Hello Everyone,
My name is Andy Kinsey and my family and I are relatively new Christmas tree growers in north Georgia. We have been working on ways to make our lives a touch easier as managing trees is quite a bit more time consuming than we had ever imagined! During January and February of this year (when the grass and weeds weren't completely out of control on our farm) I have been working on finding out ways to keep the weeds under control throughout the rest of the year. I have spoken to several different growers, professors, and salespeople during the past two months and I thought some of this information would be beneficial for other growers as well.
Listed below are five general questions I asked University of Georgia professors Dr. Jean Williams-Woodward (questions 1-3) and Dr. Mark Czarnota (questions 4 and 5). I can't say enough about either of these two professors to explain how generous and pleasant they were to talk with.
1. Cercosporidium Needle Blight. - What are the best methods for treating this? I have heard that alternating between Kocide 2000 (contact) and Quadris (systemic) every 10 days is quite effective. Would Heritage also work as a systemic?
Heritage and Quadris have the same active ingredient, azoxystrobin. The difference between the two products (aside from the price) is that Heritage is labeled for use on ornamentals, including Leyland cypress grown in containers. Quadris is labeled for use on agronomic crops (vegetables, fruits, etc.), as well as Christmas trees. The labeling for Christmas trees is primarily for more northern growers who produce pines, spruces, and firs as Christmas trees. Because Leyland cypress is grown in the south as a Christmas tree, Quadris can be used if the tree is grown for Christmas tree production. If Leyland's are grown for the landscape trade, then Heritage is the product that should be used. The company is looking at removing Christmas trees from the Quadris label and placing them on the Heritage label, but as yet this has not been done. Rotating between Quadris (Heritage) and Kocide is a good rotation for controlling the needle blight disease. Quadris can be applied at 14 day intervals and Kocide at 7 days. Rotating every 10 days is probably more than needed for Quadris and less than needed for the Kocide. I usually recommend applying two applications of Quadris at 14 day intervals, then rotating to Kocide, Fore (mancozeb), or Daconil at a 7 day interval and then back to Quadris. Quadris costs more to purchase, but when used at the recommended rate (4 oz/100 gal) and given that you have to spray less often (half as much than if you use one of the contact fungicides), it becomes more economical.
The biggest concern to achieve good control is to get the product inside the tree canopy. The fungicides need to be applied with a pistol or wand applicator with a spray volume of about 100 gal per acre. Spraying with a boom applicator that hits the ends of the foliage will not control this disease. The easiest way to test your application method is to spray water onto the tree and then feel if you can detect the water at the trunk. If you can't, then you will not control this disease because the fungicide will not reach the affected foliage.
2. Cercosporidium Needle Blight Is the above effective enough or should we also be rotating in Mancozeb or Chlorothalonil? It is my understanding that they are also contact fungicides and I was curious if it would be fruitful to swap them out with Kocide periodically.
In my spray trials, mancozeb (Dithane, Fore, etc.) worked extremely well, with Daconil and Kocide also providing good control. Rotating Quadris with any of these contact fungicides is effective in controlling this disease. It really does not matter if you rotate among the contact fungicides. They are just about as equally effective and the reason you are rotating with them is to reduce the chance of fungicide resistance development by using Quadris alone.
3. Cercosporidium Needle Blight What are your thoughts on the best time to initiate spraying? I have spoken to a couple of different growers and the general feeling is that spraying in April and May helps to significantly reduce problems in the fall.
In my spore trapping studies, I begin to detect Cercosporidium spores in very low amounts by mid- to late June. I recover no spores in early spring. I am curious if the growers spray all summer long or if they only spray in April and May and then discontinue spraying? I generally recommend that applications to protect the trees should begin by late June to July 1 and continue through the end of September to mid October. Peak spore detection in my spore traps was in August through September, which generally coincides with when growers first start seeing symptoms of the disease. I have sprayed as late as Sept 1 through Oct 31 and gotten good control of the disease. Infected trees would have been marketable for December cutting as Christmas trees. Leyland's have the ability to recover from the disease pretty well because as new growth develops on the branches, it masks the infected needles beneath it. Eventually the disease slows its progression as the foliage becomes thicker because the disease is mostly spread by water-splashing of the spores. With a full canopy, rain can't reach the interior of the tree and the spores are not released. This is why the disease tends to disappear on Leyland cypress trees in the landscape and why it is so bad on pruned Christmas trees. The shearing of the trees removes all the dense new growth and exposes the infected branches to water and spore dispersal.
