Lowndes – Echols Ag News

UGA Pecan specialists Lenny Wells shares information on scab pressure and leaf roll mites. With 10 successive days of rain behind us and no relief in site and a potential tropical storm bearing down on us, pecan growers are under the gun for scab pressure right now. Most days have provided some breaks in the rain showers that have allowed growers to get out and spray at least a portion of their acreage. But, the question is what to spray with when growers can get into the orchard.

We are currently transitioning from worrying about leaf scab as the leaves should be hardening off soon to worrying about nut scab as the nuts begin the sizing period. One of the best materials to be using at this stage with the pressure we are having would be one of the DMI/Strobi mixes (Group 3 + Group 11) like Absolute or Quadris Top if  you have not used them 2 or 3 times already. The problem we are running into is that most growers are coming off of spraying this chemistry in their last couple of sprays. If this is the case, what should growers go to at this point?

The answer would largely depend on what has been used already but in the scenario above—if you have already used a couple of group 3 & 11 mixes—you have a few options. The right choice will probably depend on variety.

For moderately susceptible varieties like Sumner, Stuart, Schley, Oconee, etc. you could go with something like a 2 qt rate of Phosphite alone or a group 3 fungicide (Tebuconazol, Propiconazol, Tetraconazol, etc.) + either Phosphite or Tin

For highly susceptible varieties like Desirable, Pawnee, Caddo, Cunard, a better option would be something like 25 oz Elast and 1 qt of Phosphite.

Regardless of what you use, it is probably a good idea to tighten that spray window to 10 days minimum on scab susceptible varieties.

We have also had a number of calls about leaves curling at the edges a seen in the photo below:

This is a result of feeding by pecan leaf roll mite. Their feeding causes galls at the outer margin of the leaflet, which causes the edges to curl up and sometimes turn brown. This distorts the leaflet but does not usually cause defoliation. Most of the time this damage is only cosmetic and does not require treatment.

Dr. Lenny Wells shares shares information on herbicide damage in pecan trees.  Row crop planting has started in south Georgia and this means herbicide drift season has arrived. I have been on the road all week looking at drift-damaged trees. Since I cannot make it to every orchard in which this occurs, here are the steps that should be taken when a drift incident happens:

Glyphosate injury on both leaves to the left. ZInc deficiency on leaf to the right.

Glyphosate injury to pecan

If growers have had herbicide drift injury occur on their trees, they should first contact their county agent and take photos for documentation. The Georgia Department of Agriculture should also be contacted to take their own samples as soon as possible if a complaint will be filed. Many of these herbicides have a very short half-life and samples must be taken quickly in order to detect them in leaf tissue.  The next step is to contact the neighbor from whom the drift originated and contact the neighbor’s insurance agency to notify them the incident occurred. Once everything has been documented it is usually a wait and see situation because of the high degree of variability from one case to the next. Often with glyphosate, glufosinate, paraquat, and flumioxazen, the injury is more cosmetic than economic unless there is extensive coverage, leading to significant leaf and flower/nut loss. Quality may also be affected if extensive foliage damage occurs because the trees must expend energy to re-grow new foliage. The only way to know the extent of damage for sure is to evaluate the crop at the end of the season. Repeated injury, of course, will lead to more serious losses and can cause long term damage to the trees.

Paraquat injury to pecan. Damage initially appears as yellowing of tissue and then turns brown and necrotic.

Older paraquat injury to pecan. All damaged tissue has turned brown and necrotic.

Dicamba and 2,4-d may throw a more complicated scenario into the equation. Based on data from the trials Dr. Eric Prostko and I have been conducting, injury from these materials, especially 2,4-D can be more serious if a high rate of the chemical makes direct contact with the tree’s tissue. In this case we have seen death of those branches that had direct contact. Once again, the degree of damage severity will depend on the rate and coverage. The same steps described above should be taken in the event of drift from these materials.

Initial appearance of auxin (2,4-D and dicamba) herbicide injury

Arrested nut development of terminals affected by auxin herbicide

Branch die-back from auxin herbicide injury