Monday, July 11, 2016

Hickory shuckworm, fall web and scab: Time to spray again

   I've been watching the weather and monitoring our pecan grove trying to keep to top of possible pest problems. I'm really worried about scab get started on our nut crop. Scab infections can spread rapidly on pecan shucks during the period of rapid nut growth that occurs during July. We have received numerous rain showers since the last time we made a fungicide application and the time has come to apply another protective layer on fungicide on the nuts (2 weeks between sprays).

    In scouting our pecan grove, we've seen three insect pests that I would like to keep under control. The first is fall webworm (photo at left). We don't have an overwhelming webworm problem in the orchard but there are just enough first generation colonies that, if left untreated,  may lead to a huge second generation problem in August.
    We have also collected several dropped nuts damaged by hickory shuckworm  You can identify hickory shuckworm damage by finding an ovipostion scar surrounded by a ring of white insect scales (photo at right). With a low to moderate crop this year I want to make sure we hold onto as many nuts as possible. Controlling hickory shuckworm will help maintain the current nut set.

    The third insect pest we have found in our pecan grove this week is Japanese beetle. This is a new pest for us and one that is just starting to move into our area. This shiny green beetle with copper-colored wing covers, usually feeds in groups of several beetles. Pecan leaves take on a tattered appearance following beetle feeding.
   In spraying for pecan scab today, we included an insecticide in the spray tank to make sure we keep webworm, shuckworm, and Japanese beetle under control.

Friday, July 8, 2016

Preventing wind damage to new grafts.

    Grafting pecan trees is one of my favorite parts of developing a new orchard. After years of practice, I can  graft fairly quickly and I have confidence that the graft will be successful. The time consuming part of grafting trees actually occurs during the summer months. Every 3-4 weeks, I return to each grafted tree to prune off trunk sprouts, tie the scion's new shoot to a bamboo stake, and remove stalked buds. The photo at right is an example of a successful graft I made earlier this year. Look carefully, you can see that I've already tied the new growth to a bamboo stake with green flagging tape in 3 places.
   I can not stress enough the importance checking on the growth of your scions regularly throughout the summer. The photo at left is an example of what can happen when the scion grows faster than expected, the new growth wasn't tied to the bamboo stake, and a thunder storm blows through the orchard. Without being tied to the stake, the wind broke off  the scion right at the top of the stock.
   With this tree, I'll let the stump sprouts grow and re-graft the tree next year. I'll also leave the bamboo stake and all the graft wrapping in place to remind me that this tree needs re-grafting.    

Friday, July 1, 2016

Be careful when pulling off stalked buds

    Yesterday, I spent the morning trimming grafts and training the scion to a nice central leader.  Just two weeks ago, I worked on these same trees selecting a single scion shoot and removing stalked buds. However, it is amazing how fast bark grafts can grow. Many grafts had grown 10 to 12 inches taller in just two weeks. Along with the new growth, the tree also developed new stalked buds (red arrows point to stalked buds in photo at right). My first step in training these grafts is to remove all stalked buds. Next, I used flagging tape to tie the new growth to the bamboo stake I already had in place.

    When I remove stalked buds I always start at the top of the scion shoot and work my way down. At some point, I will come the location on the shoot were I had removed stalked buds previously (2 weeks ago in this case). You need to watch carefully as you tear off the stalked buds. In the photo at left, the red arrow points to a stalked bud that has developed since the last time I removed stalked buds. This bud will be removed.
    The yellow arrow points to a brown scar on the stem indicating the position of a stalked bud that I removed 2 weeks ago. Below the scar is a secondary bud that is starting to grow. I will leave this bud in place to form a wide angled lateral branch. Remember, by the time a secondary bud starts to break, it will be located well below the central leader and in perfect position for lateral branch formation.

Wednesday, June 29, 2016

Don't let pecan trees get top heavy

   Earlier this year, I showed you how to use directive pruning to prevent a tree from developing a bushy, leaderless top. The photo at right is a great example of what can happen when a bushy, multi-stem top is allowed to grow unchecked.  After the foliage of this tree was soaked by a recent rainstorm, the added weight of water on the foliage was enough to bend the tree down to the ground. Fortunately, the main trunk did not break but this tree needed my immediate attention.
  Since the top of the tree was so close to the ground, I took a quick photo of the tree's apex (photo at left). I count five new shoots growing out of the top of last year's wood. With all that new growth at the very top of the tree, it is no wonder the tree became top-heavy during a rain storm.

    Fixing this tree was a two step process. First, I pruned the top of the tree. I selected one shoot to be the central leader then employed the 2-foot rule to prune the rest of the tree. I did all this pruning while the tree was still bent over on the ground (no need for a ladder!). The second step was to install a ten foot tall tree training stake to hold the tree upright. I attached the stake to the base of the trunk using some white electrical tape (white? its just what I had on hand). Next, I lifted the tree up and used additional wraps of tape to hold the tree in place against the wooden stake (photo at right). As this tree increases in diameter over the summer, it should gain enough wood strength to hold itself up without the wooden stake.