Jeanine Arana

5 articles by this author

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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…]

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…]

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…]