Weed seeds” include the seeds of all plants gener- ally recognized as weeds within this state, and includes the seeds of prohibited and restricted noxious weeds as deter- mined by regulations adopted by the department.
Weed seeds, diseases and pests are killed as a result of the high temperature.
Weed seeds” shall include the seeds of all plants other than other crop seed and pure seed and shall include noxious-weed seeds.SECTION HISTORYPL 1969, c.
Noxious Weed seeds could be carried to and from the Proposed Action by construction equipment and transport vehicles.
Weed seeds and fruits that disseminate through wind possess special organs to keep them afloat.
Noxious weeds are prohibited from commercial seed, and their removal may require additional cleaning steps and loss of good quality seed in the process.
A significant imbalance exists in the amount of data on the diversity of particular wild species. The most comprehensive information is available about the species most interesting for breeding or for those considered as noxious weeds . A. sterilis has been the most often analyzed. One thousand five A. sterilis accessions from 23 countries preserved in the United States collection were analyzed with isozymes ( Phillips et al., 1993 ). Based on these data, Turkey was identified as the center of diversity of this germplasm collection. Turkish and Lebanese accessions showed the highest polymorphism, and the highest probability of containing unique genotypes was found in populations from Iran, Turkey, Iraq, and Lebanon. One hundred seventy-three accessions from the same gene bank, which had originated from eight countries of Africa and Southwest Asia, were also analyzed by restriction fragment length polymorphism (RFLP) ( Goffreda et al., 1992 ). The highest variation was identified among accessions originating from Iran and the lowest among those collected in Ethiopia. These results also indicated large genetic divergence of the Iran–Iraq accessions from the other regional collections surveyed. Once again 24 accessions gathered in the United States collection were subjected to comparative analysis by random amplified polymorphic DNA (RAPD) and isozymes technique. Zhou et al. (1999) evaluated the similarity of A. sterilis genotypes with diverse origins by RAPD too. Fu et al. (2007) assessed the genetic diversity of 369 A. sterilis accessions, from the 26 countries, preserved in the Canadian collection using the SSR system. ISSR markers analysis was conducted by Paczos-Grzęda et al. (2009) in order to determine the genetic diversity of 27 A. sterilis genotypes used in crossing with A. sativa. Value of genetic similarity indices testify to the high diversity of the designated set of accessions.
It is important to recognize that plant invasion is not just a United States or developed world problem. China has a long history, as does the United States, of introducing plants that someone deems to be potentially beneficial or perhaps just interesting. With its fairly recent and expanding international trade, intentional introductions are now joined by unintentional introductions that may not be beneficial because they are unknown and unexpected. Diamond (2005, p. 367) notes that in Shanghai harbor, one of many international Chinese harbors, “between 1986 and 1990, examination of imported materials carried by 349 ships from 30 countries revealed as contaminants almost 200 species of foreign weeds. Weeds and poisonous grass species have spread at the expense of high-quality grass species “over as much as 90% of China's grasslands” (Diamond, p. 366).
Weeds from the Orobanchaceae family are serious parasitic pests in crop production, e.g., Striga asiatica (L.) Kuntze, Striga hermonthica (Del.) Benth and S. aspera (Wild) Benth ( Rodenburg and Johnson, 2009 ). There is another group of weeds that produce chemicals that are detrimental to crops such as P. hysterophorus with its allelopathic effect but Desmodium spp. has allelopathic effect on other weeds, e.g., S. asiatica and S. hermonthica. Allelopathic effect of Desmodium spp. to Striga spp. has been utilized to develop a push–pull technology, which is a climate smart weed management technology ( Khan et al., 2011; Pickett et al., 2014 ). Under the push and pull technologies the weeds are used to interfere with germination of parasitic weeds to enhance crop growth and they provide competition useful for increasing growth.
Table 6.1 . Critical growth stages when weeding makes the most positive influence of crop production