browning problem with arbor vitae

Hello,

I have a row of arbor vitae down one of my property lines that has started to brown. The browning seems to be more at the bottom of the plants. I have attached pictures of the green and brown sections of one of the plants. There is some scale on some of the branches and I have attached a picture of that as well. I don't know if the scale is normal or not.

I also noticed some very small black beetles on my arms after I was looking around the plants. They are about the size of the head of a pin and smooth shiny black. I don't know if they are a problem or not. Today I gave each plant 3 Tbl of 5-1-1 fish emulsion in a gallon of water and am slow watering each plant to give the roots a good soak. These plants have been very green and healthy for quite a while now, so this is a new issue.

I can post more pictures or give additional information if necessary.

LMHmedchem

This message was edited Jun 24, 2014 3:54 PM

I tried to upload three images to my original post, but only one of them made it. I am trying again with the other two.

Is the picture of the scale in the third image? It's sort of a bad resolution so it's hard to tell without a clearer image. Scale is not a normal thing as it is sucking the live out of your arbs. I'm not sure about the 'beetles' but if you have a major scale infestation it's best to knock that out with some of the hard stuff. Any systemic insecticide with imidacloprid will take care of the job. Read the label thoroughly before application and proceed as instructed. That scale could very well be causing your browning problem. If possible, would you be able to get a clear close-up of the last picture?

The scale, or what might be scale, was the third picture. I was having trouble getting my camera to focus close up.

After reading a bit about my camera, I have tried again with some additional pictures. Let me know if there are other parts of the plant I should try to get a picture of.

LMHmedchem

This message was edited Jun 24, 2014 5:04 PM

In the last picture in the last post I think I see the evidence of spider mites.

Do the leaves look almost dusted with yellow? Very fine stippling?
Spider mites and a few other pests can suck the juice out of the plants, leaving a tiny wound that turns yellow or white. When there are a lot of them the plant looks more yellow than green, looks dusty, and ultimately can die.
Spider mites also form webbing. On a broadleaf plant it is almost always on the underside of the leaf. On a plant that has no 'undeside' the webbing could be anywhere.

Keep up the irrigation, a deep soaking can help, but I agree that identifying the problem is important.

For spider mites, I've been told to take a piece of plain white paper, put it underneath a suspected branch, and then shake the branch over the paper. If what looks to be dust starts moving then it's spider mites. I've had spider mites on my hollies and the local extension suggested I get Avid to spray them down with. Avid is really expensive but you don't need that much to make the solution. I bought mine on Amazon.

I have looked up a bunch of miticides and it seems like it is difficult to get anything that costs much less than $200, which would be a bore. I will do some checking tomorrow to see if I can find any live mites.

This is the link (University of Kentucky) with the wrtiteup of miticides in case anyone else is interested.
http://www2.ca.uky.edu/entomology/entfacts/ef438.asp

The chart is at the bottom of the page.

LMHmedchem

This message was edited Jun 24, 2014 10:41 PM

Check out Amazon. Apparently cannibis plants can easily get infected with spider mites so the stuff I got, Avid, was readily available in small quantities on Amazon. For Avid you only need 1/2mL per 16 oz or something like that. So an ounce goes far.

It definitely does seem as if I have spider mites, although there were a number of things of various sizes crawling around on the paper including the small black beetles. I have some Neem oil from when I used to have an apple tree and that is supposed to work against mites. I will give that a try and see if it helps. Thanks for the suggestion about Amazon.

I see that you can get 1/2oz to 2oz volumes of Avid for less than $35.
http://www.amazon.com/s/ref=nb_sb_noss/184-8001646-0542420?url=search-alias%3Dlawngarden&field-keywords=Avid+Miticide

They also have Forbid, which kills off eggs as well as adults,
http://www.amazon.com/Ounce-Forbid-Insecticide-Miticide-Ovacide/dp/B00E0VK1PE/ref=sr_1_fkmr0_3?s=lawn-garden&ie=UTF8&qid=1403737945&sr=1-3-fkmr0&keywords=Judo+%22Miticide%22

How did you apply the spray? I have a cold fogger that I use for permethrin to kill mosquitoes and I also have a pump sprayer. The fogger does a nice job of inundating the foliage with spray, but the volume is not high.

