Just another Spring flood

 

    Over the past two days we've had 5 inches of rain in the Chetopa, Kansas area. Two to three more inches are predicted for tonight. At this point the Neosho River has already spilled over its banks and many area pecan groves are covered in flood water (photo above). Last year, a Spring flood helped recharge subsoil moisture in our drought stricken pecan groves. In fact, the flood we had on May 2, 2012 was largely responsible for helping make the 2012 pecan crop possible during a year of record heat and drought.  So this year, we welcome another Spring flood to help fill up the subsoil water reserves we may so desperately need come August.

Yellow pecan aphids and natural biological control

    When I travel to pecan meetings in the south, I often hear horror stories of massive yellow pecan aphid outbreaks in the early part of the growing season. At high populations, these sap feeding insects can literally drain the life out of pecan leaves.

Yellow pecan aphid, Monelliopsis pecanis

    Fortunately, I have never seen a springtime outbreak of yellow pecan aphids in a northern pecan grove. But this doesn't mean that yellow pecan aphids don't occur in our area. This spring, I've spotted a very light population of yellow aphids feeding on the underside of our pecan leaves (photo at left). In the photo, an adult yellow aphid is feeding on sap flowing through the main mid-rib of a pecan leaflet. Above the adult you can see a small yellow aphid nymph moving across the leaf surface in search of a good feeding spot.




 
   

Convergent lady beetle, Hippodamia convergens

    While scouting our trees, I also discovered one of  the main deterrents to yellow pecan aphid outbreaks . The convergent lady beetle is one of the most common, native, biological-control agents found in pecan-tree canopies (photo at right). Both adults and their larvae actively seek out and feed on yellow pecan aphids. 
 

     I stopped scouting for a minute just to watch a lady beetle scurry over the underside of pecan leaves in her endless search for prey (photo at right). I found it a fascinating lesson insect behavior.   

Graft placement influences scion vigor

    

    As I traveled around Mid-America conducting grafting schools a few weeks ago, I had the opportunity to see some common grafting errors made by some very well-intentioned pecan growers. One of the most common mistakes folks make is not cutting the stock tree back enough to force rapid growth of the scion. In the photo at right, a 3-flap graft was placed on a side limb of a young sapling. If you look at the top of this tree, the  stump visible between the two upper-most shoots was probably the location of a second 3-flap graft that ended up not taking.  In any case, the new shoot from the successful graft is only about 8 inches long--way too little growth for a new scion during first year after grafting. The upper portion of this tree should have been pruned off  as soon as the shoot on the successful graft was 2-3 inches long (at that point you are certain the graft has succeeded) . All those leaves and shoot growth above the graft  only served to slow the growth of the scion.
   

    When I set a graft, I prefer to cut off more of the stock right at the beginning. I know that cutting off so much of a well-tended pecan tree can cause the novice pecan grower a slight panic attack but its for the best. Cutting back the stock drastically helps to focus all the tree's root energy into growing a strong and vigorous scion.  The photo at left shows a tree I grafted about 18 inches off the ground. At  this height,  the stock tree was about 1 1/4 inches in diameter and I used a bark graft to place the scion on the stock. Once the buds on the scion had grown out about 3 inches, I selected the strongest new shoot to become my new central leader  and pruned off all the competing scion buds.  This photo was taken in mid-July and I had over 3 feet of new growth that could be easily trained to a bamboo stake.
   

Mirids on flower clusters

    

    At this time of year I like to check on the progress of pecan flowering. While inspecting pistillate flowers, I always spot numerous plant-feeding Mirids crawling around young nutlets. In the photo at right, note the two, mottled-brown insects on the flower cluster. These are examples of the Mirid, Plagiognathus caryae. In the photo, they are using their piercing-sucking mouthparts to feed on plant juices.These insects can also be seen feeding on catkins and expanding leaves. Although they look like they could be damaging, we have found that these insects do not cause significant crop losses.

If a graft fails, try again.

    Last summer's heat and drought was hard on both plants and people. Because of the stressful weather, I lost several new grafts that I had made last spring .  However, all is not lost. My pecan trees sprouted new shoots below the failed grafts, providing additional locations for grafting this year (photo at right).
  

    This morning, I grafted one of last year's failures.  I started by cutting out the failed graft from last year. I made the cut just above the uppermost side shoot (photo at left).
   

    Next, I pruned the tree leaving the two strongest, upright-growing shoots on the tree (photo at right). After pruning, I was left with two good places to make 3-flap grafts.
   

