More Algae Control Results

Jerry Moody, Doug Hundley, and I rated the trees treated in Avery County for algae control today.

Treatments. The treatments are all listed on blog posting from August 27. But I'll list them again here.

1. Untreated check
2. SA-20 disinfectant @ 1 teaspoon per gallon on May 5
3. Daconil @ 3 pints per acre on May 5
4. Dithane @ 1.5 pounds per acre on May 5
5. Kocide @ 3.5 pints per acre on May 5
6. Kocide applied twice on May 5 and May 19
7. Kocide on May 19
8. 3% bleach solution on September 25
9. Kocide on September 25

All treatments were made with a backpack mistblower except for the 3% bleach solution which was applied with a high pressure sprayer.

How we did it. Taking ratings was  hard. After all, some trees don't appear to get algae at all -- whether because of their position in the landscape, their proximity to other trees, or resistance is anyone's guess. So we first looked to see if the trees had algae on older needles. The trees with algae on older needles are the only trees we counted in the data. Then we looked specifically at 2009 growth and gave it a rating of 0 to 4 where 0 = none, 1 = very light, 2 = light, 3 = moderate, and 4 = heavy. We examined 15 trees in each treatment.

Results. The results are to the right. Remember that we only counted trees that had past algae. So, the higher the pecentage of trees with no algae in 2009, the better the product was working. And obviously the lower the algae rating, the better the product worked.

The best controls were with SA-20 disinfectant and Kocide applied May 5. The Kocide applied later in May didn't work as well. Nothing worked in the fall. Again, these materials will prevent algae from developing, not cure it.

These treatments were applied to a single row and the treatments are in order going up the hill (all except for the check row which was between the Daconil and the Dithane). There was definitely more algae the farther up the hill you went, and so that may be why SA-20 disinfectant worked well. That's also why the fall applied treatments had more algae than the check.

What next? I'd like to look further at Kocide and perhaps some disinfectants next spring. I'll also be looking for some growers who will be interested in trying the Kocide. Unfortunately it looks like if you want to control algae, you need to treat for it the last 2-3 years before harvest every spring. Once it occurs, there is nothing you can do about it. Treatments will be harder to make on large trees growing together, and in fact this is where we find the most algae. So keeping a good spacing between trees is important.

Algae Control Results

Several people have been concerned about algae again this year. However, I don't think the algae has been as bad this year as last year. In the two fields where we treated, there was definitely more of it on the 2008 growth than the 2009. We had a hot, dry spell in the summer that no doubt reduced the development of algae, but there are still problems. (Photo was taken by Bryan Davis last year showing extreme discoloration in 2009. Note that the current year's needles are not affected).

The first thing to realize when looking at algae control is that the best you can do is prevent more algae from developing. It's hard to cure algae once it's already there. It develops primarily on last year's foliage -- not this year's. It appears that it comes in the June time-frame. Therefore in these spray trials, we were looking at algae development on last year's growth -- that is 2009 growth. For the most part, we didn't do anything to reduce discoloration on 2008 growth (which developed the summer of 2009) or earlier. Still, if you can go to market with 2 years of good green color, it should be good enough.

This photo was taken under a microscope showing some algae on the needles. It is easy to see with a hand lens. It is also easy to wipe off the surface of the needle.

We applied different materials for algae control this spring before bud break at 2 sites -- one in Mitchell and one in Avery. Thanks to Jeff Vance and Jerry Moody for help in finding locations to work in and spraying the materials.

All applications were made with a backpack mistblower. At both sites, an untreated row was left between each treated row to reduce cross contamination of treatments.

At the Mitchell County site, treatments were made on rows of 10 trees. There were 3 replications. Applications were made on April 29 using one of the following materials:

1. Kocide 3000 at 3.5 pound per acre. This is a copper based material which is made up of 30% copper. Kocide label.
2. Dithane at 1.5 pounds per acre. The active ingredient of Dithane is mancozeb. Some Jackson county growers were seeing some control of algae in the fall when this material was applied. However last year, I didn't see very good results from this. Review of last year's work.
3. Daconil at 3 pints per acre. The active ingredient of daconil is chlorothalonil.

