Spraying for stinkbugs and aphids

   We've waited all during the month of August for enough rain to cause pecan weevil to emerge. And we are still waiting. In the mean time, two other insect pests have become potential problems.
    In the absence of pecan weevil sprays, stink bugs can build up in the orchard especially when the weather turns dry. Stink bugs feed on a wide variety of plants but always prefer a green and juicy host plant. Under dry conditions, the ground cover and surrounding fields start to dry up and pecans become the most desirable food available. We decided to spray this week to keep stink bug populations under control.
    Since we were making a pass through the orchard with the sprayer, I decided to add an aphicide to the mix to knock down the population of black-margined aphids currently coating pecan tree leaves with honeydew. We used Hero insecticide to control stinkbug and Provado for the aphids.    

Late summer graft maintenance

   

    In late summer, a new graft always seems to want to develop a bushy top (photo at right). This is especially a problem when fairly large trees are top-worked with a bark graft and the scion grows vigorously. The tree in the photo was grafted about 5 feet above the ground on a stump around 2 inches in diameter. In a single growing season, the scion has developed over 5 feet of new growth. Its no wonder I needed an 8 foot tall orchard ladder to get a good look at the top of this tree.

    Perched up on the ladder, I photographed the bushy top of this tree. As I suspected, numerous stalked buds had grown into lateral branches and the tree was rapidly losing its central leader (photo at left).
    Removing stalked buds has always been a priority of mine when training a young graft, so how I let this tree get so far out of control?  The answer is simple. The tree got too tall too fast for me. I usually do all my young tree training from the ground, walking from tree to tree, pinching off stalked buds when needed. When a ladder becomes part of that equation, tree training doesn't seem to happen as often as it should. 

   The primary reason I'm so insistent on removing stalked buds can be seen in the photo at right. Notice the deep crevice the has developed between the main stem and the branch that grew from a stalked bud. Left to grow, this crevice will only become more pronounced leaving the branch prone to snapping off at the point of attachment.
   Since I was up on the ladder, I removed all weakly attached branches with a pair of clippers.

     Lower down the stem of the same tree, I could easily spot where I removed stalked buds earlier in the summer.  The photo at left shows a short stub of a stalked bud that I had pinched out with my fingers. Below the stub is a plump secondary bud that will probably stay dormant until next spring when it will burst forth to create a firmly attached lateral shoot.

   In the mean time, pruning out all the branches that grew from stalked buds helped to re-establish my central leader (photo at right). Look carefully at the main stem and you will see all the pruning cuts left behind after removing poorly attached lateral branches.

   The photos above show the tree before (left) and after (right) pruning. Stepping back away from the tree I could easily see that I was successful in removing the bushy top and reclaiming a single central leader.

Squirrels feeding on pecans already

   All summer long, we have been collecting nuts that drop from native pecan trees in drop cages. In most cases these dropped nuts were damaged by stink bugs, shuckworm, casebearer, or pecan scab. However, today we found evidence that squirrels have begun feeding (photo above). A squirrel seems to be able to sense the stage of kernel development inside a green-husked nut and will crack open nut as soon as it begins depositing kernel tissue. This usually means that the earliest ripening trees in the orchard will suffer the greatest amount of squirrel damage.
   We have been trapping squirrels all summer long and hopefully we have reduced the squirrel population around our pecan grove. However, looks like we have at least one squirrel that needs a good dose of lead poisoning.  

Kernel filling: 22 August 2016

    August is the month when pecan kernels start to fill. This morning I collected some nut samples from several cultivars and cut them in half to reveal the stage of kernel fill. Warren 346 is one of the earliest ripening cultivars we have in our collections and, as you can see in the photo above, this nut is rapidly approaching full kernel fill. The Peruque nut has laid down a layer of kernel tissue all along the inside surface of the seed coat. The Kanza nut still contained ample water but I could see evidence that kernel deposition has started as the seed coat wall appears to be thickening. For a close up look at the kernel filling process, check out this post: Pecan kernel filling.     

    When I cut open nuts from several mid-season ripening pecan cultivars, I found all three cultivars still in the water stage (photo above). However, you can still see differences in the development of the kernel. As the seed coat becomes filled with water, the water accumulates under pressure and presses outwards to expand the region where pecan kernel will form. Note now the kernel space inside the Lakota nut is much larger than the Waccamaw and Greenriver nuts. Lakota has advanced further towards kernel filling than the other two cultivars.

   I've mentioned a clone we've labeled SWB617 in previous posts. We think this tree originated as a  Giles seedling so I thought it would be interesting to compare SWB617 with Giles in terms of nut development (photo above).  The Giles nut was still in the water stage while SWB617 had started to deposit kernel inside the nut. However, I spotted a potential kernel filling problem inside the SWB617 nut. Notice how thick the layer of kernel has formed on the dorsal side of each kernel half. Compare that to the thin layer that has developed next to the inner wall partition (blue arrow).  
   Uneven kernel deposition is a sign that the tree is under stress and is having difficulty pumping enough energy into the seed. Two common stresses that cause poor kernel fill are lack of available soil moisture and excessive crop load. Water seems to be the culprit in this case. However, all is not lost. A good soaking rain this weekend could relieve the water stress and this nut would still go ahead and fully fill out its kernel.