|Legaspi, Jesusa - Susie|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2003
Publication Date: 11/1/2003
Citation: Setamou, M., Bernal, J., Mirkov, T.E., Legaspi, J.C. 2003. Effects of snowdrop lectin on Mexican Rice Borer (Lepidoptera:Pyralidae) life history parameters. Journal of Economic Entomology. 96(3):950-956. Interpretive Summary: The most important pest of Texas sugarcane is the Mexican Rice Borer, a moth that invaded from Mexico in the early 1980s. The sugarcane industry in south Texas is found in the economically depressed Lower Rio Grande Valley and grosses about $65 million. As its name suggests, the borer spends much of its life inside the sugarcane stalk where it is protected from insecticides. Farmers in Texas have actually abandoned insecticides as a control measure and accept the loss of $10 to $20 million yearly caused by the borer. Clearly, the damage caused by the Mexican Rice Borer is very significant. As part of a program to study insect controls other than insecticides, we evaluated sugarcane genetically-modified for resistance to insect pests. Scientists at Texas A&M and now at the Center for Biological Control at Tallahassee, Florida, took a gene from the snowdrop lily that causes the plant to produce a substance called a ¿lectin¿ which kills certain insects that eat the plant tissue. However, the lectin has been found safe to mammals and birds and is destroyed when sugar is extracted from sugarcane. By making the sugarcane tissue itself toxic to the borer, we remove the stalk as a protection for the rice borer. We extracted the lectin from the sugarcane and fed it to the borer using an artificial diet. Borers that were fed the lectin were smaller, laid fewer eggs and had lower survival than normal. These results indicate that the modified sugarcane may be effective in reducing damage due to the rice borer in the field.
Technical Abstract: The effects of the snowdrop lectin, Galanthus nivalis agglutinin (GNA), delivered via artificial diet on growth, development, and life history parameters of the Mexican rice borer, Eoreuma loftini (Dyar), were evaluated in the laboratory. Incorporation of GNA at three treatment levels, 0.5, 1.0, and 2.0% of total dietary protein, in the larval diet significantly decreased larval survival and percentage adults emerged relative to a control diet (lacking GNA), but differences were not observed between the three treatment levels. Both larvae and pupae in the control were 8-25% larger than those in the GNA treatments, but differences were not observed between larvae in the GNA treatment levels. Furthermore, presence of GNA did not affect larval and pupal developmental periods, longevities, and fecundities relative to the control. Mexican rice borer life history parameters, such as net reproductive rate, intrinsic rate of increase, and generation time were substantially reduced by the presence of GNA in the diet, but differences were not evident among the three GNA treatment levels.