Bt Research 2024, Vol.15, No.1, 1-9 http://microbescipublisher.com/index.php/bt 4 Resistance spectrum refers to the range of pest resistance of B.t. strains. Since B.t. strains can be effective against multiple pests, it is important to select B.t. strains that have high virulence against Phenacoccus solenopsis and low resistance to other important pests of agricultural crops to ensure no adverse impact on the ecosystem. Specificity and selectivity refer to the minimal impact of B.t. strains on non-target organisms. Selecting B.t. strains that are targeted specifically against Phenacoccus solenopsis can minimize the impact on beneficial insects, other organisms, and even humans. Stability, that is, the stability and persistence of B.t. strains. It is necessary to select B.t. strains that can maintain activity and stable efficacy under different environmental conditions to ensure long-term control of the Phenacoccus solenopsis (Heckel, 2020). During the screening and selection process of B.t. strains, a large number of laboratory and field experiments are required. By comprehensively considering the above criteria and combining with practical application situations, the most suitable B.t. strain for Phenacoccus solenopsis can be selected to improve the control effect and reduce environmental impact. 3.2 Evaluation of the toxicity and efficacy of different B.t. strains against the Phenacoccus solenopsis The evaluation of the toxicity and efficacy of different B.t. strains against Phenacoccus solenopsis is conducted in both laboratory and field settings. In the laboratory, the toxicity tests are mainly carried out using artificial diets. A certain number of Phenacoccus solenopsis colonies are established, and the culture medium or extracts of different B.t. strains are added to the diets for exposure. The mortality and growth and development of the insects are then observed and recorded. The toxicity levels of different B.t. strains against Phenacoccus solenopsis are determined based on the mortality rates, growth inhibition rates, and growth abnormalities after treatment (Aalaoui and Sbaghi, 2022). Field trials are used to validate the feasibility of laboratory results and to verify the effectiveness of B.t. strains in the field environment. Treatments with different B.t. strains and control groups are set up in actual cotton fields, and the density of Phenacoccus solenopsis, population size, and crop damage are observed and recorded. By comparing the differences between different B.t. strain treatment groups and control groups, the control effect of B.t. strains onPhenacoccus solenopsis is evaluated and verified. During these assessment processes, by comparing the toxicity and efficacy of different B.t. strains, and combining the results of artificial diet and field trials, those B.t. strains with higher mortality rates, growth inhibition rates, and better control effects on Phenacoccus solenopsis can be identified. These assessment results provide a basis for selecting suitable B.t. strains for the control of Phenacoccus solenopsis. However, due to differences in environmental conditions and Phenacoccus solenopsis populations, the assessment results have certain limitations and require further practical verification and optimization to ensure the effectiveness and stability of Phenacoccus solenopsis. 3.3 The practical application effect of B.t. strains in the real environment In the real environment, B.t. strains are widely used in agricultural production and have good control effects on Phenacoccus solenopsis. They have high toxicity to pests, and have high safety and environmental friendliness. However, in practical applications, factors such as application methods, dosage selection, application time, and environmental conditions should be comprehensively considered to ensure the effective application and control effect of B.t. strains. For example, B.t. strains have broad-spectrum insecticidal activity and are effective against multiple pests. Therefore, in agricultural production, B.t. strains are widely used to control various pests, including Phenacoccus solenopsis. By spraying or applying B.t. strain preparations, the density of pest populations can be effectively reduced, reducing the harm caused by pests to crops. As biological pesticides, B.t. strains have high safety and
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