Most Strawberry disease problems are fungal in nature, and caused by soil born pathogens. A sufficient ground cover of straw or well rotted mulch will help to minimize many diseases as the spores will bounce and spread further off soil and water than they will off straw.
Strawberry Plant Diseases
Red Steele Root Rot
Red steele, or red core, is a serious disease of strawberry.
In areas with cool moist soil conditions, especially soils heavy in clay that are saturated with water the disease is more prevalent.
If Plants begin wilting and dying off in the lower portions , the cause is very likely to be red stele.
Infected plants are stunted, lose their healthy green luster, and produce very few runners. Young leaves often have a metallic, bluish-green discoloration. Older leaves turn prematurely yellow or red. Diseased plants wilt rapidly and die at the first signs of summer heat.
Diseased plants have very few new roots, when compared with the roots of healthy plants that have thick and bushy roots with many secondary feeding roots.
Infected strawberry roots usually appear gray, while the new roots of a healthy plant are yellowish-white.
Stele Root Rot of Strawberry Ohio State University Extension Fact Sheet
Management ~ Control
1. Choose Resistant varieties if this has been a issue in the past.
Resistant Varieties include
Allstar, Earliglo, Hood, Guardian, Tristar, Lateglow, Tribute
Agri-Fos is registered for treatment of Red Stele. Read all cautions and instructions related to application time and dose before applying.
Leather Rot is Caused by a soil inhabiting fungus and occurs on many plants. The fungus attacks berries in the field at all stages of development.
Fruit rot occurs when the berries come in contact with the soil. The fungus may also cause a serious crown rot, which can develop along with the fruit rot.
Strawberries will initially have brown spots on the berry itself, which gradually spreads to cover the entire berry, giving it a leathery appearance and foul odor. On ripe and ripening fruit, brown and purple spots and streaks develop, the fruit decays rendering it unpalatable.
Google Images - Leather Rot on Strawberries
Cultural controls for leather rot, once you have it, is like closing the barn door after the livestock has escaped. But it can help prevent or minimize subsequent occurrences. Leather rot requires splashing water, rain or excessively wet conditions to transport its spores to the fruit. Site selection, Mulching, soil aeration, the use of drip systems for irrigation and other common sense approaches to minimize the possibility of it becoming established, or further established as the case may be - are advisable.
Mulching, particularly plastic mulch, prevents the berries from coming into contact with the ground and minimizes rain splash, it will help control leather rot.
Commercial growers frequently use drip fumigation. This is not readily an option for home growers. The chemicals available to farmers are not always available to home growers.
The most commonly used active ingredient is chloropicrin which is a "Restricted Use" chemical. There are no resistant cultivars for leather rot and unfortunately for home gardeners - no real cure. Prevention is the best cure.
Strawberry leaf blight also known as Phomopsis leaf blight is one of the most common foliage diseases found on strawberry. It causes a rot at the stem end of the fruit. Caused by a fungus which overwinters in plant debris on the ground.
The fruit infection phase of the disease is referred to as Phomopsis soft rot.
Infection may occur early in the growing season - early to mid-April, at about the time buds emerge from the crown, the fungus attacks the new leaves and causes the primary infection. but symptoms are not visible until mid season.
Later, when fruit has formed, the green fruit cap becomes infected and turns brown.
If uncontrolled, a considerable number of fruits may be rotted by harvest time. Suitable conditions for disease development are temperatures ranging from 26-32oC and 72 hours of leaf wetness.
Chlorothalonil based fungicides are helpful in treatment.
Copper hydroxide and other copper based fungicides are also effective. Consult product labels before applying for dosage and application times.
When a strawberry plant is severely infected with Verticillium wilt fungus, the chances of it surviving to produce a crop is slim. The Verticillium fungus infects hundreds of various host plants. The fungus can survive in soil, and, once it becomes established in a field or garden, it may remain alive for decades. Cool, overcast weather interspersed with warm, bright days is most favorable for its development. Infection and disease development may occur when soil temperature is from 70 to 75 degrees F.
Anthracnose ~ The anthracnose fungus causes dark brown, oval sunken areas or spots on stems. It also causes the crown to rot, which may cause young leaves to wilt.
