Target spot fungus has become a “when” instead of an “if” for many cotton farmers and consultants, particularly in Georgia. In that state, target spot has hit some farmers hard over the past four years, and there’s little reason to suspect that it won’t occur in 2018 to some degree.
However, with an aggressive and proactive target spot management plan, farmers can get ahead of this disease before it reduces yield potential and profits.
Part of determining a disease management plan is knowing what conditions are conducive to this disease.
“Target spot is a subtropical disease so it thrives in humid, moist conditions,” said Abraham Fulmer, a technical service rep with BASF, which manufactures Priaxor, a fungicide labeled for target spot prevention. “For example, well-managed and heavily irrigated cotton fields with a dense canopy and rank growth are the perfect microenvironment for the rapid development of target spot.”
Farmers should also note that continuous cotton planting in the same field for several years makes it a likely candidate for target spot, especially if the location has a history of repeated infestations.
That’s especially the case in solid-planted stands. High moisture and humidity add to the risk.
The key to control
For effective control of the disease, a proactive approach is needed, and that begins with scouting.
“Fields may look fine from the road, or even from the first few rows, but this can sometimes be misleading,” said Fulmer. “Farmers and crop consultants should move into the middle of the field and in an area with little wind movement, if possible, then check down in the lower part of the canopy.”
Initially, the disease appears in the lower canopy, showing the circular, brown lesions that give the disease its name.
Target spot typically starts in mid- to late-July in Georgia, when the cotton canopies are across the rows. The current growth stage of the crop, in combination with recent moist and humid weather conditions in Georgia, means farmers should be out in their fields scouting for the disease.
Once the disease develops, it can spread and take over a field in just weeks, with visible lesions that illustrate the fungus spores have already been attacking the plant for a week or more.
That’s why timing is so critical when spraying. An initial fungicide application during the first week of bloom will generally put farmers ahead of the disease. But coming back 2 to 3 weeks later with another application for extended disease protection is also a good proactive management practice to follow.