تغییرات جمعیت سن‌های شکارگر Orius spp. در مزارع دانه‌‌های روغنی شهرستان گرگان

Predatory bugs of the genus Orius are an important group of polyphagous predators that feed on some pests such as thrips, whiteflies and mites on oilseed crops in Golestan province, north of Iran. This study was aimed to investigate the population fluctuation of this predatory bugs in cotton, corn, soybean and sunflower fields of Gorgan county during the growing season 2023-2024. The fields were visited in eight sampling times at a 7-day interval during the vegetative and reproductive stages of the crops. The sampling was conducted by moving zigzag along two diameters of the fields, one plant in every 10 steps (total of 20 plants in each sampling) was randomly selected and shaken five times into a white container with dimensions of 37.5×26×8 cm. The adults of Orius spp. were collected by an aspirator, transferred into a glass vial containing a mixture of 75% ethanol and glycerin and were counted in the laboratory under a stereomicroscope. The identified species of this predator in the studied fields included Orius niger and Orius albidipennis. Results showed that the highest population of Orius spp.was observed during the flowering of oilseed crops in August. The results of ANOVA showed that there was a significant difference amongmean population of this predatory bugs on the studied crops in the first four sampling times (approximately until the middle of the growing season) (p<0.05). Accordingly, the highest population density of Orius spp.in these four timeswas observedon sunflower plants with averages of 0.65, 1.80, 1.10 and 2.00 adults/plant. Mean population density in these four times was estimated 0.10, 0.35, 0.80 and 0.30 adults/plant on soybean, 0.05, 0.10, 0.10 and 0.20 adults/plant on corn and 0.25, 0.30, 0.40 and 0.25 adults/plant on cotton, respectively. In the fifth to eighth time of sampling (late July to late August), there was no significant difference among the means of population on the studied crops (p<0.05). In this time range of growing season, the mean population densities were 0.50, 0.20, 0.10 and 0.05 adults/plant on sunflower, 0.30, 0.15, 0.10 and 0.05 adults/plant on soybean, 0.10, 0.05, 0.00 and 0.05 adults/ plant on corn and 0.30, 0.20, 0.15 and 0.10 adults/plant on cotton, respectively. Due to the significant activity of this group of predators on oilseed plants, it is recommended to protect them against excessive spraying with insecticides, especially during the flowering period.