Evaluation of the value of sorghum midge resistant hybrids in the USA

Sorghum (Sorghum bicolor [L.] Moench) production in many areas of the world is reduced due to damage caused by sorghum midge (Stenodiplosis sorghicola). There are several methods of control to reduce losses due to sorghum midge, which include cultural practices, biological control, chemical control and resistant cultivars. The best long-term solution for sorghum midge control is the use of genetic resistance in cultivars and hybrids. Recently, sorghum midge resistant hybrids have been developed by several sorghum breeding programs, but there is limited information about agronomic performance relative to planting dates compared to susceptible standards. Thus, the objectives of this research project are: (1) to evaluate the value of sorghum midge resistant sorghum hybrids in the USA production system, (2) to confirm the presence of sorghum midge insect resistance in sorghum hybrids, and (3) to determine whether the resistance in eighteen sorghum hybrids is stable across two environments in Texas where sorghum midge is a damaging pest. Sorghum hybrids with different levels of resistance to sorghum midge were evaluated at College Station and Corpus Christi, Texas in 2003 and 2004, using two different planting dates and the presence or absence of an insecticide treatment. Agronomic data, sorghum midge incidence ratings and number of adult midges, were determined for all entries. All entries designated as resistant did have some resistance compared to susceptible checks. Across all hybrids, grain yield was higher in sorghum with normal planting dates compared to late planting. Under midge pressure resistant hybrids performed better than susceptible hybrids, but lacking midge pressure the susceptible hybrids were higher performing. The use of midge resistant hybrids in commercial production is only warranted when producers are reasonably sure that midge will be a problem. Otherwise, they should continue to plant early using traditional hybrids.