Studies On Biological And Ecological Characteristics Of Phenacoccus Solenopsis Tinsley

Phenacoccus solenopsis Tinsley is a new invasive pest in China. The morphic characters, habitus,developmental durations, developmental threshold temperature, effective accumulated temperature ofthis insect were studied systematically in the paper. Meantime, the life table of the laboratory populationfed on pumpkin was constructed at different temperatures. Moreover, the functional responses ofHarmonia axyridis and Menochilus sexmaculata to Phenacoccus solenopsis were studied preliminarilyand the toxicities of three types of insecticide to Phenacoccus solenopsis were determined in thelaboratory. The main results obtained were as follows:1. Morphological description: Egg is orange in colour and elongate-oval in shape. First instarnymph is yellowish in colour and moves very fast. Male and female of second instar nymphs can bedifferentiated in late-2nd instar stage. Third instar female nymph is similar to adult female. Male pupa iscovered with white silky cocoon. Adult male is red brown in colour and has one pair of transparent forewings. Adult female is oval in shape, covered with a thick layer of white waxy powder and with18pairs of lateral wax filaments, several pairs of black spots present obviously on the thorax and abdomen.2. Biological characteristics: This insect has negative geotropism and positive phototaxis. Thenymph and adult prefer to live in humid condition and aggregated. Nymph used to molt three times.This mealybug is engaged in parthenogernesis and sexual reproduction.3. Effective accumulated temperature: The developmental rate of Phenacoccus solenopsisincreased with the temperature increasing from18℃to30℃, and the relationship between thedevelopmental and temperature could be simulated by the Logistic model. It could be inferred that thismealybug can take place6~7generations in Lin' an per year.4. Life table of the laboratory population at different temperatures: At26℃the survival rate andpopulation trend index reached the highest, being77.03%and22.98, respectively. It showed that26℃was suitable for the population growth. While the population trend indices at18℃and30℃were2.99and9.80, respectively. It showed that the population development ability of Phenacoccus solenopsisTinsley was strong, but high and low temperatures were not suitable for the population growth of thePhenacoccus solenopsis.5. Predacious function: The functional responses of Harmonia axyridis and Menochilus sexmaculata to Phenacoccus solenopsis in the laboratory were simulated by Holling II model. Moreover,the theoretical maximal predation was294.1176and123.4568per day, respectively. In the same preydensity, the finding efficiency of Harmonia axyridis was higher than that of Menochilus sexmaculata.The results showed that adult of Harmonia axyridis had more effective predacious potential control thanthat of Menochilus sexmaculata to the Phenacoccus solenopsis.6. Indoor toxicity: The toxicitity of three insecticides to nymphs and adult female of Phenacoccussolenopsis was studied in the laboratory. The order of toxicity from high to low was acetamiprid,abamectin, beta-cypermethrin. The results showed that acetamiprid, abamectin and beta-cypermethrinmight be used as pesticides of Phenacoccus solenopsis management.