4. Preemergence in the Christmas trees We strip spray along the base of our trees with glyphosate products and would like to add a preemergent to this mix to reduce spraying labor, fuel, etc. The chemical would have to be placed in water to spray and preferably mixed with the glyphosate. Our chemical supplier suggested Pendulum given its lower cost. However if memory serves me you had recommended a mix of Gallery with Barricade, Pennant Magnum, or Surflan. Any advice?
I have a good list of preemergent chemicals in the 2006 Georgia Pest Management Handbook (Commercial Edition), and you can purchase this at the county extension office. Price will probably be your biggest consideration, but Gallery with Barricade, Pennant Magnum, or Surflan would be an excellent choice (~150 dollars / A, chemical costs). Solicam is also an excellent choice, but may cause some whitening of new growth (plant will grow out of this) (~60 dollars /A, chemical cost). If you are very accurate with your application (spray calibration, herbicide rate, and measurements) most of this will be avoided! Most anything can be mixed with glyphosate, and I am not aware of any pre herbicide that you cannot mix with glyphosate. One application in Feb/Mar and another in May/Jun should be good for most of the season (Sept/Oct if winter weeds are a big problem, but probably not). Would recommend using different pre herbicides every application, but if you tank mix Gallery and something else, don't worry about this. There are many other pre herbicides - these are just a few that I like!
5. Preemergence in the nursery We have been using Ronstar to prevent weed growth in our containers and it has been working quite well as long as we apply it before weed growth occurs. However, we don't always beat the weed emergence. I have heard that Snapshot is a preemergent which will burn down existing weeds in a container and then act as a preemergent afterwards. Is this accurate and effective?
If you are trying to beat back early growth, you need something with oxyfluorfen. Granular products that are available with oxyfluorfen are: OH2, Rout, Regal O-O, and Showcase. Broadstar will also do this, but doesn't contain oxyfluorfen. In containers, you need to reapply every 60 to 90 days (4 to 6 applications a year - winter months you might be able to go 90 days or more!) I also have this information available in the 2006 Georgia Pest Management Handbook (Commercial Edition). Snapshot and Ronstar don't have very good ability to control weeds after they have emerged - although both are excellent herbicides if used before weed germination.
In addition to the knowledge and advice provided by Dr. Woodward and Dr. Czarnota, I also spoke with many of the veteran growers around the state. And not surprisingly much of what they discussed with me was in direct agreement with the information above (I was cautioned that the use of Surflan and another pre herbicide named Princip may cause trees to become cork screwed).
Recently I purchased the 2006 Georgia Pest Management Handbook (commercial edition) and I won't lie to you . . . the book is thick! However, there is an entire section on Christmas trees and there is also excellent information on several other crops that many of us grow including pumpkins and blueberries. The book cost is $20 and the order form can be found at http://www.ent.uga.edu/pmh. The handbook provides information on all of the chemicals listed above including uses and flow rates.
Now that I have come to the realization that I will quite likely need some of the chemicals listed above to maintain a healthy crop of container and field grown trees I have gone ahead and priced many of them. The dealership that I received quotes from is Southern States (I spoke with Danny 770-532-6291) and is located in Gainesville. Below I listed prices and quantities of several chemicals that are available through Southern States (nope . . . there's no commission in it for me!). At the very minimum this may give you an idea of what these materials could cost in your area.
Pre herbicides in the field:
Gallery: 1 pound $167.70
Barricade: 1 gallon $318
Pennant Magnum: 1 gallon $212.20
Surflan: 2.5 gallons $247
Solicam: 10 pounds $218.25
Pre herbicides in containers:
1. Ronstar: 50 pounds $93.90
2. Showcase 50 pounds $102.70
Fungicides:
Kocide 2000: 15 pounds $51.50 (also sold in 3 pound bags)
Fore: 1.5 pounds $50.40
Quadris: 1 gallon $287.50
Admittedly I was initially intimidated by pretty much all of these prices! However, now that I have realized how far these concentrated quantities will go and how long they will last before I have to repurchase them the numbers have become less overwhelming.
Let me be sure to clarify with all of you that have taken the time to read this entirely too long e-mail that most of this information is new to me and I have little to no experience with these chemicals. If any of you have some insight with handling the situations mentioned at the beginning of this e-mail I would love to hear your perspective. Have a great day and good luck this year!
Sincerely,
Andy Kinsey
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