Comparing the Effect of the Predator Phytoseiulus persimilis and the Pesticide Abamectin on Reducing the Density of Tetranychus urticae Under Field Cultivation Conditions on Cucumber Plants in Homs Governorate, Syria

Abstract

Cucumber, Cucumis sativus L. is a vegetable crop belonging to the Cucurbitaceae family, widely cultivated in Homs Governorate. due to its high economic and nutritional value. However, this crop is susceptible to infestation by the two-spotted spider mite (Tetranychus urticae Koch), which is a major pest in greenhouses and open fields, which necessitated the evaluation of chemical and biological control methods. This study aimed to evaluate and compare the effectiveness of the chemical pesticide Abamectin (Bimectin) and the biological control agent Phytoseiulus persimilis Athias-Henriot in managing the two-spotted spider mite Tetranychus urticae Koch in a cucumber crop under open-field conditions in Deir Fool village, Homs Governorate, Syria. The assessment focused on the reduction of mite population density, speed of action, and persistence of control effect over time. The experiment was conducted using three treatments: an untreated control, chemical control treatment using Abamectin, and biological control treatment by releasing of P. persimilis. The trial lasted for one month, during which mite population densities were monitored regularly at fixed intervals. The results obtained revealed significant differences among the three treatments in their ability to suppress the T. urticae population. High infestation levels of T. urticae were observed in the control treatment. In contrast, the Abamectin treatment exhibited a rapid short-term effect and reduced the mite numbers from 301 ±1.28 to 2 ± 0.49 individuals three days after treatment. However, its effect on mite populations decreased over time and reached 115.1 ±2.37 30-days after treatment. The biological control treatment with the predator P. persimilis (T2) demonstrated a gradual and sustained reduction in T. urticae density. Although the initial impact was slower—starting from 299.7 ±1.4 individuals on day 1—it led to a steady decline in pest numbers, reaching  8.2± 1 by day 30. The Henderson and Tilton analysis indicated a cumulative effectiveness of 97.95% for the predator. These findings suggest that biological control not only serve as a viable alternative to chemical pesticides but also contribute to the sustainability of agricultural systems by reducing environmental risks associated with excessive pesticide use. This highlights the importance of integrating biological agents into comprehensive pest management strategies.

Keywords:

Phytoseiulus persimilis, Tetranychus urticae, Abamectin, biocontrol, predation, integrated pest management, Homs Governorate.