Wednesday, June 6, 2018

First nut entry by pecan nut casebearer

    When we scouted our trees this morning we found 3 pecan clusters infested with pecan nut casebearer larvae (3 out of 300 clusters inspected). Casebearer damage is easy to spot. The larva always enters at the base of the nut and creates a pile of brown frass in the narrow axis between the pedicel and nut (photo at right).
   We plan to spray our grove over the next few days adding an insecticide for casebearer control and a fungicide for scab control. The weather forecast for this weekend is hot and dry. To get the best spray coverage of the pecan foliage, I'll start spraying at daybreak and quit when temperatures top 80 degrees (F).

Tuesday, June 5, 2018

Galls on pecan leaves: Pecan leaf phylloxera

    This is the time of year when folks seem to notice bubble-like galls on the blades of pecan leaves (photo at right). These galls are caused an insect called the pecan leaf phylloxera. At this point during the growing season, the small aphid-like phylloxerans are feeding on plant sap from inside the gall. The seasonal life cycle of the phylloxera starts at leaf burst when spring crawlers emerge from the bodies of over-wintering females and crawl to rapidly growing new leaf tissues. As these wing-less females feed on the leaves, they secrete a growth regulating substance that causes the tree to grow a gall around the insect. Once inside the protective gall, female phylloxera give birth to hundreds of young.  

   Flip a phylloxera infested leaf over and you might find that some of the galls have developed an opening that almost looks like an exploded volcano (photo at left). A new generation of winged adults will emerge from this hole. The winged adults will mate and impregnated females will migrate to a hiding spot in pecan bark. The phylloxerans will remain dormant until next spring when a new generation of crawlers emerge from the body of the overwintering female. 

    I cut open a couple of galls with the hopes of photographing phylloxerans inside (photos above). However, what I found in each case was a syrphid fly larvae working to devour all the phylloxerans inside the gall. In photo "A", the syrphid fly larva had cleaned out the gall completely. In photo "B", there were just a few phylloxerans left.  Syrphid flies are probably the reason why pecan leaf phylloxera is only a minor pest of pecans. 

Friday, June 1, 2018

Summer prune young pecan trees

    I drove by a young pecan tree in my orchard and it had turned into what I call a "lolly-pop tree" (photo at right). The tree had a nice central leader but was topped by bushy ball of leaves. The ball on top was actually four new shoots that had sprouted from the top of last year's terminal. This growth pattern is normal for pecan but is the leading cause for a tree to lose its central leader. I've discussed this growth pattern in detail in a previous post HERE.
    At this point in the growing season, a couple of quick snips with the pruning shears will quickly re-establish a dominant central leader while encouraging lower buds to grow and form lateral branches.  The photo at left shows my "lolly-pop tree" after I cut off three of the new shoots growing from the top. I left the one strongest shoot to form a new central leader. This entire process took only a few seconds and will save me from having to make corrective pruning cuts next winter.

Saturday, May 26, 2018

New grafts breaking bud

    This year, I started grafting pecan trees in early May. Today, three weeks later, most of my scions have broken bud (photo at right). For me, the grafting process now shifts towards efforts to train and prune the young grafted tree. Starting today, I took steps to ensure that the scion continues to grow rapidly and does not become overwhelmed by stump sprouts that form below the graft union.
   Whenever  I see that I have a successful graft, I prune off all stump sprouts. At this point, stump sprouts are still small and easily remove by just ripping them off the trunk with my hand (photo at left).
    More stump sprouts will probably appear later this summer, but for now, all the tree's energy will be focused on growing scion shoots (photo at right). I like to visit my new grafts every three weeks during the summer to prune off stump sprouts and to train the scion to form a new central leader.