Walnut Pests and Control Methods

Managing walnut pests is essential for maintaining the health and productivity of walnut trees. Various pests can damage walnut orchards, affecting both the yield and quality of the nuts. Implementing effective control methods is crucial to protect your investment and ensure a bountiful harvest. This guide provides insights into common walnut pests and offers practical strategies for their control, helping you to keep your walnut trees thriving and pest-free.

Codling Moth [Cydia pomonella L. (Lepidoptera: Tortricidae)]

Description and Damage:

• Adults are gray in color, 10-12 mm long, and their eggs are oval-shaped and 1-1.2 mm in size.
• Larvae are 15-20 mm long and dirty white-pinkish in color.
• Moths emerge in late April-early May and lay their eggs on fruits, usually where fruits touch each other or on leaves.
• Larvae overwinter in fruits and under the soil.
• It generally produces 2-3 generations per year.

Control:

• Collect and destroy fallen fruits during the summer months.
• Avoid locating storage houses near walnut orchards.
• Wrap corrugated cardboard around tree trunks and thick branches in the summer and autumn, and kill larvae and pupae collected from these areas with weekly checks.
• Protect and increase the effectiveness of natural enemies.

For chemical control:

• Apply the first spray when fruits are the size of hazelnuts.
• Repeat other sprays 1 or 2 times at 15-20 day intervals depending on the duration of the insecticide’s effect.
• The “Prediction and Warning Model” used in apples can also be used in walnuts.

Walnut Aphids [Callaphis juglandis (Goeze)], Walnut Small Aphids (Chromaphis juglandicola Kalt.) (Hemiptera: Aphididae)

Description and Damage:

• Adults of both species are greenish-yellow in color and 1.5-2.0 mm long.
• They feed on plant sap in leaves and shoots.
• When aphid density increases in spring, there is a decrease in fruit size.
• High aphid density in the summer months causes the insides of the fruit to wrinkle.
• They also cause the formation of fumagine (black honeydew) on fruits and leaves with the sugary substance they secrete.

Control:

• Avoid close planting in new orchards, avoid excessive irrigation and nitrogen fertilization.
• Weed control should be carried out in and around the orchard, and trees should be pruned regularly each year to ensure good air circulation in the orchard.
• Protect and increase the effectiveness of natural enemies.
• Usually a single spray is sufficient in spring.

Walnut Leaf Gall Mite (Eriophyes tristriatus Nalepa), Walnut Leaf Blister Mite (Aceria erinea Nalepa), (Acarina: Eriophyidae)

Description and Damage:

• Walnut scabies mites, which are around 0.1-0.2 mm in size, cannot be seen with the naked eye.
• They overwinter in buds.
• In spring, as leaf buds begin to shoot, adult individuals emerge from the winter quarters and start feeding on the leaflets.
• They feed by sucking and cause deformation (gall, swelling) in the plant tissue with the toxic substance they secrete during sucking.
• In severe infestations, leaves fall prematurely and the shape of the fruit may be distorted.

Control:

• In mild infestations, prune and remove and destroy infested leaves and shoots from the orchard.
• Protect and increase the effectiveness of natural enemies.

For chemical control:

• Inspect leaves and shoots in spring for galls caused by the pest, and spray when damage symptoms are seen on the leaves.

Pear Lace Bug (Stephanitis pyri):

Description and Damage:

• Adults are small, ornate insects measuring 3.0×2.0 mm. Their wings are transparent and have a honeycomb pattern.
• Larvae feed on the undersides of leaves and feed on plant sap by sucking on the leaves.
• Leaves turn pale and small black spots appear.
• It produces 2-3 generations per year.

Damage:

• It causes yield loss and leaf discoloration by sucking on the leaves of walnut trees. It can reduce fruit quality.

Control Methods:

• It is recommended to protect natural enemies such as Stethocomis pyri, use selective pesticides, consider environmental factors, and use chemical methods in a controlled manner.

Woodworm (Zeuzera pyrina):

Description and Damage:

• Adults are large, white insects with dark spots on them.
• Larvae feed on the woody parts of trees and open galleries in the trunk and branches.
• These galleries can weaken and break trees and cause them to dry up.

Damage:

• It weakens, breaks and dries trees by opening galleries in the trunk and branches.

Control Methods:

• It is recommended to prune trees regularly and kill harmful larvae by inserting wires into their galleries or injecting gaseous insecticides.

Mudworm (Agalmatium flavescens):

Description and Damage:

• Adults are dirty yellow beetles, 4-5 mm in size. Larvae feed on herbaceous plants and then move to trees to lay their eggs. The pest produces one generation per year.

Damage:

• By sucking on flower buds, young shoots, and fruit stalks, it can cause wounds, discoloration, and shedding in plant tissue.

Control Methods:

• Cleaning egg sacs on trees, weed control, and pesticide use are recommended.

Walnut Leaf Miner Moth (Caloptilia roscipennella):

Description and Damage:

• These small moths lay their eggs on walnut leaves. Larvae feed by creating galleries within the leaves, causing damage.

Damage:

• By creating galleries in leaves, they can cause deformation in shoots and drying of leaves.

Control Methods:

• Chemical control, protection of natural enemies, and regular orchard maintenance are recommended.

Other Pests:

Description and Damage:

Brown scale, mulberry scale, vine mealybug, and crows can also cause problems in walnut orchards from time to time.

Control Methods:

Information can be obtained from Provincial and District Directorates of Agriculture and Forestry of the Ministry of Food, Agriculture and Livestock to address the problem.

Caution: This document is intended for informational purposes only. For walnut pest control, we strongly suggest consulting the Ministry of Agriculture and Forestry and agricultural engineers.