Category Archives: Pecans

Pawnee Nut Drop

UGA Extension Pecan Specialist Dr. Lenny Wells has this to say about Pawnee nut drop:

We have seen a fairly large Pawnee drop over the last week. It is not uncommon for Pawnee to shed a few nuts this time of year but this year’s drop looks a little heavier in places. Still, I don’t think its anything much to worry about in most cases. Most of the Pawnee trees I have seen with a heavy drop under them still have a heavy crop on them. The drop probably helped them more than hurt them. The trees should be able to produce better quality and have a better chance of a return crop.

Aborted Pawnee nuts prior to drop. Photo by Dr. Lenny Wells

 

Stages of Pecan Nut Drop (Sparks and Madden, 1985)

As the graph above shows, pecans undergo 4 separate fruit drops during the growing season, most of which are related to pollination problems. Pawnee is about a month ahead of most of our other varieties, so this drop would coincide with the 3rd drop in the graph above (which is based on Desirable). This drop occurs just before rapid fruit expansion and is due to the failure of the endosperm to develop properly. This drop is known to be accentuated by self-pollination. The low chill hours of this past winter and the resulting effect on budbreak (see Warm Winter and Pecans) could have affected cross pollination, leading to more self-pollination. If so, we may see a similar drop on other varieties in a few weeks.

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Pecan Fungicide ‘Rainfast’

 

With rain and humidity, we are having ideal conditions for scab. Some growers essentially continue to spray around the clock. A common question is, “How long does my fungicide need to dry before rain?” This is a question pathologists have worked on for some time, but there are many variables involved making it difficult to generate data. UGA Plant Pathologist Dr. Tim Brenneman recently offered the following suggestions based on his studies with pecan and also on similar studies he has conducted in peanut:

Highly systemic materials like phosphite must be absorbed into the plant. It may require as much as 1/2 a day for this process to take place so that the material can be highly effective. While DMIs and strobilurins or combination products like Absolute, Top Gard, Quadris Top, and Quilt have some systemic activity they are not as systemic as the phosphites. Still, they would need a little time to be effective, so several hours to half a day would be ideal. A surfactant (80/20 or other) would increase the uptake speed of these materials and would likely provide some benefit in the conditions we’ve had over the last week or so. However, do not include a surfactant with Phosphite.

While the DMIs and Strobis have some systemic activity they still function largely as protectants. Other materials like Dodine (ELast) or Tin are pure protectants. These materials (Dodine and Tin) would be the most prone to wash off when rain arrives shortly after spraying. Dodine does adhere tightly to the plant cuticle, which likely helps it. Rainfall that occurs less than one hour after spraying makes the fungicide pretty well ineffective. Any rainfall within 24 hrs after spraying with a pure protectant will likely reduce the effectiveness of control to some extent. For each additional hour between the spraying and rainfall you gain additional control.

Ideally, all fungicides should be applied prior to rain events. If circumstances prevent you from getting a spray on in time and you have to spray after a rain event, the DMI/Strobi combinations would be the best choice.

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Pecan Fungicides Begin

Young Trees

All of our pecan fungicides have begun at this point. We have lots of newer planted trees in the county, here are some being sprayed last week. UGA Extension Horticulturalist Dr. Lenny Wells says trees in the first few years need to be sprayed but not on a detailed spray program. For very young trees, a few fungicide applications in a season with some Tin is good. Once the trees approach production age, we need to add a few more sprays throughout the season and get closer to a full spray program.

Timing

In our area, we have been hit so hard with scab that we tend to get our fungicide sprays out real soon. Dr. Wells always says we can wait a little longer than we do. He was down last week looking at a fertilizer situation, and we looked at trees around that were leafing out at different times. He explained the issue with spraying early is not having enough leaf area for the fungicide to contact.

The most difficult part is managing orchards for more than one cultivar, which all are pretty much the same. If Desirables are in the orchard, we have to begin spray on their schedule since they are more susceptible for scab. If an orchard doesn’t have desirables and mostly Stuart, you can wait until those leaves come out. Here is a few pictures of optimum fungicide initiation Dr. Wells and I looked at in an orchard last week.

