A bad case of pecan leaf phylloxera

    I have been scouting pecan trees for signs of pecan nut casebearer activity and have made a couple of important observations. I haven't seen any casebearer as of today, June 7th and every native pecan I've looked at is loaded with nuts. It looks like 2019 will be a year of over-cropping and it may beneficial to skip the casebearer spray and to allow casebearer to help thin the nut crop.

    During my rounds of looking at wild pecan trees for casebearer activity, I came across a tree with the worst case of pecan leaf phylloxera that I have seen in a very long time (photo at right). The pecan leaf phylloxera is an aphid-like insect that causes the tree to form galls around these plant sap-feeding insects. Note that the galls are confined to the leaf blades.
   

    Once the galls are formed, there are no control measures for this pest. Later this summer, all seriously gall infested leaves fill drop from the tree. 
    Insecticide treatments are effective for control of this pest but must be applied before galls form over the insect. For pecan leaf phylloxera, a single insecticide application made at leaf burst will control this pest. Mark infested trees this summer and plan on spraying those trees next spring.
    You can read more about the pecan leaf phylloxera in a previous post.

This is why scouting for pests is so important

   For the past week, I've been expecting to see damage from pecan nut casebearer start to take off.  In fact, I have my sprayer filled with water and ready to go. The problem is, we can't find enough casebearer damage to justify spraying
   Three times per week we scout our orchard for signs of insect damage (photo at right). The results of each of our scouting runs can be found by clicking on the Pecan Nut Casebearer tab (The tab is located just below below this blog's header). We have yet to find more than 1% damage.
   In a normal year, we apply a fungicide to control pecan scab at the same time we apply an insecticide to control casebearer. Its now mid-June and we still haven't applied any pest control chemicals. So starting next Monday (June 19th) we are going to start spraying a fungicide to protect our pecans from scab.  If the casebearer population stays low, we won't be including an insecticide with this spray.
   In late June, we might see fall webworm or walnut caterpillar move into the grove. If these insects appear, we will include an insecticide in the spray tank when we make our second scab spray (around July 1).

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.  

Following the evidence: Pecan nut casebearer damage development

    This spring I've put together a separate page on this website to keep you posted on pecan nut casebearer activity (see tab above). But today, I wanted to show how the activity of casebearer larvae can be traced by careful observation of frass piles (frass=insect manure).
    As casebearer larvae feed on the inside of pecans, they push all their frass outside into a nice neat pile. In the photo above, the red arrow marked "A" points to a pile of dark, granular frass created by a casebearer feeding inside that nut.
   But that's not the entire story. If you look carefully, the red arrow marked "B" points to a small frass pile at the base of a bud. When casebearer larvae first hatch, they often feed on buds before moving onto the nut cluster. Note that the frass pile at the base of the bud is much smaller than the pile formed at the base of the nut. The smaller pile was created by a smaller, first-instar larvae. By the time the insect moved into the nut, the larvae had grown larger and was eating far more plant material.

    The photo at left is a close up of the frass pile found on the nut seen in the photo above. There are two things to notice. First, fine strands of white webbing are strung between the nut and the pedicel. This webbing serves to prevent the damaged nut from dropping off the tree,  keeping the insect within the tree's canopy.
   Next, notice that there are two different colors of insect frass in the pile. The lighter colored frass was just expelled from the nut betraying the fact that there is still an actively feeding larvae inside the nut.

    The photo at right shows a clear evidence trail of how a single casebearer larvae destroyed three nuts in this cluster. The larvae started at the base of the cluster. At the time of first nut entry, the basal nut was still small and could not provide enough nourishment for the growing larvae.  Once the caterpillar ran out of food in the first nut its moved onto the next nut up the stem. This second nut had grown slightly larger but still didn't meet all the nutritional needs of casebearer. So the larvae moved onto a third nut.
   Looking at the piles of frass at the base of each nut, notice that the size of the granules changes from nut to nut. The first nut attacked has the smallest frass granules indicating a small larvae had fed inside the nut. In sharp contrast, the frass pile at the base of the third nut has large granules that are light in color. Just by looking at the frass, I can tell a full sized larvae is actively feeding on this nut and will probably pupate inside.
    The photo above also demonstrates how webbing, spun by the larvae, holds the nut onto the tree even after a damaged nut aborts. The lowest nut in the cluster is literally holding on by a thread. At a later date, the last nut damaged by casebearer will also abort from the tree. Again, insect webbing will hold this nut in the tree but this time the nut will contain a pupal case. By not dropping to the ground, the survival of both pupae and the emerging adult moths is increased.

