Time to Scout -- Time to Treat

Twig aphid numbers. If you have twig aphids in your Fraser fir Christmas trees in western NC, you should be able to find them now. They are still quite small, but they have all hatched out. So if you treated your fields last fall for Cinara aphids, you might be able to skip treating for twig aphids this spring. But the only way you'll know for sure is to scout.

The aphids go through several molts before becoming adults. At maturity, this first stage is called the stem mother and she will produce live young aphids which quickly build up the numbers. That's why it's so hard to judge how much damage there will be by the twig aphids. It's a function of how many aphids there are right at bud break, and how quickly the new growth of the tree elongates and becomes resistant to damage. This is all modified by the weather on a daily basis.

To scout, get your plates out and start beating foliage to assess twig aphid numbers. Be sure to use a hand lens as the aphids can be quite small. It's best to wait until the foliage is dry (a challenge for this week!) but if you're good at scouting and don't mind getting wet, you can find them about any time. If you're not sure how to scout, contact your county extension agent.

If you see more than an aphid or two in a block and the trees will be marketed this year, go ahead and plan on treating this spring.

Christy Bredenkamp beating foliage to scout for twig aphids.

Look with a hand lens as the aphids are often quite small.
These tiny aphids will be having babies in just a week or two.

There are at least 6 aphids pictured here along with round balls of honey dew. When scanning a shoot
with a hand lens, you can often spot the aphids by the ball of honey dew.

Rust mites. There are several fields where rust mites are a problem this spring. Mites aren't in every field. The best way to assess rust mites is to pull some of the smaller shoots of growth and scan the back side of the needles for the tiny mites. If you don't need to treat for twig aphids but mites are a problem, you might have to treat anyway. Mark infested trees and go back to them to see if the numbers are building and treatment is necessary.

Choose shoots like this to look for rust mites.
You can also look for twig aphids, spider mites, and scales when scouting shoots.

Flowers & bees. Purple deadnettle must really like the weather we've been having. It is blooming everywhere and on sunny days, it is bringing in the honey bees and bumble bees. Wild mustard is also blooming now in fields and it is even more attractive to bees. So if you have these blooming in your field, either spray at night, or hit the ground covers with a low rate of Roundup or other herbicide to knock back the flowers before spraying.

Purple dead nettle

Bud break. The trees are just starting to move, so we should be 2 to 3 weeks away from bud break.

The Spring Rush. There's a lot to do in the spring. This week looks like it will continue to be wet and not good weather for spraying at all. When it comes to spraying fields before bud break, it's natural to want to just get it done and ignore the weather, but many times insecticide treatments fail because of too much wind during treatment or rain right after treatment. So prioritize your fields, pick your days, and pay attention to changing weather conditions. It's better to leave a field untreated and let the predators clean up twig aphids than to waste your money and pesticides and cause problems with your neighbors by spraying when it's too windy.

Useful links. Here are some links to more information. Remember our main website has changed the web address to christmastrees.ces.ncsu.edu

• Controls Based on Treatment Window -- Spring: April through Bud Break
• Balsam Twig Aphid on Fraser Fir
• Focus on Aphid Control
• Rust Mites on Christmas Trees
• Focus on Mite Control
• Tips for Keeping Bees Safe
• Weather Conditions When Spraying

2015 Scouting Project & Early Pest Observations

Brad Edwards looking for twig aphid eggs

Because of the issues that people had in 2014 with twig aphids (BTA), and the continued issues with elongate hemlock scale (EHS), this year I'm doing an intensive scouting project. I plan on visiting 2-4 farms in the main Christmas tree counties every two weeks through the spring and summer to observe how well natural predators are working at pest control. I've been visiting potential sites the last couple of weeks to set up the project and there are a few things I've already noticed.

Twig Aphids:  I'm finding that most fields have high numbers of BTA eggs in them. Actually the fields with the lowest eggs counts are the ones that have the least amounts of pesticides last spring -- such as organically grown trees or abandoned fields. That's because the natural predators ate the aphids before they could lay any eggs. That's one thing I hope to observe this year -- what predators are most important and how early in the spring they show up.

