Category Archives: Pecans

Fruit Thinning & Irrigation Scheduling

Pecans 007

We’ve had scattered rain so far this season, and nuts are beginning to size. Our scab levels are low thanks to  fungicide sprays and scattered rain. This is the period where our female flower is beginning to set physiologically in the tree, so any stress now is greater impact. There have been reports of aphids, and some growers have sprayed already. Here is some information from UGA Extension Horticulturalist Dr. Lenny Wells on fruit thinning:

Pecans 008For the brave souls willing to thin some nuts from heavily loaded trees, now is about the time for most of our mid-season cultivars. Varieties like ‘Creek’, ‘Stuart’ and ‘Cape Fear’ should be ready as early as (last) weekend and certainly by (this) week for most of south Georgia. See here for a previous post on fruit thinning and how to cut nuts to determine if your crop is ready to thin.

Even though it is hot and dry, if you plan to fruit thin, it is wise to turn off the irrigation a day or two prior to thinning in order to minimize the chances of bark damage to the tree. Also, with the hot, dry weather many growers are anxious to begin running their irrigation at 100% capacity. Bear in mind that we are still in the nut sizing stage on most cultivars with the exception of ‘Pawnee’ and a handful of other very early cultivars. We don’t need to go to full capacity until we enter the kernel-filling stage. If you have a September harvest cultivar like ‘Pawnee’ you should be operating at full capacity now in order to fill the nuts. For most other October harvest cultivars change your irrigation to full capacity about mid-August (another couple of weeks).

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Soil Testing Pecan Herbicide Strips

Pecan-Background (7)

This is pecan leaf sample time – July 7 through August 7. In addition to leaf samples, UGA Extension Horticulturalist Dr. Lenny Wells has information on soil testing, particularly in row middles.

Many have found that pH in the herbicide strip is lower than that found in the middles. When we were doing the work on fertilizer placement and comparing broadcast band applications of dry N fertilizers with broadcasting over the whole orchard area, herbicide sprayer application of N, and injecting N through the irrigation system, we observed that soil pH is always lower in the herbicide strip regardless of the fertilization method you use (Pecan Response to Nitrogen Fertilizer Placement). We do have the potential to drop the pH faster in some situations where you concentrate fertilizer N in the strip, but its always lower in the strip. This is because the vegetation growing in the middles keeps the organic matter levels up, which helps to buffer soil pH, allowing it to remain a little more stable than areas free of vegetation.

Managing soil chemistry in the herbicide strip is vitally important because that is where the tree’s feeder roots are located around irrigation emitters. After their transformation to nitrate-N, both ammonium and urea fertilizers have an acidifying effect on the soil to which they area applied. In order to manage this, growers should take their soil samples within the herbicide strip and lime based on this reading. Because the vegetation in the middles helps to buffer the pH, you probably won’t need as much lime in those locations. It would be wise to check pH in the middles every few years and make an additional lime application to the middles when pH drops below 6.0.

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Pecan Leaf Sampling

Pecans 002

It is time for us to take leaf tissue samples in pecans.  UGA Extension Pecan Specialist Dr. Lenny Wells has this information:

The general recommended period for leaf sampling is July 7-August 7.

Why does it matter when you sample?

Concentrations of N, P, and Zn on a leaf dry weight basis start off relatively high early in the season, decline rapidly, reach a fairly steady state after mid-June, and then decline near leaf fall.  K tends to start high, then decreases and plateaus at about the same time as N, P, and Zn. Most of the P and Zn that accumulates in the leaves have done so by the time the leaves reach full size. Calcium (Ca) accumulates in the leaves as the season progresses, peaking in August-September. Magnesium (Mg) Manganese (Mn), and Boron (B) also tend to increase as the season progresses, but to a lesser extent than Ca.

PecanLeafSampling

Collect middle-pair leafleats

How do we sample?

