Symptoms and prevention methods of eggplant fruit blight

When eggplants are about to mature, it will be very troublesome if eggplant fruit blight appears on the fruits. Here we will tell you how to prevent and control it.

Eggplant fruit blight symptoms

It mainly harms fruits, and occasionally harms seedlings and shoots.

If the disease occurs in the seedling stage, dark brown water-like spots will appear at the base of the seedlings, and the seedlings will shrink or fall over, but no damping-off symptoms will occur.

When the fruit is infected, a 1 cm round to oval sunken spot will appear on the surface of the fruit, which will then turn brown and become soft and rotten. The spread is rapid. When the humidity is high, white cotton-like substances will grow on the diseased part. The cotton-like substances of this fungus are longer, which is different from the cotton-rot of pepper. Severe cases are prone to cause fruit drop.

During the transportation and storage period, the diseased parts continue to decay, and some even produce a gray-brown mold layer, becoming an important market disease.

Eggplant fruit blight

Characteristics of the Pathogen of Eggplant Fruit Blight

Phytophthora infestans (Montagne) de Bary, the mycelium is colorless, without septum, 4 to 10 microns in diameter, the sporangium stalk is colorless, 10 microns wide, 1 mm long, often with branches or 3 to 5 roots in clusters, growing from the host stomata, wounds of diseased fruits or lenticels, the top of the sporangium stalk swells to form sporangia, which are terminal and pushed to the side by the sporangium stalks that grow later, ovate to inverted pear or elliptical, with nipple-like protrusions, 20 to 45 × 16 to 23 microns in size, and 1 to 16 zoospores or germ tubes are produced when germinating. Zoospores are kidney-shaped, mainly thin-walled round spores and thick-walled spores in the soil. Sporangia are in the minority. Thin-walled round spores are colorless, 18 to 24 microns in diameter, formed by the condensation of sporangia and the rounding of spore walls, and thick-walled spores are round with thick walls. Oospores can be found on diseased leaves in the field.

Mode of transmission

The fungus is a strict parasite, mainly parasitic on Solanaceae plants. The pathogen can overwinter on potato tubers, and produce sporangia in the following spring, which are transmitted to tomatoes and eggplants by wind and rain, becoming the primary source of infection. Conidia are produced on the lesions, which are then spread by wind and rain for re-infection. High temperatures of 28 to 30 degrees Celsius are conducive to the onset of the disease, especially under high humidity or continuous rainy conditions, when the disease spreads rapidly.

Conditions of disease

During the harvest, transportation, storage and sales process, poor ventilation or rain, high humidity, excessive stacking, and long storage time, the fruit pile will have vigorous respiration, resulting in high temperature and humidity, which is conducive to the occurrence and spread of the disease. The peak of field disease mainly occurs after rainfall. The Yangtze River Basin is prone to the disease in the plum rains from May to June and the autumn rains from August to September, and the rainy season from July to August in the north. In production, the disease is more severe in continuous cropping fields or low-lying land, poor drainage, and excessive nitrogen fertilizer.

Eggplant fruit blight prevention and control methods

Field management

(1) Select disease-resistant and waterlogging-resistant varieties: such as Liaoqie No. 3 and No. 4, Fengyan No. 1, Xiongyue Purple Long Eggplant, Jinan Early Small Long Eggplant, Six-leaf Eggplant, Qiqie No. 1, Early Eggplant No. 2 and other new varieties.

(2) Apply compost fermented with Japanese enzyme bacteria or fully decomposed organic fertilizer, and adopt formula fertilization technology to avoid partial or excessive application of nitrogen fertilizer.

(3) Use high ridges or raised ridges for planting, plant at a reasonable density, and drain water promptly after rain to prevent moisture retention.

(4) Rotate crops with Leguminosae, Cruciferae and Poaceae for more than three years, but Solanaceae should not be planted continuously.

Spraying of chemicals

(1) Before the rainy season comes, spray 300-400 times of 30% basic copper sulfate suspension or 500 times of 77% carbendazim wettable powder, or 1:1:160 times Bordeaux mixture in time; during the peak period of disease, spray 800-1000 times of 72% chlorpyrifos or chlorfenapyr, cymoxanil mancozeb wettable powder, 500 times of 70% phosphine·mancozeb wettable powder, 600-700 times of 72.2% propiconazole aqueous solution, 500 times of 58% metalaxyl·mancozeb wettable powder, 500 times of 64% alum wettable powder, or 600 times of 50% metalaxyl wettable powder. In areas where the above-mentioned fungicides have developed resistance, you can choose to use 1000 times diluted 69% Anke mancozeb wettable powder or water-dispersible granules, once every 10 days or so, for prevention and control 2 to 3 times, and stop using the medicine 3 days before harvest.

(2) You can also use 800 times diluted 25% metalaxyl wettable powder plus 800 times diluted 40% thiram wettable powder for root irrigation, once every 7 to 10 days. If the disease is serious, the time can be shortened to 5 days. Repeat prevention and control for 3 to 4 times.

(3) After storage or transportation or entering the market, attention should be paid to ventilation, cooling and dehumidification.