Common Misconceptions to Avoid When Using Microbial Pesticides

In current pollution-free cultivation of crops such as vegetables and fruits, microbial pesticides are receiving increasing attention. In order to improve the effectiveness of live microbial agents, precautions must be taken against misconceptions during their application.

Misconception 1

Applying at too low a temperature. Some farmers, when applying live microbial pesticides, pay no attention to environmental factors and do not choose to apply them under weather conditions with higher temperatures; they even apply them in winter or during the cold weather of early spring, and thus fail to achieve the expected control effect. This is because biological pesticides all require relatively high temperatures when applied. Trials have shown that between 25°C and 30°C, the control effect of live microbial pesticides after spraying is 1 to 2 times higher than that between 10°C and 15°C.

Misconception 2

Applying in dry weather. When applied under high-temperature, dry weather conditions such as from 10 a.m. to before 4 p.m. on a clear day, farmers report poor results. This is mainly caused by insufficient environmental humidity. It is best to apply on cloudy days, after rain, or in the morning when humidity is high.

Misconception 3

Not avoiding sunlight. Applying at noon without avoiding high temperatures and strong sunlight causes the pesticide efficacy to decline. Live microbial pesticides are most afraid of strong sunlight exposure. The ultraviolet rays in sunlight have a fatal killing effect on spores, and ultraviolet radiation can also cause deformation and reduced efficacy of parasporal crystals. Therefore, it should be used after 4 p.m. or on cloudy days, and the effect will be greatly exerted.

Misconception 4

Being washed away by heavy rain after application. Spores are most afraid of being washed away by heavy rainstorms, because rainstorms will wash away the sprayed bacterial solution. If light rain occurs after spraying (5 to 6 hours later), it will not reduce the pesticide efficacy but can instead improve the control effect, because light rain is greatly beneficial to spore germination, and once pests eat it, their death will be accelerated. Therefore, the application time should be determined according to the weather forecast.

Misconception 5

Mixing with fungicides. For example, Conidiobolus thromboides, as a fungal insecticide, achieves its efficacy through the action of the live spores of Conidiobolus thromboides. After application, the live spores infect aphids and cause death, and can continue to spread, causing mass death of the population. However, as a live fungus, if it is mixed with insecticides, they are killed by the fungicide and naturally lose their insecticidal effect.