STATUS OF WINTER CEREALS, OTHER ROTATION CROPS AND COMMON WEEDS AS HOSTS OF LESION NEMATODE (PRATYLENCHUS ZEAE)

LESION nematode (Pratylenchus zeae) occurs in almost every sugarcane field in Queensland and is perhaps the most important of a community of nematode pests that cost the Australian sugar industry an estimated $82 million/annum in lost production. Legumes such as soybean and peanut are relatively poor hosts of the nematode and, when they are used as rotation crops in the sugarcane farming system, populations of P. zeae are markedly reduced. This paper provides data on the host status of other rotation crops that might have a place in the sugarcane farming system, together with some common weeds. The capacity of P. zeae to multiply on various plants was assessed after 70 days in pots at temperatures suitable for nematode reproduction, with multiplication factors calculated as (Pf/Pi), where Pf was the final nematode population density and Pi the initial inoculum density. Sugarcane and forage sorghum had the highest multiplication factors (Pf/Pi >40), whereas the nematode population on most other plants increased 5 to 13 times. Some cultivars of wheat, oats and Rhodes grass had multiplication factors of only 3 or 4 and three crops (Setaria cv. Splenda, barley cv. Grimmett and cowpea cv. Red Caloona) were non-hosts (Pf/Pi <1). In field trials, canola, linseed and chickpea did not increase populations of P. zeae when grown as winter crops at Farnsfield, while wheat and field pea crops grown during winter at Bundaberg did not diminish the level of nematode control obtained from previous crops of peanut or soybean. These results suggest that breaking the sugarcane monoculture with a summer legume followed by a winter crop (e.g. wheat, barley, oats, linseed, canola, field pea or chickpea) will not markedly affect the level of nematode control that is achievable with a legume crop alone.