Some Ecological Aspects on the Striped Mealybug Ferrisia virgata (Cockerell) Infesting Acalypha Shrubs in Qalyubiya Governorate, Egypt

Acalypha shrubs Acalypha wilkesiana Mull.(Euphorbiaceae) found to be favorable host for the striped mealybug Ferrisia virgate (Cockerell)( Pseudococcidae) . This mealybug species is attacked all plant parts and caused considerable damages to this host. Some ecological aspects were carried out on F. virgata infesting acalypha shrubs throughout two successive years (2014-2015) and (2015-2016) in Qalyubiya Governorate. Results obtained showed that population density was more abundant during the second year than the first one, the annual means of total population were 62.02 and 52.01 individuals/leaf), respectively. Also, results revealed that, seasonal abundance of F. virgata found to be active from June to January of next year. The population density was reached its maximum activity on October during both years being 123.0 and 145.2 individuals /leaf for the first and second year, respectively. The prevailing main average temperature and relative humidity were ranging between 22.8°C, 24.2°C and 67%, 64% for the 1st and 2nd years, respectively. These conditions seemed to be favorable conditions for insect activity. After this activity period all stages of this species were disappeared from all plant parts. This phenomenon indicate that this mealybug species was overwinter during winter and spring seasons till the next summer. From these findings it could be stated that any control measurements must be early applied during June, at the beginning of activity period of this mealybug species. Also, results clarified that F. virgate was passed through two annual overlapping field generations on acalypha shrubs. Duration of the first generation was ranged between 80-85 days which occurred during summer months. While the second generation was lasted 75 days and occurred during autumn. Statistical analysis revealed that separate effect of each mean, two weeks earlier of the four selected weather factors on changes in population density of F. virgata most factors had insignificant effects except mean minimum temperature which had positive significant effects throughout the both years (r coefficient values were 0.589 and 0.677). While the combined effects of the four selected factors (mean minimum, maximum temperature, average temperature and mean percentage of relative humidity), two weeks earlier, had significant effects, as a group on the change in population density especially during (2014-2015) , the explained variance was 79.2% and F value 14.4.