Plant Health Problems
Diseases caused by Fungi:

Black root rot, Rhizoctonia solani.
Rhizoctonia is a common soil fungus which attacks a wide variety of plants and is not specific on strawberries as is red stele. Black root rot is more severe when lesion nematodes are present. The characteristic action of this fungus is to destroy the fine feeding roots, causing the plant to show symptoms of drought and low nutrition. The plant may not die. The infected roots show a dry, brown decay of the fleshy part of the root, which finally is entirely disintegrated. The central cylinder remains enclosed in a tube of the root epidermis like a wire running through a pipe.

Black root rot is difficult to control. Current recommendations include avoiding heavy wet soils and reducing plant stress. Preplant fumigation may give partial control in the first year. Rotation out of strawberries for at least two years can help reduce some of the pathogens. Research in Connecticut has shown that fertilizing strawberries with ammonium sulfate will suppress black root rot.

Red stele, Phytophthora fragariae.
Red stele is a root disease most commonly found in wet spots in the field although, in wet springs, the disease may spread rapidly over an entire field from spores carried in the soil water. The causal fungus develops only at cool temperatures, with plenty of soil moisture, and thus does the most damage in the spring. Roots may be rotted so severely that when the fruit is developing they do not provide an adequate water supply and the plants wilt and die. Red stele can be differentiated from all the other root rots by the characteristic red-brown color of the stele or central cylinder of the root. This discoloration is readily seen by scraping off the outer part of the root.

The red stele fungus will remain in the soil for at least ten years and for that time it should not be planted to strawberries without treatment. Resistant varieties are available. Although preplant fumigation will reduce red stele, planting in well-drained soils is more reliable. Among the compounds registered for use in Connecticut are metalaxyl and fosetyl-Al. Consult the label for dosage rates and safety precautions.

Verticillium wilt, Verticillium dahliae.
This disease is caused by a soilborne fungus and causes a wilt in cool temperatures. The disease causes the outer leaves to wilt and collapse while the inner leaves remain green until the plant finally dies. Damage from this disease is usually most severe the first year of planting. The fungus has a wide host range and infects many solanaceous plants and common weeds.

Use of resistant varieties is the most effective control strategy. Fungicides have not been shown to be effective.
Gray mold, Botrytis cinerea.
The fungus causing gray mold can live as a saprophyte on the dead leaves and litter under the plants. During periods of rain or humid weather, the fungus will infect any part of the plant including the green fruit. The greatest crop loss is caused by infections on the main fruit stems. Infections kill these stems and destroy the entire cluster of berries. The chief distinguishing characteristic of this disease is the masses of gray spores produced under moist conditions on all infected parts of the plant.

The disease can be managed by spacing plants to allow proper air drainage and drying of foliage. Control can also be achieved with the use of fungicide sprays applied at 10% bloom and full bloom. Among the compounds registered for use in Connecticut are captan and thiophanate-methyl. Consult the label for dosage rates and safety precautions.

Anthracnose, Colletotrichum fragariae.
The disease is caused by a fungus. In Connecticut, the disease attacks mostly the fruit. Symptoms appear as circular, sunken, water-soaked tan to brown lesions on the green and ripe fruit. When humid conditions prevail, the lesions will develop small, pink masses of spores in the center. The disease spreads rapidly during wet warm conditions.

To manage this disease, avoid using overhead irrigation and use a straw mulch to prevent splashing. Control can also be achieved with the use of fungicide sprays applied when symptoms first become visible. Among the compounds registered for use in Connecticut is captan. Consult the label for dosage rates and safety precautions.

Leaf blight, Phomopsis obscurans.
As the name implies this disease characteristically appears as a brown scorching of the foliage that appears most prominently just before fruit harvest, although it can be present at anytime during the life of the plant. The fungus also attacks the fruit stems and spreads to the calyx lobes and fruit. It causes a hard, brown rot of the fruit. On a susceptible variety, such as Pathfinder, scorch can cause a complete loss of the crop in a wet season. This fungus, like the gray mold fungus, is accelerated by wet weather, but once started, is not so quickly stopped by dry weather.

Control can be achieved with the use of fungicide sprays applied when symptoms become visible. Among the compounds registered for use in Connecticut are captan and thiophanate-methyl. Consult the label for dosage rates and safety precautions.

Leaf scorch, Diplocarpon earliana.
This leaf spot is common in Connecticut and can be easily recognized by small, dark lesions on the leaves and stems surrounded by a brilliant yellow or orange-red halo. Eventually, large portions of the leaf turn brown and somewhat resemble scorch. The fungus may infect the berries but does not cause as severe injury as scorch.

Control can be achieved with the use of fungicide sprays applied when symptoms become visible. Among the compounds registered for use in Connecticut are captan and thiophanate-methyl. Consult the label for dosage rates and safety precautions.

Leaf spot, Mycosphaerella fragariae.
Another leaf-spotting disease which is commonly found on strawberries, but it is usually not important. Infection by this fungus is confined almost entirely to the foliage where it produces characteristic small, whitish spots with red-purple borders. No leaf burning accompanies the foliage spotting.