The fungus can be carried on visibly healthy plants. Therefore, you should be sure to use only healthy certified plants for transplanting.
Anthracnose is favored by hot, humid weather. As with many plant pathogens, avoiding excessive moisture will help decrease the severity of this disease.
A ground-cover ~ dry mulch is also advisable.
Anthracnose cannot be completely eradicated with fungicides.
Potassium Bicarbonate can help to control outbreaks.
Bonide Remedy Fungicide, which contains Potassium Bicarbonate is useful for this purpose.
For large fields try Bonide Lime Sulfer Spray.
Botrytis Fruit Rot, also known as Gray mold, is caused by spores produced on dead strawberry foliage. The fungus invades young strawberry leaves without producing any initial symptoms. As the leaf matures, the pathogen spreads quickly through the dying tissue . Spores are dispersed by air, water or harvesting and ultimately infect all parts of the plant. Bonide Remedy Fungicide is effective against against Botrytis Fruit Rot.
The fungus that causes Powdery Mildew appears as a grayish-white coating on the undersides of leaves. Leaf function is impaired but symptoms develop so late in the season that berry production is seldom affected. Bonide Remedy Fungicide is effective against Powdery Mildew.
See Also: University of California: Strawberry -Powdery Mildew
Insect Pests of Strawberries
Aphids cause strawberry yield losses due to honeydew production. Honeydew deposits on fruit cause sooty molds to develop. White skins shed by aphid nymphs stick to the berry which renders the fruit unpalatable.
Corn Earworm causes damage to strawberries by burrowing into the berry. Only larvae of the first generation attacks winter strawberries. Entrance holes made by early larvae aren't visible, and the fruit must be cut to determine their presence. Larvae typically feed in the air pocket at the strawberries center. Mature strawberries containing larger larvae appear seedy and develop a shrunken surface with brown patches
Strawberry Root Weevil, a snout beetle, feeds on the roots of strawberry plants and can completely devour small rootlets and destroy the bark and cortex of larger roots. Soon after feeding begins, plants wilt and either become less productive, cease to produce and~or die off.
Milky Spore is another weapon in the war against weevils , it is not harmful to beneficial insects, birds, bees, pets or man. The product is approved and registered with the EPA, Milky Spore will not affect wells, ponds or streams.
Bacillius thuringiensis [Bt] is somewhat effective against the larvae stages it should be applied as soon as the presence of adults is evident, to head off the imminent egg laying and hatched larvae.
Neem based Products, such as Azatin or Azadirachtin [extract of the neem seed-] prevents the larvae from developing normally and is also a good alternative for later larval stages. These products degenerate rapidly in nature and need to be reapplied frequently. For effective use mix Neem oil with equal parts of water and saturate the ground around the plants, allowing it to soak in thoroughly.
In severe infestations, there are a number of broad spectrum pesticides registered for use against weevil, sold under varying trade names.
Spider Mites will retard the growth of strawberry plants which can result In plant death. Most severe losses have resulted from outbreaks starting in late fall or winter.
In the spring, mites increase rapidly. They do the greatest damage during or after the blooming period.
Lady Bugs can help to contain infestations of mites
Sprays of rosemary oil are effective as well as non toxic.
Nutrient Problems effecting Strawberry Plants
Iron deficiency, or chlorosis, is common in excessively watered strawberries. It is characterized by pale, yellowed leaves with dark green veins. In severe cases, the edges of the leaves will dry up and turn brown. Yields are typically dismal. See: Nutrient Disorders in Vegetable Gardens
Water management is vital when growing plants in alkaline soils [high pH]. In excessively wet or poorly drained soils, the chemistry of the soil degrades in some aspects and iron is depleted. Excessive irrigation in heavy clay soils or in cool climates frequently leads to a deficiency of iron. Numerous iron compounds are commercially available for treating iron chlorosis but no single product has proven 100% successful in all situations. Furthermore strawberries do not always respond well to foliar sprays of iron.
If you notice symptoms of chlorosis, reduce the frequency of watering. If the condition persists, apply Iron sulfate using recommendations on the bag. Sequestrene will also do the trick.