The Latest Control Methods for Zucchini Powdery Mildew

Powdery mildew is a major disease of zucchini and occurs everywhere, most commonly in spring and autumn. The incidence rate is 30-100%, with a clear impact on yield, generally reducing it by about 10% and, in severe cases, by more than 50%. Besides harming zucchini, this disease also harms cucumber, pumpkin, winter melon, loofah, melon and many other cucurbit crops. Let us take a look together at the control methods for zucchini powdery mildew!

Harmful Symptoms

Zucchini can be infected from the seedling stage to the harvest stage. It mainly harms the leaves, followed by the petioles and stems, while the fruit is less affected. In the early stage of leaf disease, small round white powdery spots appear, which later gradually expand into irregular white powdery mold patches (that is, the pathogen's conidia). The lesions can join together into patches, and the affected parts of the leaves gradually turn yellow. In the later stage, many yellow-brown small granular dots appear on the lesions (that is, the pathogen's cleistothecia). When the disease is severe, the diseased leaves turn brown and die, and the white powdery mold turns grayish white.

Disease Occurrence Pattern

The pathogen of zucchini powdery mildew overwinters in the soil as cleistothecia with diseased residues, or overwinters by causing damage in protected cultivation areas. In southern vegetable-growing areas, the pathogen overwinters and oversummers on hosts as mycelium or conidia, and spreads through airflow, rain and irrigation water. Disease can occur at 10-25°C, and with alternating high temperature and dryness and humidity, the disease develops rapidly. In the late growth stage, the plants grow weakly and the disease is severe. Excessive planting density and lack of fertilizer during the growth period also lead to more severe disease.

Control Methods

1. Seedling stage prevention: Use chlorothalonil, carbendazim or thiophanate-methyl in rotation and spray once every 7-10 days. It prevents many diseases and has a good effect.

2. Ventilation and light penetration: Timely remove the old leaves, yellow leaves and diseased leaves from the lower part of the plants to increase ventilation and light penetration. This can greatly reduce the incidence of powdery mildew and at the same time increase the rate of flowering and fruit setting.

3. Chemical control: In the early stage of disease, evenly spray the formula of tetraconazole + Zhantou + Baifei, or the formula of Xingnong 50% sulfur suspension concentrate at 250 times + Zhantou + seaweed extract. If growth is too vigorous, use the formula of Guanxin + Score + Zhantou + Baifei for control.