FAQ: Weed Control
FAQ: Weed Control
- A mixture of Treflan plus Sencor can be applied and incorporated before tree planting.
- The exception is when planting non-rooted cuttings – they will not root if Treflan (trifluralin) is used in the soil.
- Linuron/Lorox can be applied as a late fall, dormant application, to provide weed control in shelterbelts/tree plantings. This treatment requires moisture for incorporation and effectiveness.
- For weed control in plantings of hardwood species Casoron is very effective.
- Casoron and some trifluralin products are available in granular form. It is important that granular trifluralin be mechanically incorporated.
- When using Casoron, the tree species listing, on the label, must be closely adhered to.
- Glyphosate can be applied as a directed or shrouded spray for the control of quack grass in tree plantings.
- Poast Ultra can be applied as an over-the-top spray at the early stage of quack grass growth. Repeated applications may be required to provide control.
- Lontrel can be applied over-the-top, in plantings of villosa lilac, acute willow, Colorado spruce, white spruce, buffaloberry and choke cherry for control of perennial thistles. For these and other tree species, glyphosate can be used.
- However, use only as a directed or shrouded spray.
- The possibility exists for trees to suffer severe injury or mortality as a result of exposure to drift of preharvest glyphosate.
- Symptoms may not be noticed immediately; the full extent of the damage usually becomes apparent the following spring.
- NOTE: Glyphosate can kill anything that is green – including target and non-target plants.
- Many chemicals, including trifluralin products such as Treflan and Rival, or glyphosate, are registered for use around your shelterbelts for weed control.
- However, even these chemicals can cause damage if used incorrectly or applied near species they are not registered for.
- Method of application can also affect how your trees will perform after chemicals are used nearby.
- Regular field sprayers release the chemical fairly close to the ground minimizing the risk of drift damage.
- High clearance sprayers increase the risk of drift and, therefore, the risk of damage to your trees. This can be particularly serious when these sprayers are used to apply non selective chemicals like glyphosate.
- When applying glyphosate as a pre-harvest treatment, caution should be used around your shelterbelts and following the 15 m minimum setback from your trees is well advised.
- Spray on a near calm day or when the breeze is blowing away from your trees.
For aerial application of glyphosate the need for caution is even greater.
- It takes only one mistake to end years of hard work.
- If you are considering the aerial application, make sure your applicator obeys the minimum 100 m setback regulations for planted shelterbelts and other trees/natural bluffs and riparian areas.
- With the higher application height the risk of drift is greater than with traditional spray methods.
- Ensuring regulations are followed and caution is used when spraying will minimize the risk of destroying shelterbelts and natural bluffs.
- The application of any lawn herbicide product containing ‘dicamba’ (Banvel, Dyvel, Par 3, Premium 3-way, Rustler, Target) has potential to severely damage or kill spruce trees growing near lawns.
- People use dicamba products to control dandelions in their lawns (weed ‘n feed products) but they can accidentally harm or kill their conifers.
- Dicamba is highly water soluble and very persistent; it remains active in the soil for several years.
- The conifers are not harmed by drift of the product but instead are damaged when herbicide is taken up by the roots of the plant – roots of trees are very large and extend out into lawn areas which are well beyond the drip line of the tree.
- Use caution when applying herbicides in the root zone.
- After planting non-rooted cuttings, linuron can be applied over-the-top, before the cuttings begin active growth.
- Linuron requires precipitation for effectiveness.
- Non-rooted cuttings will not grow in soil treated with Trifluralin.
- Glyphosate uptake by tree/shrub suckers can be very damaging and possibly lethal to the parent plant.
- If vegetation is required for weed control and/or soil stabilization, then plant a non-competitive grass (sheep’s fescue) between established tree rows.
- Caragana produce large quantities of viable seed, they do not sucker, but the seed can become a potential weed problem.
- Where practical/possible, watering to the saturation point, over an extended period of time, will kill caragana.
- The herbicide Lontrel has also shown effectiveness for control.
- Removal by large equipment is effective but costly.
- Plastic mulch is an effective weed barrier. It is a black, embossed polyethylene fabric with a max thickness of 2.7 mm that contains a UV inhibitor. It is available in rolls of 450m (1500 ft) in length.
- It requires specialized equipment, called a plastic mulch applicator, to install over newly planted seedlings.
- Plastic mulch prevents weeds from growing around the trees and competing for moisture, nutrients and light.
- The plastic also helps retain moisture in the soil, which will help improve tree survival and growth.
- In a study conducted at the Agroforestry Development Centre comparing trees in plastic mulch versus no mulch, it was found that growth of caragana increased by 100 % and survival improved by 18% when trees were grown under plastic mulch. In the same study, growth of green ash increased 27% and choke cherry by 8% when plastic mulch was used.
- Plant bare root stock (trees) first.
- Next, apply the plastic directly over the newly planted tree seedlings. This must be done before the seedlings leaf out to minimize damage.
- The plastic mulch applicator operator makes a small mark in the plastic at the location of each seedling.
- The trees are then pulled through the plastic via a small hole which can be made in the plastic at each mark.