February 2015. Mealybugs have been found on Bt cotton in India, and the farmer asks what they are.
First it was suggested that it was the cotton mealybug, Phenacoccus solenopsis, but that was thought to be incorrect, and that it was more likely to be the striped mealybug, Ferrisia virgata (Cockerell) (Pseudococcidae). This species is cosmopolitan in distribution and with a host range of more than 100 plants, an extremely polyphagous species. An identification of mealybugs based on photographic material alone is not accurate enough and needs confirmation by a specialist with slide mounted specimens.
Phenacoccus solenopsis does not secrete long, stiff, glassy wax filaments that are clearly visible in the pictures; also the distribution of the dark patches on the mealybug is wrong for P. solenospsis. The glassy filaments are typical of species of Ferrisia.
F. virgata is very common throughout India; the species has been established in India for a very long time. However, in the southern part of India (Karnataka and Maharashtra, and probably some other states) there is a second species, F. malvastra (McDaniel), which has been established in India since at least the 1970s.
F. virgata was present on cotton when a member worked on the crop in 2003, so this is not a species new to that crop.
Mealybugs are not affected by Bt toxins in cotton, so using Bt cotton will not stop mealybug infestations from occurring. The mealybug outbreak might be due to heavy use of pesticides killing their natural enemies in the crop (lacewing and ladybeetle larvae, and parasitoid wasps).