Update From Dr. Bob Kemerait, UGA Plant Pathologist:
PEANUT
1. Current conditions (warm weather with developing afternoon thunderstorms) create favorable conditions for leaf spot diseases and white mold.
2. It appears that chlorothalonil (Bravo, Echo, Chloranil, etc.) will be “short” in our supply chain this year .
3. Here are our UGA strategies for dealing with the shortage of chlorothalonil in peanut production:
A. Consider using a strong leaf spot fungicide like “Headline” (9 fl oz/a, 45 days after planting) to initiate an excellent leaf spot program and to replace potentially 2 applications of chlorothalonil (30 and 44 days after planting).
B. Reduce the rate of chlorothalonil used in a leaf spot applications by partnering with another fungicided. Examples include mixing chlorothalonil (1 pt/A) with Tilt (propiconazole, 2 fl oz/A) or Alto (cyproconazole, 5.5 fl oz/A) or Topsin-M (5 fl oz/A).
C. We DO NOT recommend a solo application of Alto (5.5 fl oz/a) for early-season management of leaf spot. Although Alto tank-mixed with Abound has provided very nice results in management of leaf spot, Alto alone may not have the “umff” that growers need. Just as we would never recommend spraying Tilt (4 fl oz/A) alone without Bravo, likewise we would like to see the Alto go out with a tank-mix partner. Alto IS NOT a white mold material, it is just for leaf spot!
CORN
1. Rust is being found early this year. More importantly, it is widespread and found in fields that have not yet reached the tassel stage. (See our current map at https://scr.ipmpipe.org/).
1. Rust is being found early this year. More importantly, it is widespread and found in fields that have not yet reached the tassel stage. (See our current map at https://scr.ipmpipe.org/).
2. Sporadic afternoon and evening thunderstorms are likely to further move rust spores and also provide the moisture important for infection.
3. This is the most significant threat of southern rust in Georgia in the past 10 years.
4. Southern corn rust (SCR) reduces the photosynthetic capacity of infected leaves. More importantly, a field where SCR is not controlled may develop extensive lodging problems as the stalk is cannibalized for nutrients to feed the ear.
5. Protecting a crop from rust though the dough stage is beneficial.
6. I recommend that growers spray by tassel growth stage and then again 2-3 weeks later, depending on the product used in the first application.
7. On corn where rust is a severe problem, we have seen fungicides protect 25+ bu/A.