13 December 2023, US: Tan spot, also known as yellow leaf spot, is a prevalent disease in wheat crops, especially under conditions of high humidity and frequent rainfall.
Caused by the fungus Pyrenophora tritici-repentis, which can survive in wheat residues and infect new crops, the disease manifests as tan-colored lesions on the leaves, often bordered by a yellow halo.
The disease can stress the plant during the critical stage when the wheat is determining the number of spikelets per head, leading to substantial yield losses. In severe cases, yield losses can reach 25 to 30%.
How to Scout for Tan Spot
The initial step in managing tan spot is scouting. It’s crucial to start scouting wheat fields for leaf diseases between growth stages 6 (jointing) and 8 (flag leaf emergence). This period is when diseases begin to manifest on susceptible varieties.
Scouting should involve randomly collecting 30 to 50 tillers from various parts of the field and looking for tan spot symptoms. If you detect tan spot in a field planted with a susceptible variety, monitor its development over the next week to decide whether to apply fungicides.
How to Manage Tan Spot in Wheat with Fungicides
The decision to use fungicides should be based on several factors: the susceptibility of the variety planted, the level of disease in the field, weather conditions, and the yield potential of the field. When the disease level in the field is high on the top two leaves, fungicide application could be beneficial. However, in low disease years, fungicide applications may not be economical.
Fungicides should be applied when one to two lesions are detected on the leaf below the flag leaf on a susceptible variety, anytime between growth stage 8 (flag leaf emergence) and 10.5.4 (flowering).
Fungicides to Manage Tan Spot in Wheat
There are several fungicides available for use on wheat. If tan spot is the target disease, then Willowood Teb 3.6SC could be applied; this product has demonstrated good effectiveness against tan spot and other leaf diseases.
Always refer to the product label for specific application rates and instructions.
Crop Protection from FBN®
Proactively scouting for and responding to fungal presence in your fields will help reduce potential crop damage and improve yield. FBN has a wide variety of effective fungicides to help address agronomic pressures and keep your operation on track.
With transparent pricing, straightforward online ordering, detailed product labels and fast direct-to-farm delivery, FBN can help you get the products you need to protect your crops.
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