This study evaluated the thermal requirements for development of the cotton mealybug Phenacoccus solenopsis depending on different biological parameters on Okra leaves Abelmoschus esculentusat under two constant temperatures (20ºC and 30ºC). The effect of temperature on eggs was ineffective since it hatched shortly to 1st nymphal instars after deposition. While the tested temperature caused significant effects on nymphal durations, pupation rate (pre-male stage), females emergence %, pre-oviposition, longevity, post-oviposition periods and fecundity in females (egg deposition, ovisacs numbers and hatchability %). The thermal constant and developmental zero were calculated to be 7.29ºC and 79.9 DDs for eggs, 11.67ºC and 272.9 DDs for nymphal stages, 11.06ºC and 46.4 DDs for males and then 3.31ºC and 554.1 DDs for females, respectively. The duration of the life cycle was 65.6 ± 10.36 days at 20ºC; this was shortened to 35.51 ± 1.12 days at 30ºC. The thermal requirements to complete the insect development for one generation was 8.2ºC for the developmental zero and 774.1 DDs for the thermal constant. Based on the thermal requirements values, the average life cycle duration from January to December 2016 was 61.78 days and the number of annual generations was 7.143 when the average annual temperature was 23.29ºC.
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