Effects of Nitrogen Fertilization on the Life History of the Madeira Mealybug (Phenacoccus madeirensis) and the Molecular Composition of its Host Plant

The aim of this study was to investigate how different nitrogen fertilization rates of host-plants influence the development, fecundity, and nutritional status of a pest insect,the Madeira mealybug (Phenococcus madeirensis Green, Hemiptera: Psuedococcidae).This study evaluated the effects of nitrogen fertilization (0, 75, 150 and 300 ppm N) onthe growth, % nitrogen, % carbon, lipid, and protein contents of basil plants (Ocimum basilicum L., Lamiaceae), and the subsequent impacts of host-plant nutritional status onthe life history and total lipid and protein contents of the Madeira mealybug. Heights androot lengths of plants fertilized with 75 ppm N were greater than those of plants of anyother nitrogen level. Plant leaves and stems from the 300 ppm N level had the highest %nitrogen, but the leaves did not exhibit significant differences in protein content acrossplant nitrogen levels. Plants might be allocating nitrogen to maintain proper functioningof photosynthetic organs. No consistent patterns were observed for plant tissue %carbon, and no significant differences were found in plant tissue lipid absorbance values across nitrogen levels. Developmental times and survivorship of mealybugs between instars and from egg to adulthood did not differ across nitrogen levels. Mealybug females reared on plants fertilized with 0 ppm N had the fewest eggs. Net reproductive rates, intrinsic rates of increase, and finite rates of increase did not differ amongmealybugs reared on plants fertilized at all nitrogen levels. Females reared on plantsfertilized at 0 and 75 ppm N had the longest and shortest generation times, respectively.Adult females reared on plants fertilized at 0 ppm N had the highest protein contents andproduced the most eggs, but their eggs had the lowest protein contents compared to those of their counterparts from the other nitrogen fertilization levels. Adult females reared on plants fertilized at 300 ppm N had lower total protein contents and produced fewer numbers of eggs than those from unfertilized plants, but their eggs were the highest in average protein content. This finding indicates that Madeira mealybug females are able to differentially allocate nutrients based on host-plant nutrient status.