Document Type : Research Article
Authors
1
Department of Plant Protection, College of Agriculture, Razi University, Kermanshah, Iran
2
Department of Plant Protection, College of Agriculture, Ilam University, Ilam, Iran
Abstract
Introduction
Bean (Phaseolus vulgaris L.) (Fabaceae) is one of the most cultivated plants of legumes in most countries. Several of insects with piercing-sucking mouthparts such as thrips, leafhopper, aphids, and plant bugs are as pest on beans. Thrips can attack beans from the seedlings emerge through to flowering, but it is the damage some do during flowering that has the greatest impact. Thrips tabaci Lindeman 1889, the onion thrips is a cosmopolitan species. It has hundreds of host plants but of these, the economically most important crop plants are onion, cabbage, tobacco, pepper, bean and tomato. Here, population fluctuation and spatial distribution of thrips was investigated in the bean fields of Sanandaj county (Kurdistan province, west of Iran).
Materials and Methods
Sampling was done from bean leaves from two leaves stage until ending growing season in the bean fields (bean Canyon variety) located in Arandan village (N 35° 23' 10.96", E 46° 54' 53.16", alt. 1660 m), Sanandaj county during the years 2022 and 2023. Bean leaf was selected as sampling unit. Sampling was done weekly and four rows were sampled each time. A systematic sampling pattern was used to collect the samples. In this way, in the selected rows, 24 plants at the beginning and end of each row were ignored, and the 25th plant of each row was the first plant on which thrips were counted. After that, 24 plants were left and counting was done on the 25th plant after the first plant. In this way, 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300 and 325 plants were sampled in each row. Weekly sampling was done in a similar style, but each time, different rows of crops were selected for sampling. Sampling was done weekly, and for this purpose lower, middle and upper leaves were selected from each bean and the leaves were shaken on a white tray and then the thrips were put into Eppendorf containing ethyl alcohol 75%. In order to accurately count thrips, by using a stereomicroscope, some samples were separated and microscopic slides were prepared from some samples and finally the number of samples was recorded. Spatial distribution of adults of thrips was estimated using Taylor’s power law and Iwao’s patchiness regression methods.
Results and Discussion
The results showed that the population of onion thrips was observed from July and gradually increased and in 2022 its maximum was in the first week of August with an average of 11.65 ± 0.14 thrips and in 2023 its maximum was in the end of week of August with an average of 11.29 ± 0.23 thrips at the sampling unit. In addition, the highest mean number of onion thrips was observed with a significant difference in the lower leaves compared to the middle and upper leaves. The results of the spatial distribution of the pest showed that based on the variance-to-mean ratio, Taylor’s power law and Iwao’s patchiness regression methods, the spatial distribution of onion thrips was clumped, randomized and clumped, respectively. In general, the results showed that the peak of population of onion thrips reaches in early of August. Furthermore, based on goodness of fit, the Iwao’s patchiness method was more suitable than the Taylor’s power law method for estimating the spatial distribution of the pest.
Conclusion
It can be concluded that, at the beginning of the growing season of beans in the field, a low population of onion thrips was activated, and gradually with the warming of the weather and the change of the growing stages of the beans, the population of the pest in the field increased, so that the largest population of onion thrips were observed in the first week of August. In addition, based on the sampling, the highest average number of onion thrips was observed in the lower leaves of beans compared to the middle and upper leaves. The relationship between population fluctuations of onion thrips with average positive temperature was obtained. In examining the spatial distribution pattern with the Iwao’s patchiness method, it was found that the spatial distribution of onion thrips is uniform. Considering the high activity and damage caused by onion thrips on various crops, especially on beans, it is necessary and important to conduct more studies on its various characteristics in various regions and crops of Kurdistan province so that a suitable management plan can be developed to control this pest.
Acknowledgement
This paper is extracted from part of the master's thesis of the senior author, who was financially supported by research vice-chancellor of Razi University, Kermanshah, Iran.
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