Pheromone traps for monitoring pecan nut casebearer

   We use a rope and pulley system to install pecan nut casebearer traps up into the canopy of our pecan trees (photo at right). Since these insects spend their entire life cycle in pecan trees, we need to place the traps in a location where casebearers are flying. Male casebearer moths enter our traps when they detect the female sex pheromone being released from a small rubber septum placed inside the trap. The moth then gets stuck in the sticky goo spread on the inside floor of the trap (see photo below).

    We usually capture our first male moths during the middle of the pollination season and we found one moth last night. In the photo at left, the casebearer moth is pointed out by a red arrow. This arrow also points to the ridge of scales on the wings that helps to identify this small, gray moth as a pecan nut casebearer. You can also see the grey rubber septum that emits the female sex pheromone.  The rubber septum is roughly 3/4 inch in length and the casebearer moth is 3/8 inch long.

Casebearer damage near peak

    Here's the figures on this year's pecan nut casebearer population in an unsprayed native pecan grove at the Pecan Experiment Field (above). As of today, 10.7% of nut clusters in this orchard have been damaged by casebearer. I don't expect the damage level to go much higher at this point, probably leveling off at around 12% damage for the year.

Watching casebearer larvae work

   

Two nuts have been destroyed by a single casebearer larva

    Pecan nut casebearer larvae continue to feed on pecan nut clusters. This morning, we found 5.3% of nut clusters infested with a casebearer larva in untreated plots. The larvae are starting to move into a second nut in the cluster (photo above right).
    If you look carefully at the photo, the full story of how these pecans were destroyed is revealed.  The smaller, brownish nut at the bottom of the photo was attacked first. As soon as this nut was damaged by the casebearer larva, the nut stopped enlarging and began the process of aborting from the tree. By the time this photo was taken, the damaged nut had formed an abscission layer and had separated from the stem.  With great foresight, the casebearer larva wisely attaches the nut to the tree with several strands of white silk. This prevents the nut from falling to the ground and allows the larva to remain in the tree. Since one pecan is not enough to satisfy all nutritional needs of a growing caterpillar, the casebearer larva moved to the lowest nut in the cluster and began tunneling inside. You can tell that the caterpillar had grown larger in size by the time it got to the second nut because the pile of frass (i.e. insect poop) at the base of the nut is larger and more coarse.

    There are times when a casebearer larva never finishes it meal of pecans. In the photo at left, two nut were destroyed by a casebearer. Judging from the size of these damaged pecans, the larva should have attacked the third and final nut in the cluster. However, it looks like an insect predator might have gotten to the casebearer larva before it could attack the third nut. During my survey this morning, I spotted several wheel bugs actively searching the pecan canopies for insect prey. Casebearer for breakfast--what a lucky wheel bug!

Casebearer damage at 3.3%

   

The entire nut cluster can be destroyed by a single casebearer larvae

    We scouted our "no-spray" native pecan grove today and found 3.3% of the nut clusters infested by pecan nut casebearer larvae. The warm, dry weather we are currently experiencing has caused insect development to move quickly. All northern pecan producers should be carefully scouting their orchards at this time. The window for effective economic control of this pest is rapidly drawing to a close.

Casebearer update 19 June 2013

 

    We found 1% nut entry by first summer generation pecan nut casebearer larvae this morning.
We captured 2 additional moths in all 5 of our pheromone traps. I looked at the weather forecast early this morning and discovered we would have good conditions for spraying today (low wind, temperatures below 85 and little chance of rain). Besides applying an insecticide we also made our first application of a fungicide to control pecan scab.

Casebearer update 16 June 2013

    Today we found the very first pecan damaged by a pecan nut casebearer larvae. If you look carefully at photo at left, you will see a small pile of insect frass near the base of the nut on the left side of the cluster. Pecan nut casebearer larvae always enter on the upper side of a nut close to the point where the nut is attached to the peduncle. When scouting for PNC damage look for the pile of frass along with some fine white webbing the insect strings between nut and peduncle.
  

     In addition, we are still catching moths in our pheromone traps (data below). Based on today's findings we are planning to spray our pecan trees for PNC and pecan scab starting on Wednesday the 18th of June.

Casebearer Update 14 June 2013

 

    We scouted our pecan trees for signs of casebearer (PNC) activity again today. As of today, we have yet to find nut entry by any first generation larvae. We are still catching male moths in pheromone traps (data above) but the numbers seem to be dropping off. Pecan nuts are just starting to show signs of enlargement indicating that the PNC egg laying period is rapidly approaching. At this point, we are preparing our sprayers to apply this year's first spray sometime next week. Monday's scouting report should help pinpoint an optimum spray date.   

