{"id":14284,"date":"2025-03-19T10:18:37","date_gmt":"2025-03-19T11:18:37","guid":{"rendered":"https:\/\/www.premium-partners.net\/?p=14284"},"modified":"2025-03-19T11:21:49","modified_gmt":"2025-03-19T11:21:49","slug":"gosss-wilt-and-leaf-blight-a-new-disease-in-south-african-maize-production","status":"publish","type":"post","link":"https:\/\/www.premium-partners.net\/fr\/builder\/gosss-wilt-and-leaf-blight-a-new-disease-in-south-african-maize-production\/","title":{"rendered":"Goss\u2019s wilt and leaf blight \u2013 a new disease in South African maize production"},"content":{"rendered":"

This post<\/a> was originally published on this site<\/a><\/p>

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By Dr. Rikus Kloppers<\/span><\/p>\n

Goss\u2019s wilt and leaf blight is caused by Clavibacter nebraskensis, <\/i>a bacterium <\/i>that derives its name from the fact that the disease was first noted in the US state of Nebraska in 1969. The bacterium is therefore neither new nor unknown and has also been around in South Africa for a long time, albeit in other guises, such as tomato wilt that is caused by Clavibacter michiganensis<\/i> subspecies michiganensis<\/i>.<\/span><\/p>\n

Goss\u2019s wilt in SA<\/strong><\/p>\n

In South Africa, Goss\u2019s wilt was first noted and reported early in the 2024 season. Most cases were found in Northwest, with some unconfirmed reports in Gauteng and on the Eastern Highveld.<\/span><\/p>\n

However, it is possible that the disease has been in the country since the early 2000s but that it remained undetected due to its symptoms being similar to those caused by other disease or stress conditions and because it was not widespread.<\/span><\/p>\n

Despite the first positive confirmations taking place in February 2024, the Department of Agriculture only officially declared the disease\u2019s presence in SA by the end of the year. Any potential new disease must be carefully investigated and identified without doubt in view of the phytosanitary implications for international trade in seed and commodities. These concerns became reality when Botswana and Namibia immediately suspended all imports of maize, sorghum and wheat grain and seed as soon as the International Plant Protection Convention (IPPC), to which SA is a signatory, issued an official statement on 14 January 2025 that Goss\u2019s wilt had been confirmed in SA.<\/span><\/p>\n

To the local grain industry\u2019s great relief, the Department of Agriculture, and role players such as GSA, managed to convince our neighbours that grain constitutes a low disease transmission risk and the ban on grain imports was lifted in its entirety. Seed exports, however, remain subject to certain conditions.<\/span><\/p>\n

The Department of Agriculture still considers Clavibacter nebraskensis<\/i> to be a regulated organism under its control and surveys are currently underway to determine the distribution and extent of Goss\u2019s wilt. In support of this effort, growers are advised to report disease occurrences to their representatives. There is no risk whatsoever that farms will be quarantined and prevented from delivering their grain.<\/span><\/p>\n

What growers need to know
<\/strong>The bacterium that causes Goss\u2019s wilt is carried by seed from one continent to another but, within an area, distribution only happens when infected crops are harvested, and bacteria become airborne and are blown onto adjacent fields. The inoculum settles in plant debris that becomes the source of infection in the following season, rapidly infecting susceptible hybrids under ideal growth conditions. Insects are not known vectors for this disease.<\/span><\/p>\n

Grain harvested from fields in which Goss\u2019s wilt and leaf blight occurred is safe for human and animal consumption and can be delivered without any grading complications.<\/span><\/p>\n

This does not mean, however, that the disease is harmless. In heavily infected fields, yield losses can reach up to 50% in highly susceptible germplasm when conditions are favourable, and hail or wind damage occurs. The latter provides the plant lesions in which bacterial infections develop and flourish. Fields with previous Goss\u2019s wilt infections may not see significant disease development without weather-related injuries. For this reason, and due to disease resistance in maize hybrids, Goss\u2019s wilt is regarded as only the fifth most important maize disease in the US.<\/span><\/p>\n

Yield losses are primarily due to the disease\u2019s leaf blight phase, which reduces the photosynthetic area and causes premature plant death. The disease grows cumulatively severe in subsequent years as the inoculum load increases in crop residue and alternative hosts, such as grasses. Inoculum from the crop residue infects the new crop and spreads through the canopy by means of rain splash, irrigation and wind. Early infections lead to significant yield losses, while late infections often have minimal impact.<\/span><\/p>\n

Symptoms of Goss\u2019s wilt and leaf blight<\/strong><\/p>\n