In Avery County we didn't replicate, but instead treated a long row with 30 or more trees. Original treatments were made on May 5 using either Kocide, Dithane or Daconil at the treatment rates described above. Addition treatments were as follows:

1. Cosan, an organic disinfectant, at 2 teaspoons per gallon
2. SA-20 disinfectant at 2 teaspoons per gallon. This product is made of 10% dimethyl benzylammonium chloride and 10% dimethyl ethybenzyl ammonium chloride. It is used to disinfect pots, greenhouse areas and tools.
3. Kocide applied twice -- on May 5 and again on May 19
4. Kocide applied once on May 19

Jerry, Doug Hundley and I looked at the Avery County treatments yesterday, and Jeff Vance and I looked at the Mitchell County treatments this morning.

There appeared to be more algae developed at the Avery than the Mitchell County site. This surprised me as the Mitchell County site was much worse last year. (This photo, taken in Mitchell County, shows a shoot from an untreated tree with algae on last year's growth).

All treatments appeared to have some effect on the algae. The Dithane and Daconil didn't work as well as the other products. Kocide appeared to work best. Applying it twice seemed to work a bit better, and applying it later in May also seemed to work some better.

This photo is of a shoot from a treated tree. Note that there is no discoloration on 2010 or 2009 growth. If the treatment hadn't worked, you would see discoloration on 2009 growth. The material didn't reduce the discoloration already present on 2008 growth. 

This is typical of any fungicide. They prevent disease from developing. They don't cure disease. Therefore a successful treatment will keep algae from developing the year it is applied. But that's similar to all of our pests. When you treat for twig aphids or spider mites, you don't do away with the damage you already have. Instead you cover it up with new, undamaged foliage.

I would like to repeat this next year, applying materials with either a high pressure sprayer or backpack mistblower. I suspect that the high pressure sprayer will give better control, but that most growers will prefer the speed of the mistblower. I also hope to try out some Kocide this fall to see if it will help "cure" some of the algae. I don't think it will, but since I didn't try it last year, I want to make sure. 

Take home message: It looks as if Kocide and perhaps some other materials will reduce and in some instances prevent algae from developing when applied in the spring. In fields where algae development is expected because of woods or the trees are growing close together, a preventative treatment is required starting the year before sale and continuing until all the trees are harvested.

A big thanks goes to Kelly Ivors and Gary Chastagner for their help in identifying possible treatment windows and materials.

Algae Treatments

Just got finished putting out materials for algae. There are 2 plots -- one in Avery and one in Mitchell. The initial treatments were made the first part of May. Today Jerry and I made a second treatment of the Kocide in one plot, and also treated some trees with the new growth out.

With all this rain and cool weather, I'm thinking that we might have a lot of algae in trees again this year! I'll keep everyone posted on the results, but it will probably be August before we know anything.

Algea

We had more growers with algea problems last year than ever before. We tried various products in the fall to get rid of the discoloration including Prev-Am, chlorox solutions, Dithane, horticultural oil, or zerotol. I even tried painting some trees. But nothing seemed to work.

That's when Kelly Ivors, our plant pathologist, talked with Gary Chastagner about it. They have been using copper based products in the spring out west to prevent algea from appearing.

So this week I hope to put out two studies looking at algea control -- one in Mitchell County with the help of Jeff Vance and one in Avery County with the help of Jerry Moody. We are going to be applying fungicides with a backpack sprayer. We'll treat some trees only once. Other's we'll retreat in about two weeks.

One of the products we're using is particularly recommended by Chastagner, called Kocide. The active ingredient is copper hydroxide. Kocide 3000 is labeled for fir trees in Christmas tree plantations to control needle casts at the rate of 0.75 to 1.75 pounds per acre and to control lichens at the rate of 3.5 pounds per acre. It should be applied before bud break.

I don't know yet if it will work, but it is a labeled product that you can try if you had a serious problem last year and think you'll have a problem again this year. I would only recommend this treatment in fields that are humid, such as those near woods, creeks, or where the trees are getting large and growing together. The label can be found at:http://www2.dupont.com/Production_Agriculture/en_US/label_msds_info/labels/SL-1344-2.pdf