Prevention and control methods of sponge gourd rot

Today I will introduce to you the sponge rot of sponge gourd and how to better prevent and treat it?

Symptoms

Infection at the seedling stage causes damping-off, which mainly occurs when the seedlings grow 1 to 2 true leaves. Water-soaked spots first appear at the base of the embryonic stem above the soil surface, and the diseased part soon turns yellow-brown, shrivels and shrinks into a thread. The diseased part dies off before the cotyledons wither. Damage to the fruit is significantly reduced after 3 true leaves form. Infection at the fruit causes cotton rot, which initially appears as water-soaked spots, which expand and become large yellow or brown water-soaked spots with a clear boundary from the healthy part. Later, half or the entire fruit rots, and a dense layer of white cotton-like mycelium grows around the diseased part. The infection of the fruit begins at the navel or invades through the wound.

Symptoms appear near the wound, and then the whole fruit rots. The growth period of loofah fruit is long, and the incidence of cotton rot is serious, especially in the south of the Yangtze River.

Loofah rot

Morphological characteristics of the pathogen?

Pythium aphanidermatum (Eds.) Fitzp. is called Pythium aphanidermatum and P. deliense Mours is called Pythium deliense Mours. Both belong to the Mastochorhynchus subphylum. On CMA, the fungus is white and cottony, with well-developed mycelium, branched and without septa, and the width of the mycelium is 3 to 7 microns; the zoosporangium is terminal, swollen into an irregular ginger shape, and forms a spherical vesicle after germination, which contains 8 to 29 zoospores. The zoospores have kidney-shaped double flagella, and are spherical when resting, with a size of 11 to 12 microns; the oospore is terminal and spherical, colorless, and 18 to 36 microns in size. The anther is homofilamentous or heterofilamentous, nearly elliptical; the oospore is spherical and smooth, not full, light yellow, and 17 to 28 microns in diameter.

Transmission routes and conditions of disease onset

The fungus is highly saprophytic and can survive in the soil for a long time. The pathogen overwinters in the soil or survives adverse environmental conditions as oospores. When conditions are suitable, it germinates to produce zoospores or directly grows germ tubes to invade the host. The hyphae that lives a saprophytic life in the soil can also produce sporangia, which release zoospores to infect melon seedlings, causing damping-off disease. Sporangia and zoospores are produced on the diseased remains and splashed onto the fruit near the ground by rainwater. After invading, they form cotton rot and repeatedly infect the field. The main transmission method is wind, rain, running water, and organic fertilizers with bacteria. After autumn, the pathogen forms oospores in the diseased tissue to overwinter. The disease is prone to occur when it is rainy and stagnant moisture during the melon-bearing period. [2]

Prevention and treatment methods

Basic Methods

① Choose moisture-resistant varieties such as Green Wang, No. 3 Loofah, Short Water Melon, and Long Water Melon.

② During the seedling raising period and before the loofah grows 3 true leaves, pay attention to prevent seedling damping-off disease. For specific methods, refer to cucumber damping-off disease.

③ When planting, use high ridges or ridges to plant melons. In the south, the ridge surface is made into a turtle back shape, and the drainage ditch is about 30 to 40 cm deep to prevent water accumulation in the ridge after rain. Apply fully decomposed organic fertilizer or compost fermented by enzyme bacteria to the planting hole. The loofah rack should be built higher, and the drooping fruits should not touch the ground. At the same time, pay attention to ventilation to prevent moisture retention. In the north, pay attention to timely planting racks, less watering in the early stage, more inter-cultivation, and pay attention to ventilation and humidity reduction when cultivating in the greenhouse.

Pharmaceutical Method

① At the early stage of the disease on the seedlings, spray 600-700 times diluted 72.2% Prolike aqueous solution, 500 times diluted 58% metalaxyl mangozinc wettable powder, 500 times diluted 64% alum wettable powder, 500 times diluted 70% fosfoline·mangozinc wettable powder, 800-1000 times diluted 72% chlorpyrifos, chlorfenapyr or cymoxanil mangozinc (chlorfenapyr) wettable powder.

② In the middle of the growth period, you can choose 18% mancozeb or 47% carbendazim wettable powder 800-1000 times liquid, 56% Kaoshan water-dispersible microgranules 800 times liquid, spray about 60 liters of the right liquid per 667m2, once every 10 days in the rainy season, and control 2-3 times continuously. For those who are resistant to the above fungicides, you can use 69% mancozeb wettable powder or water-dispersible granules 1000 times liquid instead. Stop using the medicine 5 days before harvest.

③ Biological control method. That is, using antibiotics. Applying artificially cultivated antibiotics to the soil can inhibit the growth of pathogens. For example, applying cultures of Bacillus subtilis or Trichoderma harzianum to melon fields can help antagonistic microorganisms in the soil to breed, thereby achieving the purpose of inhibiting the growth of pathogens and achieving the effect of preventing diseases and increasing production.