What are the methods for controlling pests and diseases of walnut trees?

Walnut trees have many kinds of pests and diseases, and the control methods differ for each. Diseases include rot disease, black spot disease, branch blight, brown spot disease, powdery mildew, and anthracnose, which can be prevented by spraying lime sulfur before budding or during the flowering period. Pests include the walnut fruit moth, the white tiger moth, the angular-striped ancient tussock moth, the cloud-spotted longhorn beetle, the globular mealybug, the small jewel beetle, and the aromatic carpenter moth, which should be controlled by spraying the corresponding pesticides before the pests occur.

1. What pests and diseases affect walnut trees?

The diseases of walnut trees include rot disease, black spot disease, branch blight, brown spot disease, powdery mildew, and anthracnose, while the pests include the walnut fruit moth, the white tiger moth, the angular-striped ancient tussock moth, the cloud-spotted longhorn beetle, the globular mealybug, the small jewel beetle, and the aromatic carpenter moth.

1. Walnut rot disease: it mainly damages the cortex of the trunk, with peak periods of infection in spring and autumn, and the most severe damage from mid-April to late May. Walnut trees are generally susceptible to this disease when management is extensive, the soil layer is poor, drainage is poor, fertilizer and water are insufficient, and the tree vigor is weak or the tree has suffered frost damage or salt damage.

2. Walnut black spot disease: it mainly damages leaves, new shoots, and fruits. The pathogen generally overwinters in branches or buds, and in the following spring it exudes bacterial fluid that spreads via wind and rain.

3. Walnut fruit moth: it mostly begins to cause damage in June-July, mainly harming fruits and leaves. The damaged fruit peel turns black and begins to sink, causing early fruit drop, and the infestation is severe in places with high soil moisture and dense weeds.

2. How to control pests and diseases of walnut trees?

1. Walnut rot disease: do not apply excessive nitrogen fertilizer; increase phosphorus and potassium fertilizer to improve the plant's own disease resistance; do a good job of ventilation and dehumidification to reduce or avoid leaf condensation; irrigate appropriately, and do not water on rainy days or in the afternoon, to prevent frost damage. Spraying lime sulfur before the disease occurs can prevent and control the disease; during the disease period, promptly remove diseased plant residues, diseased fruits, diseased leaves, diseased branches, etc., and after uprooting the vines, thoroughly remove diseased and residual fallen leaves and residues.

2. Walnut black spot disease: after leaf fall, apply tree-protecting general to the trunk and branches to hinder the pathogen from multiplying on the tree body; for pruning cuts and wounds, promptly apply callus antiseptic film to prevent pathogen invasion and rain contamination; for diseased tree bodies, promptly spray pesticides for control.

3. Walnut fruit moth: in late autumn or early spring, deeply turn the soil under the tree canopy to destroy the overwintering cocoons; during the peak egg-laying period of adults and the initial hatching period of larvae, spray fenitrothion or phoxim to eliminate the larvae before they bore into the fruit; before adult emergence or when individual adults begin to emerge, spray phoxim to poison and kill the adults emerging from the soil.