Host-plant resistance in sugarcane to pink ground pearls, Eumargarodes laingi Jakubski (Hemiptera : Margarodidae): Confirmation and further screeningof clones

The response of 11 commercial cultivars and nine experimental clones of sug arcane to the margarodid Eumargarodes laingi Jakubski were evaluated over t he plant (first harvest) and two successive annual ratoon harvests in a fie ld trial in southern Queensland. Clones varied in the number of cysts devel oping on the roots with the lowest numbers on Q147, Q135 and Q182 and the h ighest on Q124, Q141, Q184 and 85S1247. The effect was similar over the thr ee crops and indicates the presence of antibiosis and/or antixenosis. Clone s also varied in cane and sugar yields and sugar content, with Q136, Q135, Q155, Q147 and Q124 giving the highest cane and sugar yields and 87S7364, 8 7S7367, 85S1247, Q141 and Q184 giving the lowest. Deviations from a general relationship between number of cysts and yield suggest that clones such as Q136, Q124 and Q155 have tolerance to E. laingi. Good concurrence in the r anking of clones between harvests and between this trial and previous work indicates that the resistance is stable and could be selected for on the ba sis of data from 1 or 2 years.