Status of resistance of sorghum hybrids to the aphid, Melanaphis sacchari (Zehntner) (Homoptera: Aphididae)

Abstract

Four field trials were conducted over four seasons during the period from 1996/97 to 2000/2001 to determine the status of resistance of South African sorghum hybrids to natural infestation by the aphid Melanaphis sacchari. Aphid damage symptoms were evaluated on a scale of 1 to 5. Pronounced differences were observed in levels of resistance of hybrids. However, hybrid reaction was in many cases not similar over seasons. PAN8446, SNK3939 and NS5511 exhibited medium to severe damage symptoms in some seasons but only light to medium damage was observed in others. The hybrid NK283, which is the most commonly planted in South Africa, was highly susceptible to aphid damage and exhibited severe damage symptoms in most of the seasons. In the 2000/2001 season, yield of hybrids was determined under aphid infestation as well as in a trial that was protected from aphid infestation by means of insecticide application. Significant differences in yield loss between hybrids were observed in the 2000/2001 season, ranging from 24 to 73%. Tolerance to aphid damage was identified in some hybrids. Results can be applied for selection of hybrids to be planted in areas where aphid infestation is likely.