Resistance to Diatraea (Lepidoptera: Crambidae) stem borers in sugarcane is independent of species.

Evaluation of host-plant resistance on sugarcane to the sugarcane stem borers of Diatraea spp. is normally conducted in Colombia under field conditions, where environmental variations make the study of the insect-plant relationships difficult. Additionally, several species (i.e., D. saccharalis, D. indigenella, D. tabernella, and D. busckella), which are predominant in Colombia, can overlap in their distribution, raising the question of whether different varieties have the same responses to different pest species. The present study conducted evaluations of host-plant resistance under screen house conditions using two contrasting varieties (CC 93-3895, resistant, and CC 93-3826, susceptible) that were infested with the above-mentioned borer species. Observations of pest injury were conducted on internodes, leaves, and spindles. Survival and size (body mass) of the individuals recovered were analyzed and a Damage Survival Ratio (DSR) was proposed. The resistant CC 93-3895 exhibited less stalk injury, less emergence holes on internodes, and lower DSR; additionally, recovery of pest individuals was lower in comparison with CC 93-3826, independent of the borer species. Insect-plant interactions are discussed, as no previous information was available for three of the species tested (i.e., D. tabernella, D. indigenella, and D. busckella). This screen house protocol is proposed to characterize host-plant resistance among several cultivars from the Colombian sugarcane germplasm bank, using CC 93-3826 and CC 93-3895 as contrasting controls and D. saccharalis as the species model.

Biology of the Most Widely Distributed Sugarcane Stem Borers, Diatraea spp. (Lepidoptera: Crambidae), in Colombia.

Most studies on insect biology and ecology of sugarcane borers have focused on Diatraea saccharalis (Fabricius), the most widely distributed species in the Americas. Little information is available on the biology of other borer species present in Colombia, such as D. indigenella Dyar & Heinrich, D. busckella Dyar & heinrich, and D. tabernella Dyar, that present greater expansion and damage in sugarcane-growing regions. The biology of all four species was accordingly studied under laboratory conditions. Diatraea saccharalis presented the shortest development time (39.4 days) and D. busckella the longest (58.2 days). Immature survival was higher for D. saccharalis (83%) and D. tabernella (77%), with the latter also presenting the highest pupal weight (256.6 mg). Observations on reproduction indicate that D. tabernella develops a larger number of egg masses per female (67.3) as compared with D. saccharalis (28.7). All three species spent more time in the pupal stage and resulted in greater pupal size than D. saccharalis; in particular, D. indigenella showed longer female longevity than D. saccharalis. High immature survival rate and greater reproductive success in D. tabernella could potentially generate a larger population in the field, whereas D. busckella takes longer to complete its development, thus increasing the chances of causing greater injury to sugarcane plants. Discussion on biology, ecology, and pest management of these little-known species is done using as model the better-known D. saccharalis.