top of page

October 2011


 It’s time for my annual reminder about a persistent problem, Coryneum blight.  If you found blight marked fruit in your bins this year, starting your clean-up program this fall will go a long way towards a more profitable crop next year.  The first autumn rains can start the spread of the disease.  Infection can take place in the dormant season if proper moisture and temperature conditions occur.  Spores, spread primarily by splashing water, can remain viable several months.  The key to control is PREVENTION.  This is especially true if you’re farming with organic methods.  Establishing a protective barrier with copper is vital to keep Coryneum from germinating and spreading.  Good sprayer coverage is important! The disease usually starts low inside the tree where moisture persists, so be sure and target this area.  The most common application timing is at 50% leaf fall.  It’s not necessary to wait for that to happen.  How aggressive you need to be with rates and applications depends on if you need to clean up a problem or are just performing routine maintenance.   A  fieldman  friend in Washington state mentioned that he has his growers add a sticker to all their Fall copper sprays.  He said it's easy to still see the copper on the tree in February. The following quote comes from the 1996 Colorado Tree Fruits crop management guide.   “Once established in an orchard, Coryneum blight is difficult to eradicate.  Infected buds and twigs may produce spores for 2 to 3 years.  A conscientious annual program of chemical control with particular emphasis on fall sprays and removal of dead wood is necessary over a 3-year period to alleviate the problem.  Summer sprays also may be needed until control has been obtained.”  


 Zinc Sulfate crystals will not dissolve completely in water at pH 7.5 or above. They do not dissolve very well until the pH is below 6. If you experience any white precipitate in your sprayer screens when using zinc sulfate, add or increase the amount of buffer (phosphoric acid) you are using.

I came across this quote the other day, “If you never change your mind, why have one?”  That strikes home with a lot of us and our farming programs.  When was the last time you thought through your farming “habits”  and made a few changes?   Insects, weeds and employees can all develop resistance to the same old same old year after year.


The basic ingredient in most generic glyphosate products is the same. Monsanto manufactures most of the technical grade glyphosate used in the United States for the formulation of generic products by other suppliers. What may be different and undetectable on the label is the amount and quality of the surfactants in the formulation. Additional surfactant (Bio 90) is relatively inexpensive and will go a long way toward ensuring reliable, consistent performance.

Tim Smith, an extension agent with WSU, put together a demonstration project using “low volume” Roundup applications.  He used a 1:1 ratio of Roundup and surfactant. For every quart of Roundup in the mix there was also a quart of surfactant. He later reduced the surfactant to 1 pint for every quart of Roundup with little or no reduction in weed control.  What Tim found out however, was that the concentration of the glyphosate in the mix is very important. For average, to kill weeds (annual grasses, young broad leaf weeds, etc) an adequate concentration is one quart in 20 gallons of water plus the surfactant. For difficult to kill weeds (bindweed, clovers, mature lambsquarter, mallow, etc)  2 quarts of glyphosate per 20 gallons of water is needed.

Glyphosate is not active in the soil because it quickly binds to the positively charged soil particles. Some of this same action may happen in the spray tank when the water you use is not “pure”. (It may look clean and clear and still be “hard” water.) You have two options; either add a deionizing compound such as ammonium sulfate or add more glyphosate to compensate for the loss. The AMS is cheaper…..

All glyphosate products work best when applied in concentrated, low volume applications.

Due to the possibility of injury, I make it a practice in my own orchard to not use Glyphosate or Amine 4 until the fourth leaf.  If you use these products in young blocks,  make every effort  to not contact the green bark.

Tim Smith did his work at 20 gallons per acre. Roundup PowerMax is formulated to work best at 12 to 15 gallons of water per acre. It does not perform as well when applied at 50 gallons per acre.  Using a higher rate of water per acre may make you feel better because it’s easier to see the spray pattern and the weed looks wetter, but it’s costing you money. And in most cases the weeds won’t be any deader after two weeks. In fact they will die slower with a low concentration, high volume application than they will when a high concentration, low volume application is used.


Weed control in the tree row is much more than cosmetic. There is a measurable benefit to tree growth from the reduced competition for water and nutrients. Mouse populations are lower when there is little or no weed cover for them in the tree row  The most economical time to control weeds, regardless of the material that you choose, is in the fall before leaf fall or with the leaves raked away, up until the ground is frozen.  I once did an early December application in Cedaredge.  The next spring you could see to the row where I had sprayed. This application will control the fall germinating annuals that otherwise will require treatment in the spring.  Your VERY, VERY busy spring!  It is always easier and cheaper to prevent a problem than to cure it.


The constant factors in safe and effective weed control are calibration, uniform coverage and timely incorporation of residual materials into the soil by irrigation or rain. Some residual herbicides can injure trees if the application rate is higher than the immobilizing ability of the soil and they are carried deep enough into the soil to contact tree roots. In other words, light soils are more risky than heavy soils. I know that a number of you use backpack or 4-wheeler tanks to spray weeds with contact herbicides.  Using a hand wand to apply residual materials is risky at best.  It’s next to impossible to get a uniform, proper amount applied.  Some labels do not allow for application with a hand wand. Check to be sure your nozzle style and configuration delivers a uniform pattern on the soil surface. Account for the overlap that you will have in the center of the tree row. Don’t double the actual rate of applied material in this area by hanging extra nozzles or increasing nozzle size on the end of the boom.


