The Control of bacterial wilt (Ralstonia solanacearum) of potato by crop rotation in the highlands of Papua New Guinea.

Abstract

A trial was conducted to compare the effect of rotation with different crops or fallow treatments and for different duration on the level of bacterial wilt infection in subsequent potato crops. Land severely infected with bacterial wilt (Ralstonia solanacearum biovar 2, race 3) at Tambul, Western Highlands Province, was selected for the trial. Potato crops were rotated with maize, sweet potato, bare fallow or weed fallow. Yield and wilt infection in subsequent potato crops were then observed. After one break crop, wilt infection remained high in all treatments. Two or three break crops of maize or bare fallow were effective in reducing wilt incidence. Alternating potato with maize over five crops was just as effective. Sweet potato breaks alone were ineffective in controlling wilt. Weed fallow breaks did not reduce the level of wilting and actually reduced yield of subsequent potato crops. This suggests that weed fallows permit the survival of the pathogen, and raises the possibility that a weed host of R. solanacearum may be present. Potato yields were significantly higher (P < 0.01) after two or three maize crops or bare fallows than after continuous potato or potato following two or three weed fallows. Alternating potato with maize showed similar improvements. Potato crops interspersed with one maize and one sweet potato crop (in either order) also out-yielded continuous potato, but the incidence of wilting was still high.