     The shoots that developed below the failed graft were vigorous, long and about 1/2 inch in diameter. These were the perfect size for 3-flapping (photo at left). Although I placed two grafts on this one tree, I'll need to prune this tree down to one growing point by mid summer. However, I am willing to sit back and watch where the strongest shoot will develop.
    

    I finished off making my 3-flap grafts in the usual fashion including attaching aluminum foil, plastic bag, and bird perch (photo at right). I also installed a deer cage around the tree to prevent browsing on emerging shoots.
    With the later than normal arrival of Spring, the grafting season started late this year.  however, I looked at the long term forecast and it looks like were are going to have at least another week for grafting pecans.

Pecan pollination half way complete

    After receiving some welcomed rainfall, I spent some time checking of the progress of our pollination season. All pecan cultivars have pistillate flowers showing and many of our protogynous cultivars have fully pollinated nutlets. One cultivar that was fully pollinated was Oswego (photo at right). After a nutlet is pollinated, the stigma of the flower turns black in color. 

    Compare the color of the Oswego stigmas (above) to the bright red stigmas now visible on Faith pecan trees (photo at left). Faith stigmas are just entering the stage when they become receptive to pollen. Oswego is an example of a protogynous cultivar while Faith is protandrous. At this point in the season Faith trees have released all their pollen while the pollen sacs on Oswego catkins have yet to open.
    

    If you are watching the pecan flowering process on your trees, the first sign that a pistillate flower has been pollinated is the appearance of black tips of the stigmatic surface. The Posey flowers pictured at right provide a prefect example of a recently pollinated flower.

Pollen starting to fly

  

Osage

     After a week of warm weather, the pecan flowering process is quickly moving ahead. Today, I noticed the first release of pecan pollen from Osage catkins (photo at right). As catkins mature they change color from green, to yellow, and finally brown. Tap brown colored catkinswith your finger and a puff of yellow pollen will drift into the air. Osage is a protandrous cultivar is among the earliest to shed pollen.
  

Giles

     I looked at two other protandrous cultivars for signs of pollen shed. The catkins of Giles had fully enlarged pollen sacs that were starting to turn yellow (photo at left). No sign of pollen shed at this point. 
   

Major

 

Major catkins looked to be at the same stage as the Giles catkins. With continued warm weather in the forecast, both Giles and major will begin pollen shed this weekend.

Warm night temperature advance pecan tree growth

Greenriver pistillate flower development

     Just two days ago I posted a photo of the female flowers on a Greenriver shoot. On Monday, the pistillate flowers were just peaking out between emerging leaves (photo above, left). Today, the pistillate flowers of Greenriver are clearly visible and much enlarged (photo above, left). In just two days, our trees have made impressive growth,  all due to warm nighttime temperatures. Monday night/tuesday morning the mercury only dropped to 65 F, while last night, temperatures bottomed out at 67 F.  Pecan is a warm weather crop and what we have seen in just the past two days confirms that fact.

Scouting for Sawfly larvae

    Every since the arrival of clear sunny weather, I been looking for the sawfly larvae that feed on expanding pecan foliage. Once the larvae become active, the damage is fairly easy to spot. You will find a cluster of small holes cut into leaflet blades (photo above, right).
    

    These small holes were created by the feeding of Periclista marginicollis (Norton), a small green sawfly larvae (photo at left). When inspecting damaged pecan foliage you will usually find these insects on the underside of leaflets. Full sized large grow to about 9/16 inch long before dropping to the ground to pupate. There is only one generation per year.
   In the past, we have experienced severe outbreaks of this pest. Larvae became so numerous that trees were defoliated. Although outbreaks of this sawfly are rare, we scout the pecan grove every spring to avoid letting this insect become a problem. 

    Chewing large holes, or entire leaf blades is another, less-common sawfly. The larvae of Megaxyela major (Cresson) is yellow in color with prominent black spots and a black head capsule. Larvae grow to 3/4 inch long before dropping to the ground and pupating. This sawfly has the curious habit of curling around a leaf's rachis or midrib during daylight hours (photo at right). As night falls, the larvae continue to feed on entire leaves often leaving just the midrib. We have never had a serious outbreak of this sawfly species.

Pistillate flowers just starting to emerge

   

    I am starting to see pistillate flowers emerge from the terminals of this year's new growth. Of  the dozen cultivars I looked at today, the pistillate flowers of Osage were most noticeable (photo at right). The red arrow points to the still growing cluster of flowers.
    Looking back over previous blog posts, I discovered that  I first noticed pistillate flowers as early as April 6th in 2012.  That represents a 5 week swing in crop development from 2012 to 2013. In 2012, we were three weeks early. This year we are 2 weeks late.  In  2011, we had a more normal spring with female flowers first appearing on April 28th.  
   

