Protecting Pollinators & Groundcovers

Field site in Ashe County

If you follow NCSU Christmas Trees on Facebook, you saw that Jeff Owen, Brad Edwards and I treated some groundcovers -- mainly purple deadnettle -- with either Roundup, Stinger or Goal last Friday.

Why is this important? After all, the groundcovers are just now starting to grow. Typically, growers wait until late April or into May before doing any type of herbicide application. These little purple deadnettles certainly aren't impacting tree growth. When the weather gets warm, they die back naturally.

The goal of these treatments is to burn back the flowers so that bees won't be in the trees.  On warm days, bees have been in this particular field  for the past month. If the grower needed to treat with an insecticide and had to spray during the day with a high pressure sprayer, bees in the area would be at risk.

Early spring is a tough time for bees. The population of a bee hive fluctuates through the year according to the season and resources. The number of worker bees declines at the first of the year, reaching the lowest number in February/March. This is the time of the year the queen is starting to lay eggs when there are fewest bees to feed and take care of the young. A queen may produce 1,500 bees daily. Honey and pollen resources have been depleted and there are few places for bees to forage. They work red maple when it's blooming which provide both pollen and nectar. In tree fields, purple deadnettle and wild mustard bloom early and bees will be foraging in the trees.

The hope is that by using a suppressive rate of a herbicide over the top of the trees the flowers will be burned back, but the good groundcovers -- especially the clover -- won't be killed out. We tried 3 commonly used herbicides at the typical suppressive rates to determine if they would knock back the purple deadnettle and how long flowering would be suppressed.

Of course it's too early to tell completely, but I went back today to see if any materials had made a difference. It's been five days after treatment.

The only treatment that worked so far was the Goal at 13 ounces per acre. The purple deadnettle had been burned back and there were few to no flowers. So this appears to be a quick way to clean up a field of flowers. Of course, Jeff reminded me that this would only work up until the time the trees break bud. After that the Goal will burn the new growth as well.

Purple deadnettle after treatment with Goal.

The Roundup was starting to have some effect, but there were still quite a few flowers. We'll check back next week to see if it's working any better.

Purple deadnettle after suppresive rates of Roundup.

The Stinger hadn't worked at all yet on the purple deadnettle. It looked like the check. It appeared that the deadnettle had grown since Friday in these rows.

Purple deadnettle after suppresive rates of Stinger.

We'll be trying these and other materials on other spring groundcovers and other weather conditions, as well as following how long it takes for the groundcovers at this site to green back up. But it looks like Goal at suppressive rates will burn back some flowers.

Bees Already?!?

Brad Edwards and I were looking in a field treated with Safari last July to look at scale control. Long story short, the Safari worked well. I'd estimate 99% control. But what really caught our attention was what was going on under the trees. There was an almost continuous carpet of purple deadnettle that was starting to bloom. And it was full of bees! Most had pollen sacs full of red pollen.

This field was at just under 3,000 feet in elevation and southern exposure. The high was only 51 ^oF in Jefferson today. They say bees don't get out and start working until it's 55 ^oF. Obviously the bees don't read too well.

In any case, if you need to apply an insecticide, it's important to look and see if bees are in your trees. Pick a warm day at mid-day and look for bees. If you can spray at night, you should be OK. But if you have to spray in the day, clean up the field of flowers by using Roundup at suppression rates a week or so before treatment. Know if you have bee hives close by, and if you do, tell the bee keeper what you plan on doing. They may want to shut up the hive while you are spraying so the bees aren't exposed.

For more information about how to protect bees in trees see: FRASER FIR PEST CONTROL PORTAL: Tips for Keeping Bees Safe.

Post Harvest Pests

Heard about my first post-harvest pests today. Cinara aphids. Anyway, here are links to information about these pests.

1. Grower information on Cinaras.
2. Information for the retail lot operator.
3. Retail lot information in pdf format.
4. Photos of Cinara aphids.
5. Consumer education information on post harvest pests including Cinaras, praying mantids, and spider mites.

