Study On Population Ecology Of Potato-colonizing Aphids

Aphids are the main potato virus vectors of which the virus spreading is usually more harmful than the direct feeding. This paper investigated the spatial distribution, population dynamics, effects of temperature on the growth, development and reproductions of potato-feeding aphids, biotypes and the resistance to aphids among26potato varieties in the field. The main results are as follows:1. Either the fixed population or the single Myzus persicae or Aphis gossypii population indicated an aggregated distribution in the field. The population and ratio of plants colonized by M. persicae were both higher than A. gossypii while both of the two aphids had a steady age structure.2. By using the optimal segmentation method, the population dynamics was divided into four periods:(1)Colonization period:the alate aphids began to immigrate into the potato fields during early-middle June with the rise of temperature and the growth of potato plants, and the aphids occupied on seldom plants in lower quantity and high aggregation intensity.(2) Slow increase period:the density rose slowly with the reproduction of aphids and the aphids diffused with the highest aggregation intensity from late June to middle July.(3) Quick increase period:the density increased sharply due to quick reproduction of aphids, and the aphids distributed over the whole field with the decrease of the aggregation intensity from late July to middle August.(4) Eclipse period:after late August when the temperature declined and the potato plants were aging to die, a lot of alate aphids emigrated from the potato fields and the aphids density declined quickly. The aphids occurred only on seldom stumps and the aggregation intensity rose again.3. Temperature had significant effects on the growth, development, mortality and reproduction of three aphid species. Macrosiphum euphorbiae was more adapted to low temperature while A. gossypii to high temperature. The intrinsic rate of increase of M. euphorbiae was lower than those of M. persicae and A. gossypii in temperature range from10to25℃. The intrinsic rate of increase of A. gossypii was higher than that of M. persicae at25℃.4. The effective temperature accumulations (ETA)of A. gossypii were the lowest in each development stage among three aphid species tested. The ETA of M. euphorbiae for one generation was the highest, secondly M. persicae and finally A. gossypii. The developmental threshold of A. gossypii for one generation was much higher than those of M persicae and M. euphorbiae.5. The main biotypes of M. persicae and A. gossypii in the field were red and deep green which could be induced by low temperature and the same for the alate type of M. euphorbiae. The crowding stimulated the two biotypes to development to alate aphid.6. Resistance to aphid of potato variety Atlantic was significantly lower than those of the varieties Zhongshu12, Zhongshu10, Jinshu15, Kexinke18and Mengshu17.