Eight Key Precautions for Applying Smoke Agents in Greenhouses

In winter and early spring, because the temperature inside plastic greenhouses is low and the humidity is high, vegetables are prone to various diseases and pests. Using smoke agents to control diseases and pests in greenhouse vegetables is a new technique in which pesticides are vaporized and then condensed into smoke particles, or pesticides are directly dispersed into smoke particles to control diseases and pests. It has the characteristics of being simple and labor-saving, having good efficacy, avoiding an increase in humidity inside the greenhouse, having relatively low medication costs, and leaving little pesticide residue. Its control effect is clearly better than application methods such as spraying and dusting, especially during cloudy and rainy days or during disease outbreaks. However, if the method of use is improper, the desired effect cannot be achieved. In order to improve the quality of control, the following points must be noted during application:

1. Check the greenhouse surface. Smoke agents use smoke as the carrier to achieve the purpose of application, so before using smoke agents in a greenhouse, the greenhouse surface must be checked well and holes must be patched so that the greenhouse surface is tightly sealed. The tighter the seal, the better the control effect.

2. Select a suitable formulation. There are many types of smoke agents on the market, including tablets, dusts, and granules. The choice should be based on the characteristics of the greenhouse. Tablets are most suitable for chive greenhouses, which have many application points and are narrow and long. Dusts and granules are suitable for relatively wide vegetable greenhouses and fruit greenhouses such as those for tomatoes and cucumbers.

3. Apply the pesticide according to the target. Before application, the occurrence of diseases and pests should be identified and the pesticide should be used according to the target. To control downy mildew, phytophthora blight, gray mold, and similar diseases, 10% chlorothalonil smoke agent or 15% kejunling smoke agent can be selected, with 200-250 grams per mu; to control powdery mildew, 15% kejunling smoke agent can be selected, with 250-300 grams per mu; to control aphids, 22% dichlorvos smoke agent or aphid-killing smoke agent can be selected, with 300-350 grams per mu.

4. Use the pesticide early. During the vegetable growing period, investigation of the occurrence of diseases and pests should be strengthened and control should be timely. Generally, disease control should be used before onset or in the early stage, once every 7-10 days, for 3-4 consecutive times; pest control should be used in the early stage of occurrence to control it early.

5. The dosage should be appropriate. The amount of smoke agent applied in a greenhouse should be neither too high nor too low. If the dosage is too high, the pesticide is wasted and pollution is worsened; if the dosage is too low, the ideal control effect cannot be achieved. Therefore, the optimal application dosage should be selected. Specifically, it should be determined according to the size of the greenhouse space, the degree of disease and pest occurrence, and the effective content of the smoke agent. For example, to control cucumber downy mildew and gray mold, 45% chlorothalonil smoke agent can be selected, with 200-250 grams per mu, fumigated once every 7-10 days, for 3-4 consecutive times. Greenhouses with severe disease or poor sealing can appropriately increase the dosage.

6. The application method must be correct. (1) Determination of ignition points: In relatively large greenhouse spaces, smoke agents with various effective ingredient contents can be used. The effective ingredient content of smoke agents is generally 10%-50%, and there can be more ignition points, with 6-10 points per 667 sq m. To prevent phytotoxicity caused by long-term high-concentration smoke fumigation near the ignition points, the ignition points should be slightly away from the crops; for relatively low greenhouses, smoke agents with low effective ingredient content (10%, 15%) should be selected, and the number of ignition points can be appropriately increased; small greenhouses less than 1.2 m high should not use smoke agents, otherwise phytotoxicity is likely to occur. (2) Ignition method: Because smoke deposition has the characteristic of avoiding heat, application under sunlight has poor efficacy, and use at dusk after sunset when work is ending is best. When igniting, light them in order from the inside of the greenhouse outward, and finally light the smoke agent at the greenhouse entrance. Note that if there is an open flame after ignition, it must be blown out so that it produces smoke normally. After igniting, quickly seal the greenhouse, and carry out agricultural operations only after ventilation in the early morning of the next day.

7. Alternate and rotate pesticides. When controlling diseases and pests, select 2-3 kinds of smoke agents for alternate and rotational use according to the control target, avoiding repeated continuous use of a single smoke agent.

8. Smoke agents should be stored in a dry place. Keep them away from fire sources. Smoke agents can be used alone or alternately with dusting and spraying methods.