Considerations for now:
- In Georgia, at least south of the “Gnat Line”, we had a fairly mild 2021-2022 winter. Regrowth cotton and volunteer peanuts and corn survived longer than was helpful and fed the nematodes that didn’t want to go to bed for the winter because soils were warm enough to keep them active. Nematodes in warmer winter soils with a food source just want to stay up late and that leads to more nematodes.
- Cotton growers should consider the following in their nematode management plans. a) Are nematodes are threat to the cotton in their fields? If the answer is “no”, then don’t worry about them this year. If the answer is “yes” or “I don’t know”, then growers should consider ways to protect their cotton crop. c) A good way to protect the crop is to plant varieties resistant to root-knot or root-knot and reniform nematodes (unless the problem in the field is sting or Columbia lance nematodes). d) if not planting a resistant variety and the grower has a nematode problem, it will be a tremendous mistake to miss the chance to use a nematicide, or to use a nematicide that won’t get the job done. Fumigation with Telone II (3 gal/A) is our most aggressive and effective solution when a nematicide is used, but it is also most expensive and most complicated. If not fumigation, growers can use AgLogic 15G (a granular product at 5-7 lb/A) or Velum (a liquid product at 6.5-6.8 fl oz/A). Growers can use seed treatment nematicides, but there are most appropriate for lower populations of nematodes. Growers can SUPPLEMENT but NOT REPLACE earlier nematicide applications with Vydate CLV applied at about the 5th true leaf stage.
- Peanut growers can follow (should follow) similar advice as above when Peanut Root-Knot nematodes are a threat. a) Growers can plant Georgia-14N or TifNV-HiOL, both of which have resistance. b) They can use Telone II (4.5-6 gal/A) of AgLogic 15G (7 lb/A) or Velum (6.8 fl oz/A). Vydate CLV is also labeled and available for use in-furrow for peanuts. We at UGA continue to evaluate Vydate for management of nematodes and thrips. Stay tuned….
- Peanuts and in-furrow fungicides.
- most peanut growers will be using Rancona or Trebuset as seed treatments this year, both of which will be better than Dynasty PD for management of Aspergillus crown rot.
- Conditions today for our peanut growers COULD indicate “hotter and drier” at planting. Planting peanut seeds into “hotter and drier” soils increases risk to Aspergillus crown rot, especially (but not always) when farmer-saved seed is planted. Also, a “heads up” to growers- Hotter and Drier at planting increases risk to Aspergillus Crown Rot. HOTTER early in the season increases risk to growers for WHITE MOLD (southern stem rot, Dr. Dufault…) as well. Be prepared.
- Growers who have used Velum for nematode control will ALSO get additional benefit for control of Aspergillus crown rot. (NOTE: Because of cost and other options, I would not use Velum if I was not first-and-foremost trying to control nematodes. Additional management of crown rot is simply a “bonus”.)
- Azoxystrobin (e.g., Abound) in-furrow adds benefit in fighting Rhizoctonia seedling disease (if such is needed) and offers some, but not much extra benefit for Aspergillus control. Coupled with a seed treatment, azoxystrobin in-furrow may not be great (if won’t be) for control of Aspergillus control, but it may be enough.
- Proline in-furrow is MOST appropriate for management of Cylindrocladium black rot (CBR) and, to a lesser extent, for early-season white mold control. A banded, concentrated application of Proline 21-35 days after planting would be a better strategy for early-season white mold control. I wouldn’t use Proline simply for extra Aspergillus control.
Nematodes- plant parasitic nematodes, especially on corn, are the most pressing thing in my world right now.
Bottom line– a lot of row crop growers in Georgia, even now on corn, are recognizing that poor growth in their fields COULD BE nematodes! This is a giant step from when they thought it was a) fertilizer spreader problems, b) pH problems, c) herbicide damage, or d) sorry dirt (whatever that is). That growers now are aware that damage from nematodes is a REAL threat to production and yield is a GIANT step. Acceptance is the first step to recovery.
But is it REALLY nematodes? Because stunting can be caused by a number of things, as listed above and nematodes are only one of the causes. For sure the guy who spread the fertilizer or who applied the lime wants to think it is nematodes and not something misapplied.
So how do you know? Here are steps I take..
1. Look for patterns. Potential damage (stunting, etc) from nematodes tends to be more severe in some parts of a friend than in others. Often this has to do with a) soil type or b) field history/prior crop.
2. Occasionally there can be a row pattern, indicative of a stopped-up nozzle where a liquid or granular nematicide was not delivering product.
3. Take a shovel and carefully dig up roots focusing on finer secondary roots for typical damage and possibly galling. It can be a little tough with corn where symptoms may be less showy than on peanuts or cotton or soybeans. In corn, look for “nubby” roots or “balls of atypical” root growth. Obviously, you must know what healthy roots look like.
4. Take soil samples. Soil cores should be taken from DIRECTLY in the root zones. That’s where the ‘todes are. Take multiple cores for a “bad” sample. But also take multiple cores from a “good” area so that results from good and bad can be compared. These samples could be submitted not only for nematode testing, but also nutrient testing and testing soil pH. REMEMBER that soil for nematodes MUST be kept cool!
5. Submit quickly for testing. Keep refrigerated if you can’t send quickly until you can send.
Interpreting you nematode results, things to remember….
1. Remember that our nematode economic damage threshold levels are based upon samples taken at harvest. That samples collected early in the season come back with ANY “bad guys” could easily be indicative of a nematode problem. We do not have spring thresholds.
2. It looks like nematode damage both in terms of patterns in the field and apparent root damage, but the soil sample came back “ZERO” for parasitic nematodes. What does that mean? It could mean several things 1) Maybe it’s not nematodes. 2) Maybe because it is early in the season, there were enough nematodes to cause damage but not enough time for significant reproduction to occur. In other words, we missed them. 3) Maybe because of how the sample was collected (outside the root zone or in dry soil) we missed them. BOTTOM LINE- if you are still convinced this could be a nematode problem, or that nematodes are at least a part of the problem, consider waiting a week or two and pulling samples again. Sometimes new results are more conclusive.