Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2004
Publication Date: 6/20/2004
Citation: Liu, Y. Distributions of nasonovia ribisnigri (homoptera: aphididae) in lettuce plants.. Journal of Economic Entomology. 2004. v. 97. p. 883-890 Interpretive Summary: Lettuce aphid, Nasonovia ribisnigri, has become a major pest of lettuce in the western United States. This pest prefers feeding deep inside lettuce hearts and is difficult to control. Information on its distribution in lettuce plants is very limited. It is not known whether head formation would affect host colonization by lettuce aphid. Such information could be used to determine management strategy. This study determined distributions of lettuce aphid in iceberg lettuce. Lettuce plants were susceptible to colonization by lettuce aphid in all stages of their development. Initially, aphids distributed mainly in heads. As population size increased, distribution shifted toward loose outer leaves. Wrapper leaves had highest aphid densities. Effects of aphid densities on production of winged aphids and catches of winged aphids on yellow sticky traps were also studied.
Technical Abstract: Field study was conducted to determine distributions and population development of lettuce aphid, Nasonovia ribisnigri (Homoptera: Aphididae), within iceberg lettuce plants. Iceberg lettuce plants were transplanted and caged in a field plot and inoculated with apterous N. ribisnigri at different times. Fifteen to 50 d after inoculations, lettuce plants were harvested and number of alates and apterous N. ribisnigri were counted on each leaf. Regardless the time of inoculation, N. ribisnigri presented through out lettuce heads. However, for newer inoculations, N. ribisnigri populations were relatively smaller and aphids presented mostly within heads. For older inoculations, N. ribisnigri populations were larger and distributions shifted towards outer loose leaves. More aphids were present on wrapper leaves than on other leaves. Proportion of alates in populations did not vary significantly with population density. Yellow sticky cards were used to monitor alates in each cage. Catches of N. ribisnigri alates on yellow sticky cards had significant correlations with total numbers of alates as well as total population sizes on individual lettuce plants. The results indicated that lettuce plants were susceptible to colonization by N. ribisnigri throughout their development regardless formation of heads. Yellow cards may be useful to detect presence of N. ribisnigri in the field.