Abstract
Late wilt, a disease severely affecting maize fields throughout Israel, is characterized by relatively rapid wilting of maize plants before tasseling and until shortly before maturity. The disease’s causal agent is the fungus Harpophora maydis, a soil-borne and seed-borne pathogen, which is currently controlled using reduced sensitivity maize cultivars. In a former study, we showed that Azoxystrobin (AS) injected into a drip irrigation line assigned for each row can suppress H. maydis in the field and that AS seed coating can provide an additional layer of protection. In the present study, we examine a more cost-effective protective treatment using this fungicide with Difenoconazole mixture (AS+DC), or Fluazinam, or Fluopyram and Trifloxystrobin mixture, or Prothioconazole and Tebuconazole mixture in combined treatment of seed coating and a drip irrigation line for two coupling rows. A recently developed Real-Time PCR method revealed that protecting the plants using AS+DC seed coating alone managed to delay pathogen DNA spread in the maize tissues, in the early stages of the growth season (up to the age of 50 days from sowing), but was less effective in protecting the crops later. AS+DC seed coating combined with drip irrigation using AS+DC was the most successful treatment, and in the double-row cultivation, it reduced fungal DNA in the host tissues to near zero levels. This treatment minimized the development of wilt symptoms by 41% and recovered cob yield by a factor of 1.6 (to the level common in healthy fields). Moreover, the yield classified as A class (cob weight of more than 250 g) increased from 58% to 75% in this treatment. This successful treatment against H. maydis in Israel can now be applied in vast areas to protect sensitive maize cultivars against maize late wilt disease.
Highlights
Late wilt, or black bundle disease, is a vascular wilt disease of Zea mays caused by the soil-borne and seed-borne fungus, Harpophora maydis [1, 2]
All the agar-embedded, anti-fungal compounds tested in this assay led, at a 100 ppm dosage, to high and significant (P < 1.0E-03) suppression of H. maydis growth
We had previously established the use of drip irrigation to implement selected fungicides and the chemical seed coating as separate beneficial methods against late wilt in the field [16, Fig 5
Summary
Black bundle disease, is a vascular wilt disease of Zea mays (corn, maize) caused by the soil-borne and seed-borne fungus, Harpophora maydis [1, 2]. Effective treatment of maize late wilt disease. The primary disease symptom is a rapid wilting of maize plants, generally 70 to 80 days before tasseling and until near ripeness. Necrotic lesions may appear on the roots of susceptible maize plants as early as three weeks after inoculation [9], and at that time, infected seedlings have shortened roots [10]. The lower stem dries out ( at the internodes) and has a shrunken and hollow appearance, with dark yellow to brownish softened pith and brownish-black vascular bundles [10]. Infection results in a reduction in the number of vascular bundles in the cross-section of the internode [12]
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