Preventing the Buck Rub Blues

    Once a young pecan trees grows to a point that it has a trunk 1 to 1.5 inches in diameter, it seems like it becomes the perfect target for a big buck deer to rub a massive scar on the young tree (photo at left). With deer populations growing out of control in rural areas across the US, growers will need to take preventative actions to prevent deer damage. Bucks rub the bark off of young trees starting in late August, so to prevent this type of damage preventive measures need to be in place by mid August.

     One of the first products designed to prevent deer damage were solid plastic "Tree Shelters" that can be placed over the trunk . Over time we learned that tree shelters cause almost as many problems as they prevented. Trees grown in shelters suffer temperature related bark injury (from the greenhouse effect inside the tube) and trunks often become twisted inside the tube by the action of the wind on upper branches. If anyone has heard me talk about tree shelters in the past they know I've renamed them "tree coffins". The damage they cause is as bad or worst than the damage caused by buck rub.

    Recently I've come across a new product that provides a protective shield against buck rub but doesn't alter the environment around the tree's trunk (pictured at left). These "tree bark protectors" are made of heavy gauge plastic and look a lot like wire hardware cloth. The tree bark protectors are pre-formed in tube shape but need to be held together with a twist tie or cable tie. The only down side of these protectors is that you need to monitor you trees closely and prune off any new sprouts that attempt to grow though protector. The holes in the plastic mesh are about 5/8 inch across so side limbs can easily become trapped in the mesh.

    On my farm, I use a 2" x 4" woven wire cage (5 feet tall)  to protect a new graft from deer browsing. As soon as the graft grows big enough to accept a 3 ft. tall tree protector, the wire cage comes off (to be used for next year's grafting season) and the tree protector goes on. I purchased the tree protectors from A.M. Leonard (www.amleo.com).

Stalked buds and branch attachment

    I mentioned the term "stalked bud" in my last post and this morning I thought it might be a good idea to show you exacting what a stalked bud on pecan trees look like. The development of stalked buds is most prominent on fast growing trees, so my hunt for buds to photograph started in our scion wood block. The trees in the scionwood block are severely cut back every spring to provide scionwood to growers across the area. This means that trees grow extremely fast in response to the heavy pruning often creating lots of stalked buds. The photo at left was taken  of a Colby tree. In the photo, you can plainly see the green leaf scar on the stem. Above the leaf scar is the secondary bud and above that is a "stalked" primary bud. Stalked buds are not usually associated with the Colby cultivar but under the right growing conditions any cultivar can produce stalked buds.

    On that same Colby tree, I noted a stalked bud that had begun to grow into a side shoot. In the photo at right, the leaf petiole is still attached to the branch. Above the petiole is the secondary bud and above that is the stalked bud that has started to grow into a side shoot. This shoot was about 8 inches long and you can already see the development of a bark crevice on the upper side of the branch attachment. This crevice will only get more prominent and deeper with each passing growing season. So when I'm doing summer pruning of young trees, I always make sure I remove all stalked buds as soon as I see them. It seems so much easier to pinch out a stalked bud than try to prune out a branch with poor branch attachment 3-4 years down the road.

Branch Attachment

 

    I was picking nuts from the young trees planted all around my house, when a came to a Kanza tree that just screamed at me to take its picture. Not for all the nuts it was producing but for the extremes in branch attachments I could see, all on the same tree. The lowest branch on the tree (above left) had the classic worst case scenario for a branch attachment--a deep crevasse on the upper side branch union. These kind of branch attachments are very prone to breakage and often lead to massive trunk tearing when the limb breaks out. Further up in the tree all the branches had picture-perfect,  branch attachments displaying a textbook version of a strong branch collar (above right). The question is, how did these branches form and is there anything that can be done to encourage strong branch angles?

    I noticed when training these young trees that fast growth rate promoted the development of stalked buds (buds on the ends of stem like projections) in the upper portion of the tree. By mid-summer these stalked buds were all starting to sprout and I had to remove all of these new shoots to maintain a strong central leader. Leaving a stalked bud to grow is a big mistake, because the branch that forms from this bud will produce a branch attachment like the bad one pictured above-left.  By pruning off the stalked buds, I forced the tree the sprout from secondary buds the following spring. When these buds grow they tend to make great branch attachment unions. In the case of my Kanza tree, it looks like I missed a stalked bud early in the life of my tree. This problem branch will not be a problem much longer--I'll be removing this branch early next spring. 