Another thing we've observed already is that BTA eggs started to hatch the 2nd week in March which is actually earlier than normal. Typically it takes about 3 weeks for all the eggs to hatch. This may well mean that we have an early overall hatch this year. (I'll keep you posted).

For scouting, that means that by around April 10, you should be able to go out into the field and beat the foliage over a plate to see if aphids are present or not. If you sprayed last fall with a synthetic pyrethroid, this would be the time to check to see if you can get away without treating this spring. Don't look before that time as all the eggs haven't hatched yet. And also evaluate other pests such as rust mites, which leads me to the next observation.

Rust Mites: There are already a few fields with active rust mites in them. It might be a good idea to go ahead and check fields where rust mites have been a problem in the past, or fields treated last spring with a pyrethroid, to see if they are making an appearance. If rust mites are a problem, you might need to treat this spring even if twig aphids have been controlled. Also keep an eye on the weather. Rust mites love long springs. I have a feeling that this year there will be good weather for them to be a factor in many fields.

Keep Posted and Thanks! In any case, thanks to the growers who are letting me work in their fields and to the county extension agents who are helping me to make these evaluations. I plan on posting observations here so stay tuned! This work is funded in part by the North Carolina Christmas Tree Association.

Changes to Safari Label

Honey bee in white clover

Many of you are no doubt following the news about bee decline in the US and worldwide. Due to concerns about neonicotinoids in particular, the US EPA is making changes to the labels of these products.

Many growers are using Safari (dinotefuran), a neonicotinoid, for the control of elongate hemlock scale in Fraser fir Christmas trees. This product has proven to be the most effective at controlling scale in western North Carolina. Safari can be sprayed on the foliage or it can be applied as a trunk application. Both have proven effective.

The previous label of Safari indicated that plants shouldn't be sprayed if bees are visiting the treated area. This allowed the product to be applied of an evening or at night when bees weren't active.

The new Safari label which came out in 2014, is far more restrictive. The label now states that this product is "toxic to bees exposed to residue for more than 38 hours following treatment. Do not apply this product to blooming, pollen-shedding or nectar-producing parts of plants if bees may forage on the plants during this time period." The label also indicates it can't be applied "while bees are foraging" or "to plants that are flowering. Only apply after all flower petals have fallen off."

In other words -- no flowers period.

So what's a grower to do? Ground covers in Christmas trees are an integral part of integrated pest management. Besides controlling erosion and making the soil cooler so tree roots are closer to the surface, ground covers keep problem weeds from coming into a field and they are habitat for natural predators such as lady beetles, hover flies and lacewings.

In 2013, Jeff Owen conducted several demonstrations to find ways to keep good ground covers while getting rid of flowers and therefore bees. What he found was that our typical chemical mowing with Roundup will burn back flowers in ground covers including white clover within one to two weeks depending on the weather. Therefore, it's important when applying Safari, to time applications after a herbicide treatment. It's also important to scout before making an application to see if bees are visiting the area any further.

Protecting bees from pesticides is important, but flowering ground covers are also important to provide forage for bees as well for natural predators as well. With a little forethought, Fraser fir Christmas tree growers can create a win-win situation for themselves and pollinators.

White Pines in the Loading Yard

It's not always easy to tell why trees start to decline

THE VALUE OF WHITE PINES IN LOADING YARDS: Many Fraser fir growers in the mountains are fortunate enough to have loading yards shaded by white pines. These trees create a cooler and more humid environment for harvested trees.

White pines are native to western North Carolina so you'd think they'd have fewer pest problems. A fast growing tree, most people view white pines as being a lot 'tougher' than Fraser fir. After all you can plant white pines where Frasers have died from Phytophthora root rot and they will most likely survive, even though they are also susceptible to the disease. But white pines do have pest problems and are sensitive to poor sites which, unfortunately, are often associated with loading yards.

Recently, Brian Heath, Forest Health Specialist with the NC Forest Service, helped me walk through a local loading yard that utilized white pines for shade. We discussed some of the pest issues that face these important trees and what a grower can -- and more often cannot -- do about them.

