|Setamou, Mamoudou - TEXAS A&M UNIVERSITY|
|Bernal, Julio - TEXAS A&M UNIVERSITY|
|Legaspi, JR., Benjamin - TEXAS AG EXP ST, TEX A&M|
|Mirkov, T. - TEXAS AG EXP ST, TEX A&M|
Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 23, 2001
Publication Date: January 1, 2002
Interpretive Summary: Control of a secondary pest of sugarcane, the sugarcane borer Diatraea saccharalis, has been successful in south Texas using an exotic parasite, Cotesia flavipes, since massive numbers of this parasite were released in the late 1970s. Currently, the major pest of sugarcane is the Mexican rice borer, Eoreuma loftini which is estimated to cause economic losses of $10- 20 million annually. To mitigate these losses, a variety of sugarcane was transformed incorporating an insecticidal gene from the snowdrop lily called GNA (Galanthus nivalis agglutinin). Previous studies have shown GNA to be toxic to insect pests in transgenic potato and in limited studies against Mexican rice borer in transgenic sugarcane. Our objective in this study is to determine the effects of transgenic sugarcane on biological control of Cotesia flavipes in the field. Females of C. flavipes were provided sugarcane borer larvae that fed on an artificial diet containing transgenic sugarcane tissue and artificial diet containing non-transgenic tissue. We found that the parasites that were exposed to sugarcane borer larvae fed artificial diet and transgenic sugarcane tissue had reduced parasitism rates and longevity compared to those exposed to sugarcane borer larvae fed a non-transgenic tissue diet. No differences were found between the two treatments in egg production and developmental period of the parasites. Potential impacts of the transgenic sugarcane on biological control of sugarcane borer by Cotesia flavipes are discussed.
Technical Abstract: Cotesia flavipes (Cameron) is a parasitoid responsible for maintaining populations of sugarcane borer (Diatraea saccharalis F.) below economic levels in south Texas sugarcane fields. Transgenic sugarcane expressing snowdrop lectin (Galanthus nivalis agglutinin, GNA) was developed against Mexican rice borer (Eoreuma loftini Dyar), the primary pest of south Texas sugarcane. The potential impacts of GNA-expressing sugarcane on various biological and fitness parameters of Cotesia flavipes (Cameron) were studied in the laboratory to gain insight on likely impacts of the transgenic sugarcane on biological control of sugarcane borer by C. flavipes in the field. Females of C. flavipes were offered sugarcane borer larvae fed one of two diet treatments for oviposition for two successive generations: (i) artificial diet containing transgenic sugarcane tissue, or (ii) artificial diet containing non-transgenic sugarcane tissue. Significant negative effects of artificial diet containing transgenic sugarcane tissue were evident in the rate of host suitability, number of cocoons and adult parasitoids emerging per host, percentage cocoons yielding parasitoids, and sex ratio and adult lifespan of parasitoids. These effects were variable between the two parasitoid generations examined. In contrast, differences were not detected between diet treatments in rates of host acceptance, egg load of females, and egg to adult developmental periods. The negative effects of transgenic sugarcane on C. flavipes detected in this study are important because GNA levels in the diet (~ 0.5% of total protein content) containing transgenic sugarcane tissue were ca. 50% the level expressed by transgenic sugarcane plants.