Catching pecan nut casebear moths

  

    We set up pecan nut casebearer (PNC) pheromone traps after last weekend's flood receded (photo at right, arrow points to trap). However is wasn't until we got a warm night (above 60 degrees) that we found large numbers of male moths in the traps the next morning (Thursday June 6).
  In setting out PNC pheromone traps, I like to place the trap as high up into the tree as possible. To make checking traps a ground level operation, we use a rope and pulley system to raise the trap up into the tree's canopy and to lower it for counting moths.

    The photo at left shows the simple pulley system we use for hanging traps. We start with a 2 foot piece of 3/8 inch steel rod and bend it into the shape of a huge fish hook. At the long end of the steel hook we drill a 3/16 inch hole then place a loop of "bailing wire" through the drilled hole. The wire loop acts as our pulley for the braided nylon cord used to raise the trap up into the tree.
   The steel hook is placed over a limb using a 20 foot long piece of 1 inch diameter PVC pipe. I start the installation process by threading an ample amount of nylon cord through the wire loop on the end of the hook. I then place the long end of the hook inside the pipe (with cord hanging out). Lifting the pipe upright, I place the hook over a tree limb. This will get the trap about 25 feet up into the canopy, a height where PNC moths are actively flying.  To hold the cord in place and the trap high in the tree, I pound a nail into the trunk of the tree and tie the cord to that nail.
   

 

    The photo above is an example of one of our pheromone traps. We use a trap that has a plastic top and cardboard bottom.  We've found the plastic top helps to make the trap more rain proof.  The cardboard bottom is covered in a sticky substance that ensnares male moths as they enter the trap. The little grey stopper inside the trap is what contains the PNC pheromone. This trap had captured 16 moths.
  

Here's  a close-up of a PNC moth caught in a trap (photo at right). The casebearer moth is small, grey and cigar shaped. However, PNC moths have a distinctive ridge of scales across the upper third of their forewings. You might find other insects caught in the trap but only PNC moths will have that ridge of scales.

Time for weevil control

  Wide spread rainfall over this past weekend has enabled pecan weevil adults to emerge from the soil in large numbers. Growers from Kansas, Oklahoma, and Missouri have all reported catching lots of weevils in their 'Circle' weevil traps.The time to control this perennial pecan pest is NOW!
     We started spraying our pecan orchard this morning and this year we are using Sevin XLR insecticide. Other isecticides labeled for pecan weevil control include Warrior II, Silencer, Hero and Proaxis.
   The photo shows a female pecan weevil looking for just the right spot to drill through shuck and shell to enable her to lay 5 to 7 eggs inside the pecan. To control pecan weevil, you must prevent female weevils from laying eggs.

Time to set out weevil traps

     Its time to set out pecan weevil traps (photo at right). You can build your own traps by following the instructions given in this previous post.
    With this summer's intense drought pecan weevil emergence will be delayed until your farm gets a good soaking rain. Since the only kind of rain anyone has received this summer has been a pop-up thunder storm, it is very important to have weevil traps set out in all you pecan groves.  It seems like my farm has missed every shower while it has rained just 2 miles away. With this kind of hit or miss rainfall, weevils can emerge in one location while they are still trapped in dry ground at another location.

Building a pecan weevil trap

    Knowing when to spray for pecan weevil is the first step towards controlling the number one insect pest of pecans. "Circle" pecan weevil traps have proven to be the best method for determining when pecan weevil adults are emerging from the soil.
    In this post I'll be giving step-by-step instruction for building a weevil trap. Before starting you will need to gather the following tools and supplies.

Tools
     Metal shears
     Heavy duty staple gun
     Book binder's stapler
     Hot glue gun
     Ruler

Supplies
     Aluminum screen wire, 36 inches wide
     Wood strips, 1.5 inches wide and 0.5 inches thick
     1/2 and 3/8 inch staples for staple gun
     1/4 inch staples for book binder's stapler
      Deck screws  (3 inches long)
      10 gauge wire
      glue sticks
      Boll weevil trap top assembly (order here)

Step 1. Measure out 24 inches of screen wire and cut with shears.

Step 2. Fold screen wire in half (length wise). Press on the fold just enough to mark the center of the screen.

Step 3. Use a round object (8.5 to 9 inches diameter) to help trace a semi-circle at the marked half way point on the screen wire.

