Interactions between Amblyseius ovalis (Evans) (Acarina: Phytoseiidae) and Bemisia argentifolii Bellows & Perring (Homoptera: Aleyrodidae) on Cucumber

• Main Authors: Kuei - Fang Pai, 白桂芳
• Other Authors: Chain-Ing Shih
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/94556318979212785598

博士 === 國立中興大學 === 昆蟲學系 === 91 === Both male and female silverleaf whitefly (SLWF), Bemisia argentifolii Bellows and Perring, feeding on cucumber, matured in 19.7 ~ 19.9 days at 28 ℃. Adult females laid 101 eggs in 25.6 days of oviposition period with a rate of 3.64 eggs per female per day. Peak reproduction rate was found at either day 4 (6.52 eggs/female/day) or day 8 females (6.02 eggs/female/day). SLWF population multiplied 101.5 times in a mean generation time of 29.6 days with 0.156 eggs/female/day of intrinsic rate of increase. The strategies successes used by SLWF for host adaptation, if not on all kinds of hosts but at least in cucumbers, are maturity rate and adult longevity instead of reproduction rate. Feeding on cucumber pollen, 68.8% Amblyseius ovalis (Evans) females developed into adults, but none on honey-dew of silverleaf whitefly (Bemisia argentifolii, SLWF). Females of A. ovalis deposit most of their eggs on the top of chaeta of underside of leaves with 26.8 eggs per female in an average of a 24.4 day life span. The daily reproduction rate per female is 1.1 eggs. Two highest daily reproduction rates (2.0 ~ 2.1 eggs/female/day) of females were found at female aged 4 and 8 ~ 10 days; the female sex ratio (female/ (female + male)) of offspring was 0.68. A total of 16.7% females feeding on cucumber pollen did not reproduce eggs, but the females resumed egg reproduction when first instars of SLWF were supplied. A. ovalis feeding on eggs, 1st and 2nd instar of silverleaf whitefly, Bemisia argentifolii has shorter developmental duration, better survival rate, and longer longevity. All the predator females reproduced eggs when they fed on the 1st or 2nd insatr of SLWF, but only 50.0 % did on SLWF eggs and 61.1 % did on eggs and pollen. Feeding on 2nd instar of SLWF with pollen, A. ovalis females gave the highest fecundity, while A. ovalis feeding on eggs with pollen added gave the lowest one. The daily reproduction rates (0.1 ~ 1.3 eggs/♀♀/day) of A. ovalis were significantly varied due to stages of SLWF preys. The net reproductive rate (Ro) of 4.28 ~ 21.86 and the intrinsic rate of increase (rm) of 0.140 ~ 0.288 and generation time (T) of 10.41 ~ 12.17 days were found while A. ovalis fed on tested stages of SLWF. The larvae of predator didn’t prey on SLWF, but other stages (protonymph, deutonymph and female) foraged an average of 43.9 first instar or 16.7 second instar of SLWF in the life-time of A. ovalis. Deutonymphs and females of A. ovalis showed a Holling typeⅡfunction when it fed on eggs and immature stages of SLWF. Female of A. ovalis retained the highest daily predation rate (predation plateau) 5.88 nymphs in 4 cm2 leaf disc at prey density of 28 1st instar nymphs in 24 hours (a: 0.6286, Th: 0.1723). A. ovalis female showed highest daily reproduction rate of 1.0 ~ 1.5 eggs/female/day when offered 24 ~ 32 nymphs in 4 cm2 leaf disc. Consequently, the stage-specific effects of SLWF were found and evaluated from the response of developmental duration, pre-oviposition period, oviposition period, longevity, fecundity, sex ratio of progeny, and intrinsic rate of increase of A. ovalis. The variations on functional and numerical responses of A. ovalis were also correlated to the different B. argentifolii stages. Feeding on SLWF, A. ovalis completed its maturity with high survival rate and reproductive rate. Furthermore, the development rate, longevity and fecundity of A. ovalis were enhanced when the additional cucumber pollen was added. We conclude that A. ovalis prefers SLWF 1st and 2nd instars later instead of eggs; therefore, SLWF 1st and 2nd instars are suitable food for population growth of A. ovalis. The vertical distribution of Bemisia argentifolii was stage-specific by eggs, nymphs and adults on cucumber. Adults and eggs appeared at upper leaves, while the 1st & 2nd instar nymphs and 3rd & 4th instar nymphs appeared at middle and lower leaves, respectively. A high density of active stages of Amblyseius ovalis was attracted by the 1st and 2nd nymphs of whitefly which aggregated on the middle leaves. The spatial distribution patterns of B. argentifolii and A. ovalis were aggregated according to Taylor’s Power Law (a: 0.401, b: 1.257 and a: 0.311, b: 1.074) and Iwao’s Mean Crowding Regression (α: 1.325, β: 1.090 andα: 1.477, β: 1.014). Population densities of both predacious mite and whitefly did not depend on temperature in summer season (Jun. ~ Sep.) but did in the period of October to May. A. ovalis or B. argentifolii did not positively correlate with weekly precipitation. Population density increases of A. ovalis and B. agrentifolii on cucumber appeared highly synchronized (Y = 0.4458x + 0.4123, R2 = 0.7740, p < 0.0001). Apparently, the A. ovalis was an important density dependent factor of B. argentifolii on cucumber. A. ovalis showed same degree of effectiveness as chemical measures did to suppress SLWF population increases on cucumbers. The cucumber yield was 1.74 times on A. ovalis released plots than the no predator released plots. In order to gain a better suppression on SLWF density and a higher yield of cucumber fruitage, we released A. ovalis of 7 adults/plant or 14 adults/plant. Inoculative release of A. ovalis in cucumber field could increase the cucumber yield at the lower population density of SLWF. We suggest that A. ovalis can be adopted for integrated control of SLWF with carefully selected pesticides.