Many of the present day varieties are resistant to this trouble and control measures are unnecessary. Control can be achieved with the use of fungicide sprays applied when symptoms become visible. Among the compounds registered for use in Connecticut are captan and thiophanate-methyl. Consult the label for dosage rates and safety precautions.

Powdery mildew, Sphaerotheca humuli.
Mildew is usually of little importance on strawberries because it appears late in the season after the season’s growth is nearly complete. Like other powdery mildews it is a superficial white powdery growth on the foliage. Occasionally it will cause some distortion of the leaves.

If control seems necessary, the use of fungicide sprays applied when symptoms become visible are effective. Among the compounds registered for use in Connecticut are thiophanate-methyl and sulfur. Consult the label for dosage rates and safety precautions.

Diseases caused by Bacteria:

Angular leaf spot, Xanthomonas fragariae.
The disease is caused by a bacterium. Symptoms first appear as tiny, water-soaked lesions. When the leaf is held up against a light source, the lesions are translucent. Over time the lesions begin to form chlorotic halos and resemble leaf scorch and leaf blight. The bacterium is spread by rain and wind.

Control is difficult. Rotation out of infested fields should be practiced. Some success has been demonstrated with the use of copper sulfate/elemental zinc applied when symptoms first become visible. Consult the label for dosage rates and safety precautions.

Diseases caused by Viruses:

Viruses.
Virus diseases of strawberries are not well enough distinguished to warrant treating them other than as virus complexes. Neither are the symptoms well enough defined to warrant specific descriptions. Symptom expression can vary from stunted chlorotic plants to just slightly off color and vigor, or perhaps all symptoms are masked.

There are no known control measures, but with the advent of virus-free plants in commercial quantities, the losses from virus diseases can be easily avoided. The virus-free plants are not virus-resistant and will not remain virus-free permanently.

Diseases caused by Nematodes:

Root-knot nematodes, Meloidogyne hapla.
This nematode causes swellings on the roots. These swellings interfere with normal root functions and decrease plant growth and vigor. The knots are caused when the female nematode enters the root and becomes encysted in the tissues.

This root-knot nematode persists in the soil for long periods and becomes increasingly difficult to control with time. Whenever found, prompt treatment of the area with a suitable nematicide should be made. Rotation of crops is not beneficial as the nematode is not specific on strawberry but infests a wide variety of plants.

Insect Problems:

Black vine weevil, Otiorhynchus sulcatus.
This species is more commonly found in strawberries in Connecticut than strawberry root weevil. The grubs devour the roots and crown. During the summer, the tops of severely injured plants turn brown and die. In the fall, the foliage of plants with injured roots are the first to turn red. The 1/2" long adult weevil is black, with a beaded appearance to the thorax and scattered spots of yellow hairs on the wing covers. Only females are known, and the adults are flightless. They feed nocturnally, notching the margins of the foliage. For plants with injured crowns, defoliation by adults can prevent recovery and the plants die. The legless grub is white with a brown head and is curved like grubs of other weevils. Adults and large larvae overwinter, emerging from May - July. The adults have to feed for 3-4 weeks before being able to lay eggs. Egg-laying starts and peaks during strawberry harvest, but may continue through August. Foliar insecticides available to homeowners are ineffective against black vine weevil adults. Treating the soil with insect pathogenic nematodes during May controls larvae. Overwintered larvae are somewhat affected, but eggs laid later in the season fail to develop through larval stages once insect pathogenic nematodes become established in the soil.

Cyclamen mite, Phytonemus pallidus.
This tiny mite feeds on newly formed buds and leaves, distorting them. Be sure to purchase clean plants. Predatory mites are being investigated. Dicofol, which is among the compounds registered for use against this pest in Connecticut, applied after harvest, to new foliage will control mites. Other, restricted use products that are effective include endosulfan and abamectin). Consult the label for dosage rates and safety precautions.

Garden millipede, Julus hortensis.
This millipede often injures strawberry plants, especially where the crown is infested with the crown borer. They eat into the crown and allows decay. When abundant, these millipedes also injure bulbs and the roots of various other plants.

Spittlebugs, Philaenus spumaris.
The nymphs are recognized by the froth or spittle mass which covers them. Feeding damages both leaves and fruit. Nymphs are present only in the spring. A spray of methoxychlor, which is among the compounds registered for use against this pest in Connecticut, applied when blossom buds first appear, has given control.

Strawberry aphid, Chaetosiphon fragaefolii.
This aphid transmits a virus disease of strawberry. The aphids winter over in the crowns of the plants. They develop wings in April and migrate to other plants. On newly set plants, frequent sprays of malathion, which is among the compounds registered for use against this pest in Connecticut may be used to control these aphids. Consult the label for dosage rates and safety precautions.

Strawberry bud weevil, Anthonomus signatus.
Also called the strawberry clipper, this weevil lays an egg in the flower bud, then eats the pedicel partly off. In severe infestations, this insect may cause a loss of 50 to 60 percent of the crop. However, strawberry plants usually compensate for clipped buds and loss of yield is not often detectable. The beetle is about 1/10" long, and varies in color from black to reddish brown. The larva feeds almost entirely on pollen and the eggs are laid almost wholly in the buds. A spray of methoxychlor, which is among the compounds registered for control of this pest, can be used only when the blossom buds first show, and is justified when there is more than two buds clipped per foot of row.

