Variation in resistance to Eumargarodes laingi (Hemiptera: margarodidae) in Australian sugarcane

The responses of 24 commercial cultivars and 1 experimental clone of sugarcane to the margarodid Eumargarodes laingi Jakubski mere evaluated over the plant and 3 ratoon crops of a field trial in southern Queensland. Clones varied in the number of cysts that developed with lowest numbers on Q147 and Q135. This effect was similar over all 1: crops and indicates the presence of antibiosis or antixenosis. Clones also varied in the cane and sugar yields and sugar contents, with Q136, Q145, Q147, and Q138 giving the highest cane and sugar yields. Outliers from a general cyst numbers versus yield relationship indicate ti-lat cultivars such as Q145, Q138, Q155, Q154, and Q124 may have good tolerance and that Q68 and CP44-101 may be particularly sensitive E. laingi. Although there were significant quantitative differences between clones in yields over the 4 crops, the rankings for yield components and for cyst numbers did riot differ significantly between crops. Hence, clones could be selected for resistance to E. laingi on the basis of data from 1 or 2 yr. However, clones that showed good antibiosis/antixenosis resistance to E. laingi showed poor resistance to the root pathogen Pachymetra chaunorhiza, and this may provide a conflict in the breeding program. Combining cultivars such as Q147, Q135, and Q138 with other cultural controls should minimize the detrimental impact of E. laingi on sugar production.