Growers in Southwest Georgia are faced with an unusually cool planting season this year. This will mean delayed planting and favorable conditions for seedling diseases.
Dr. John Beasley, Peanut Agronomist with UGA Cooperative Extension, recommends planting by mid-May this year to maximize yields. In a typical year he would rather have us planting from mid-April through mid-May, when spoil temperatures reach 70 degrees at a depth of four inches. This year, weather has not cooperated but we would still like to see the peanuts in by mid-May. From Dr. Beasley’s research over the last few years, he has seen a significant reduction in yield when planting occurs in late May and June.
Below is a chart of the soil temperatures at the four inch depth for the past few days. This data was taken from georgiaweather.net from the weather stations in our area.
|4 in. Soil Temperature (°F)|
|May 4th||May 5th||May 6th||May 7th|
Weather conditions are also favorable for peanut seedling diseases. With the cool, wet spring that we are having, many fungal pathogens will play a larger role then they have in the past few years. Dr. Bob Kemerait, Plant Pathologist with UGA Cooperative Extension has written a few points about the 2013 spring weather and potential for disease. (Above picture of Dr. Kemerait examining peanuts for disease)
Cooler and wetter weather has a tremendous impact on the potential for seedling disease. Cooler soils slow the germination of seeds and also slow the growth of seedlings. Fungal pathogens, like Rhizopusstolonifer that causes seed rot and Rhizoctonia solani that causes seedling disease in peanuts, cotton and soybeans, flourish when soil moisture is abundant. Given cooler soil temperatures and abundant rainfall, germination of peanut seed will be slowed, growth of the seedlings could be less vigorous, and fungal pathogens like those mentioned above will have an upper-hand on the young peanut crop. Interestingly enough, Aspergillus niger, causal agent of Aspergillus crown rot of peanut, should be less important in 2013 as this pathogen is most aggressive when early-season soils are hot and dry.
Note: Because cooler and wetter conditions slow growth of seedlings, such conditions may also increase the importance of thrips and thrips damage in 2013. The effect on severity of tomato spotted wilt this season is unknown.
Management strategies to reduce seedling diseases when conditions are cooler and wetter include:
- Plant only high-quality seed.
- Always plant seed that has been treated with an effective fungicide.
- Where seedling diseases have been a problem in the past, consider use of an in-furrow fungicide like Abound.
- Plant seed at an appropriate depth. Seed that is planted too deep will be most affect by and susceptible to seedling disease. DO NOT PLANT SEED ANY DEEPER THAN NECESSARY.
- If a period of wetter and cooler weather is predicted, growers are advised to delay planting if possible until conditions are better for rapid germination and growth.
Over the past couple of seasons, we have spent a significant amount of time talking about the importance of Proline used within 5 weeks of planting to lay the foundation for an excellent white mold program. Outbreaks of white mold are earlier and more aggressive when soil temperatures early warmer than normal. This has been the case in recent years, years when growers have seen little of another important disease- Cylindrocladium black rot (CBR). Cylindrocladium black rot is less widespread than white mold; however this disease can be devastating in fields where it occurs and management of CBR is much more difficult than for white mold. CBR is favored by cooler and wetter conditions at planting, much like we are experiencing now. Although the symptoms of CBR do not become evident until much later in the growing season, the fungal pathogen becomes established by infecting the roots of young seedlings. Effective management of CBR requires protection of the crop at planting.
If cooler and wetter conditions continue in 2013, use of an in-furrow application of Proline (5.7 fl oz/A) will be an important consideration for the management of CBR. Early-emergence applications of Proline are effective for management of white mold when conditions are very warm; however for best control of CBR, the Proline needs to be placed IN THE FURROW in order to provide protection to the developing root system. The benefits of such an application will not be observed until later in the season; however such a practice, or fumigation with metam sodium, is critical for the management of CBR.
The take home message is to plant peanuts when weather conditions are ideal and as soon as possible this spring. For additional information or help with a crop issue, contact your local county extension agent.