Strawberry crown borer, Tyloderma fragariae.
The grubs of this flightless weevil tunnel downward through the crown of the plant and by the time they are fully grown, the plants are severely injured. From one to three grubs may tunnel in a plant. The mature grub is about 1/5" long and is white with a darker head. The grubs mature in July and transform to weevils within the burrow. The adults are chestnut brown in color, have three darker spots on each wingcover and are about 1/6" long. The weevils emerge and feed for a time, but on the approach of colder periods go into the soil to overwinter. They appear in early spring and the females lay eggs singly in cavities eaten in the plant near the surface of the ground. There is one annual generation. Insect pathogenic nematode applications may help to reduce populations of this pest.

Strawberry flea beetle, Haltica ignita.
This small metallic blue or green flea beetle in early spring feeds upon the leaves of strawberry, often riddling them. It is about 1/6" long, and the females lay eggs on the leaves of the evening primrose, upon which the larvae feed. When mature, they enter the ground to pupate and overwinter, and the adults emerge the following spring. There is one annual generation. Spraying with methoxychlor, which is among the compounds registered for control of this pest in Connecticut, will protect the foliage. Consult the label for dosage rates and safety precautions.

Strawberry leafroller, Ancylis comptana.
The two halves of strawberry leaflets are often folded and webbed together. Greenish or brownish caterpillars live and feed inside. These leaves soon turn brown and die. In severe infestations, the fruit fails to mature. The adult moths appear in May and the females lay eggs singly on the undersides of the leaves. The eggs hatch in about a week, and the larvae feed for about a month. When fully grown they are about 1/2" long and vary in color from yellowish green to greenish brown with a brown head. They transform to brown pupae within the folded leaves and 10 days later the moths emerge. There are probably two generations each year in Connecticut. The insect overwinters both as a larva and a pupa. The moth is light reddish brown with forewings marked with wavy lines of darker brown and white and with wingspread of slightly more than half an inch. This insect can be controlled by spraying with rotenone, which is among the compounds registered for control of this pest in Connecticut, in spring about a week after the moths first appear. Consult the label for dosage rates and safety precautions.

Strawberry root aphid, Aphis forbesi.
This aphid feeds on roots. It passes the winter as a shiny egg on strawberry leaves. Ants may be partly responsible for aphid infestation. No control is known. Planting uninfested plants on clean land is the usual suggestion. Control of ants might help control the root aphid.

Strawberry root weevil, Otiorhynchus ovatus.
The legless grubs are white with brown heads and about 1/4" long. They feed on the roots of strawberry plants. There is one generation a year. The adults are wingless weevils with a short stubby snout. For control, see black vine weevil.

Strawberry whitefly, Trialeurodes packardi.
This whitefly is rarely destructive to strawberry plants. The eggs are laid on the undersides of the leaves, where the nymphs remain and suck the sap. The insect overwinters as eggs attached to the leaves, and these eggs hatch in early spring. The nymphs feed for about a month, pupate, and the tiny, mealy whiteflies appear to lay eggs for another generation. The number of generations each year is not known. The worst infestations are usually in patches, rather than over the whole field. In a small garden, it is possible to spray the underside of leaves with insecticidal soap or 1% ultrafine oil.

Twospotted spider mite, Tetranychus urticae.
This is a serious pest of strawberries. It infests the undersides of the leaves, which become light yellow in color, and the plants have a generally unhealthy appearance. Sometimes the mites form webs, which more or less enclose the upper as well the lower leaf surface. Among the compounds registered for control of this pest in Connecticut are insecticidal soap and ultrafine horticultural oil. Spraying with insecticidal soap will give sufficient control if applied at least twice at 7-10 day intervals. The predatory mite, Neoseiulus fallacis, is most commonly found feeding where there are mite infestations. A single application of ultrafine horticultural oil (1/2 - 1% dilution) can be effective if predatory mites are present. Special care should be taken with soap or oil to obtain thorough spray coverage, because they only work on contact. Commercial growers may also consider using abamectin, a restricted use product. Consult the label for dosage rates and safety precautions. Avoid applying carbaryl or pyrethroids, which tend to be much more toxic to the predators than to the pest spider mites.

White grubs
White grubs, the larvae of scarab beetles, sometimes cause severe injury to strawberry fields by eating the roots of the plants. Species involved include the Japanese beetle, oriental beetle, European chafer and Asiatic garden beetle, all of which are described under the lawn section. Sod land should be avoided when establishing strawberries. There are no effective control measures to protect the roots from larvae, so the best option is to reduce white grub populations in surrounding turf areas. See Lawns, oriental beetle. Two species, the Japanese beetle and Asiatic garden beetle, also feed on foliage as adults. Japanese beetles feed on foliage during the day; Asiatic garden beetles at night. This damage usually is minimal, so control of adults is not warranted.