Why is it important?
Weeds are serious yield and profit robbers. Not only do they compete against crops and ornamental plants for moisture and nutrients, but they can also harbor insect and disease pests which then move to your valuable plants.
Basic Weed Identification
What is a weed?
A weed is a plant in an undesirable location. Corn can be a plant in your cornfield, but in a bean field, it is normally considered a weed. Weeds can rob your desired plants of nutrients, moisture, and sunlight, causing lower production and profits. Weeds can also harbor insects and diseases and contaminate grain.
Steps to Avoid Weeds
- Grow healthy crops. Weeds grow in spots not occupied by desirable plants. Give your crop or ornamental plants the best possible start by carefully testing and correcting soil fertility, pH, salinity, and compaction as needed. Early planting and narrow rows can give your plantings a head start on weeds. Once the desirable plant canopy has filled out, weeds have a much tougher time competing for sunlight, water, and nutrients.
- Monitor regularly and use weed maps. Always check fields after treatment and determine which, if any, weeds have escaped treatment and why.
- Identify weeds very carefully. Many herbicides are species-specific and will not affect against the wrong weeds.
- Learn weed life cycles. When does the seed germinate? When will new seed heads form? When is the weed most susceptible to cultivation or herbicide treatment? The answers to these questions can make a difference between successful weed control and yield loss.
- Use action thresholds to make treatment decisions. Do not treat unless your return will more than cover the cost of the treatment. Check with your local Cooperative Extension agent or private consultant for action thresholds for your region.
- Know that accurate timing can make the difference between success and failure. Many herbicides have a narrow window of maximum effectiveness. Whichever control method you choose, be sure to take action before weeds go to seed. Always carefully remove seeds from clothing and equipment when moving from an infested area to a clean field.
How to Identify Different Weeds
Weeds can be broken into two main categories: Broadleaves and grasses. Broadleaf weeds are identified by those features that make them different than grasses. For seedlings, this primarily is done by examining the cotyledon or seed leaf. Cotyledons are the first pair of leaves to emerge. The shape of the cotyledon is a way to initially identify different broadleaf plants. Plants can have linear, oblong, oval, round, or butterfly-shaped cotyledons and different extremes of each.
The next step in the identification of broadleaves is to notice other features of the plant. Do the true leaves attach on the stems alternately or opposite of each other? How do the leaves attach to the petiole? Are the leaves waxy or hairy, thick or thin? What type of root system does the plant have? A single taproot, tuber, or rhizome can help distinguish between two similar plants.
Grasses can be a little more challenging to identify. The characteristics that make each different can be very hard to see with the naked eye. Nearly all of the characteristics of grasses are found in the collar region. This is the area of the blade that bends off of the stem. In this area, you need to look for ligules and whether they are absent, smooth, jagged, small, or large. Whether or not the area is hairy, how long the hair is, and how much hair is found are all important. If a plant has auricles or a triangular-shaped stem, this is a quick way to identify the plant easily.
All of these things need to be noted to correctly identify any weed. Once you know all of the features of the weed species you would like to identify, there are many books, pamphlets, and charts to compare your findings. Weeds can vary from region to region, so make sure your reference covers all of the weeds that can be found in your area. Otherwise, you might not find the plant you want to identify listed.
What tools are needed?
Very little is needed to help identify weeds. A general-purpose magnifier will help reduce eye strain while studying grass collar regions. The most important tool is a good reference guide to weed identification. Preen offers an easy-to-use guide. Check it out here.
How to Effectively Control Problem Weeds
Treatment Options
Herbicides are only one of many weapons in your arsenal against weeds. Others are:
- Cultivation. Manual or mechanical cultivation is often the best option, especially for post-herbicide spot cleanup. Early in the season, careful cleanup is especially important to prevent late-season weed population explosions.
Well-timed cultivation and herbicide use can sometimes allow reduced herbicide use and costs. Shallow cultivation (one to two inches deep) is often best to avoid breaking a previously applied herbicide barrier, bringing up dormant weed seeds, or disrupting desirable plant roots. - Crop rotation. Changing the plants you grow in any one location from season to season can help overall weed management. Weeds that thrive alongside one crop can be suppressed by planting a different crop that is antagonistic to that weed the following season. Crop rotation also aids in herbicide resistance management.