White pine aphids

Tree with pine bark adelgid

PESTS OF WHITE PINE: According to the US Forest Service, there are 227 insects and 110 disease organisms that can attack the eastern white pine. That's a lot of pests! Sill, they seldom cause problems particularly of mature trees. Some, like the pine bark adelgid, can literally cover the trunk of the tree, turning it white, but seldom harm the tree.

White pines grown for Christmas trees or nursery can suffer from several pests such as pine needle scale, introduced pine sawfly, rust mites, white pine aphids (a species of Cinara aphid), weevils including white pine weevil and Pales weevil, and needle blights including ozone injury, but these problems are primarily cosmetic and will not affect trees being grown for shade.

Introduced pine sawfly

STRESS THE MAJOR ISSUE: When it comes to loading yards, it is stress that is the primary cause for concern. Stressed trees attract pests like bark beetles and are more likely to succumb to other pests that usually aren't a problem. The stress, however, is the underlying factor.

White pines in the mountains typically grow on stream banks in areas that are well drained. They grow well on poorer. sandier soils where they can out-compete hardwoods. They do best when planted in undisturbed forest soils. But most loading yards are on level ground that used to be a field or are near a building site. This past soil disturbance affects white pine growth. They may grow well for 20 years, but then often start to decline for no apparent reason. If planted on forested land, those same trees would live as long as 200 years.

Stress continues in the loading yard. Soils are compacted with equipment movement, and trees may be injured by equipment or deicing salt. If the ground is watered to keep cut Christmas trees moist, the white pine roots may stand in water.

Pitch tubes

Stressed white pines are attractive to bark beetles including southern pine beetle, black turpentine beetle, several species of Ips beetles, and Pityogenes beetles. Signs of beetle attack include small holes in the bark and pitch tubes created as the tree tries to keep the beetle out. The beetle lays eggs under the bark and the larval feeding creates distinctive galleries. Several beetles also carry a blue-stain fungus which disrupts the flow of water to the tree's crown.

Cutting pines adjacent to white pines in a loading yard can also bring in a host of problems such as more bark beetles and weevils. In addition, Annosum root rot will infect cut stumps and grow along the roots into adjacent, living trees -- even Fraser fir.

Bark beetles attacked this tree because
it was under stress.

In the loading yard that Brian and I visited, we found black turpentine, Ips and sawyer beetles, pine bark adelgid, and evidence of injury from road construction and/or salt injury. But many symptoms of decline couldn't be pinned down to a specific problem. Procera root rot is also a common disease found on white pines growing in fields, but was not observed at this particular site.

KEEPING WHITE PINES HAPPY: The best possible set up for a loading yard is to put it to the south of a bank planted in white pines. Setting the white pines on undisturbed soil and allowing no traffic on the roots will greatly reduce stress to these trees.

Tree spacing is another issue. You might want to initially plant trees every 6 feet, but they should be thinned to 12 or more feet apart as they get larger. If you are planting two or more rows on a bank, they should be thinned to around 20 feet apart.

Trees growing too close together will experience more stress

If such a setup isn't possible and you have to plant the white pines in areas where greater stress is likely, be prepared for a much shorter lifespan for your trees. They may only live 20 years or so. That means it will take them 10 years to reach a size where they are creating appreciable shade and they may only provide shade for 10 years.

Setting up two loading areas that you could rotate between every 10 years would be the ideal situation but replanting in an existing loading yard is the only option most people have. Just realize that survival may be low. Plant more trees than necessary to replace declining trees, but thin out trees as they get older to 12 or more feet apart.

And don't become too concerned if trees start to decline. That is to be expected. There really isn't any need to treat the trees for incoming pests, the best thing to do is keep them as stress-free as possible.

READ  MORE ABOUT IT:

US Forest Service -- Eastern White Pine

White Pines for Windbreaks

Procera Root Rot of White Pine

Pine Bark Beetles

Rust Mites!!!!

I really wouldn't have thought this would be a bad year for rust mites. After all, everyone was hoping that with such a hard winter, there would be fewer pests.

Looks like we were wrong!

Rust mites are cropping up in many fields. They will probably limit the number of fields that can go without an insecticide treatment this spring. But don't just assume you have to treat. Scout first! Twig aphids are now mostly hatched and even spider mites are hatching out. So scout and determine what you need to do.

