A Comparative Study Efficiency of Three Predators on Grapevine Mealybug, Phenacoccus Madeirensis under Laboratory Conditions

A Laboratory study was carried out for three predators; Cryptolaemus montrouzieri (Mulsant), Nephus crucifer Mogulones (Coleoptera:Coccinellidae) and Diadiplosis hirticornis (Felt) (Diptera:Cecidomyiidae) as biocontrol agents for Grapevine Mealybug, Phenacoccus madeirensis Green (Homoptera: Pseudococcidae). The study investigated some biological parameters under laboratory conditions at temperature of 25±1˚C and R.H. 60-80% and a light duration of 9 hr.
   The generation time of C. montrouzieri (Mulsant), N. crucifer Mogulones and D. hirticornis was 27.37±1.82, 36.5±3.22 and 18.8±0.26 days, respectively. The average longevity of males and females of  C. montrouzieri (Mulsant) was 20±0.42, 27±0.20 days respectively in compare with 21±0.31, 30±1.12 and 8±0.13, 10±0.22 for males and females longevity of N. crucifer Mogulones and D. hirticornis respectively. Predation rate of the females and males of the two predators, C. montrouzieri (Mulsant) and N. crucifer Mogulones on nymphs of Phenacoccus madeirensis was 522±7.42, 453±8.38 and 228±7.91, 202±8.48 nymph respectively, whereas, the predation rate of the larva of C. montrouzieri (Mulsant), N. crucifer Mogulones and D. hirticornis was 756±23.27, 350±16.03 and 287±11.53 nymph respectively.
The obtained results showed that the prey host plants; Carpobrotus edulis, Aptenia cordifolia and Delosperma brunnthaleri caused death to the larvae of Cryptolaemus montrouzieri (Mulsant), Nephus crucifer Mogulones (Coleoptera:Coccinellidae) and Diadiplosis hirticornis (Felt) (Diptera:Cecidomyiidae), and were not susceptible as host plants whereas, sprouted potato tubers were suitable for laboratory rearing of the three predators.
   Rearing of C. montrouzieri (Mulsant), N. crucifer Mogulones and D. hirticornis (Felt)is recommended on Phenacoccus madeirensis Green (Homoptera: Pseudococcidae) as prey and sprouted potato tubers as host plants.