Remove large weeds that prevent uniform spray coverage of the soil surface, the ‘shadow’ from existing weeds will be where your weed control will fail first next year. Do not spray over the top of a heavy leaf drop; many of the small germinating annuals will be protected from the contact materials in the mix. If a windstorm moves the leaves before the next good rain, your residual material may be gone also. The cleaner the soil surface at the time of application, the more effective the material will be. Organic matter on the soil surface will bind up some of the material before it can get into the soil. If you still have irrigation water available, incorporate the material soon after application with an irrigation of  ¼” - ½” . This will ensure no weather degradation and allow the residual control material to bind close to the soil surface where it is most effective. A long irrigation set will drive the material deeper into the soil, resulting in a weaker weed barrier and possible damage of young trees.


When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it.  If it comes out of the ground easily, it is a valuable plant.  ~Author Unknown


I’ve listed a few of the materials that I have experience with and have a comfort level using in our area.  Once again, PLEASE give me a call so we can discuss a program for your orchard, block by block.  Residual herbicides are a safe, great management tool when used properly.  In all cases read the label carefully for crop and soil limitations, a material that can safely be used on your apples or pears may seriously injure your stone fruit or grapes.


Residual materials

Simazine is available in liquid.  It is labeled for Apples, Pears, Grapes and Sour Cherries only. This was one of the first soil residual materials to be widely used and is still quite effective on annual broad leaf weeds with limited control of annual grasses at a comparatively low cost. It is best tank mixed at a reduced rate with another material that is highly rated on grasses if they are present. Simazine can leach into the root zone and damage trees when used on light soils, do not use on trees that have been in the orchard less than 12 months.


Diuron (Karmex) is available in a dry flowable (80 WDG). It is labeled on Apples and Pears that have been in the orchard for more than one year, except not for use on full dwarf rootstocks, it may be used on Peaches that are 2 years old if used at a reduced rate. This is another one of the first residual materials to be commonly used and is also quite effective against most annual broad leaf weeds with slightly more control of annual grasses and some established perennials than Princep. It is best tank mixed at a reduced rate with another material that is highly rated on annual grasses if they are present. Diuron can cause tree damage on light soils; Granny Smith is quite sensitive.


Oryzalin 4 AS (Surflan) is labeled on all fruit crops and may be applied after the first irrigation or rain has settled the soil after planting. Oryzalin controls weeds by disrupting the growth process during seed germination, it will not control any established weeds and is one of the safest effective materials that we have available for bearing trees. Oryzalin must be tank mixed with either glyphosate or Gramoxone if there are existing weeds that must be controlled. Tank mixing with Simazine or Diuron at reduced rates where possible broadens the spectrum of weeds that will be controlled.


Casaron 4G is labeled on Apple, Pear and Cherry. The material is very persistent in the soil; careful calibration is needed to avoid leaf symptoms on the tree the following year. Casaron provides a broad spectrum of weed control in both annual and established perennials when used at the maximum rate. Do not apply in the fall until the soil has cooled, just before the first snowfall is perfect timing. Casaron applied on warm soil must have irrigation following immediately to be effective.


Goal is labeled on all tree fruits for control of annual broad leaf weeds, tank mix with other materials for control of grasses. Goal must be applied after harvest and before bud swell the following spring to avoid possible damage to the foliage, hardened wood is tolerant. There is no tree age limitation in the label. Goal provides good residual control of common Groundsel.


Prowl, Prowl H2O may be applied as soon as the ground has been settled after planting. It provides pre-emergence control of most grasses and some broad leaf weeds, it will not control existing weeds, the mode of action is similar to Surflan/Oryzalin.  Tank mixes with Gramoxone or Glyphosate where appropriate must be used to control existing weed growth.


“My reading of history convinces me that most bad government results from too much government.”  Thomas Jefferson


In November of 2010, the US EPA announced that all uses of endosulfan, an insecticide used somewhat commonly in insect management in vegetables and fruit, is to end in the near future. Dates for which use of endosulfan becomes illegal vary among crops, but for many crops, the date is July 31, 2012.  Application of endosulfan becomes illegal as of July 31, 2012, for apricots, plums and prunes, stone fruits and tart cherry. Use of endosulfan is allowed until July 31, 2015, on apples.  For the long list of crops where the endosulfan label expires, it is important to note that after this date endosulfan may NOT be used on these crops despite crop listings on the label of products purchased in the past.... July 31, 2012, is not far off.


Similarly, Guthion (azinphosmethyl), has been the subject of a phase-out program for a few years. In 2012,  1.5 pound of the active ingredient may be applied per acre per season on apples and pears, 3/4 pound of active ingredient on cherries.  It is essential that growers recognize that 2012 is the LAST year that Guthion / azinphosmethyl may be used on apples, pears and cherries.  Left-over Guthion cannot be used legally in 2013.


Orchards  are a form of autobiography.  ~Sydney Eddison


Every year I get calls about trees losing their leaves early.  Perhaps the culprit is dry soil conditions. I came across the following relating to trees that have been drought stressed in the fall.  I am not a fan of drying out trees post harvest (or anytime).  This quote also speaks to the mechanics behind a fall urea program.  According to "Fundamentals of Fruit Production" by Garner, Bradford and Hooker, drought can cause stress problems and maybe growth irregularities. The following is a quote from this text: "It is a common observation that trees suffering from drought in late summer and early fall shed their foliage early. The function of the foliage during late summer and fall is to manufacture food materials which for the most part, are stored through the winter for use in tissue building in the spring. Premature defoliation, from drought or any other cause, therefore is likely to result in a check of growth the following spring through cutting down the available reserves."


The most important question I can ask this month is “How’d we do?” Grand Mesa Discount works hard to provide the most cost effective products, service and expertise possible. If you think we fell short of that goal, PLEASE call me and bend my ear a bit.  

bottom of page