Radio-Tolerance of various Developmental Stages of Striped Mealybug, <i>Ferrisia virgata</i> (Hemiptera: Pseudococcidae) to Gamma Irradiation Doses

This study examined the effect of gamma radiation on striped mealybug, Ferrisia virgata (Cockerell) by exposing its first instar, second instar, and adult stages to various doses (0, 30, 60, 90,120, 150, 200, and 250 Gy) over an eight-week period in the phytosanitary laboratory of plant protection division, Nuclear Institute for Food and Agriculture (NIFA) Peshawar, Pakistan. The findings indicated that a dose of 250Gy exhibited the most satisfactory results among the evaluated gamma doses. Mortality significantly increased throughout all developmental stages, both in terms of dose and time duration. First instar nymphs appeared to be highly radio-sensitive showing complete mortality (100%) in the 5th week with a radiation dose of 250 Gy. Similar trends were also observed in second instars where (100%) mortality was achieved in 5th week at 250 Gy; however, the overall weekly mortality was a bit lower compared to 1st instar. Adults were found to be the most radio tolerance stage in terms of mortality with complete mortality (100%) achieved in week-8, at 250 Gy. Irradiation disturbed juvenile developmental process with progressively lower adult formation when first and second instar nymphs were irradiated at dose ranging from 30 to 150 Gy, however no adult formation was recorded at 200 Gy and above. The sex ratio indicates a dose-dependent reduction in female percent formation from immature nymphal stages, where at untreated group (80.43%) and (81.11%) female was recoded and sharply reduced to (62.5%) and (73.93%) when irradiated as 1st and 2nd instar nymphs respectively at dose of 150 Gy. The data combined showed that gamma irradiation has a complex inhibitory impact on F. virgata, adversely affecting survival, development, and sex ratio in a dose-dependent way. The findings robustly endorse the utilization of gamma irradiation (≥200 Gy) as an effective phytosanitary treatment and population reduction method for the integrated management of striped mealybug, F. virgata.