Cotton mealybug Phenacoccus solenopsis (Hemiptera : Pseudococcidae)‎ population density in eggplant and okra plantations and effect of some insecticides

الملخص EN

The cotton mealybug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is a polyphagous sap sucking insect with a wide geographical and host range causing serious losses in several economically important crops.

Thus, laboratory and field experiments were conducted at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate during the seasons 2018 and 2019 to study the population density of P.

solenopsis on eggplant and okra as affected by weather factors and to determine its, efficiency to certain synthetic insecticides.

In both seasons, the infestation of P.

solenopsis started during the early July.

The highest population densities were recorded in the third week of August and first of September.

The infestation of cotton mealybug was high significantly and positively correlated with the maximum and minimum temperature, while populations had insignificant negative correlation with relative humidity.

Based on the multiple regression analysis and the coefficient of determination values (R2), the maximum and minimum temperature and the relative humidity were responsible for the changes in the insect population by 47.5 to 65.3%.

Thiamethoxam was the most effective insecticide (LC50= 3.19 and 3.46 mg AI L-1) against the third instar nymphs of P.

solenopsis using the leaf-dip method, while buprofezine was the least toxic one with LC50 value of 121.79 and 146.14 mg AI L-1 on eggplant and okra.

In an attempt to control this pest, seven toxic materials viz., imidacloprid, acetamiprid, spirotetramat, buprofezin, dinotefuran, thiamethoxam, and abamectin + thiamethoxam, belonging to different chemical groups, were tested for their influence against P.

solenopsis on eggplant and okra under field conditions.

Abamectin + thiamethoxam, imidacloprid, thiamethoxam, and acetamiprid showed the highest efficacy against P.

solenopsis recording 91.05 to 81.50% reduction of the insect population.

Spirotetramat was the least in this pest control.