  1. Collect 50- 100 middle-pair of leaflets from the middle leaf of this year’s growth (right). Use terminal shoots exposed to the sun. Avoid twigs from the interior of the tree. Collect leaflets from all sides of the tree. Avoid leaflets damaged by insects and diseases.
  2. Abnormal trees or trees not representative of the area should be sampled separately. A complete and accurate description of abnormalities should accompany these samples.
  3. Sample trees of the predominant variety in a given block. If Schley is the main variety, sample Schley; etc.
  4. Immediately upon collection, wipe leaves (entire surface, both top and bottom) with a damp cellulose sponge or cheese cloth to remove dust and spray residue.  Do not allow the leaves to come into contact with rubber or galvanized containers. Partially air dry and place in the large envelope of the mailing kit.
  5. If recent soil test data is not available, it would be advisable to collect a soil sample and have it sent to a soil testing laboratory.  By sampling the same trees each year, growers can more readily see the results of any changes to their nutritional programs.

**Some growers have taken leaf samples throughout the growing season to determine the fertility needs of the tree. This is really unnecessary. Leaf analysis does not necessarily reflect the actual use pattern of mineral nutrients, but instead indicates concentrations of those elements in the leaf at the time of sampling. The tree knows what it needs and when it needs it.

Concentrations of mineral nutrients in the leaves change as leaves emerge, expand, and finally senesce in the fall. For many elements, the least change in concentration occurs from early July-early August.

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Pecan Mouse Ear

Mouse ear is a growth abnormality from a nickel deficiency in pecan trees. This disorder occurs mostly on newly transplanted trees in established orchards. This is the first time I’ve seen it, but it is close to the text book pictures and easy to ID. Mouse ear first appears on the spring growth flush. The most common symptom of mouse ear is a rounded or blunt leaflet tip. Other symptoms include dwarfing of tree organs and necrosis of leaflet tips. The degree of severity with the tree canopy typically increases with canopy height.

Mouse ear symptoms

Mouse ear symptoms, rounded or blunt tip

Necrotic leaf tips due to build-up of lactic acid from Ni deficiency.

Necrotic leaf tips due to build-up of lactic acid from Ni deficiency.

There are 4,000 seedling trees in this nursery and probably half are affected by the Ni deficiency. At this point we need to spray a foliar application of nickel now and again in one month. UGA Pecan Horticulturalist Dr. Lenny Wells says mouse ear may consistently reappear from year to year, or appear on occasion. For mouse ear prone sites, it is recommended to have a foliar spray of nickel in med-late April when leaves are in the parachute stage. (Ni is not absorbed in the plant until leaves are in parachute stage.) We follow up with an additional application in late September or early October to prevent mouse in the following spring.

Long-term Management (From Southeast Pecan Grower’s Handbook)

  1. Monitor leaf and soil samples for availability of Ni to trees.
  2. Don’t make excessive applications of zinc. Zn competes with and inhibits uptake of Ni. Foliar Zn should only be applied when Zn leaf levels are less than 50 ppm or when visual Zn deficiency symptoms are present. Do not allow soil to become acidic (making Zn more available.)
  3. Maintain good soil moisture at budbreak. Ni is relatively low in the soil in most orchards, and it is absorbed by the tree in the lowest of many nutrients.
  4. Maintain soil pH at 6.5.
  5. Do not give late applications of N, to ensure that senescing foliage can translocate to shoot and bud storage prior to defoliation.
  6. Manage phosphorus, iron, and copper levels in soils. These nutrients affect uptake of Ni. They may also alter the availability of Ni within the leaf.
Rosetting of leaves from Ni deficiency.

Rosetting and necrotic tips from Ni deficiency.

 

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Pecan Budbreak: When To Spray?

PecanBudbreak 003

With Friday’s heavy rain and the arrival of budbreak, pecan growers are anxious to get their first fungicide spray on for scab protection. Infection has historically been bad in our area, and growers like to get started early. Here are some points from UGA Extension Horticulturalist Dr. Lenny Wells:

At this point, the only pecan variety growers should be concerned about is ‘Desirable’. Most varieties that have budded out far to this point are less susceptible to scab and is less of an urgency to get those covered. If ‘Desirable’ is to the point where the leaves are unfolding, and you are located in a scab prone area (below 300′ elevation or surrounded by woods), it may not be a bad idea to spray this week. If the leaves are still tightly enclosed in the form of a swollen bud or you are in an area with good air flow, I would hold off at this point.

