20 articles tagged "Weed Management".

Scientific names: Erigeron canadensis or Conyza canadensis Horseweed, also known as marestail, fleabane, or colt’s tail, is a common and troublesome weed throughout North America due to its high seed production, wind dissemination, lack of seed dormancy, and adaptability to dry and moist soil. Moreover, horseweed populations have shown to be resistant to Group 2 (ALS-inhibitors) and Group 9 (glyphosate) herbicides. Historically, horseweed has had many uses. Native Americans in the Zuni River Valley of New Mexico inserted crushed horseweed flowers into their nostrils to stimulate sneezing and help relieve rhinitis. Other Native Americans used the leaves to treat sore throat and dysentery. Dried plants were scattered in animal bedding to prevent fleas. Young leaves were used as a flavoring substitute for tarragon. Identification: Seedling is a basal rosette. Cotyledons are oval, and young basal leaves are egg-shaped with toothed margins. After the stem elongates, basal leaves deteriorate. Stem leaves[Read More…]


Scientific name: Chenopodium album Common lambsquarters is originally from Eurasia. It is an aggressive weed, adapted to grow vigorously in many different climates and soils, and has been able to establish worldwide. In North America it was once grown as a vegetable crop. In Asia and Africa, it is still cultivated to use as a spinach alternative or as animal feed. Identification: Cotyledons are linear to lanceolate. The leaf surfaces and stems of the youngest seedlings are covered with clear, shiny granules that turn into a white powdery coating (Figures 1 and 2). Common lambsquarters with a purplish powdery coating can also be found (Figure 3). Margins on young leaves are entire or have few teeth. Mature leaves are alternate, often broadly triangular with irregular, usually shallow toothed margins and are pale gray-green in color. They often fold upward along the central vein. Stems are vertically grooved with red, purple[Read More…]


If they have not already, your early season residual herbicides will soon run out of steam. Depending on the crop and production system, you may soon lose the ability to cultivate row middles. Now what? For many vegetable crops, managing emerged weeds is difficult with few postemergence herbicide options. This article will focus on cucurbit crops, but many of the principles translate to other crops as well. General Guidelines: Do not rely solely on postemergence options: I know hindsight is 20/20, but if you have more escaped weeds than you’d like this year, now is the time to start evaluating changes for next season. With most crops, a weed control program that relies entirely on managing weeds after they’ve emerged is a formula for failure. Consider combining postemergence herbicides with other management tactics including stale seedbed, plastic mulch, mechanical cultivation, cover crops, or residual (AKA soil-applied) herbicides. Always “start clean”.[Read More…]


Dicamba has been in the headlines the last two weeks.  In case you’ve missed it, here are the highlights: On June 3 the United States Court of Appeals for the Ninth Circuit ruled against the Environmental Protection Agency and its 2018 registration of over-the-top dicamba products Xtend, Engenia, and FeXapan and vacated their registrations. The suit did not include a fourth over-the-top dicamba herbicide, Tavium. The ruling can be viewed here: https://cdn.ca9.uscourts.gov/datastore/opinions/2020/06/03/19-70115.pdf Between June 3 and June 8, state regulators across the middle part of the country were forced to interpret the ruling, with some choosing to ban the products and others continuing to allow them. Extension row crop weed scientists across the county pulled together recommendations for managing broadleaf weeds without dicamba, including Purdue (https://extension.entm.purdue.edu/newsletters/pestandcrop/article/well-now-what-do-i-do-if-i-cant-spray-a-dicamba-product-in-xtend-soybean/). On June 8 the EPA issued a cancellation order for the three dicamba products, but allowed applicators to use products in their possession. The[Read More…]


Waterhemp is prevalent in the Midwest and the Great Plain States. It became a significant agricultural weed in 1990s. Before then it was present in crop fields, but it is presumed that it rarely reached economic infestations. It became a problem in Indiana by 1998. Waterhemp is best adapted where less aggressive tillage is practiced. The adoption of conservation tillage might have aided in its widespread establishment. Also, the use of herbicides in the late 1980s coincided with the spread of waterhemp, and it quickly became resistant to Group 2 herbicides (ALS-inhibitors). Today waterhemp populations have been documented to also have resistance to Groups 5 (Photosystem II-inhibitors), 9 (glyphosate), 14 (PPO-inhibitors) and 27 (HPPD-inhibitors or “bleachers”). Identification: At the seedling stage, it can be difficult to distinguish waterhemp from other pigweeds. Cotyledons are egg- to ovate-shaped (Figure 1). When plants are larger, waterhemp can be differentiated because it has no[Read More…]


