Per Lenny Wells:
We’re getting near the end but still have a little ways to go on the 2023 pecan crop. Most growers are tired of spending money and ready to see it start flowing back in. But, don’t let your guard down yet. August is a critical month for pecan trees. Here are some things you may observe as well as some things to watch out for and consider.
Water split
Rain has been seemingly continuous in much of Georgia since May. The trees are taking up a lot of water at the moment as most are at shell hardening and beginning to or about to begin the kernel filling process. Each year at this time, the trees drop some nuts. Much of this is the result of water stage fruit split or water split. This can result in an alarming number of nuts under the trees but be assured they are not going to drop them all and while it may look like a lot on the ground, there are still nuts in the tree. Usually the trees with the heaviest crop load shed the most nuts by volume. On a percentage basis they will shed roughly the same amount although varieties with thin shells and large nut clusters tend to shed the most from water split. We are seeing this on many varieties at the moment. See previous post for more info on water split.
Scab
This has been probably the wettest growing season I can recall. It always seems to happen in years ending in “3”. 2013 was a wet year. 2003 was previously the wettest season I can recall and remains the worst scab year I have ever seen. This year would likely be worse than 2003 were it not for the phosphites and Miravis Top. Yes, there is some scab out there this year but in a year as wet as this, there is no fungicide that will keep scab entirely at bay on susceptible varieties in all locations, especially if those spray intervals were stretched more than 10 days on varieties like Desirable.
Such wet years also bring some things to light that have remained hidden in more temperate years. We are seeing a lot of scab on Stuart in many locations this year. In some orchards, scab is worse on Stuart than on Desirable. You may recall that each pecan variety has its own race of scab. The race of scab infecting Stuart may be adapting and creating some resistance issues in places. Our pathologist, Dr. Tim Brenneman is currently investigating this. We have also seen orchards where scab is worse on Pawnee than on Desirable under the same program. In most orchards, it is the opposite. Years with this much rainfall also reveal the value of good air flow in an orchard. You may not notice it in drier years, but scab control will always be more difficult in an orchard surrounded by woods or in a low area than those out in the open on high ground. There’s little you can do about the elevation once the orchard is planted but if you own the wooded land surrounding your orchard, you may want to consider pushing those woods back from the orchard a bit to create more air flow. I have seen this done many times and have never seen it fail to improve disease control in the orchard.
You should be able to stop Pawnee fungicide sprays at this point. We are past the point of shell hardening and the nuts are between the gel and dough stages in the kerenl filling process. For most other varieties were are at the point of shell hardening and the kernels are beginning the filling process. For such varieties that are clean, where you have good air flow and good to moderate disease resistance (Cape Fear, Sumner, Oconee, Creek, etc.), you should be able to stop spraying fungicide after this week or next week. You still need to apply at least one more fungicide spray beyond shell hardening on Desirable or other highly susceptible cultivars or on those where scab is currently present.
Insects
August is the month when bugs seem to explode in the orchard. Be on the lookout for black aphids and mites. They have been light so far but rest assured, they are coming before the month is out. Whatever you choose to spray for these insects, do not use the same material repeatedly. We have a number of options for both so rotate to preserve the chemistries and future options. If you will be spraying bifentrhin or another pyrethroid for weevil this month be sure to include an aphid and mite material with that spray or (and this appears more effective to me but also more costly) plan to go back a week or so later with an aphid and mite spray. Nexter is a good choice for that final clean up spray to follow weevil applications because it has good efficacy on both black aphids and mites. But don’t wait until these insect populations are totally out of control to spray.
Water Management
Its tricky to manage irrigation when it is raining frequently but you are at peak water demand for the crop. You want to rely on the rain as much as possible but you don’t want the trees to get water stressed. This can affect not only the current crop quality but also, next year’s crop load. If the ground stays too wet and you get some wind in one of these afternoon thunderstorms, you could find yourself propping up or cutting out fallen trees. So, where’s the balance?
As I said, its tricky and there is no one answer because the needs on each soil type and in each orchard will vary. Tree age, hedging, variety, and crop load all play into the equation as well. The best advice I can give you is to pay very close attention to your soil moisture in the orchard. Our recommended irrigation schedule for pecans from mid August to mid September is to run at full capacity, especially if you have a good crop load. Trees with little to no crop load will require less water. As a general rule of thumb we recommend irrigating daily and turning the water off for 3 days only when you get a 2″ rain during this period. However, as wet as the soil is this year, and as frequent as the rains have been, you may want to modify that based on your situation. Perhaps turning off the irrigation for 3 days when you get a 1″ rain if you have been wet leading up to this period. If you get a 1/4 inch or 1/2 inch within that 3 day period, maybe leave it off a day or 2 longer. Examine your orchard soil and make a judgement call based on how long that soil moisture appears to persist.
It seems odd to say that soil moisture monitors will come in handy when its wet but they are designed to tell you when you need to water, not just how wet or dry the soil may be. This is a perfect situation to get the most out of a soil moisture monitoring system. Each orchard will have a certain value for full soil capacity. On some soils that value will be 30% and on some it will be 15%. Whatever that value is for your soil, you want to keep that soil moisture at no less than 2/3 capacity at 8″during this time to ensure adequate water for filling and to keep the trees stress free. Watch your soil conditions and watch the forecast closely.
