Technical annual report 2000-01
Dept. of Regional Development, Primary Industry, Fisheries and Resources technical annual report; Department of Regional Development, Primary Industry, Fisheries and Resources technical and annual report; Reports; PublicationNT; Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295
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Agriculture -- Northern Territory -- Periodicals; Fisheries -- Northern Territory -- Periodicals
Dept. of Primary Industry and Fisheries
Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295
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Technical Annual Report 2000/01 201 In summary, Fusarium wilt free sweet basil seed can be used where the soil is not known to be contaminated with the disease. The disease can affect Vietnamese basil, but observations suggest that this basil is both more resistant and tolerant to Fob infections. Nufar F1 sweet basil is more resistant to Fob than conventional sweet basil and is also acceptable to the market, but at a lower price than conventional basil when this is available. PROJECT: Management System for Major Diseases of Asian Vegetables - Cucurbit Mosaic Viruses Project Officers: B. Cond and I. Arao-Arao Location: Darwin Objective: To identify the viruses affecting cucurbit crops in the Darwin area and to elucidate their epidemiology so that an effective management system can be developed. Background: Mosaic virus caused serious damage to cucurbit crops last year and this year. Until 1989, PRSV-W (papaya ringspot virus cucurbit strain, an aphid transmitted potyvirus) was the only virus of importance in cucurbit crops. SqMV (squash mosaic virus, a beetle transmitted virus) was recorded from one crop having been transmitted to the plants through the seed. The SqMV did not spread. Unlike the situation in Queensland, WMV-2 (watermelon mosaic virus strain 2, a potyvirus) has not been found in the NT. In 1989, ZYMV (zucchini yellow mosaic virus, a potyvirus) was found for the first time in the NT in a crop of zucchini at Berry Springs and gramma (Cucurbita moschata) in a home garden at Nightcliff. ZYMV has been recorded from the NT several times since 1989. With the increase in cucurbit crop production among Vietnamese and other growers, there has been a dramatic increase in the incidence of mosaic viruses of cucurbits over the past few years. Method and Results: Severe mosaic was found on a farm in Humpty Doo in July 2000 in which 100% of the Blackjack zucchini and at least 50% of a Sunburst squash crop were infected. Owners estimated a 50% loss. The zucchini had bubbled fruit and the golden squash had fruit with colour break, and so could not be sold. Samples were taken for virus identification. Discussions were held with the owners on the virus, its spread, its epidemiology and some suggestions for management. Because of this severe outbreak, an information sheet and photographs were produced and presented to an NT Horticultural Association - Asian Vegetables Group meeting on 7 August. Initial herbaceous indicator tests again indicated that this virus was ZYMV and not PRSV-W. Another farm at Webb Road Humpty Doo had serious problems with mosaic viruses in September 2000. A zucchini crop was 100% infected. Squash and a new cucumber crop were 80% and 60% infected, respectively. Again, the virus responsible appears to be ZYMV; differential herbaceous indicators will be used to confirm its identity. The farmer had not undertaken any aphid control; aphids (Aphis gossypii) were free to build-up on infected plants, picking up the virus to transmit to uninfected plants. Greg Owens of Horticulture brought to our attention a suspected incidence of mosaic virus on bitter melon in November 2000. The vines were very old at the end of their production life but leaves displayed a vague light and dark green mottle. Samples were taken and inoculated onto Jap gramma indicators. Symptoms on the indicators were not positive for virus. One bitter melon plant was experimentally inoculated with a ZYMV culture and failed to show symptoms. Thus it appears that the symptoms on the bitter melon leaves were nutritional rather than due to virus infection. A farm in Darwin River Road lost several thousand dollars worth of crops of yellow squash and Lebanese cucumbers in June 2001. Fruit production was reduced and yellow squash had colour break and Lebanese