Nuts on young trees

    After successfully grafting a tree, you wait eagerly for that young tree to produce its first cluster of nuts. And when those first nuts split the shuck, you run out to the tree to peel the pecans out of the shucks, not caring that your fingers will soon turn black. The nuts looked so impressive all summer long. But when you peel them out of the shuck, the nuts are often small and often don't even look like the cultivar you thought you had grafted. Fear not! This is normal. Young trees, and I'm talking about trees 2-3 inches in diameter, often produce smaller-than-normal nuts. In the photo above you'll see 2 large, blocky nuts compared to 2 smaller, oval-shaped nuts. They are all samples from the same cultivar (KSU-OF1) but produced by 2 different trees. The large nuts were produced by a tree nearly 12 inches in diameter while the 2 smaller nuts represent the 1st crop produced by a tree 2.5 inches in diameter.
    The explanation for this common occurrence is simple. As a pecan tree grows, it becomes more and more of a dominate force in its environment. Larger trees are just better at competing with the ground cover for water than younger trees. More water means bigger and normally sized nuts. So don't be discouraged by small nuts on young trees, the time will come when a larger tree will be covered with large beautiful nuts.

Vivipary

    Vivipary is the word we use to describe the condition when nuts start to germinate in the fall while still encased in the green shuck.
 Vivipary is a major problem for pecan growers in the most southern regions of Texas but rarely occurs in the north. This year, however, I've come across more premature germination then usual. This morning, I even found a hican sprouting on the tree (note the root emerging from the nut at left). Now, while vivipary is still not a major problem in our area, it is worth noting because by the time we sell the 2010 crop you may see some embryo rot in your nut sample. This rot occurs when the germinating embryo dies from lack of moisture and fungal attack through the split shell.

Graft hickories on pecan

    There is a small but dedicated group of hickory and hican lovers around the country. This post is for them.

    I went out to our 'Wilson' hican tree this morning to collect a nut sample. This tree is loaded with nuts this year but what caught my attention was the graft union. We grafted this 'Wilson' hican onto a pecan tree that had previously been grafted to 'Major'. The hican graft was placed about 6 feet up the trunk and is now about 12 inches in diameter. In the photo at left,  the change above and below the graft union is dramatic. Below the graft is the typical checkered bark seen on any 'Major' tree. Above the graft is the smooth gray bark typical of a young shellbark hickory (the hican is a cross of shellbark hickory and pecan). Also note that the pecan portion of the trunk is starting to show its faster growth rate as compared to the hican. This is why I always recommend that hickory lovers graft their trees onto pecan rootstock. The pecan roots outgrow the hickory and seem to push the hickory to grow faster and bear nuts earlier. The 'Wilson' hican is among the best of the hicans I have seen. The tree bears a huge crop ever other year and the nuts are generally well filled averaging 38% kernel. The nut kernel has a somewhat bland flavor closer in taste to its shellbark hickory parent.

KSU-OF1

    Sometimes you find potential new cultivars in your own back yard. This was the case with KSU-OF1. The original tree  (pictured at left) of this promising clone is located along the fence line just north of my office building. The tree is a Greenriver seedling that has excellent scab resistance. The nut is slightly smaller than Greenriver but the tree is far more productive that its parent. The original tree of KSU-OF1 is growing in a upland site that is a very poor location for pecans. It wasn't until we grafted this clone into a trial down in the river bottom that we recognized this tree's potential. Outstanding nut quality is one of the most recognizable traits of this clone.
    If  you look at the original tree, you'll find that many nuts are infested with both pecan weevil and hickory shuckworm. High rate of insect infestation is an indication of 3 things. One, we don't spray this tree. Two, upland pecans always seem to have more weevil. And, three, nut feeding pests will always build up on trees that bear nuts every year. That's the one thing about KSU-OF1, it  always seems to produce a crop even under  stressful conditions.
    For all those interested,  this clone's designation "KSU-OF1" is simply short hand for office tree number 1.

Potential New Cultivar?

    The pecan on the left is Kanza. The pecan on the right comes from a tree in our pecan breeding block. This seedling was one of the first in the block to start bearing and looks to be scab resistant. Ripening date is early like Kanza. We are going to collect some samples this week and will display them at the harvest tour and the Annual Meeting. I'm excited about the possibilities for some good cultivars to come out of this block.