Dual Magnum® is registered for use in numerous row crops and specialty crops in the state of Indiana. While some vegetable crops (beans, peas, potatoes, pumpkins, rhubarb, and tomatoes) appear on the specimen or national label (Section 3 label), most do not. Numerous specialty crops that do not appear on the specimen label are included in the 24(c) special local need label. But finding the 24(c) label, which was recently updated in 2019, can be difficult. The new 24(c) label is available on the National Pesticide Information Retrieval System web site: http://npirspublic.ceris.purdue.edu/state/state_menu.aspx?state=IN. To find it, type “SLN IN” and “130003” in the first two boxes for “EPA Registration Number” and click the search button. The product report will show “DUAL MAGNUM – TRANSPLANTED BELL PEPPERS.” Click on the ALLSTAR symbol. On the page that opens, click on the Company Label ID number “IN0816048DA0319.” This will open a pdf of the label. The[Read More…]


Figure 2. Young giant ragweed seedling with three-lobed leaves. Photo by Stephen Meyers.

Scientific name:  Ambrosia trifida Giant ragweed is a weed member of the sunflower family (Asteraceae) and native to the United States. It is extremely competitive and difficult to control in broadleaf crops. It emerges as early as March and continues to germinate through spring and early summer. Controlling giant ragweed during summer is not only important for crops but also for human health because giant ragweed pollen can be an allergen for some people. Identification: Seed leaves of giant ragweed are large and oblong. The first pair of true leaves are often unlobed and lance shaped (Figure 1). Subsequent leaves are large and three- or five-lobed with serrated margins (Figures 2 and 3). Growth habit: Erect summer annual, reaching 3 to 16 ft (Figure 4). Grows at approximately twice the rate of most annual weeds, and is likely to be 8 to 12 inches tall when other weeds are 3[Read More…]


Figure 1. Overwintered Canada thistle shoots emerge in April in central Indiana.

Spring is here and with it comes the emergence of weeds- especially problematic perennials like Canada thistle (Figure 1). Below is some information about Canada thistle and methods to manage it. Keep in mind two things: 1) many of these strategies will work for other perennial weeds, and 2) management of perennial weeds often requires persistence and an integrated approach. Scientific name: Cirsium arvense (L.) Scop. Legal status: Canada thistle is considered a noxious weed in 46 states including Indiana. It is a non-native invasive species from Europe, and landowners with Canada thistle on their property are obligated to take measures to control it. Growth habit: Deep-rooted and colony-forming perennial. Plants form a low-growing rosette in the spring prior to bolting in mid-to-late May. Reproduction: By seeds carried up to 1/2 mile by wind and through adventitious shoots that develop from root buds. Control: Often multiple types of control measures[Read More…]


In the October 2019 issue of the Vegetable Crops Hotline, I referenced the new regulatory changes to herbicides containing the active ingredient paraquat. One of the new requirements is for closed system packaging. To quote the Environmental Protection Agency (EPA): “New closed-system packaging (is) designed to prevent transfer or removal of the pesticide except directly into proper application equipment. This will prevent spills, mixing or pouring the pesticide into other containers or other actions that could lead to paraquat exposure.” Earlier this month I had a chance to see one of the ways chemical companies are complying with the new regulation. At the Weed Science Society of American Annual Meeting, Syngenta presented their closed packaging and transfer system. It contains a closed system cap that cannot be removed or opened by hand (Figures 1 and 2). In order to remove herbicide from the container, the cap must be connected to an[Read More…]


As the production season winds down there are two weed-related news items that producers should be aware of: New Requirements for Users of Paraquat Herbicide.  Paraquat dichloride is the active ingredient in products such as Gramoxone®, Devour®, Cyclone®, and Quik-Quat®. Earlier this year the Environmental Protection Agency (EPA) announced the following changes to paraquat requirements: Additional labeling requirements and the distribution of supplemental warning materials at the point-of-purchase are now required and highlight the toxicity and risks associated with paraquat products. Paraquat use is now restricted to certified applicators only. No longer can an uncertified handler use paraquat, even under the direct supervision of a certified applicator. Specialized, approved paraquat training is now required for anyone who will mix, load, apply, or handle paraquat. New, closed-system packaging will be used to prevent the transfer or removal of paraquat into unapproved containers or equipment. These changes were sparked by unnecessary deaths[Read More…]


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