Step 4. Use the tip of the shear to trace the semi-circle onto the screen wire.

Step 5. Use the shear to cut out the semi-circle.

Step 6. Fold over the screen wire along the edge of the semi-circle to form a smooth edge.

Step 7. Place a 17 inch piece of wood strip down the middle of the screen wire. Fold the screen wire over twice along the bottom to make a smooth strong edge.

Step 8. Flip the screen wire over and staple the screen to the wood strip using 3/8 inch staples. The first staple should be placed 2 inches down from the semi-circle. Continue stapling down the wood strip every 2 inches until you get to the bottom of the wood strip

Step 9. Attach an 11 inch strip of wood along the upper edge of the screen wire, again staring 2 inches below the semi circle.

Step 10. Clamp a 30 inch long piece of 2x4 into a bench vise at a slight upward angle from horizontal. Place the long wood strip on top of the 2x4 and slip a boll weevil trap top under the screen wire.

Step 11. Staple trough the screen wire and boll weevil trap into the wood strap using a 1/2 inch staple. Use a hammer to make sure the staple is driven in tightly.

Step 12. Turn the trap over, wrapping the screen wire over the boll weevil trap top and place the short wood strip on the 2x4. Pull the screen tight, setting the trap top on top of the wood strip but under the screen wire. Staple in place with a 1/2 inch staple.

Step 13. Wrap the other side of the screen around the trap top then staple at the top with another 1/2 inch staple.

Step 14. Firmly attach the rest of the screen wire along the short wood strip using 3/8 inch staples. You should now have a cone shaped trap with a boll weevil trap top at the apex.

Step 15. Along the outer edge of the trap (the edge that hasn't been folded over yet), fold the screen wire over about 1.5 inches. As you make the fold, tuck the fold under the short wood strip.

Step 16. Cut a 36 inch piece of 10 gauge wire to place under the fold on the outer edge of the trap.

Step 17. Use the book binder's stapler to hold the wire inside the fold of the screen wire.

Step 18. Crimp the screen wire tightly around the boll weevil trap top. Fill in any gaps between the screen wire and trap top with hot glue.

Step 19. Use a standard No. 2 pencil to widen the hole in the top of the boll weevil  trap top. (pecan weevils are larger than boll weevils)

Step 20. Install the plastic cylinder and perforated top to the boll weevil trap top assembly.

Step 21. Install your new pecan weevil trap on a tree with a history of weevil problems. Scrape the rough bark off the tree at the point of trap installation. Use 2 deck screws to attach the long wood strip to the tree. Stretch out the screen wire across the bottom of the trap and staple to the tree using 1/2 inch staples.

Monitoring Traps

     Install traps by the 1st of August. Check traps at least 3 times per week. If you capture an average of 2 weevils per trap it is time to spray for pecan weevil. Continue to monitor traps after applying the first insecticide treatment. If weevils continue to emerge, wait at least 10 days before making a second insecticide application.

Pecan Nut Casebearer Trap Catch Data

    The table below represents the capture of pecan nut casebearer moths we have set out around the state of Kansas. The casebearer moth flight begins in southern most counties and works northward over time. Growers should start scouting their orchards for damaged nut clusters 10 days after the moth flight has begun. You should starting seeing larval activity 12 to 16 days after first moth capture. Control measures should begin when you see first significant nut entry (2-3% of nut clusters have larvae feeding on nuts).
    Check this post regularly for data updates including additional locations.  General information on casebearer can be found here.

Trapping Pecan Nut Casebearer

    The pecan nut casebearer is a major nut feeding pest. Shortly after the pollination season casebearer moths lay eggs near the tip of young nutlets.  The larvae that hatch from these eggs crawl down to the base of a nut and start feeding. The insect chews its way into the center of the nut, hollowing out the inside. You can identify casebearer feeding by the light strands of webbing the caterpillar uses to fasten nuts to the stem (so the damaged nut doesn't fall off) and by the pile of frass at the base of the nut (photo above).
     Each spring, we monitor the activity of the insect by using pheromone and orchard surveys.This year, I've enlisted the help of several growers around the state of Kansas to follow this year's casebearer moth flight using pheromone traps.

    Pheromone traps are easy to use as long as you can identify the target insect.  In the photo at left, two male casebearer moths have become stuck in a trap. The moths are grey, about 3/8 inch long, and feature a prominent ridge of scales across their wings. You can see other insects caught in the trap and even a fallen catkin, but casebearer moths will be the only insect that have a ridge across their backs.
    The spring 2011 flight has begun in the southern most areas of Kansas as of May 20.