Male and female fertility, seed germination, and progeny fertility were used to determine cultivar fertility in species of Lythrum. One short-, 11 mid-, and six long-styled cultivars were included in this study. Duplicates of several cultivars from different nurseries and three unknown cultivars from Minnesota gardens were also collected. Plants from 17 Minnesota and one Wisconsin population of L. salicaria served as fertile male and/or female testers. Pollen stainability (usually 100%) showed low levels of male gamete abortion. Pollen size within and among anther type varied widely; possible 2n gametes were present in primarily the short- and mid-anther morphs. Seed production per capsule from legitimate cross-pollinations, using cultivars as male parents with Minnesota or Wisconsin female testers, averaged 48 ± 36 across style morphs. Cultivars differed as males, as did anther morphs. With female fertility tests, seed set per capsule ranged from zero to 152 and averaged 54 ± 40 in legitimate pollinations (i.e., pollinations between stamen and styles of the same length). Seed set for other crosses showed similar trends. Only `Morden Gleam' produced no seed with all legitimate pollinations, although illegitimate selfs or interspecific crosses produced seed. Seed from legitimate crosses of L. salicaria × cultivars had 30% to 100% germination. Common male and female parents within each legitimate crossing group were not significantly different. This study showed that the cultivars are highly fertile when used as male or female parents with wild purple loosestrife, native species (L. alatum Pursh.), or other cultivars. Thus, cultivars grown in gardens could serve as pollen or seed sources for the continued spread of purple loosestrife. The implications of cultivar fertility, especially interspecific F1 hybrids, is discussed in relation to the spread of noxious weeds in wetlands.
Neil O. Anderson and Peter D. Ascher
Gladis M. Zinati
A question/answer discussion session was conducted at the conclusion of the workshop “Pest Management During Transition to Organic Farming Systems”. The following categories were used to summarize the discussion: 1) questions and answers related to cultural and biological practices and their effects under various climatic conditions, 2) recommendations for pest management, and 3) future research needs. While many tactics are available, selecting and adopting the most suitable approach depends on soil conditions of the land, location, and the availability of the resources at affordable prices. Definitely, more research studies are needed on 1) weed seed banks under various cultural practices at different regions, 2) relationships between soil nutrients, and pest control, and 3) approaches to increase profitability of organic production during the transition period.
E. Darmo and M.S. Strefeler
Purple loosestrife populations have developed into a highly aggressive and invasive weed in several Northern states (MN, NY, NJ etc.). How these populations arose is a key question in developing control strategies. Therefore, we initiated a study to elucidate the origin and genetic structure of invasive populations using isozyme analysis. The germplasm examined included invasive populations found in MN, NY, NJ, WI and MD, populations of Lythrum alatum, populations of L. virgatum and 22 cultivars of L. salicaria, the suspected progenitor of the invasive populations.
Unique isozyme patterns for most cultivars was observed and these were consistently indicative of that clone over repeated sampling. Clones of putative “salicaria” origin could not be distinguish from those of putative “virgatum” origin.Significant isozyme polymorphism was observed within and among the 26 Lythrum populations. Indicating that isozymes can be an important tool in studies on the structure and evolution of invasive loosestrife populations.
To date, our isozyme analysis indicates that L. salicaria and L. virgatum are not distinct species. It appears that the decision by the MN Department of Agriculture to add all horticultural lines to the noxious weeds list regardless of origin was a prudent decision.
Nancy P. Cain
The effect of site preparation on the establishment of a perennial wildflower and a prairie mixture was compared on five highway rights-of-way in southwestern, central, and northern Ontario. The site preparation treatments of the existing perennial cover were: 1) control, 2) broadcast glyphosate herbicide application, or 3) broadcast glyphosate herbicide application plus cultivation. The sites were mown prior to drill seeding. The experiments were planted in 1990 and 1992 and evaluated for total cover, cover of seeded species, and noxious weeds. The wildflower mixture established more rapidly than the prairie mixture. The wildflower seed mixture established better with either site preparation treatment compared to the control regardless of the type of vegetation present prior to planting. By 3 years after treatment the original vegetation had reinvaded to a greater degree with the herbicide treatment, indicating that the herbicide plus cultivation provided better control of the original perennial cover. Four years after seeding, neither seed mixture had established in the control, indicating that control of perennial vegetation was crucial for establishment of these seed mixtures on existing sites.
John M. Ruter
. 1:1–5. Harvard Univ., Boston Natural Resources Conservation Service 2006 Invasive and noxious weeds. 28 June 2016. < http://plants.usda.gov/java/invasiveOne?startChar=C >. Raulston, J.C. Grant, G. 1994 Trumpetvines ( Campsis ) for landscape use. Proc
Lyn A. Gettys
-specific insects or pathogens as a means to manage invasive species. This strategy has been used with varying levels of success to reduce populations of a variety of noxious weeds, including waterhyacinth ( Tipping et al., 2014 ), alligatorweed [ Alternanthera
Manoj G. Kulkarni, Glendon D. Ascough, and Johannes Van Staden
In traditional farming systems, the burning of fields was a common practice that alleviated the infestation of noxious weeds and insects ( Altieri, 1993 ). Apparently, smoke as a consequence of burning is being used directly or indirectly by
Andrew J. Hephner, Tyler Cooper, Leslie L. Beck, and Gerald M. Henry
Weed Technol. 13 172 175 Parsons, W.T. Cuthbertson, E.G. 2001 Khakiweed, p. 158–159. In: Noxious weeds of Australia. CSIRO Pub., Collingwood, Victoria, Australia Sholedice, F. Renz, M. 2006 Khakiweed. New Mexico State Univ. O & T Guide W-8 Cooperative
Andrew J. Hephner, Tyler Cooper, Leslie L. Beck, and Gerald M. Henry
704 710 Parsons, W.T. Cuthbertson, E.G. 2001 Khaki weed, p. 158–159. In: Noxious weeds of Australia. CSIRO Pub., Collingwood, Victoria, Australia. Senseman, S.A. Armbrust, K. 2007 Herbicide handbook. Weed Science Society of America, Lawrence, KS. p. 94
Kelly J. Vining, Ryan N. Contreras, Martin Ranik, and Steven H. Strauss
remain economically important to the nursery industry and local communities. For these plants to remain marketable, sterile forms may need to be developed. Of the genera included in Table 1 , those with species listed as noxious weeds and/or banned in