Studies on the Biology of Margarodes vitium, a Ground Pearl (Homoptera: Margarodidae) on Roots of Grapevines

Abstract

The density in the soil profile of the cysts of M. vitium (Giard) increased down to a level of 4 ft in a heavily infested vineyard, reaching a level of 31 cysts per liter. Below 4 ft, at which level very rocky soil was encountered, much-reduced numbers of roots and cysts were found down to 7 ft, beyond which cysts did not occur Less than half the cysts were attached to living roots. In the laboratory, cysts were subjected to varying temperature regimes (—5, 5, 20, 25, 30, and 35°C) at 2 levels of soil moisture (15 and 20%) followed by varied holding temperatures (20, 25, 30, and 35°C) to obtain emergence of adult females. The different levels of soil moisture had no effect, and the best emergncce (24%) came from constant storage at 20°C. Resulting females laid viable eggs, and large numbers of larvae were obtained.