petals begin to fall off the newly pollinated fruit. Make additional applications at the shuck split stage and then at 2-week intervals to include three more applications.

Catfacing Insects. "Catfacing" is a term used to describe damage to fruit which causes them to be deformed and pitted. Catfacing is caused by insects feeding on growing fruit. These pests include stink bugs, leaf-footed bugs, green June beetles and others. Use control measures when these pests are observed.

Peach Tree Borers. The peach tree borer is the larval stage of a moth. The larvae bore into peach or plum trees close to the ground level. Heavily infested trees may be girdled, which will kill the trees. This pest is controlled in mid- to late August. For best results, thoroughly cover the trunk with insecticide.

Major Pecan Pests

Pecans are extremely vulnerable to insect pests. Major pecan pests can be divided into two groups-those that feed on foliage and those that feed on nuts. The timing of pesticide applications is extremely important if pecans are to be protected from these pests.

Scale Insects. Obscure scale can cause severe damage to pecans. It is a small pest which attaches itself to small limbs and sucks juice from the tree.

Phylloxera. Phylloxera are small, aphid-like pests that cause galls to develop on leaves and petioles early in the growing season. They are a common problem on pecan trees.

Pecan Nut Casebearers. The pecan nut casebearer is the larva of a small moth. These larvae bore into small nutlets and destroy them. They are capable of destroying the entire nut crop if not controlled. To control this pest, look for the eggs on the tip of young nutlets, about the time of pollination. Time insecticide applications to egg hatch for best control. A second generation of pecan nut casebearer occurs about 6 weeks after the first, but this generation usually does not need to be controlled.

Hickory Shuckworms. The hickory shuckworm is the larva of a small moth. It feeds on the shuck surrounding the developing pecan. This prevents the pecan from developing fully and often stops development completely. This pest occurs in mid- to late August. It takes two insecticide applications at 2-week intervals to give good control.

Aphids. Aphids may occur from late spring until late fall. It is best to leave aphids alone or use only soapy water to wash them off the tree.

Pecan Weevils. The pecan weevil occurs only in the northern half of the state. It becomes a pest in mid- to late August. The larvae of the weevil (often called "redheads") eat the nutmeat and bore a round exit hole in the pecan shell.

Foliage Pests. A number of foliage-feeding larvae can damage pecans. Some of the most important are the fall webworm and the walnut caterpillar. Watch for infestations of these pests. When extensive foliage feeding is observed, control the pests with applications of the same insecticides used on the pecan nut casebearer.

Diseases

Homeowners involved with growing fruit and nuts often experience reduced fruit quality or quantity due to plant diseases. Fruit and nut crops are susceptible to one or more disease problems throughout their lives. Effective disease control involves using both cultural and chemical practices. Most diseases that infect fruit and nuts are caused by bacteria, fungi, viruses or nematodes.

Bacteria. Several bacteria cause serious problems on fruit plants. Fire blight of pear and apple, bacterial leaf spot and bacterial canker of peach and plum are three of the more frequently observed diseases in the home garden. Bacterial diseases are found in all areas, but they are generally more severe in areas of high to moderate rainfall. Bacterial diseases are controlled by resistant varieties, fungicides and cultural practices.

Fungi. This group of organisms is the most widespread and damaging to fruit and nut crops. Fungi survive on diseased plant material or on alternate crops. Vascular wilts; root, trunk and fruit rots; and leaf spots are all symptoms of fungal infection. Disease problems are most severe during periods of high humidity or when the plant tissue is covered by a thin film of moisture. Temperatures between 70o and 85oF are favorable for most fungi.

Viruses. Viruses are submicroscopic pathogens that increase in number once they are inside the host plant. Viruses can be spread by insects, nematodes, seeds and infected propagating material and by mechanical methods. Individual virus cells can be observed only with the aid of an electron microscope. Symptoms can often be confused with those of plant mutations, nutrient deficiencies, toxicities or other pathogens. Virus diseases are controlled with the use of resistant varieties, rotations, and weed and insect controls.

Nematodes. Plants infected by nematodes develop distinct symptoms based on the type of nematode parasitizing the plant. Root knot nematode, the most common and damaging nematode pest, will cause galls or swellings on the roots, stunting and minor element deficiency. Resistant rootstocks, rotation and pre-plant nematicides are used to control nematode problems in home and fruit plantings.

Disease Spread. Many disease-causing organisms are blown by wind from diseased trees or plant parts to nearby healthy plants. Brown rot of peaches, black rot of grapes and scab of pecans are spread by spores carried by air currents. Once plants become infected, rain or irrigation water splashing on diseased parts further spreads the pathogens.

Disease-causing pathogens can also be spread mechanically during pruning, thinning, irrigating or cultivating. Equipment used to cultivate the orchard can also injure the roots and limbs of the trees. These injuries create wounds through which disease-causing pathogens can enter.

Disease Prevention

Preventing fruit and nut diseases is more effective than controlling them. Once a plant becomes infected, there is little to do other than pruning out the diseased part or removing the entire plant in the case of root rots or virus infection.

