As we move into mid-July, Dooly County peanuts should be blooming and most should have begun pegging. This is the time when the plants are setting their yield, and can be most affected by dry conditions, insect damage, weed competition and other factors. Management over the next four to six weeks will determine yield.
Water requirement – Peanut water requirements vary depending on days-after-planting. Due to the spring rains, some peanuts were not planted until mid-late May, while other have been in the ground since late April. At 40 DAP, peanuts require around .75″ of moisture(rain or irrigation) per week. That amount goes up to over 1.5″ at 80 DAP. At peak fruiting(around 14 weeks), the peanut plants can use up to .3″ per day. With the sporadic rainfall in Dooly County this summer, be sure to stay on top of your irrigation schedule, and be sure to adjust irrigation amounts based on your planting date.
Insects – Most peanut fields in the state will have some caterpillars right now, but fields treated early with a broad spectrum insecticide like acephate or chlorpyriphos will be at a higher risk . It is important to monitor caterpillar populations in these high risk fields. The current UGA recommended threshold for caterpillars in peanut is 4-8 per row foot. Spraying is not needed until populations exceed that threshold. Also keep an eye out for lesser cornstalk borers and spider mites. As conditions grow hotter and drier, we will see larger infestations of these two pests. There still is not an economic threshold for three cornered alfalfa hopper.
Disease control – Dr. Kemerait –
Current conditions (warm weather with developing afternoon thunderstorms) create favorable conditions for leaf spot diseases and white mold.
1. White mold on peanuts: warm soils, increased growth of peanut crop and irrigation/rainfall have created ideal conditions for development and spread of this disease and fungicide programs should be implemented accordingly.
2. My graduate student Abraham Fulmer is finding development of early and late leaf spot in his unsprayed peanut plots. A further indication that it is time to spray.
3. As mentioned in my previous e-mail, it appears that chlorothalonil (Bravo, Echo, Chloranil, etc.) will be “short” in our supply chain this year and I am already getting many calls and questions about it.
4.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 is may not have the “umff” that our 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. (By the way, Alto IS NOT a white mold material, it is just for leaf spot! Also, despite words to the contrary, Alto is not as good as Headline. True, both are very good leaf spot materials; however Headline has a longer protective window.)
PEANUT Rx: Using “prescription” fungicide programs based upon risk assessment in the field may also be an excellent strategy to reduce use of fungicides in general.