Introduction
The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most damaging pests of beans (Phaseolus vulgaris L.). As Iran's climate changes to warmer and drier conditions in most parts of Iran, the prevalence of small sucking pests, including spider mites, has increased. While the main method of controlling T. urticae is the use of chemical acaricides, the rapid growth and high reproductive rate of spider mites leads to the rapid development of resistance to most chemical pesticides. Also, chemical acaricides used to control spider mites can be harmful to human health and the environment. However, tolerant varieties and plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) can reduce mite populations by enhancing growth and the production of secondary metabolites. The effects of six bean varieties, along with the impact of three probiotics: Biofarm, Bioguard, ProBio96 (water as a control), and the interactions of these factors, were evaluated in the biological suppression of spider mite populations.
 
Materials and Methods
Three probiotics (Bioguard at a 0.5% concentration containing (Propagule g^-1 10^6) Trichoderma harzianum and (CFU g^-1 10^7) Bacillus velezensis along with 5% humic acid; Biofarm at a 4% concentration containing (CFU ml^-1 2×10^7) of each of the three bacteria Azotobacter sp., Pseudomonas sp., and Azospirillum sp. in equal proportions; and Probio96 at a 2% concentration containing (CFU g^-1 10^8) Bacillus velezensis from the Naturalist Biotechnology Company as PGPR and AMF, and (water as control), as well as two kidney bean varieties (local Khomein and Kousha), two white bean varieties (Shokufa and Dorsa), and two red bean varieties (Yaghoot and Ofogh), and the control treatment (local Khomein, Khoshderi kidney bean breeding bank) were tested. The experiments were conducted in a factorial split-plot design (variety as the main factor and probiotics as the sub-factor) within a completely randomized design with 24 treatments and three replications, totaling 360 pots. Inoculation was performed using Khoshderi bean leaves containing (15 female mites). Counting of the different mite stages continued for up to 6 weeks.
 
Results and Discussion
Analysis of variance of the data showed that bean varieties, three probiotic combinations, and sampling time, as well as the interaction effect of variety × probiotic combination, were significant at the 99% confidence level. Mean comparison showed that the varieties Ofogh, Yaghout, and Dorsa had fewer mite populations compared to the local varieties Khomain, Shokoufa, and Kousha. The Bioguard treatment on the Kousha and Ofogh varieties resulted in the lowest numbers of adult mites in Kousha (6.61 ± 0.91), nymphs in Ofogh (10.61 ± 1.65), and eggs in Ofogh (21 ± 3.64). Bioguard on the Yaghout variety had the lowest number of adult mites (6.72 ± 0.94) after Kousha. The Biofarm combination had the lowest adult mite population on the Ofogh cultivar (7.89 ± 1.32).
 
Conclusion
The effect of cultivar on pest population indicates the existence of differences in tolerance or induced resistance of different cultivars to T. urticae mites. The effect of the biological agent on the mite population suggests that probiotic substances can play an effective role in reducing mite density. The interactions of probiotics varied among different bean cultivars; for instance, some bean cultivars such as Ofogh, Yaqut, and Dorsa had fewer mites compared to other cultivars. The interaction of Biogard on cultivars like Ofogh, Yaqut, and Dorsa caused the greatest reduction in population, while ProBio 95 and the local Khomein cultivar had the least effect on population reduction. Therefore, some beneficial soil bacteria and fungi, while stimulating plant growth, prevent the growth and reproduction of two-spotted spider mites. The presence of T. harzianum fungus, B. velezensis bacteria and humic acid by strengthening beans, induces resistance and reduces spider mite feeding pressure. And Biofarm, which contains resistance-inducing Bacillus, reduces the susceptibility of beans to spider mite feeding by increasing the activity of defense enzymes. The results show that the use of Bioguard and Biofarm can be used as part of an integrated pest management program to reduce spider mite damage in beans. The use of probiotics along with variety selection is an effective approach in sustainable pest management. According to the results of this study, the Koosha variety inoculated with Bioguard probiotic is recommended for biological control of spider mite populations.