Causes Of Strawberry Leaf Distortion

 

 

 

These mites are very tiny, so you can’t see them even with a magnifying glass. Symptoms are small distorted leaves that are cupped upward and have an “off” color. Often only individual plants show symptoms at first, but because the mites are sticky and can be spread on equipment or worker’s hands, patches of plants will eventually show symptoms. If symptoms are not recognized and plants are not treated, entire plantings can become infested. Plant vigor is affected, and severely infested plants remain very small with only tiny leaves and fruit present. If the problem is recognized early when only a few plants are lightly infested, predatory mites can be released to bring the problem under control.

 

 

 

 

Plants can also be treated with Thionex – but only in perennial (i.e., matted-row) fields or with Portal. Be aware that after July 31, 2016, Thionex can no longer be used on perennial strawberries. Its use had already been discontinued on annual strawberries as of 2012. Either Thionex or Portal must be applied at times of the year when the spray can penetrate into the crown area, which is where the cyclamen mites are found. That means that there are only two windows of opportunity for treatment – early spring when only a few leaves are present, and at renovation after leaves are mowed off. High volumes of water (200 gallons per acre) should be used.

 

 

Cold injury can also cause leaves to emerge distorted either fan-shaped or lopsided, as if they had been exposed to a growth regulator type of herbicide. In some cases, they also look crinkly or bubbly. New leaves that emerge subsequently are normal in appearance when cold injury is the cause of leaf distortion.

 

 

Growth-regulator types of herbicides cause curled, fan-shaped, or lopsided. So far, we’ve seen symptoms of damage from spot applications of clopyralid (Stinger), and glyphosate (Roundup and other trade names). When Roundup is the cause of the leaf distortion, the leaves will usually be “strappy” in appearance and chlorotic as if they have a nutrient deficiency.

 

 

Viruses can cause leaf distortion and discoloration, and this might be what people think of first if they remember the widespread virus situation from 2013. In that year, nursery plants had become infected with two different viruses, and infected plant material was sent to a number of growers in the eastern U.S. Much more stringent testing protocols are now in place at a number of nurseries, so hopefully we won’t see a similar situation anytime soon.

 

 

Potato leafhopper feeding can cause leaves to become distorted, yellowed, and curled, though it is a little early for widespread issues yet this year. Symptoms are most apparent when plants are drought- or heat-stressed and growing slowly so that symptoms accrue. New plantings of matted-row strawberries, where the plants have few leaves for photosynthesis, are often most severely affected. The leafhoppers can be difficult to spot as the adults fly quickly. The nymphs cannot fly; however, they are usually on the leaf undersides so the leaves should be flipped over to find them.

 

 

Powdery mildew will cause leaves to curl upward, usually with some purpling on the leaf undersides. The typical white powdery appearance is usually only apparent on the upper leaf surface, if it is apparent at all. In some cases, powdery mildew is apparent on the fruit, and in other cases, it’s less apparent but grows around and under the seeds, causing them to easily rub off during harvest. Usually some scarring is present where the seeds had been. Powdery mildew is most problematic when the weather is warm, dry, and humid. There are a number of fungicides with FRAC codes 1, 3, and 11 that are effective, though resistance is a serious concern within these chemical classes, so materials in these classes should not be overused.

 

 

 

 

 

Boron deficiency causes symptoms that are nearly identical with cyclamen mite damage. Boron deficiencies are most common on sandy soils. A plant sample should be submitted for nutrient analysis to correctly identify the problem before applying corrective amounts of boron. If applying boron to correct a deficiency, take care to apply the correct recommended rate (either 4 pounds per acre of Solubor as a soil application in early spring or late fall, or 1.5 pounds of Solubor in 100 gallons of water per acre in early spring and after renovation). Solubor contains 20% boron, so you are applying only 0.8 pounds or 0.3 pounds of actual boron per acre per application, respectively. Boron can quickly become toxic if over-applied.