Soil fertilization modulates development and reproduction of the invasive cassava mealybug Phenacoccus manihoti

The global invader cassava mealybug Phenacoccus manihoti is quickly spreading throughout SE Asian fields, this threatening cassava productivity and sustainability. Mealybug infestations can lower yields up to 80%, but multiple factors are affecting herbivore’ performance. Host plant nutrition is likely to influence both insect’ development and reproductive outputs. We evaluated the effect of nitrogen (N) and potassium (K₂O) fertilization treatments on mealybug biology using potted plants and applying three concentration rates (0 Kg/Ha, 90 Kg/Ha and 180 Kg/Ha) for each nutrient. Increasing rates of both nitrogen and potassium reduced insect development time by 2 and 1 days respectively, but no effects on survivorship were noticed. Mealybugs feeding on plants grown at 90 and 180 N Kg/ Ha weighted significantly more compared to those developed at 0 N Kg/Ha, while the intermediate regime of potassium produced the heaviest mealybugs. Adult mealybugs developed on plant grown at rates of 90 and 180 Kg/Ha for both nutrients produced more eggs than females feeding on non-fertilized plants (0 Kg/Ha), with nitrogen having the most positive effect on fecundity. We described how fertilization regimes modulate the performance of an invasive herbivore, this adding important knowledge to be used in predicting herbivore and natural enemies proliferation and developing control strategies.