What are the main disadvantages of Bt preparation?

① Non-quick-acting: Bt preparation has a slow insecticidal effect, and it is often sprayed with 2? Insects die in 4 days, so when the density of pests is high, the population cannot be reduced quickly to reduce the harm.

② Short residual period: Therefore, in order to obtain better effect, it is necessary to spray continuously for many times, which will undoubtedly increase the cost.

③ Unstable control effect: Unstable control effect is one of the fatal shortcomings of Bt field application. There are many factors that affect the control effect of Bt, mainly including the species of Bt, the dosage form and application technology of Bt, the species of target insects, insect age, insect population density and habits, high temperature and strong ultraviolet rays of environmental factors, etc.

④ Narrow insecticidal spectrum: insensitive to some target pests. Although there are many kinds of insects that Bt can infect, some strains have little or no insecticidal effect on some kinds of pests in production, so Bt cannot be used to control all pests in production.

⑤ No systemic action: It can't kill pests that feed on crops, such as borers, borers, etc.

⑥ There are many problems in the processing of Bt preparations: the main reason is the single variety of dosage forms. At present, the dosage forms of Bt in China are only powder, wettable powder, suspending agent and granule, and the quality is poor. At the same time, the processing technology is backward, and various synergists and synergistic factors are lacking to improve the insecticidal activity of the existing strains.

⑦ Although Bt can be mixed with pesticides, chemical pesticides may weaken the advantages of Bt pesticides on natural enemy safety and environmental pollution.

⑧ There are still insufficient effective components in the commercial preparations of Bt produced in China, that is, the number of live spores is not up to standard, the suspension performance of suspending agents is poor, the samples are obviously layered, and the fermentation residue particles are coarse; Wettable powder has insufficient fineness and poor wettability. The antiseptic effect of some products is poor, and there is secondary fermentation after product pollution. All these have affected the control effect of Bt commercial preparations in the field and the large-scale popularization and use of Bt preparations, which is also one of the main reasons why it is difficult to be accepted by farmers.