If you need me to speak with retailers or consumers about this issue, email me at: jill_sidebottom@ncsu.edu

Jeff Vance is holding a bottle of insecticidal soap.
This works well against aphids and is completely safe
around children and pets. It does have a bit of an odor.
You can buy this pre-mixed in high end garden centers.

This is a photo I received from a consumer a few years ago.
Surprisingly it's never hard to ID Cinara aphids from the  strange photos I receive.

Impact on Predatory Wasps

Yellow sticky card placed in a Christmas tree that has EHS.

On January 5 of this year, I posted about the parasitic wasps I was finding on cut Christmas trees that were infested with elongate hemlock scales (EHS) (see Parasitic Wasps on Scale Infested Trees). If you will remember, Jerry Moody and I placed yellow sticky cards in cut trees to determine if scale crawlers were coming off of them. Yellow sticky cards are about 3 X 5 inches and coated with a sticky clear substance that traps insects once they step onto it. The yellow is particularly attractive to many insects. During our little study, there were only a few wasps per sticky card coming out once the trees were displayed in water in a warm room just like they would in someone's house.

These parasitic wasps are very important to control of the EHS. They are very, very small -- the size of a single scale. You'd never see them flying around, and in fact you have to use a microscope to see them on the yellow sticky cards. These wasps, Encarsia citrina, are available commercially and are often used for whitefly control in greenhouses. But they also love scales. Whenever you see a scale that has a round hole in it, you know that one of these wasps has developed inside it and killed it.(Think ALIEN with Sigourney Weaver!) I especially enjoy probing into scales this time of year and finding the immature wasp inside one. Sometimes the tiny little wasps even move their heads! (Nature is so cool!)

This scale has been parasitized. The arrow points to the exit hole the wasp made to get out
once it had fully formed.

The arrow points to a wasp that is still forming inside this scale. The eyes are to the left.

Over the last week, I've put out some yellow sticky cards in trees infested with scales in an Ashe County Christmas tree field (pictured up top). Travis Birdsell, the new county agent in Ashe County and I looked at these cards on Thursday after leaving them for 48 hours. I was amazed at how many wasps there were! We put two cards in one tree and there were 56 wasps on one of them and 34 on the other. In a second tree we had one card and it had 15 wasps. This was in a field where there were some scales, but they had never become really bad as they are in some fields.

I was surprised that there were so many wasps out now. So I became curious. Could I see a difference in the number of parasitic wasps in fields that had been treated with a synthetic pyrethroid compared to those that hadn't? I've thought for a long time that the increased use of the bifenthrin products in particular might be causing a lot of the increase problems in scales.

It just so happened that Jerry Moody and I had created the perfect place to test out this theory. We were working in a small field of trees in Avery County where few insecticides had been used and scales had become a problem. I already knew there were lots of parasitic wasps as I had seen them inside the scales. We had sprayed a block of these trees two weeks ago with Safari and a bifenthrin product, in this case, OnyxPro. We are treating a different block of trees every two weeks to see how late in the season we can get good scale control.

So on Friday, when we were making another treatment, I put a yellow sticky card in three untreated trees and three trees treated two weeks ago with Safari + OnyxPro. The two sets of trees were probably only about 75 feet apart. Today I looked at the cards (after 72 hours) and was amazed at the results.

There was an average of 45 wasps on the cards placed in untreated trees (79, 35, and 22) and an average of 5 on the trees that had been treated (10, 3, and 1). That is a 90% reduction in the wasps just two weeks after treatment! And though I didn't look at scale control, I am sure there is very little yet as Safari takes a long time to work.

I plan on looking more at this issue, trying to evaluate different chemical combinations put out at different times of year to see what the optimum time is to get control of scale without doing away with the parasitic wasp. But the early take home lesson is that the use of synthetic pyrethroids can have a profound affect on these important natural controls. Hopefully in the coming months we can determine when these materials can be used with the least negative impacts.

New Website

I've just completed a new website that will help sort through all the pest control options.

FRASER FIR PEST CONTROL PORTAL

There's lots of information on these pages, so skim through them all. If you see any errors let me know. If you're having trouble navigating, let me know as well. It was hard deciding how to set up the navigation, so I'd be happy to change anything to make it easier.

