Friday, July 29, 2016

Time to set out pecan weevil traps

    Today, we set out several pecan weevil traps on trees that we expect to find plenty of weevils (photo at right).  With all the rainfall we have received this week, soil conditions should be perfect for weevil emergence. However, only a very few weevils usually emerge during the last week of July. The bulk of the weevil population emerges in mid-August if soil conditions remain moist.
    The long term forecast calls for hot and dry weather next week. As the soil dries and become hard, weevils will be unable to move out of their underground homes and adult weevil emergence will stop. The emergence period will not continue until we receive more rain. By setting out weevil traps, we will know exactly when weevils become active in the grove.
   Complete instructions for building your own weevil traps are given HERE.  

Thursday, July 28, 2016

Pecan development: 28 July 2016

   We received nearly 2 inches of rain earlier this week and I though that the sudden jolt of soil moisture might kick pecan nut development into high gear. So today, I collected some nut samples of several cultivars and cut them open to check on the progress of kernel development.
   The first group of nuts I cut open included samples from Posey, Pawnee, and Kanza (photo at right). The kernels of Posey and Kanza were at 1/2 water stage while the Pawnee was not as far along. This came as a surprise because Pawnee normally ripens before Posey and Kanza in the fall and I had expected to see more advanced kernel development at this time during the summer. I'll be cutting more nuts in the weeks ahead so we'll see if this year's Pawnee crop stays behind in terms of nut development.

   The second group of pecans I cut open included cultivars that are becoming mature trees in our cultivar trials. Surecrop and USDA 61-1-X had kernels at 1/4 water stage (photo at left). The Jayhawk nut was in the large heart stage and the Caddo nut showed a kernel in the small heart stage. This Fall, Surecrop and 61-1-X should ripen by early Oct. Jayhawk will ripen at the same time as Giles, in Mid Oct. Caddo will ripen late, splitting shuck in late Oct. or early Nov. Some years, Caddo nuts fail to ripen before our first hard freeze.  

Wednesday, July 27, 2016

Storm damages young pecan tree

   A strong wind during a mid-summer thunderstorm can undo years of careful tree training.This was the case when I discovered a tree broken over and laying on the ground (photo at right).

     It seems the force of the wing was so strong that it bent the tree over so far that the main stem fractured into hundreds of splinters (photo at left).  Fortunately, I paint the graft union white on all my trees to provide an easy visual record of which trees are grafted and which are not. This tree broke well above the graft union so I could use one of the small branches below the break to serve as a new central leader. 

    After looking over the tree, I decided to cut the damaged trunk off just above a small lateral limb. At first, I thought it would be a good idea the start cutting at a point just above the side shoot (photo at right). However, cutting into the curve of the break meant that all the downward force of the broken tree was working to bind the saw in its kerf. I quickly pulled the saw out and opted for a different angle of attack.

     By cutting the tree on the back of the break, I soon learned sawing through the wood was much easier (photo at left). The weight of the fallen tree was pulling open the saw kerf allowing the saw blade to move freely. However, cutting from this direction meant that I had to draw an imaginary line across the stem so I would finish the cut just above the point that little side branch. I also needed to trim this trunk at a 30 degree angle just like we do when trimming up a bark graft.

      After making the angled cut across the trunk, the tree looks just like a recent bark graft (photo at right). However, unlike a bark graft, I decided to leave emerging stump sprouts above the graft union to grow for the rest of this summer. This tree has suffered a tremendous loss of leaf area in the middle of the summer and these emerging shoots will help shade the trunk to prevent sun scald to the trunk. Next year, I'll go back to proper pruning and training to make sure I develop a well structured tree.

    To help train the remaining small side shoot into a new central leader I drove a 1 x 2 inch wooden stake in the ground next to the trunk. I then secured that stake to the trunk of the tree with black electrical tape. Next, I carefully lifted the side shoot to an upright position. If I pulled too hard, I ran the risk of breaking the shoot off the tree. After pulling the shoot upright, I used green flagging tape to hold the branch in position (photo at left).
   It will take a couple of years to heal over the wound created by the break in the trunk. I'll keep the new central leader tied to the stake until the healing process is complete. 

Friday, July 22, 2016

Pecan fruit sizing during July

     July is the month when northern pecans enter a period of rapid fruit enlargement. Even though pecans are a nut crop, we call it fruit enlargement because the shuck and seed within are collectively termed a pecan fruit. Botanically, pecans are similar to peaches. The hard-shelled seed of a peach tree is surrounded by a fleshy outer-layer that we just love to eat. However, we discard the peach pit or seed. With pecans, we disregard the fleshy outer-layer and eat the seed within.
    On Thursday, July 21, I collected a few pecan fruit from several cultivars to check on the status of fruit enlargement. The first group were pecans from early ripening cultivars (photo above right). Cutting open these nuts I found that these nuts ranged in kernel development from 1/4 water stage (Colby) to nearly full water stage (Warren 346).   

    The next group of cultivars had pecans that were all very similar in size at this point in the growing season (photo at left). However, these cultivars represent a wide range of ripening dates. At harvest, Peruque will be the smallest nut while Maramec will be nearly twice the size of Peruque. 

    After cutting open each nut, I could see differences in kernel development (photo at left). Peruque was at 1/2 water stage while the Maramec kernel was still at the small heart stage. The Faith and Waccamaw nuts were approaching 1/4 water stage. 

   The final group of nuts I collected were from four scab free cultivars (photo at right). The Kanza and Hark nuts looked plump and well on the way to full fruit sizing. Lakota looked narrow and not as far along. Oswego, a nut that at harvest will be similar in size to Kanza or Hark looked significantly smaller.

    Cutting open each nut I found Kanza and Hark to be at 1/4 water stage. The Lakota had slightly less kernel development. But Oswego kernel development was far behind, still at the small heart stage.

Monday, July 11, 2016

Hickory shuckworm, fall webworm 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.