Left – This is time to spray Desirable
Right – This is too early for Desirable

Optimum time to initiate Stuart fungicide sprays

Fungicide Schedule

Below is an 8-spray fungicide schedule from UGA Extension Horticulturalist Dr. Lenny Wells provided as an example to use for pecan scab management in light of emerging scab insensitivity issues surrounding some fungicides. Since Tin is an integral part of our fungicide arsenal for pecans, and we do see some orchards with insensitivity to Tin, we are recommending saving any Tin sprays for the nut scab period since this material is better on nut scab than it is on leaf scab.

1. Absolute

2. Tebuconazole+Topsin M+Phosphite

3. Absolute+Phosphite

4. Elast/Tin

5. Absolute

6. Elast/Tin

7. Elast/Tin

8. Elast/Tin

If rainfall during the growing season is excessive, more than 8 sprays will be required for management of scab on susceptible cultivars. Therefore, the following program serves as an example of how to accommodate this need:

1. Absolute

2. Tebuconazole+Topsin M+Phosphite

3. Absolute+Phosphite

4. Elast/Tin

5. Absolute

6. Elast/Tin

7. Elast/Tin

8. Quadris Top

9. Elast/Tin

10. Elast/Tin

These examples serve only as two possible options for fungicide programs to manage scab. Many more could be developed. If an orchard has a documented high level of insensitivity to any of the fungicides listed above, the grower should contact one of the UGA Extension for specific recommendations.

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2017 Pecan Beginner’s Course

The 2017 Pecan Beginners Course will be held at the UGA Tifton Campus Conference Center in Tifton. GA on Tuesday, April 18, 2017. There is a registration fee of $10 . Registration at the door will be $15 until we reach capacity of 300 people. Please pre-register so that we will have a head count for the meal. Lunch and refreshments will be provided.

Register at the following link: Pecan Beginners Course Registration

The program for the course is found below:

9:00        Welcome                                                                                           

9:10        Cost of Pecan Production                                                                            

Lenny Wells, UGA Horticulture

9:30        Pecan Varieties                                                                                                                                               

                Patrick Conner, UGA Horticulture            

10:15     Break

10:45     Pecan Irrigation                                                                               

Lenny Wells, UGA Horticulture

11:15     Pecan Tree Planting & Establishment                                   

Lenny Wells, UGA Horticulture

12:00     Break for Lunch               

                Meal Sponsored by Savage Equipment                                 

1:00        Pecan Insect Management                                                                                                         

Will Hudson, UGA Entomology

1:45        Pecan Fertilization

Lenny Wells, UGA Horticulture

2:30        Break

2:50        Pecan Disease Management

                Jason Brock, UGA Plant Pathology

3:20        Pecan Weed Control

Timothy Grey, UGA Crop & Soil Science

4:00        Pecan Equipment

Lenny Wells, UGA Horticulture

Please contact Debbie Rutland @ 229-386-3424 for further infromation

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What Is The Problem With Late Stuarts?

Everybody is talking about how late the Stuarts are on budbreak this year. UGA Horticularlist Dr. Wells was down with us this morning looking at fertilizer rates, and I asked him about this. This could be an issue if Stuarts miss pollination. Dr. Wells provides this information below:

If you have spent any time in pecan orchards in Georgia over the last couple of weeks you have noticed budbreak progressing on most varieties with one particularly notable exception. At this point Stuart is further behind most other major varieties than I have ever seen it. Why is this? Stuart has a relatively high chilling requirement—more so than many other varieties we grow. This results in later budbreak in general for Stuart. But, following a mild winter such as the one we just had (see previous post on this topic), Stuart’s late budbreak gets even later.

The biggest problem this presents is issues for pollination. Varieties that normally match up well with Stuart, like Cape Fear, Creek, Desirable, and Schley, will likely be finished shedding pollen by the time Stuart pistillate flowers are receptive. Of those, Schley may have the best chance since it is also lagging behind other varieties. If all this does translate in to poor pollination, what does that mean for the Stuart crop?

Stuart is a type II or protogynous (stigma receptivity precedes pollen shed) cultivar. Cross pollination is more important for these cultivars than for type I or protandrous (pollen shed precedes stigma receptivity) cultivars. In Type II cultivars like Stuart there tends to be complete separation of pollen shed and stigma receptivity. This helps them to avoid self pollination (which in nature results in a less fit individual). Although self-pollination is undesirable for nut production as well (it leads to increased fruit abortion and reduced percent kernel), it is better than no pollination which leads to even more fruit abortion and quality problems.

