Transpiration Burn

Transpiration burn may sound like a bad deal, but it refers to the damage caused by mite feeding.
 
What is transpiration?

Plants exhale water through tiny openings called stomas in a behavior known as transpiration. Stomas are generally found on the underside of leaves, but they also occur on stems and flowers. Stomas open and close to allow for gas exchanges necessary for photosynthesis [carbon dioxide in; oxygen out]. Transpiration also helps move plant nutrients, such as zinc, into and within a plant.


The combined effects of plant transpiration and evaporation of water from the soil are called evapotranspiration. Maintaining the proper water levels within a plant is critical to its health. When mites start feeding, that balance changes.


Types of mites

There are over 42,000 different types of mites in the world. They can be black, yellow, green, brown, or red. They are tiny. Gall mites, spider mites, European red mites, and thread-footed mites are common garden pests. Some mites prefer buds, others raise blisters on plants, and others create rust patterns. All mites have piercing mouthparts used to suck nutrient-rich fluids from your plants. Transpiration burn occurs when mite feeding reaches critical levels.


Symptoms of transpiration burn

Mite feeding often causes leaf stippling. The loss of water and nutrients from countless microscopic punctures threatens plant health, especially in areas with scorching summers prone to drought. As temperatures rise, mite feeding increases and bronzing occurs. The accumulated water loss from mite feeding reaches a point where entire areas of the leaves die, leaving spots of dead brown or black tissue. Less leaf area means less photosynthesis, reduced crops, and unhealthy trees. Transpiration burn is a common problem of pear trees.


Preventing transpiration burn

A large, well-hydrated tree can lose up to 100 gallons of water a day during the peak of summer. Proper irrigation, using irrigation rings or soaker hoses, can prevent water stress on fruit and nut trees, helping them counteract the damage caused by mites.


Mite control is tricky. These pests quickly develop resistance to chemicals, so pesticides don’t work. You can use a strong stream of water from a garden hose to displace mites. You can also buy predatory mites that hunt and feed on the mites feeding on your plants. Insecticidal soaps and oils can also kill mites, but use them carefully. They can cause sunburn damage and other problems.


Keep your plants healthy and monitor them regularly for webbing and stippling, so you can deal with mite populations before they get out of hand.