LMHmedchem

I would use the pump sprayer. I think it would have a stronger spray to get inside the plant, then adjust it to a finer mist for the outer parts.
Spray each branch from several angles to get under, over, and sides, especially when the branches and foliage are twisted.

I would use the pump sprayer. Make sure you are getting all sides of the leaves when doing it or it won't work as well. Also, your arbs may benefit from a second application of whatever you use.

Consider identifying what you have before spraying specifically the black bugs that you referred to. The local extension office or master gardeners hot line or local tree nursery might be able to help with the identification on both the scale and bugs. I catch a sample of whatever it is, bag it, and take it in. Then I know what exactly I am dealing with and can treat it accordingly.

My local extension office is not that local, in fact it's about a 2.5 hour drive from here. I send my soil samples there to be tested, but I don't think I can send random insects in the mail. I will check and see if there is someone there I can talk to by phone or email. I could get a photo, but they are so small that even on macro I'm not sure you would see much of anything.

There were at least three things that came off onto the paper I shook the branches over. There were very small dots like specks of dust that were moving around. These are what I assume to be the mites. There were a couple of things the looked like very small silverfish and the small black beetles that look like the plastic head of a colored straight pin, but black and a about half that size.

I have sprayed with need oil and will check again in a week. What exactly am I looking for here in terms of results? I would expect that browning to not get worse but will the color improve?

LMHmedchem

You can use the Neem but it won't kill the mites. All that does is keep them from reproducing and you'll have to spray frequently for about a month or so to control the infection. IMO you should be using something to kill them like Avid where if you spray right, you only need one application, maybe two for good measure.

Sorry to hear they are so far away.

I associate spider mites infestation with plants being under stress e.g. not enough nutrients or lack of water.

Here is info on spider mite infestation - cause and control. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7405.html

In the article one of the predators of spider mites is a black bug called Spider Mite Destroyer Lady Beetle. Click on the hot link and it will bring up photos. Is the black bug you are seeing on the Arborvitae? http://www.ipm.ucdavis.edu/PMG/NE/spider_mite_destroyer.html

In the article under biological controls there are a number of beneficial insects listed some of which look like silver fish.

In the article they also caution about what you use as a chemical to control them as some chemicals either only kill of their predictors or actually cause them to reproduce faster.


Under Management - "Adequate irrigation is important, because water-stressed plants are most likely to be damaged. Broad-spectrum insecticide treatments for other pests frequently cause mite outbreaks, so avoid these pesticides when possible. Sprays of water, insecticidal oils, or soaps can be used for management. Always monitor mite levels before treatment."

Under Biological Control - "Some of the most important are the predatory mites, including the western predatory mite (Figure 7), Galendromus (formerly Metaseiulus) occidentalis, and Phytoseiulus mite species. Predatory mites are about the same size as plant-feeding mites but have longer legs and are more active; they also are more teardrop-shaped than spider mites.

Various other insects are also important predators—sixspotted thrips (Scolothrips sexmaculatus) (Figure 8), the larvae and adults of the spider mite destroyer lady beetle (Stethorus picipes), the larvae of certain flies including the cecidomyid Feltiella acarivora (Figure 9), and various general predators such as minute pirate bugs, bigeyed bugs, and lace­wing larvae. Western flower thrips, Frankliniella occidentalis, can be an important predator on spider mite eggs and larvae, but this species will also inflict severe damage to plants if mites aren’t present on which to feed."

Well I have applied the Neem oil twice at 7 day intervals. I am no longer able to find live mites using the same method as before. These bushes also get fogged with permethrin for mosquito control, but I don't think that is effective against mites.

The appearance of the leaves has not changed much. Looking carefully, it looks like the very tips of the leaves are starting to get bright green and I assume this is new growth. If I do have the mites under control, at what point should I expect to see the condition of the plants returning to normal? I have also watered the bushes with more fish emulsion to give them a bit more nitrogen. I will use fertilizer spikes in the fall but wanted to give them a boost.

LMHmedchem

The damaged parts, brown, will not turn green. New growth will come out and will stay green unless the mites come back.

Read the UC Davis link several posts up. They are very good and complete about how to help plants with pests or diseases.