Stuarts have to make up a lot of ground quickly to avoid production problems this year.

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Pecan Irrigation & Early Insects

We are now seeing budbreak on our older trees. UGA Extension Pecan Horticulturalist notes that our budbreak timing is pretty close to last year – thanks to the cooler weather of a couple of weeks ago. Pecans across the state narrowly missed serious damage from the freeze. We won’t know about young trees until May or June. In Thomas County, it doesn’t look like the duration was long enough to have a major effect.

Dr. Wells points out though budbreak has begun, he is concerned that it may be somewhat uneven as a result of the warm winter. This could affect pollination. With the arrival of budbreak, there are other things to keep in mind.

Irrigation

It has been abnormally dry in south Georgia for weeks, and the trees will need water as they wake up. Mature trees should be irrigated at 17-18% of full capacity at this time. Young trees in the 1-3 year old range need about 4 hrs every other day throughout the season beginning now. Rain is in the forecast for Friday so if you receive a 1″ rain or more, turn the irrigation off for 3 days.

Pecan Budmoth Damage- Photo by Dr. Lenny Wells

Budmoths

Be on the lookout for budmoths in young trees. They begin feeding soon after budbreak and can destroy the buds making it difficult to establish a good central leader. Treat with chlorpyrifos, a pyrethroid, Intrepid, or Dimilin as needed.

Phylloxera

Phylloxerra damage was particularly severe last year. If you plan to treat for Phylloxerra, do so now for those varieties that have started to break bud. These treatments must be made when budbreak begins or you will miss the window for treating them. Chlorpyrifos or imidacloprid are the materials of choice.

You can read more about Pecan Leaf Phylloxera on this blog post from last year.

Galls from Pecan Leaf Phylloxera

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Pecan Budbreak & Cold Weather

It’s been about two weeks since we observes some budbreak in young pecan trees. We had a day of rain across much of the county this week, and it then dropped to 31 degrees Thursday morning. The picture above is an orchard with frost on the ground. What will happen to our trees now? UGA Extension Horticulturalist Dr. Lenny Wells has this to say:

Those areas with forecasts for 30 degrees or more should be ok. Other areas (North GA) that reach temperatures of 28 degrees or less could see damage to any foliage that may already be out. Fortunately, there is very little of this. I have seen and heard of a little sporadic budbreak here and there—mostly on newly planted or very young trees. Those on which the outer scale has split – and you only see a little green peeking through or the buds are just swollen – should be ok. But, any new growth that has started to lengthen and expand will be most susceptible if temperatures stay at 28 degrees or less for a few hours.

Most mature trees still have buds closed or are barely showing some green (most of this is deep into south Georgia). Those trees on which the buds are still closed should be fine. The level of damage a tree receives in this type of situation is completely dependent upon its level of dormancy.

March 3rd, 2017 – Photo by Mat Thompson

Developing foliage exposed to 28 degrees or less for several hours (usually 3 hours or more) will be burnt off by the freeze. The trees will bud out again, but that will probably wipe out any crop on a mature tree for the year. Since there are not many trees out this far yet, we should be ok. Even those on which we see budbreak only have a small percentage of the shoots breaking bud, so this will help.

The biggest danger will come in the form of cold injury, mostly to younger trees. This damage is usually expressed as longitudinal bark splitting, separation of bark from wood, and sunken areas on trunks, browning of the cambium (the normally bright green tissue normally observed just under the surface of the bark when scraping with a pocket knife), and sparse canopy development. Much of this may not be readily obvious until temperatures heat up in May/June and the water demand increases. The freezing temperatures destroy the cambium cells and the tree then can’t get the water and nutrients it needs. Sometimes the trees may have enough healthy tissue to keep it going for a year or more before it collapses. The more dormant the tree is, the less susceptible it will be. If the sap is rising, there is a risk for cold injury. Trees in low elevation areas will be most susceptible. Any damaged trees will then become more attractive and susceptible to ambrosia beetles, so be vigilant for these as well.

Young Elliot – Photo by Mat Thompson

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