Establishment of common milkweed (Asclepias syriaca) in corn, soybean, and wheat

Abstract

The establishment of common milkweed in corn, soybean, and wheat and rotations of corn-soybean and soybean-wheat was determined in field studies at Rosemount and Morris, MN. Common milkweed seedling density 115 d after initial seedling emergence was 500, 15,000, and 31,300 seedlings ha−1in corn, soybean, and wheat, respectively, in 1990; 500, 7,300, and 15,600 in 1991 at Rosemount and 2,900, 26,500, and 37,000 in 1990; and 2,200, 6,700, and 8,100 in 1991 at Morris in the year of seedling establishment. Common milkweed seedling defoliation by mon arch butterfly larva was 1,31, and 0% at Rosemount and 20, 78, and 0% at Morris for corn, soybean, and wheat, respectively. In the 2nd and 3rd rotational years, corn-soybean rotations had fewer shoots ha−1115 d after shoot emergence than soybean wheat rotations. Seedling densities 115 d after initial seedling emergence were greater in corn-soybean rotations where soybean rather than corn was the rotational crop and in soybean-wheat rotations where wheat rather than soybean was the rotational crop immediately following common milkweed seeding. Conventional tillage treatments had lower common milkweed shoot density than conservation tillage in all years of all rotations except in the initial count, when soybean was the first rotational crop in which shoot density was greater in conventional than in conservation tillage treatments. Cyanazine, imazethapyr, or bromoxynil applications in corn, soybean, or wheat rotational crops, respectively, reduced common milkweed shoot density.

Effects of Corn Plants and Corn Pollen on Monarch Butterfly (Lepidoptera: Danaidae) Oviposition Behavior

“…and J.J.O., unpublished data; J.E.L. et al, unpublished data), which conÞrms earlier reports that milkweed plants in cornÞelds are colonized and fed on by monarchs (Yenish et al 1997).…”

“…The monarch butterßy, Danaus plexippus (L.), is of particular interest because it is a specialist on milkweed (Asclepiadaceae), a secondary succession plant that frequently occurs in and around the edges of cornÞelds (Yenish et al 1997;Bhowmik 1994). Recent work shows that monarch larvae fed leaves of Asclepias curassavica L. dusted with Bt-corn pollen suffered higher mortality than larvae reared on leaves with untransformed corn pollen or leaves without pollen (Losey et al 1999, Jesse andObrycki 2000).…”

Modeling Investments in Seeds, Clonal Offspring, and Translocation in a Clonal Plant

“…However, high levels of genetic diversity in clonal plant populations indicate that seedlings do establish (Ellstrand and Rouse 1987, Alpert et al 1993, Eriksson and Bremer 1993, Widen et al 1994, Schläpfer and Fischer 1998 and that sexual offspring may be important to genet fitness (Bell 1985, Stearns 1985, Kondrashov 1988, Ladle 1992, Lynch et al 1993). In addition, seeds that colonize new habitats may contribute disproportionately to genet fitness; the success of clonal plants as weeds (Lapham 1985, Santos et al 1997, Smeda et al 1997, Yenish et al 1997 and invasive species (Smith 1985, Cudding and Stone 1990, Room 1990, Soukupova 1992, Schmid and Weiner 1993, Philbrick and Les 1996 suggests that when colonization is successful, colossal payoffs ensue. Finally, in some cases ramets may incur few or no costs from producing seeds (Reekie and Bazzaz 1987, Wikberg et al 1994.…”

Field deposition of Bt transgenic corn pollen: lethal effects on the monarch butterfly

“…from early June to mid September (Urquhart 1960;Borkin 1982). Milkweed is commonly found in corn fields and adjacent non-cultivated habitats where it is a food plant for monarch larvae (Cramer and Burnside 1982;Bhowmik 1994;Yenish et al 1997;Hartzler and Buhler 2000;L.C. Hansen, unpublished data).…”