For most other varieties, especially Stuart – which is further behind in its progression of bud break – there is no need to spray just yet. While we had significant rain Friday and there is a chance of rain one night this week, low temperatures are forecast to remain in the mid to low 40’s, especially toward the end of the week. The optimum temperature range for scab infection is 59-77 degrees F and a leaf wetness of about 12 hours. If the cooler weather this and last week slows down budbreak, it will likely slow down scab as well. Except for ‘Desirable’ in the situation described above, I would plan on waiting until next week to begin scab sprays in most areas of the state.

For an example of a proven fungicide program to consider see a previous blog post on: Example of Fungicide Program to Manage Scab.

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Pecan Budbreak – Spray For Phylloxera

PecanBudbreak 004Bud break of pecan has arrived in south Georgia. If you have problems with phylloxera, UGA Extension Pecan Horticulturalist Dr. Lenny Wells says it is time to consider making an application for this pest. The southern pecan leaf phylloxera, is a tiny aphid-like insect that feeds on the foliage of pecan trees. The insects are rarely seen, but the galls that they cause are prominent. The southern pecan leaf phylloxera is primarily a pest on mature pecan trees, but it can be found on nursery and young trees.

Some products are taken up by the plant systemically, and this may provide an easier control option. Last season, we put out a trial to test drenching Admire at different times. After rating, we found no difference in drenching from December through March. We are thinking of other ways to test this theory. Until then, foliar spraying is our best option. The timing is critical.

Life Cycle

Overwintering eggs hatch beginning the first week of April and continue until the first of May.  The newly hatched stem mothers crawl to the expanding leaves where they settle down and begin feeding.  Feeding causes rapidly growing gall tissue which encloses the immature stem mother within a few days.  Stem mothers mature by mid-April at which time they lay eggs within the gall.

Phylloxera inside gall

Phylloxera inside gall

Light populations are most probably of little consequence. However, each gall results in dead leaf tissue and numerous galls can cause premature leaf shedding. Hickory shuckworm uses phylloxera galls for first generation larval food.

Stem Phylloxera

Of much greater concern than leaf phylloxera, a separate species, stem phylloxera can be much more damaging. They produce a hard swelling or tumor like galls, one tenth to one inch in diameter on leaves, leafstalks, succulent shoots, catkins, and nuts of new growth. Heavy infestations can completely destroy an entire nut crop and the accompanying malformed and weakened, infested shoots reduce tree vitality to such an extent that damage may reduce the following years production. This is rarely seen in managed orchards but where it does occur it needs attention.

Imidacloprid is a good, inexpensive, systemic choice for phylloxera control. Phylloxera sprays should be applied just after bud break or no later than when the leaves are one-third grown. Once galls are  observed it is too late to spray until next year.

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Pecan Herbicide Programs

Young Pecans

There are reports of budbreak in the state. Many growers are in the process of getting out herbicide strip applications. There are many herbicide options for pecan growers to choose based on weeds, pre and post emergence, and herbicide activity. UGA Extension Pecan Horticulturalist Dr. Lenny Wells has these thoughts on herbicide choice:

  1. Glufosinate and Paraquat would be better selections for burndown than glyphosate under newly planted and young trees because they are contact materials and any potential drift would cause very limited and only temporary damage unlike the systemic glyphosate. Just be sure to protect the bark from any herbicide.
  2. Burn down herbicides should include glyphosate where grass is a major issue. Just be careful about drift where using this material under young trees. Paraquat and Glufosinate normally will not give long term control on a thick covering of Bermuda grass.
  3. Include pre-emergent herbicides in your program. Again, we have many options here. Alion is an excellent pre-emergence material that gives long lasting control. It has a high price tag, but will significantly cut down on the number of applications you need to make, which offsets the cost. Use the 5 oz/A rate in the first year that you use Alion. After that, you can drop down to the 3.5 oz/A rate. Previously Alion was only labeled for trees 3 yrs of age or older. I was recently told by Bayer representatives that this has changed and can be used on 1st year trees and older. We have tested it for a number of years on 1st year trees at high rates and have never seen a problem.
  4. Flumioxazin (Chateau) is also an excellent pre-emergence herbicide for use on trees 1 year and up. Its residual is not quite as long as Alion, but it’s close. Even if you are using Alion, rotation between Alion and Flumioxazin from one year to the next is a good idea to manage resistance and limit the over-use and buildup of indaziflam (Alion) in the orchard.
  5. We have many other options for pre-emergence which can be utilized in pecan orchards. These include Surflan, Simazine, Prowl, and Diuron. Isoxaben (Trellis) and rimsulfuron (Metric, Solida, and Pruvin) are recent additions to this arsenal. Of these, Surflan, Prowl, Isoxaben and Rimsulfuron can be used on 1st year trees and up. Trees must be 2 yrs old for Simazine and 3 years old for Diuron. Also, do not use Diuron on sandy soils. Consult the current UGA Pecan Spray guide here for a complete list of herbicides available for pecan and their uses.
  6. Tank mixing burndown and pre-emergent herbicides will reduce the number of trips made over the orchard but be sure to have at least 75-80% bare ground when using a pre-emergence material. Most of them need good soil contact to be effective.