- Mowing. Properly timed mowing of weeds before they form seeds can be an excellent management tool in pasture and rangeland, row middles, field borders, etc.
- Sanitation. Don't allow a thriving weed patch to "seed" your planting areas. Use appropriate controls along ditch banks, fence rows, driveways, and other areas that may provide sources of weed seeds. Be sure straw or hay mulch is free of weed seeds when used.
- Flaming. This is useful as a spot treatment or a large-scale treatment. Fieldwide burning is still used in some crops, such as asparagus. More commonly, propane-fed burners are mounted on mechanical cultivators or toolbars.
It's not necessary to fully burn weeds to kill them. A sure test is to press your thumb into a flamed weed leaf. If the impression of your thumb remains, weed cell walls will be disrupted, and the weed will die. Flaming also kills insects and does not risk runoff, water contamination, or residue or result in carryover effects on non-target crops. - Biological control. Living plants, animals, or even insects can often be used to manage weeds. Techniques such as using cover crop residues to suppress specific weeds, grazing with livestock, or encouraging or applying insect and disease pests can suppress a number of weed species.
- Mulches, barriers, and ground covers. The goal is to suppress weeds by preventing seeds from germinating and growing. Options include a killed-sod barrier, fabric, plastic, or foil mulches, straw mulch, or a cover or inter-planted crop of a non-competing plant, such as Sudan grass.
- Herbicides. When herbicide application is the best option, be sure to follow label instructions carefully. Consider treating hot spots rather than the entire field. Investigate application technology that "targets" weeds and does not treat bare ground or crop plants. Try alternative herbicides such as soaps, oils, or biologicals where appropriate.
NOTE: Always check Cooperative Extension or private consultant recommendations for your crop and region.
How to Scout for Weeds
- Make a weed map. Sketch an outline of the weeds' locations, noting field boundaries, landmarks, fences, waterways, and buildings. Make copies of this map for future use.
- Walk the field. Spend some time walking through each quarter of the field, noting on your map the location and relative numbers of each weed type you observe.
- Rank the weeds. Rank weeds from most to least abundant. Your ranking can be used to determine which weeds are over the action threshold. Select control measures which will eliminate the most important weed pests.
Complete this process in the late season when walking through the crop is still possible. Use the data you collect to plan weed management actions for next season.
Repeat the process early the next season, and use the information to make last-minute adjustments to your plan. Save all your maps to compare weed problems from year to year and improve long-term planning.
Pasture Weed Management
Scouting, accurate identification, knowledge of life cycles, and using thresholds are the keys to weed management in pastures and rangeland. Learn which plants can be toxic to your livestock and move them up on the priority list for management.
Mowing can be especially effective in keeping broadleaf and annual weeds below thresholds. Don't move livestock directly from a weedy pasture to a clean pasture, or they will likely carry weed seeds with them. Be sure any hay brought into pastures is free of weed seeds and noxious plants.
Do's and Don'ts of Weed Identification
Do
- Take the time to properly identify weeds.
- Get a good reference guide to help identify the different species.
- Keep records of weed problems to compare from year to year.
Don't
- Forget about other control methods in addition to chemical controls.
- Remember plants cannot be identified as seedlings.
- Only scout for weeds once in the season
Top Weed Control Products from Gemplers
Gemplers carries a wide variety of products that can help you combat weeds in your landscape, garden, and greenhouse.
- Weed Barrier Paper can be used to combat weeds before they start. Use this product when you are planting a new crop. Simply spread out the paper and transplant seedlings during season, and the paper will stop the weeds from sprouting. Once the season is over, the weed barrier paper can be tilled into the soil.
- The Red Dragon Weed Burner Kit is the best in the business for burning off weeds effectively and efficiently.
- For smaller plots and landscapes, Gemplers carries a selection of cultivation tools that make weeding easier.
- Triple Threat Broadleaf Herbicide is the product you need for taking care of weeds, but is gentle on grasses.
