Incidence of soilborne diseases in Australia's sub-tropical tomato industry

Abstract

A survey of soilborne diseases in 34 tomato fields in the Bundaberg region of Queensland showed that the incidence of Fusarium wilt (caused by Fusarium oxysporum f. sp. lycopersici race 3) was relatively low. Less than 1.3% of plants were affected in fields fumigated with methyl bromide or metham sodium, or in crops grown in rotation with sugarcane. In non-fumigated fields that had recently grown tomato, high disease levels (4.4 and 8.6% affected plants) were observed in only two of eight fields. Base rot caused by Sclerotium rolfsii was rare in fields cropped previously to sugarcane, but was observed in about half the fields with a recent history of tomato production. However, except for one field where 10.3% of plants were affected, disease incidence was never greater than 0.3%. Root-knot nematode (Meloidogyne spp.) was widespread on tomato crops but gall ratings and nematode populations were relatively low at harvest, suggesting that the nematode was having little impact on yield. Heavy infestations of nutsedge (Cyperus rotundus) were observed in six fields. Beds in four of these fields had been fumigated with methyl bromide and in these cases there was a heavy weed infestation in the untreated inter-row and negligible levels of nutsedge in the planting row. The implications of these results are discussed in relation to the imminent withdrawal of methyl bromide.