Celebrate Earth Day with a Christmas Tree

This week while scouting a field for twig aphids and mites, I came across this little nest full of eggs. It reminded me of how Christmas tree fields are home to many creatures -- a perfect reminder of Earth Day.

The most important creatures that tree growers invite into their tree fields are natural predators, brought in when ground covers are managed rather than killed. The next photo is from a field I was also in last week, showing a diversity of flowering ground covers.

That means that tree growers don't have to purchase natural predators like the lady beetles sold here for home gardens. Predators are attracted to the diversity of flowers and insect activity in the ground covers and will feed on any aphids or mites found in the Christmas trees themselves. It's free pest control.

One of the lessons from the Extension organic field in Alleghany County has been that the ground covers that come in when low rates of Roundup are used are far superior to all the grass that grows in the organic trees. After all, we grow grass in our lawns because grass tolerates mowing. Mowing ground covers in the organic trees has promoted grass and actually decreased biodiversity in the ground covers as compared to the lower portion of the field where conventional practices have been used up until this year. In this photo, you can clearly see the line where the clover stops and the grass starts. That's the line between the trees that have been grown organically since 2008 and those that are switching to organic production this year. Mowing promotes grass and it has certainly taken over to the detriment of the trees and the natural predators as well. (For those wanting to grow Fraser fir organically, it will be important to plant clover and other beneficial ground covers in a field the year before the Christmas trees are set -- something that wasn't done on this site. But that's for another blog entry!)

These ground covers, however, are also forage for bees. Clover, wild mustard, and purple deadnettle especially bring the bees in. Protecting bees can be as simple as choosing the time of day when you spray with an insecticide. Spraying trees in the late afternoon or at night for mistblower operators, is a good way to avoid problems with bees. Switching pest control to the fall is also a good way to avoid problems with bees. Be aware if someone has a commercial or even a hobby hive near your tree field. For fields close to bee hives, a mid-March application of horticultural oil will control most Fraser fir pests without causing a problem with bees at all.

April 22 -- Earth Day -- might seem like an odd time to think about Christmas trees. But those involved in the Christmas tree industry in western North Carolina know that every day is Earth Day in a Christmas tree farm!

Strange Spring: The Continuing Saga!

This spring continues to be unique. I was in a field in Avery County at a fairly high elevation yesterday, and one in Transylvania County at a low elevation today, and bud break was about the same. Only a few trees had broken a few buds in both fields, but it looks like the trees are ready to pop. I think the cooler weather this week has slowed things down.

But don't expect the cooler weather to slow the bugs down. The twig aphids are reproducing. This typically happens right before bud break, and they are doing the same again this year. The difference is that it appears that bud break and perhaps shoot growth might take longer than normal. That means that the trees will be at their most vulnerable to twig aphid attack for a longer period of time. Also, the warm spring has allowed for good aphid survival and reproduction. It all adds up to a potentially bad year for twig aphids.

That is why I've always warned people that if you are beating the foliage and finding even a few aphids, they will reproduce and end up being a problem. Each female aphid can produce 10 to 15 live young -- making what you saw last week 10 times more this week.

Rust mites are also quite active and will remain so until temperatures really warm up.

The good news is there has also been a lot of rain, which will help the trees grow out of any twig aphid damage. The following aren't very good photos, but they illustrate my point. The first picture is of a tree with twig aphid damage in May. The second is of the same tree in July. Most of the damage has straightened back out.

Shoots actively growing show lots of needle curl...

... but the mature growth has little damage.

So don't get too concerned with twig aphids. Use your judgement. Still, it's a good idea to recheck the trees that you plan on cutting this year that are your best trees, and treat them if necessary. Dimethoate is a good choice at this point as it will penetrate the cones and any broken buds. However, remember that Dimethoate is quite toxic, and is especially a problem when bees are active (which they are now in ground covers). Consider spraying later in the day, or if you are using a mistblower, of an evening.

With as much wind as we've been having this spring, I know how hard its been to get sprays out. Just remember, that poor conditions for spraying will give poor control results. There's little need to waste time, money, and put the environment to risk by forcing a spray job under windy conditions.

Let me know if you have any questions, and good luck!