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Ambrosia Beetles: First Flight Reported

Ambrosia beetle toothpicks

Ambrosia beetle toothpicks

UGA Extension Pecan Entomologist Dr. Will Hudson confirmed the first ambrosia beetle flight reported yesterday in southern Grady County. ABB initial flight usually occurs when temperatures go over 70 degrees. A few days ago, Dr. Hudson said they will likely fly this week. Growers with young pecan trees, especially under 5 years, need to check their traps. Remember, we are looking for the “toothpicks” on the wood. This is the frass from the beetles as they bore into the tree.

Once we see AAB attacking the traps, we need to spray. Trunks of young trees should be sprayed with a pyrethroid. Barrier sprays of Lorsban will not work for AAB. The beetles are particularly attracted to stressed trees (although they will attack non-stressed trees.) Pay close attention to trees planted in poorly drained soil. Once a flight is observed with the traps, it is advisable to spray each week in problem areas until the trees have leafed out.

Dr. Hudson speaks at 2016 Thomas County Pecan Update in Thomasville

Dr. Hudson speaks at 2016 Thomas County Pecan Update in Thomasville

 

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How Will GA’s Rising Pecan Acreage Affect The Long-Term Market For Pecans?

Here is information from UGA Extension Pecan Horticulturalist Dr. Lenny Wells:

I can’t tell you how many times I have been asked about or heard someone comment on the great potential for the pecan market to bottom out a few years down the road thanks to all the new acreage being planted. Make no mistake, anything that goes up is bound to come down at some point. But just how far down do you expect pecan prices to fall? The answer to this question depends on your level of optimism. There are a number of things to consider in all this to truly make an educated guess about the future of the pecan market.

Foremost on this list of considerations would have to be our export market, which is currently driven by China. China’s economy has many people concerned, but the Chinese demand for pecans has remained strong in the face of downturn in their economy. In addition, the fundamentals for long-term growth of the tree nut market, including pecans, in China are in place. There is an excellent article explaining the details of the optimistic outlook for the tree nut market in China available here: China’s Potential as an Export Market for Tree Nuts. The greatest unknown factor we face in the Chinese export market is our future political relationship with China. We all hope this remains strong, but if anything goes wrong, all bets are off. In addition to China, aggressive marketing of pecans is taking place in India, Turkey, and South Korea among others to help grow the world-wide demand for pecans.

Another important aspect that many of the naysayers are probably not considering is the potential of the Federal Marketing Order for pecans, and the this impact for domestic consumption. Growers will be voting on the referendum probably within the next 3 to 6 months. Federal Marketing orders for pecan were attempted in the past, but none has had the unified support the current proposed program has garnered. If the FMO does indeed get voted in, pecans will, for the first time, have significant funding to launch a national marketing campaign on par with some of the other tree nuts, which have reaped great rewards with their own programs. This will allow the pecan industry to get the message out regarding the remarkable health benefits of pecans on a large scale, which is a necessity for increasing domestic demand.

The other necessity for increasing domestic demand for pecans (and this may be the trickiest part) is a solid, consistent supply of pecans. Currently, we do not have the pecans available in the U.S. to develop as large and sustainable a market as we would like to see. This makes it difficult to coax large companies within the food industry to develop, produce, and market products using pecans as ingredients. I hear people constantly groaning that when all these trees we’ve planted come into production, we won’t be able to give pecans away. If we continued down the same path of marketing our crop as it has been done for the last 100 years, they would be correct. But, the fact is, we need the increased production to develop the market we need for pecans. There will likely be growing pains along the way, as we try to balance increasing the demand for the crop with increasing our production. But this is a good problem to have.

