Sunday, July 19, 2020

Insects feeding on pecan leaves

    Over the past week I've been scouting my pecan orchard for signs of summer foliage feeders.  At this time of year, we can have outbreaks of Fall webworm and/or walnut caterpillar and I don't want to be caught unaware. 
    I did not find any colonies of  either species of caterpillar in my orchard but spotted several Fall webworm nests on roadside trees (photo above).

  Fall webworm colonies are the easiest to spot because they spin a white web over the entire colony designed to protect the caterpillars inside from birds and predacious insects. In the close-up photo at left, you can see numerous Fall webworm larvae clustered in the center of the web. These larvae will move to the margins of the web at night to feed on green foliage and spin silken threads to expand their web.  Once the larvae reach full size, they will drop out of the web, fall to the ground, and pupate in the leaf litter.  The colony of webworms I spotted this week represent the first summer generation. A second and often larger generation will appear in late August.
    While I collecting leaf samples this past week, I also spotted a few Japanese beetles feeding in my trees (photo at right). The Japanese beetle is an introduced pest that has moved steadily across the US since first landing in New Jersey in 1916. I've seen it sporadically on my farm for the past 3 years. Last year, a large colony of Japanese beetles practically defoliated a young sweet cherry tree in my fruit orchard before I sprayed the tree with an insecticide.

   I have yet to see large numbers of beetles feeding on my pecan leaves. For the most part the damage has been minor and not damaging enough to warrant pest control measures. The photo at left illustrates the light feeding damage I found on one tree in my grove. This insect seems to scrape off the surface of a leaf until it finds soft leaf tissue between the veins. At that point, the beetle eats through the leaf blade leaving an irreagular shaped hole.
   I don't think Japanese beetle will become a major problem in commercial pecan groves where insecticides are applied regularly to control major nut-feeding pests.  

Friday, July 17, 2020

Collecting leaf samples for analysis

    This week I collected leaf samples from my pecan grove so I could submit them for nutrient analysis. Leaf analysis is the best way to discover if pecan trees are getting all the nutrients from the soil needed to ensure optimum tree grow and nut production.

    Before I show you how to collect a sample of pecan leaf tissue for leaf analysis, I thought it best to review the parts of a pecan leaf. The photo above shows a single pecan leaf attached to a small section of stem. Pecan trees produce a pinnately compound leaves with 13 to 17 leaflets. The leaflets are attached to the rachis (pronounced ray-kiss) which ultimately attached to the stem. New buds are located within the axis of rachis and stem.
     In sampling pecan leaves for analysis, I collected leaf tissue that represents the entire tree's nutritional status. Pictured at right is the current season's new growth. I located a mid-shoot leaf and harvested two leaflets from that leaf. I repeated that process on a total of ten shoots moving around the tree at random. For each sample, I collected leaflets from ten trees selected at random across the orchard. My first sample was entirely Kanza leaves while my second sample was drawn from my breeding plot.
     The photo at left shows how I collected the middle pair of leaflets from a mid shoot leaf. In theory, selecting the middle pair of leaflets from a mid-shoot leaf, best represents the average nutritional status of an orchard.
     I collected the leaflets in paper bags and brought them in to dry. I used a food dehydrator set at 105 degree F to hasten the drying process. In 24 hours the leaflets were fully dry, crispy, and ready to be sent off to the lab.
     Both State Agricultural Colleges and Commercial Laboratories process and analyze pecan leaf samples. Check with your local County Ag Agent to discover your best options.

Thursday, July 2, 2020

Bearing pecan trees compete with ground-cover for water

    The weather this year has been wild. During the month of May, over 9.5 inches of rain fell on my pecan grove. When June arrived, Nature's spigot seems to turn off completely. We've recorded only 0.37 inches of rain during the entire month. Things have gotten very dry, very quickly.

    This morning, I noticed a ring of wilted grass around each of my young Kanza trees. It almost looks like I sprayed herbicide around the tree but that's not the case. I haven't been able to do any chemical weed control so far this year because of spring floods and muddy soil conditions during the months of March through May. When the ground started to dry up in early June, I was finally able to mow the grove for the first time this season.
   The circle of wilted vegetation that rings each tree represents that area of soil where pecan roots are out-competing grass and weeds for soil moisture. Fortunately, pecan trees are pretty good at handling dry soil conditions. However, the trees are now entering the nut enlargement phase of pecan development. During the month of July and into early August, pecans grow rapidly in size. If dry conditions persist, nut enlargement will be stunted and we'll be harvesting a lot of small pecans this fall.