干旱区生态环境知识资源中心

Although the aphelinid parasitoid Eretmocerus eremicus Rose & Zolnerowich is the most abundant naturally occurring parasitoid of Bemisia argentifolii Bellows & Perring in the U.S. desert southwest, its effectiveness in different cropping systems varies. Development and reproduction of a population of this parasitoid attacking B. argentifolii infesting cotton, Gossypium hirsutum L., and sweet potato. Ipomoea batatas L,., were quantified and compared. Females <24 h old contained an average of 20 ova that averaged 0.072 mm in length and 0.034 mm in width. Adult females lived an average of 5.9 d on cotton and 4.1 d on sweet potato and laid a lifetime average of 22.9 eggs on cotton and 23.1 eggs on sweet potato; there were no significant differences of these parameters between host plant species. A preoviposition period of 0.61 d was recorded, and a maximum number of eggs laid in a day was 69 on cotton and 13 on sweet potato. The average preimaginal developmental periods for males and females on either host plant were not significantly different and averaged 22.58 d. The mean number of progeny produced on cotton was 25.4 with 51.5% of these female, whereas the mean number of progeny produced on sweet potato was 7.5 with 46.7% of these female. Life table parameters showed the net reproductive rate (R-o) was 11.64, the generation time (T-c) was 26.06 d, and the intrinsic rate of natural increase (r(m)) was 0.0959 for parasitoids on cotton, with a preimaginal survival assumed at unity. On sweet potato R-o was 3.75, T-c was 24.18 d, and r(m) was 0.055 with preimaginal survival calculated at 0.3247. These profound differences relate to, among other things, differences in female foraging and oviposition behavior on host plants with different morphological features.