Tunneling by larval soybean stem borer, Dectes texanus LeConte, reduces kernel weights and yields. Larvae girdle stalks before overwintering in tap roots, making plants vulnerable to lodging if harvest is delayed. The soybean stem borer that infests soybean, Glycine max (L.), is thought to be the same species found in sunflower, Helianthus annuus (L.). However, morphological comparisons of larvae and pupae and mating compatibility of adults from soybean and sunflower have not been reported. Soybean and sunflower residues infested with soybean stem borer were collected from Texas and Kansas and evaluated at West Texas A&M University. External stalk diameter, tunnel diameter, larval weight, length, and head-capsule width, and pupal weight, length, and sex were determined. Diameter of soybean stalks was 7.0 mm, 69.1% smaller than that of sunflower. Larval soybean stem borer from soybean weighed 28.9 mg, 58.4% less, than those from sunflower and were 22.8% shorter (11.1 and 14.3 mm for soybean and sunflower). Head-capsule width of larvae from soybean (1.2 mm) was 25.0% smaller than that of larvae from sunflower. Pupae reared from soybean weighed 29.4 mg, 47.5% less, than those from sunflower and were 19.5% shorter (10.1 and 12.5 mm for soybean and sunflower). Reciprocal crosses of adult soybean stem borers reared from the residues were made to determine mating compatibility. In a field study, nine varieties of soybean are being evaluated for resistance to soybean stem borer and for yield potential. These results should lead to improved cultural management and resistance to this insect pest.
Species 1: Coleoptera Cerambycidae Dectes texanus (soybean stem borer, sunflower stalk girdler)
Keywords: morphometric comparison, plant resistance
Back to Student Competition Display Presentations, Section F. Crop Protection Entomology
Back to Student Competition Posters
Back to The 2003 ESA Annual Meeting and Exhibition