A disease prevention program should use a combination of cultural and chemical treatments. This requires some understanding of the disease-causing organisms and the chemicals to be applied.

Cultural Practices. Normal management practices can frequently help to control the spread of disease-causing organisms. These practices should be followed on all fruit and nut crops to help ensure that the fruits and nuts are free of disease.

Chemical Controls. In most cases, chemical treatments are required to supplement cultural practices to produce high-quality, disease-free fruits and nuts. Pesticides should be used only according to the label instructions. Applications should be sufficient to maintain control but not excessive. When applying a material for disease control, make sure the foliage, fruit or nuts are well covered with a protective fungicide film. Most products used for disease control are effective for only 10 to 14 days, and for a shorter time in wet conditions. Repeated applications are needed as long as weather conditions are favorable for disease development and the plant is susceptible to the pathogen.

Weeds

Good weed control is a key to successful fruit and nut gardening. Weeds and grasses can stunt and even kill young trees and berries, and the competition for water and nutrients will seriously limit production of bearing fruit and nut trees.

Mechanical Control. Hand-hoeing is still the best answer to weed control in the home orchard. Mechanical tillage equipment is satisfactory, but till only up to 2 inches deep to avoid serious damage to shallow feeder roots.

Mulches. Mulching provides multiple benefits, including weed control, reduced water loss, and cooler soil temperatures. Thick mulches keep light away from seedlings and provide a mechanical barrier to emergence. Mulching works best against weeds that come up from seed each year (annuals).

Organic mulches gradually deteriorate, and fertilizer is used in this decomposition. If you are applying fertilizer on top of a thick organic mulch, apply extra fertilizer to compensate for this loss.

It may be aesthetically desirable to have a grass cover around fruit and nut trees that are a part of the landscape. Mature trees compete with grass much better than young trees do, so keep a weed-free circle around the tree for the first 3 to 4 years.

Herbicides. Do not use herbicides in your home orchard unless you fully understand all aspects of safe handling and application. Glyphosate (Roundup), a systemic weed and grass herbicide, has become popular in orchards because of its ability to kill persistent perennials such as bermudagrass and Johnsongrass. But glyphosate can also kill fruit trees and berries if there is significant contact with leaves or green bark. Spray drift as well as direct spray contact is dangerous, so apply glyphosate or other contact herbicides when there is little or no wind and shield small plants.

Pre-emergent herbicides, which prevent germination of weed and grass seed, require specialized accurate spray equipment. Pump-up garden sprayers and most other types of hand-gun equipment are unsuitable. These chemicals should be used only by people who have the proper spray equipment and have a full understanding of calibration procedures.

Stay well away from fruit and nut trees and berries with selective lawn herbicides that contain 2,4-D. This hormonal-type herbicide kills broad-leaved weeds but does not injure grasses. Slight spray drift or 2,4-D residue remaining in a sprayer can seriously damage or kill trees and berries. Grapes are especially vulnerable to 2,4-D.

If you do not fully understand safety and application procedures, you should not use any herbicide. A safe rule of thumb is: "If in doubt, hoe it out."

Pest Controls For Home Use

As a home gardener, you need to be able to recognize pest species and to be familiar with their damage. Also, you should be able to recognize beneficial insects which help control pest species. For guidance in learning to identify and control pests of fruit and nuts, refer to Texas Agricultural Extension Service publications L-1876, "The Peachtree Borer"; B-1238, "Managing Insect And Mite Pests Of Commercial Pecans In Texas"; and B-5041, "Homeowner's Fruit and Nut Spray Schedule." These publications are available from your county Extension office.

You should inspect your orchard frequently. If you find damage and insect pests, apply an insecticide. Repeated applications may be necessary with some pests. Check the plants 2 to 3 days after application to see if adequate control has been achieved. Apply insecticides only according to label directions.

Helpful Hints. Home fruit growers continuously battle insect pests. Certain practices help to control fruit pests and protect the quality of produce. Some helpful hints are listed below.

Pesticide Formulations. Several pesticide formulations are available for home orchard use. At certain times one formulation may be better than another. The choice of formulation depends upon your personal preference, convenience, the equipment available and, at times, the pest that must be controlled.

Dusts are ready to use in the desired concentration and require no dilution or mixing. They are easily applied and are most effective when used thoroughly but sparingly. Dusts cannot be mixed with water.

Soluble powders and wettable powders are purchased as concentrates. They are to be diluted before use by mixing with water. Do not use them as dusts as this may damage plants.

Emulsifiable concentrates are liquid formulations which are to be diluted with water to obtain the desired concentration for treating plants.

Granules are dry, granulated materials that come ready to use. Spread them on the surface or work into the top 2 to 3 inches of soil.

Baits contain a desired food of the pest in addition to a toxic substance. When the pest eats the bait, the pest ingests enough toxicant to kill it. Baits are applied to areas that pests frequent.

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