2017 News You Can Use

May 2017

How Do You Select the Appropriate Herbicide to Control Weeds in Your Area?

Image of herbicide product
Herbicide product (Photo: Leslie Beck, NMSU)
Image of dandelion in turf
Dandelion weed in turfgrass area (Photo: Leslie Beck, NMSU)

How Do You Select the Appropriate Herbicide to Control Weeds in Your Area? Always Consider the Labeled Active Ingredients of each Product Rather than the Trade Name

Spring is in the air, which is also the time for focusing on the management of weeds germinating within lawns that are coming out of winter dormancy. If you are located in the southern regions of New Mexico you've probably had summer annual weeds germinating for a few months now. However, both daytime and nighttime temperatures are still within the ideal range to prompt the continued germination of these summer weeds over the next couple of months. In contrast, the more northern portions of the state are probably starting to notice the summer annual weeds germinating within the past few weeks which will also continue through the spring and summer months. Regardless of your location, this time of year is a great reminder of how important it is to read herbicide product labels, both synthetic and organic, prior to every application.

When trying to select the right herbicide for your weed management needs at your local garden center, there are two names at the top of every label to take into consideration. One is the trade name, also known as the brand name. Every manufacturer has a trade name for their products which are the registered trademark name for their specific product. A great example is the trade name 'Roundup' which is given by the company to products that they manufacture which traditionally contained the herbicide glyphosate in some measurable quantity. Another product with the trade name 'Eliminator: Weed and Grass Killer' is manufactured by a different company, but it contains the same herbicide. The second, and most important, name to consider when choosing or applying an herbicide is the active ingredient. The active ingredient (a.i.) is the chemical or chemicals in a synthetic or organic herbicide product that is responsible for the injury which ultimately controls the target weed. In the case of the two products mentioned above,'Roundup' and 'Eliminator' the active ingredient that actually controls the weed is glyphosate, which is available under numerous different trade names.

It is important at all times when purchasing, and most certainly when applying, any synthetic or organic herbicide to pay special attention to the active ingredients within the product. Remember, it is these active ingredients that will be responsible for the control of your target weed. A great example of the importance of reading the label, and paying more attention to the active ingredients over the company trade name, can be observed in a new product on the shelves called 'Roundup for Lawns'. Since 'Roundup' is so commonly associated with the active ingredient glyphosate, it is possible that this new product may be applied incorrectly if the label directions are not followed. 'Roundup for Lawns' does not contain glyphosate, which injures both grasses and broadleaf plants' instead the active ingredients could include: MCPA, quinclorac, dicamba, sulfentrazone, and / or penoxsulam. These active ingredients are used to specifically injure broadleaf weeds while causing minimal damage to the surrounding desirable turfgrass. There are multiple readily-available herbicide products that contain combinations of these active ingredients, such as 'Weed-B-Gon', 'Spectracide', and 'Touch Up'. If the directions specifically contained within that product's label are not followed when making an application, not only will it not result in the expected injury or control of your weeds, these active ingredients may also have the potential to cause unintended injury to surrounding desirable vegetation (i.e. trees, shrubs, horticulture plants, gardens).

Why trying to choose the most appropriate herbicide for your weed control needs, it is important to remember that the label is the law! To avoid unintentional injury and ensure a safe and effective application, it is imperative to always, always, always read and follow the directions / restrictions specified within the label.

Disclaimer: Trade / brand names appearing in publications are for information purposes only. The author and New Mexico State University assume no liability resulting from their use. No endorsement is intended, nor is criticism implied of similar products not mentioned. By law, persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.

For more information, please contact: Leslie Beck, Extension Weed Specialist

March 2017

Alfalfa Weevil Alert for 2017

Image of damage on alfalfa caused by alfalfa weevil
Alfalfa weevil damage and larvae (Photo: Mark Marsalis, NMSU)
Image of an alfalfa weevil adult
Adult alfalfa weevil (photo: Patricia Monk, NMSU

Alfalfa Weevil Alert - It looks like 2017 will likely be the worst year for alfalfa weevil in over 20 years. Some fields are actually going to have 3 insecticide applications before the first cut. Southern counties have been seeing threshold levels of weevil larvae for 3 weeks while central NM (e.g. Valencia Co. and I-40 corridor) have been seeing threshold levels this past week. Even Dona Ana County, which often has few fields treated relative to other counties, is seeing many fields with damage.

Often our two species of parasitoids keep alfalfa weevil larvae below threshold in the Mesilla Valley. Other areas of NM have lower levels of control due to only having one species of parasitoid, and sometimes low numbers of that parasitoid. There are also likely some differences in behavior that might affect control since we have three different weevil strains in New Mexico.

Not all fields are seeing high populations. Our own fields in Artesia are still below threshold and are likely to remain so given high populations of beneficials, but we thought it was worth warning you since in many areas weevils are often not enough of a problem to warrant close attention. Don't wait for damage to be obvious from the pickup. Some years it works but this year that strategy might result in an unhappy surprise if high populations of small larvae seem to overnight grow big enough to do some real damage.

Effective management strategies and more photos can be found in the NMSU Extension Publication Guide: A-338: Alfalfa Weevil Control Options in NM.

Insecticides: In addition to those insecticides listed in the publication, Steward is recommended by many consultants. It has quick knock down, a short cutting restriction and is softer on beneficials than the other insecticide options. Although the residual activity might be a bit shorter than some other products, the impact from one application and conservation of beneficials might allow natural enemies to keep weevils below threshold after one application. Technical representatives recommend Steward 6 oz / A plus Silken 4 oz / A or some other organosilicone surfactant using at least 5 gallons per acre. With chemigation use 0.1-0.2 inches of water / Acre. A surfactant is not needed with chemigation. If there are adults you can add a pyrethroid like Mustang Max but if beneficials are abundant consider just using Steward. If a second treatment is necessary you can go back 7-10 days later with 5.1 oz of Steward and 4 oz of Silken or switch to a product with a different mode of action. I was told by a consultant in eastern NM that Lorsban which has been recommended for adults is not performing well there. Organic Growers can suppress weevil populations with Entrust 2-4 oz / A. It is a Dow Agrosciences Spinosad product.

Disclaimer: Trade / brand names appearing in publications are for information purposes only. The author and New Mexico State University assume no liability resulting from their use. No endorsement is intended, nor is criticism implied of similar products not mentioned. By law, persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.

For more information, please contact: Jane Pierce, ASC Artesia, Mark Marsalis, ASC Los Lunas, Leonard Lauriault, ASC Tucumcari or Carol Sutherland, NMSU / NMDA Las Cruces