Drought and Pest Pressures: How to Save Your Stressed-Out Trees

Drought and Pest Pressures

Spongy moth is the new common name for Lymantria dispar, formally known as the gypsy moth. Read more at: Spongy Moth is the New Name for and Old Pest

As temperatures begin to rise across the country and spike even higher in traditionally warm areas, protecting drought-stressed trees should take precedence in your recommended treatment plan. Trees suffering from drought stress have increased risk of damage from attacking insects, diseases, heat, and cold. Here are some pests to be aware of and treatments to preventatively protect drought-stressed trees from harm.

Pine Bark Beetle

After a period of drought, many areas will see an increase in Pine Bark Beetle (PBB) population. PBB can cause widespread tree death. They infest conifers throughout North America, commonly attacking high numbers of trees and causing extensive vascular injury and ultimately tree death. Symptoms of infestation include pitch tubes, reddish boring dust, adult exit holes, and yellowing foliage.

Research studies using TREE-äge have demonstrated great results. This formulation must be injected into active sapwood and will actively control pests for up to two years with a single application.

Invasive Shot Hole Borer

Invasive Shot Hole Borer (ISHB) is an exotic ambrosia beetle that attacks both healthy and drought-stressed trees. The “ambrosia” name refers to a symbiotic fungus that is carried by the female in special organs in her mouth parts. The fungus is grown in the beetle galleries and both the adult beetles and larvae feed on the fungi. Infestation and spread of this pest is likely to continue unabated without treatment. ISHB commonly attacks the main stem and larger branches of trees and shrubs, but injury can be found on twigs as small as 1 inch in diameter. It produces a very precise, perfectly round, tiny (< 0.1 inches in diameter) entry hole in most trees. Depending on the tree species attacked, PSHB injury can be identified either by staining, gumming, or a sugaring response on the outer bark. Infection with the fungus carried by the borer can cause leaf discoloration and wilting, dieback of entire branches, and tree mortality.

We suggest using a combination of insect and disease control products to combat ISHB. TREE-äge provides two years of control, while Propizol protects trees from the fungi introduced by the pest.

Spongy Moth

After a series of dry years, Spongy Moth population tends to explode, leaving trees at risk of defoliation. In the last few years, the Spongy Moth population in New England in particular has expanded rapidly. After unusually dry weather, the parasitic fungi and viruses that usually keep this pest in check are suppressed, allowing larvae to escape, attack, survive, and defoliate trees. Trees that are completely defoliated may re-foliate 3 to 4 weeks after feeding ends, expending an enormous amount of energy. Repeated defoliations may kill trees or severely weaken them, exposing them to native secondary disease or insect organisms.

Trunk injection with TREE-äge provides both preventative and curative control depending on the time of year treatment is applied. It protects trees from Spongy Moth and up to 51 other types of pests, including Emerald Ash Borer and Winter Moth. Use ACE-jet in combination with TREE-äge when treating an active population for fast knockdown and residual to carry through the pest life cycle.

Additional Recommendations

We suggest persuading your clients to protect high-value trees with at least one deep watering weekly. Slow, deep irrigation is preferred over more frequent, lighter watering. Ask clients to “pre-water” trees that are to be injected with insect control formulations and to irrigate again after treatment. This assures effective movement of the treatment within the tree and reduces risk of adverse reaction due to treatments made to drought-stressed trees.

Hydretain and CytoGro are two products that should be used to prevent drought stress, aid in the recovery of drought-stressed trees, and improve the efficiency of nutrients and control products. Hydretain maximizes the water available to the tree roots by condensing free water vapor, or soil humidity, back into usable liquid water, making it available for the roots to absorb. CytoGro’s rooting hormones help trees increase root mass, which can take up more water and nutrients from the soil. More moisture and nutrients for the plants mean better stress tolerance and quicker recovery.

Trees recovering from years-long drought will benefit from nutrition to promote root development, water management, and microbial support. We recommend adding soil-applied NutriRoot to root zones for this purpose. This will enhance soil water-holding capacity, improve root development, assist in new plant establishment, improve water penetration in desiccated soil, and provide key micronutrients, while stimulating plant response.

Also consider adding soil-applied Shortstop 2SC plant-growth regulator to your plant protection strategy. It increases fine root-hair development which enhances plant survival. It also improves chlorophyll production and reduces water loss by reducing stomata size.

Though warm temperatures are unavoidable this season, you can help your clients protect their trees from drought and pest pressures ahead of the curve. Contact your local Regional Technical Manager for more information specific to your area and situation.