Season-long Disease and Nematode Control – Dr. Bob Kemerait:
“Planting season is upon us and critical decisions with regards to season-long disease and nematode control must be made before the furrow is closed.
- Nematode management for corn producers. Options are Telone II, Counter 20G, Propulse, and Avicta Complete Corn (a seed treatment).
- Peanut seed issues- I spoke with Dr. Tim Brenneman this morning and he continues to analyze results from work he has done on addressing our seed-quality issues. In a “nut shell”- A) Fungicide seed treatments are a MUST on peanut seed. B ) Where high quality seed is planted, use of Rancona or Dynasty PD is likely sufficient. C) Where seed quality is an issue, or MAY be an issue, Rancona has been a much better product for suppressing Aseprgillus flavus and, to some degree, Aspergillus niger, on the seed. D) Where Dynasty PD is used on seed and where seed-quality is an issue, use of either Proline or Velum Total in-furrow is recommended (as opposed to azoxystronin/Abound). E) Where Rancona is used and there is question on seed quality, growers may use Proline, Velum Total or Abound, as Abound and Rancona contain different chemistries. F) If growers are using Velum Total in-furrow already for nematode control, they do not need to add additional Abound in-furrow for extra protection against seedling diseases. G) If your grower wants Rancona and cannot get it, BEWARE of “offers” that come for products that are “just as good”. To date, we at UGA are talking about Dynasty PD, Rancona, Proline, Velum Total, and azoxystrobin (Abound).
- Cotton nematodes- warm soils and cotton left in the field that never died add up to greater risk for nematodes in 2020
- Kudzu and Asian soybean rust- we know that kudzu survived the winter and is infected with Asian soybean rust. It is very possible that we will have earlier outbreaks of soybean rust in 2020. Soybean producers should be anticipating this.”
Clarification on Phosphite Materials (for Pecans) – Dr. Lenny Wells
Based on conversations I have had with a number of growers it sounds as if there is a need for some clarification regarding phosphite materials. Phosphite has become a very valuable tool for us in the battle against pecan scab. Dr. Tim Brenneman first began testing phosphite materials on pecan primarily for efficacy on some of our minor foliar diseases like anthracnose a number of years ago (since at least 2009).
In the course of Dr. Brenneman’s research he began to notice that phosphite also had a significant effect on scab—especially leaf scab. As his research continued, he developed a large data set on phosphite over several years, using many different phosphite products. UGA Extension recommendations for phosphite use are based solely on Dr. Brenneman’s research. Initially it was only recommended for use in combination with other products, never as a stand-alone. Dr. Brenneman now has the data to show that at rates of at least 2 qts per acre, phosphite can be used alone for leaf scab during the pre-pollination stage. It is an excellent leaf scab material and this is where its best use lies. It can be used during nut sizing as well but in high scab pressure situations, should be tank mixed with another fungicide for nut scab.
Now, what exactly is phosphite? Phosphite (H3 PO3 ) is derived from Phosphorous acid, NOT Phosphoric acid (H3PO4) which is a fertilizer. Phosphorous acid dissociates to form the phosphonate ion (HPO3 2-), also called phosphite. Phosphites are highly systemic and very stable in plants. There is evidence that phosphite may stimulate host defenses .
Phosphite or Phosphorous acid is not converted into phosphate, which is the primary nutrient source of P for plant . There are bacteria capable of transforming phosphite into phosphate, but this process is so slow that it is of no practical relevance. To date, no plant enzymes are known to convert phosphite into phosphate. Therefore, any claims that phosphite can contribute to P nutrient requirements for plant growth should be taken with much caution.
As a matter of fact, phosphite can trick plants into thinking they have enough P, which may potentially contribute to P deficiency when phosphite is over-used (see the article linked here for more info on this topic).
There is apparently some concern out there about the salts present in many phosphite products. If purity of product is of specific concern to you, then you should use a phosphite product that does not have salts present (bear in mind, that your soil applied potash [KCl] is also a chloride containing salt). However, Dr. Brenneman’s research has shown no negative effect from phosphite products containing salt in his research going back at least 10-11 years. There is no evidence for greater toxicity risk in phosphite products containing salt than for those without salt.
If you are concerned about the long term effects of products containing salt, you may also want to consider the fact that phosphite itself is not metabolized by the plant and we also do not know what the long-term ramifications of that may be. Let me be clear, we do not have any evidence that would lead us to believe this will cause any detrimental effects to pecan trees. Nor do we have any evidence to suggest the salts present in some phosphite products will cause any detrimental effects. If independent research on either topic leads to more information on this, we will let you know.
In short, Dr. Brenneman’s research trials have shown that as far as efficacy is concerned, all the phosphite products Dr. Brenneman has tested (which include most of those we currently use in pecan—I won’t list them because there are too many to be named) work equally well on pecan scab and the other minor diseases from which phosphite provides protection and there is no more risk of toxicity with one phosphite product than there is with another.
Farm Recovery Block Grants Info – HERE