     At this point, most of the pistillate flowers are still hidden under the folds of new leaves. The photo at right is typical. If you look carefully you can see a pistillate flower poking out from between newly forming leaves (red arrow points to flower).  If the temperatures stay warm, it won't be too long before we can get a feel for the size of the 2013 nut crop.

Spring time in a native pecan grove

    A yellow carpet of swamp buttercup flowers adds to the spring beauty of this native pecan grove. (Photo taken near Chetopa, KS)

Slight freeze damage on young pecan leaves

  

     Last week, temperatures dropped to near freezing and we had a record breaking snow in May. Since that time,  spring temperatures have returned and pecan trees have resumed growing new leaves and shoots. Once the new growth expanded a little bit, I noticed a touch of frost bite along the margins of some leaves (photo of Gardner terminal at right).  Not every leaflet is affected and the terminals of new shoots look fine.
    This marginal leaf burn reminds me of potato leaf hopper damage. However, if you inspect the leaves carefully you won't find the feeding scars on main leaflet veins that are the tell-tale sign of leaf hopper damage. This cold weather leaf burn appears more random, with the severity and location of damage related to the leaf growth stage during the cold snap more than anything else.
   

    So far, I've found some freeze injury on all  pecan cultivars  and native pecan trees I've inspected. However, some trees have only a few minor spots of cold injury (like  USDA 75-8-9 pictured at left).

    Since new shoot terminals were not damaged on any pecan tree I've looked over, pistillate flower production should not be effected by last weekend's cold and snow.  

Snow in May sets new record

 
    This morning I traveled to Miami County, Kansas  for a grafting school and was able to capture a photo (above) of some of the record breaking late snowfall that fell across Eastern Kansas and Western Missouri last night. The snow melted quickly and temperatures never fell below freezing (32 F). Since emerging green tissues on pecan trees can tolerate down to 28 F without injury it looks like the 2013 pecan crop is still OK. However, the record cold spring we have been experiencing has delayed pecan tree growth by nearly 2 weeks. 

Catkin appearance and pecan flowering habit

   

    Before a single grain of pollen is shed, the timing and appearance of catkins can give you a pretty good idea of the flowering habit of a pecan cultivar. As you know, pecan cultivars can have one of two flowering habits. A tree that is "protandrous" sheds its pollen before the pistillate flowers on that same tree become receptive. In contrast the pistillate flowers of a "protogynous" cultivar become receptive to pollen before the catkins produced by the same tree start shedding pollen. These flowering habits were designed by nature to ensure cross pollination and to limit self-pollination.
   In the photo above, look carefully at the shape, size, and texture of the catkins produced by the Kanza and Osage cultivars.  At this time during the season, the catkins on the protandrous Osage shoot have already grown plump with the individual pollen sacs clearly visiable. It won't be long until these catkins will begin to shed pollen. In contrast, the catkins on the protogynous Kanza shoot are narrow, not yet fully extended, and the pollen sacs still tightly bound along the catkin's stem. These catkins will release their pollen much later.

   The photo at left shows another comparison between protandrous and protogynous cultivars: this time is Chetopa Vs. Giles.  Both of these cultivars have yet to put out a lot of leaves but differences between catkin shape and texture are still evident. Catkins on the early pollen shedding Giles shoot are thicker and more course (pollen sacs showing). Chetopa catkins are thinner and smoother.
    As the season progresses, the differences in catkin size and shape become even more striking. Check out the photos from last spring.

Sapsuckers drill new holes each spring

  

     Rows of shallow holes carved into pecan trunks is the sure sign of Yellow-bellied sapsucker activity.
In the photo at right, two new holes have been drilled to the right of three holes made the previous season by this bird.
    Sapsuckers drill holes in the bark starting at pecan bud swell. These birds create the holes in order to feed on the abundant and sugary sap that is flowing up the tree trunk in early spring. You will find that sapsuckers prefer certain pecan cultivars over others. I have never seen a 'Stuart' pecan tree that isn't riddled with sapsucker holes.
 

Sapsuckers are migratory birds (photo at left). They overwinter in Central America and spend the summer breeding season in the far northern States and Canada. This means that in our area, yellow-bellied sapsuckers are just 'passin thru' each spring and fall.  They drill holes in the bark and feed on sap in the spring, then primarily feed on insects during the fall migration.
     Although truck damage can look awful, a well tended pecan tree can withstand sapsucker feeding without significant yield loss.