Drought Stress

Among the most common preventable tree problems is drought stress.  Drought impacts a tree in many ways because water drives all the processes within a tree.  From photosynthesis to root growth and nutrient uptake, water is a part of it all. As trees grow, they expend energy in creating a root system that will support them in times when water is scarce.  In urban landscapes we often create situations that expose trees to drought stress.  While trees can survive initial drought conditions, prolonged periods of drought stress on trees make them susceptible to insects and diseases.

Treatment Strategy

The best treatment strategy for drought is prevention.  Watering during dry periods as well as supporting the tree's health otherwise can be helpful.  The use of a growth hormone regulator called Cambistat® has been proven to increase fibrous root growth and therefore drought tolerance if drought is a common problem in your area.

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Drought Stress Treatment Option 1

Supplemental watering

Adequate water is a key factor in maintaining healthy trees.  Trees need an inch of water per week during the spring, summer, and fall.  If it rains less than one inch per week, trees need to be watered to help maintain soil moisture and minimize drought stress.  Use a soaker hose or a trickle from a garden hose around the drip line of the tree.  Watering in the evening for several hours is a good strategy because it minimizes evaporation.  For more information on proper tree watering, check out our blog on watering drought stressed trees.

Mulching

Since fibrous roots are so close to the soil surface, they can dehydrate and die when the soil loses significant moisture and becomes over heated.  The removal of any turfgrass and the addition of 3 inches of wood chips or shredded bark under the drip line can have a very beneficial effect by holding in moisture and promoting healthy fibrous roots. Check out our blog for more information on mulching the right way.

Application Type - Cultural Practices

DIY Equipment Needed: 

• Soaker hose (for watering)

• Mulch

• Rake and shovel

Drought Stress Treatment Option 2

Using  Cambistat®

Cambistat® is a plant growth regulator used to extend the life of trees by keeping them at a manageable size for a longer period of time. Research shows that Cambistat® slows the growth of trees, allowing the tree to redirect some of its energy from canopy growth into defense chemicals, fibrous root production, and stored energy. This reallocation of energy results in a healthier, more durable tree.

Research shows Cambistat® increases drought resistance by helping the tree reduce water losses during dry, hot periods, and it increases fine root growth. The leaves of Cambistat® treated trees tend to be greener (higher concentrations of chlorophyll) than untreated trees and have a thicker leaf surface and denser surface hairs, which help to prevent excessive moisture loss.

Application Type Soil Drench or Soil Injection

DIY Product/Equipment Needed:

Cambistat®

• Gloves

• Measuring or diameter tape

• Soil drench: bucket or watering can

• Soil injection: HTI Soil Injection Kit

Drought Stress DIY Kit

Option 1:

Application Type - Cultural Practices

DIY Equipment Needed: 

• Soaker hose (for watering)

• Mulch

• Rake and shovel

Option 2:

Application Type Soil Drench or Soil Injection

DIY Product/Equipment Needed:

Cambistat®

• Gloves

• Measuring or diameter tape

• Soil drench: bucket or watering can

• Soil injection: HTI Soil Injection Kit

How Is It Spread?

Why urban trees are drought stressed

Less Water is Available – Unless regularly irrigated, urban trees generally have less water available than their counterparts in natural settings.  Why? Paved surfaces encourage runoff instead of absorption, and these surfaces cause higher soil temperatures and faster evaporation of rainfall.

Restricted Root Space – Building foundations, streets, driveways, and other obstacles limit the expansion of tree roots and significantly reduce the amount of water and minerals available to the tree.

Compacted Soils – Urban soils are usually compacted from human activity, and this creates stress for a tree. Soils can become difficult for roots to penetrate, and compacted soils hold much less water and oxygen which are critical for tree health.

Competition – Most yards have a dense layer of turf that surrounds a tree. Turf aggressively competes for minerals and water, which reduces their availability to other plants. 

Susceptible Trees

All trees are susceptible to drought stress.

Symptoms

The symptoms of drought stress on trees are similar to many other insect and disease problems and include:

• Wilting of the leaves (usually starts at the top of the tree)

• Slowed growth

• Chlorosis (yellowing of the leaves)

• Thinning of the canopy

• Leaves are smaller than normal

• Marginal necrosis (the leaves turn brown from the outside moving inward)

Related/Similar Problems

Aphids, Chlorosis, Spider mites and wood boring beetles

Timing

Year round

Urgency

High

Risk of Spreading

High

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