Causes and Control Methods of Eggplant Fruit Rot

"Rotten eggplant" is the collective term used by vegetable growers for gray mold, cotton blight, and sclerotinia rot. In winter and spring, eggplant fruit rot in greenhouses is mainly caused by gray mold, with sclerotinia rot as a secondary cause, and the two often occur together. The main symptoms are that the disease mainly affects small fruits and green fruits, and can also affect leaves. When fruits are affected, the residual filaments and receptacles are usually infected first, then the disease spreads to the fruit and fruit stalk, causing the peel to become grayish-white and soft-rotted. In the late stage of the disease, a large amount of grayish-white mold grows at the fruit stalk, after which the fruit loses water and becomes mummified. However, the disease conditions are most suitable under low temperature and high humidity, with an optimum temperature of 23°C and an optimum humidity of 95%. In winter and spring, greenhouses, conservatories, low temperatures, insufficient light, or more than a week of continuous rainy weather are conducive to the occurrence and spread of this disease.

At present, according to the author's survey of greenhouse bases in Huxi, Yangshantou, Baolao and other places in Fenglin Town, Yongjia County, nearly 80% of eggplant greenhouses have "rotten eggplant" disease to varying degrees. In severe eggplant greenhouses, 40% of plants are affected, and the usual incidence rate is about 15%, with an estimated reduction of about 20%.

The main characteristics of the current meteorological conditions are continuous rain and unstable temperature recovery, and the possibility of a late spring cold snap cannot be ruled out. In response to these characteristics, the following control recommendations are proposed for current greenhouse eggplants.

I. Control principles: For the control of "rotten eggplant", prevention should be the main approach, with integrated control; agricultural control should be the main approach, with chemical control as a supplement. Early prevention, early treatment, and thorough treatment should be achieved.

II. Agricultural control

1. Dig ditches for drainage to avoid water accumulation in the field. Generally, do not irrigate unless the soil is dry; when necessary, use hole irrigation or run-through water. Fields with lower terrain should pay even more attention to drainage management.

2. Cover with straw to suppress water. In eggplant greenhouses where the relative air humidity exceeds 90%, cover the bed width with more than 5 cm of rice straw or other crop stalks to effectively inhibit the rise of moisture and reduce air humidity.

3. Appropriately extend the venting time. When the average daytime temperature is above 15°C, the venting time can be advanced and the closing time delayed. Venting can be advanced to 7 a.m., and closing can be delayed to 4 p.m. In this way, by extending the ventilation time, it is helpful for dehumidification. At the same time, attention should also be paid to the growth condition of the eggplants.

4. Pruning, leaf removal, and removal of rotten fruits. Under normal circumstances, remove all side branches and leaves below the "first eggplant". Other leaves should be removed promptly and fully on the principle of not causing corresponding shading, so as to strengthen ventilation between plants and reduce disease occurrence. Remove rotten fruits promptly and handle them safely. The removed leaves and rotten fruits should be kept away from the eggplant greenhouse and away from irrigation water, and burned centrally or buried deeply to prevent the pathogen from reinfecting. Vegetable growers with the conditions can set up quicklime disinfection belts in the greenhouse, which can effectively prevent disease from being brought into the greenhouse.

In addition, according to production practice, removing the petals and stigmas of young fruits and residual seedlings can achieve a control effect of more than 80%.

III. Chemical control

Gray mold pathogens easily develop resistance. Drugs should be selected that are highly effective, low-toxicity, low-residue, and highly selective, and they should be used alternately. Pesticides should be applied strictly according to concentration, and the number of uses of the same pesticide should be controlled throughout the entire growth period to ensure the production of pollution-free vegetables.

1. Dipping flowers in liquid pesticide: Add 0.1% Procymidone or Iprodione wettable powder to the prepared anti-drop agent or 2,4-D flower-dipping solution, then dip the flowers. This effectively prevents the occurrence of gray mold.

2. Chemical control: In the early stage of the disease, one of 50% Procymidone, 50% Iprodione, 65% Wanmeiling, 50% Heihuijing, Shijiale, Junsa, Procymidone, or Nongliling can be selected and mixed with chlorothalonil to prepare a 1000-fold solution for spraying, once every 7-10 days, for 3-4 consecutive applications. At the same time, attention should be paid to alternating use.

3. Smoke agent fumigation or dust application: In case of low temperature and continuous rain, to avoid spraying pesticides increasing humidity in the greenhouse and worsening disease occurrence, during the disease period, 10% Procymidone smoke agent can be used, with 250-300 grams per 667 sq m, fumigated in the evening with the greenhouse closed. Alternatively, 10% gray mold powder can be used, with 1 kg per 667 sq m, applied once every 507 days, for 2-3 consecutive applications.

In addition, according to reports, using "Deli" cold-fogging preparations for control in the evening has a relatively good control effect.