And what about the increasing acreage? Just how much is it increasing? And what does this mean for the future volume of pecans produced? Other states are planting pecans, but from what I hear, probably not at the scale Georgia is planting. Let’s look at Georgia to illustrate this point, since Georgia produces about 30% of U.S. pecans. It is extremely difficult to pin down exactly how many acres of pecans we have because of orchard turnover, new plantings, unclear distinctions between managed and hobby orchards, and the complications brought about by the proliferation of yard trees and their inconsistent production.

All this makes Georgia’s pecan acreage virtually impossible to accurately determine. The most recent U.S. Census of Agriculture (2012) placed Georgia’s pecan acreage at 123,415 acres. That same year, the UGA Farm Gate Survey accounted for 163,933 acres. So, lets shoot for somewhere in the middle and say we have 140,000 producing acres. We tend to average somewhere around 95 million lbs of pecans annually. If you do the math using the 140,000 acres that’s an average of only 678 lbs/acre. (This number obviously takes into account production from hobby and non-managed orchards.) Commercial producers in Georgia produce much more than this—usually close to twice that amount—but this brings into question, just how many of these trees being planted now will contribute significantly to future production?

Our survey estimates indicate somewhere around 20,000-25,000 new acres have been planted over the last 5 years in Georgia. At 678 lbs/acre, that’s only another 17 million lbs, which would bring us up to an average annual production of 112 million lbs. With a growing market, I don’t think this number is any a death toll for the pecan industry. We need this production to develop the market we are striving to have.

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Time To Set Ambrosia Beetle Traps

Evidence of ambrosia beetles appear as "toothpicks" on the bark

Evidence of ambrosia beetles appear as “toothpicks” on the bark

Last year was a big year for ambrosia beetles. These beetles live all around us and in the woods. They generally attack stressed or injured trees. The pecan trees they affect are young trees, maybe 5 years and younger. They are identified by “toothpicks” on the outside bark. This is the boring dust pushing out of the tree. UGA Extension Entomologist Dr. Will Hudson says there is not a preventative management of these beetles. Treating is essentially a “shotgun” approach. Ambrosia beetles are hard to predict since they also attack other woody tree species.

The one thing growers can do to limit losses is trap adult beetles to pin point their first flight. Based on previous studies, February 1st is the best plan for South Georgia to set out traps. The traps are something producers can do to pin point when the first flight originates.

Trap Design

Dr. Hudson explains how to design the trap:

The simplest and most efficient (trap) is made from a bolt of wood with a hole drilled down the center.  Any hardwood will work, and a branch 2” – 4” in diameter about 2 feet long will do the trick. Drill a ½” (+/-) diameter hole down the center as far as you can (but not all the way through) and fill it with ethanol (grain alcohol, not rubbing alcohol; denatured is OK).  Put a stopper of some sort (a cork, for instance) in the hole and then hang the bolt about waist high at the edge of the orchard.  It will probably take several traps per edge, but edges along woodlines are most likely to catch beetles first.

Photo by Dr. Pete Schultz, VPI&SU.

Photo by Dr. Pete Schultz, VPI&SU.

Photo by Dr. Pete Schultz, VPI&SU

Photo by Dr. Pete Schultz, VPI&SU

Once attacks are detected on the trap, close-interval scouting can be initiated (check the trees every day or so for signs of beetles).  If you see toothpicks on the trees, apply a pyrethroid spray quickly to minimize damage and losses.  Unfortunately, barrier sprays applied as a preventative measure for other borers are not effective on these beetles.  They will provide protection for a few days or a week, depending on the weather, but ambrosia beetles do not eat the wood or bark so once the volatility of the insecticide has faded a bit they are not affected.

You can also reduce losses by removing the irrigation pipe collars that protect young trees from herbicides. Ambrosia beetles will attack inside the pipes where they can’t be seen.  This adds work, and means you have to delay herbicide application until they can be reinstalled once the trees leaf out completely. But, collars have definitely contributed to extra losses for a number of growers. The spring green-up period is when the trees are most vulnerable, and once they have leafed out completely the risk of attack drops to almost zero unless there is some stress factor for the trees.

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