Population Responses of Pulvinariella mesembryanthemi and Pulvinaria delottoi (Homoptera: Coccidae) to Nitrogen and Water Conditions of Their Host Plant

Abstract

Pulvinariella mesembryanthemi (Vallot) and Pulvinaria delottoi Gill are closely related soft scales recently introduced to California, where they attack aizoaceous ground covers. Populations of both species were cultured on Carpobrotus edulis (L.) × aequalateris (Haw.) under greenhouse conditions to determine their responses to various fertilizer formulations and concentrations and five water regimes. We measured scale growth, survivorship, ovisac size, fecundity, and developmental time for each treatment population. There were no differences in population responses of P. delottoi to any water or fertilizer regime. Although all fertilizer treatments increased growth rate of P. mesembryanthemi , we found no significant correlation between amount or form of nitrogen addition and survivorship, ovisac size, or fecundity. Survivorship was similar among P. mesembryanthemi populations treated with different water regimes. However, as watering frequency increased, P. mesembryanthemi grew faster, ovisacs were larger, fecundity was greater, and developmental time was shorter.