From my pest management survey, I've learned that a lot of people are depending on either a bifenthrin product such as Sniper and/or dimethoate in the spring for pest control. But with rust mites so bad, neither product is probably the best choice.

Miticides such as Envidor provide a lot longer control of rust mites and spider mites both. Though more expensive, you can treat and pretty much walk away from the situation. So if mites are the only problem and you don't have twig aphids because of a fall treatment, consider just using the Envidor without mixing another product in. That will protect your natural predators.

I also think that bifenthrin is a much better product to use in the fall for Cinara aphid and twig aphid control. Then it should have much less effect on the parasitic wasp that controls the elongate hemlock scale.

The following links will provide help for mite control, twig aphid control and/or scale control.

On other thing... is flowering mustard blooming in your trees? If so, watch out for bees when you spray! Mustard seems to be the plant that brings the most bees in when it is flowering. It is far more attractive to bees than other flowers such as clover. So take special care when mustard is blooming. The following link will help with controlling pests without hurting bees.

If you have any questions, please let me know.

Cryptomeria Scale Resurfaces in Ashe County

On September 1, 2010, I make the following post: Cryptomeria Scale Found in Ashe County. If you went to any of the meetings where I spoke at the following winter, you probably heard about this new scale problem. I've not really talked much about this scale since then and with good reason -- I've not seen it again.

After making this post in 2010, the grower cut down many trees and treated the rest. I couldn't find any live scale after treatment. Since then I've been back to that field several times and scouted in close-by field and never found any more Cryptomeria scale (CS) until today.

Cryptomeria scale (Aspidiotus cryptomeriae), like elongate hemlock scale (EHS), is another introduced pest from the Orient. It affects many conifers including hemlocks and firs. It causes serious and striking yellow mottling of the foliage and premature needle drop. On the trees we examined today, most of the damage was on the south side of the tree. A few trees were heavily damaged all over with scales even on the needles of the terminal. This is one scale you really don't have to hunt for to find. If it's there, you should see it.

Damage from Cryptomeria scale.

The scale has a very different appearance to EHS. The scales, especially the small immature ones, are round, and they line up in two rows along the backside of the needle on either side of the midrib. They look like fried eggs with a yellow center. The 'white of the egg' is actually where the scale has pushed up the waxy covering of the needle. Older scales are more indistinct.

These younger scales look like they might have been killed, perhaps from a fall
insecticide treatment.

Crawlers will start to appear in another month or so.

The life cycle of CS is similar to EHS. It has two generations per year and is most active in the summer months. It seems to spread very quickly and cause damage very quickly. However, it is much easier to control than EHS.

The scale is spread through crawlers and on infested plant material. This scale was found in three adjacent fields owned by different growers. Next week, we hope to scout other farms in the area to see how far the scale has spread.

Typically when I've found CS, I've also seen the twice-stabbed lady beetle. We didn't find any today. Perhaps it's still too early in the year for this helpful predator.

The grower in 2010 treated in early September and got excellent control. We didn't see any crawlers today, and so it's probably a bit too early to treat -- especially since we are having such a cold, wet spring that's keeping everything from getting active. But we'll definitely be following control from any grower treatments and pass results on.

Twig Aphid Hatch -- Spring Pests

Twig aphids. Looked at twig aphid hatch again today. I found just over 90% of the eggs hatched (it worked out to 93%) and there were a couple of aphids that had molted. However, when Jerry Moody and I were doing beats on trees, we were still finding that they were hard to find. So if you do start scouting for twig aphids in the next few days, if you find any at all, you should probably treat in go-to-market trees.

Aphids should all be hatched out in the next few days.

Woollies. Last week we found that only a few balsam woolly adelgid eggs have been lain. This week there were whole lot more. The adults still haven't produced much wool.

Spider mites. I found my first spider mites crawling around today. Many are encysted. That means that they are molting from an immature to more mature state. When they do this, they look like they are dead. They don't move, but they are in fact alive. They are just molting and it takes awhile.

The next couple of days are supposed to be wet, but after that, start scouting trees that were treated last fall to determine if you need to treat this spring for twig aphids or for mites.