Certified Crop Advisors’ Perceptions of Giant Ragweed (Ambrosia trifida) Distribution, Herbicide Resistance, and Management in the Corn Belt

Abstract

Also known as great ragweed, horseweed, horse-cane, richweed, bitterweed, bloodweed, blood ragweed, tall ragweed, palmate ragweed. Classification and Description:Giant ragweed is an erect summer annual that is native to the U.S. and it can be commonly found throughout many parts of the country. It can reach heights from 3 to more than 16 feet. Giant ragweed is a member of the Asteraceae, or sunflower, family of plants. Seedling giant ragweed has a purple hypocotyl and cotyledons that are round to oblong and thick. The first true leaves do not have lobes but do have toothed margins and are lanceolate (long and thin) in shape. Subsequent leaves are opposite, blades simple, hairy and large (4-10 inches long and up to 8 inches wide). Leaves occur on petioles and most often have three prominent lanceolate-shaped lobes, although they can occasionally have five lobes. The lobes originate from the same point (palmate). These large, three-lobed leaves make giant ragweed a very distinctive plant. Leaf margins are serrated. Stems can be reddish and are erect, branching above, rough and sometimes hairy. Stems can be reddish. Giant ragweed has separate male and female flowers. Male flowers occur in slender racemes (columns) in the upper terminals. Female flowers occur in clusters in leaf axils below the male flowers. All flowers are small and greenish-yellow. Fruit is a large, black, woody achene that is egg-shaped, except the widest part is towards the end instead of in the middle. The widest end has one single short beak and other shorter projections, which make it resemble a crown. Seed is small and enclosed in the fruit. Reproduction is by seeds. Weed Status and Injury:Giant ragweed can readily be found along fence rows of agronomic crop fields and pastures in Tennessee. Increasingly, it is becoming established in agronomic crop fields. Herbicides commonly used on agronomic crops, like glyphosate, only provide partial control, and so giant ragweed is becoming an increasing problem in row crops. It can also be found in pastures, low woods and young Seedling giant ragweedGiant ragweed in a fence row W119Programs in agriculture and natural resources, 4-H youth development, family and consumer sciences, and resource development. University of Tennessee Institute of Agriculture, U.S. Department of Agriculture and county governments cooperating. UT Extension provides equal opportunities in programs and employment.

Economic Performance of Crop Rotations in the Presence of Herbicide‐Resistant Giant Ragweed

“…There is a need to compare the economic net return and financial risk of crop rotations common to the midwestern United States, a region where herbicide-resistant giant ragweed is widespread (Regnier et al, 2016). The objectives were to evaluate the crop yield and the economic net return for multiple crop rotations and determine the most risk-averse crops and crop rotations using stochastic dominance analysis.…”

Differential antioxidant enzyme activity in rapid‐response glyphosate‐resistant Ambrosia trifida

“…Giant ragweed ( Ambrosia trifida L.) is a highly competitive weed in corn ( Zea mays L.) and soybean [ Glycine max (L.) Merr.] production and, in a recent survey of Certified Crop Advisors throughout the Corn Belt, is listed among the most pernicious weeds . Crop grain yield losses attributable to A. trifida interference have been reported as greater than those attributable to any other summer annual weed .…”

Physiological and molecular analysis of glyphosate resistance in non‐rapid response Ambrosia trifida from Wisconsin

“…Ambrosia trifida is one of the most difficult weeds to manage in the Midwestern United States and has expanded as a crop weed in its native range of North America over the last three decades . The ability of A. trifida to germinate early in the growing season and grow rapidly, combined with seed size polymorphism and embryo dormancy that allow for prolonged emergence, contributes to the difficulty of its effective and season‐long management.…”

“…Evolved herbicide resistance has also contributed to the difficulty of managing A. trifida . Glyphosate resistance has been confirmed in A. trifida populations in 12 states in the U.S. and in Ontario, Canada .…”

“…However, multiple resistance to both glyphosate and ALS inhibitors has been found in three states in the U.S. and in Ontario. Notably, a recent survey of certified crop advisors in the Corn Belt concluded that respondents perceived more areas to be affected by herbicide resistance in A. trifida than have been documented officially, particularly resistance to ALS inhibitors, and multiple resistance to glyphosate and ALS inhibitors …”