Recipe for Homemade Aphid Control for Willows

Pest Identification

• Melon aphid adults are normally wingless, and in hot, dry summers, they are bright yellow. Occasionally, adults become more slender than pear-shaped and develop wings in order to leave a heavily infested plant for easier feeding elsewhere. Giant willow aphids are also pear-shaped, but they have long antennae and may have brown or grayish bodies and black spots. Nymphs are translucent and dark yellow. Also brown or gray with black spots, giant bark aphids have darker heads and the spots may are often easier to see than those on willow aphids. Both giant aphid species have long, spidery legs. Heavy infestations of aphids can cause dieback, defoliation and, in some cases, death of willow trees.

Basic Insecticidal Soap Formula

• The simplest homemade insecticidal soap is quite capable of killing aphids on willow trees. Adding 2 tablespoons of mild dishwashing soap to a gallon of water makes basic insecticidal soap. Baby shampoo or pure castile soap can be used in place of dish soap. It is important that the soap contain no bleach or degreaser and be as pure as possible.

Insecticidal Oil Formula

• Formulating a homemade insecticidal oil is also easy. Add 2 tablespoons of vegetable oil to 1 gallon of the insecticidal soap concoction and mix well. Because oil and water separate easily, this mixture needs to be shaken or stirred in the sprayer reservoir to keep it properly blended.

Application

• Pour insecticide mixture into a sprayer and thoroughly coat the foliage of the willow, paying special attention to the undersides of leaves. Insecticidal soaps kill all insects present on the tree at the time you spray, including beneficial insects, but have no residual effect. If aphids persist, repeat spray weekly until the bugs are gone.

Tips and Warnings

• It's a good idea to test your homemade spray on a small area of the willow. Wait two or three days, and if the willow tolerates the insecticide, go ahead and spray the rest of the tree.
  Once the insecticidal soap dries, it should be washed off with plain water from the garden hose to prevent buildup on the foliage.
  Don't spray in temperatures above 90 degrees Fahrenheit or when the plant is in full sun, as this can cause phytotoxicity. Spraying in the morning or early evening helps prevent problems.