Parasitic weeds

In Hawaii, Faust (2000) contended that the hair sheep, St Croix breed, not only has a unique resistance to parasitic worms but also keeps the coffee, avocado and citrus orchards free of tropical weeds. 

Strigol is a natural product with unusually strong properties as a germination stimulant for parasitic weeds of the genera Striga (witchweed) and Orobanche (broomrape). 

Much remains to be accomplished in the separation, isolation, and identification of both naturally occurring and synthetic bioactive materials effective in the germination of parasitic weed seeds. Structure-activity studies suffer from the lack of separation of isomers in most synthetic samples. Strigol is an important tool in basic studies on the effect of chemicals on seed germination, but it is highly unlikely that the compound will meet practical field... 

Proceedings of the Second Symposium on Parasitic Weeds. North Carolina State University, Raleigh, N. C., 1979. 

Solarization effects on weed population was hypothesized to be due to different mechanisms, such as changes in cell metabolism and ultrastructure (Singla et al. 1997), microbial parasitism on seeds weakened by sublethal temperatures, seed dormancy interruption by raising temperatures, and foliar scorching of weeds under the plastic mulch (Egley 1990 Katan and DeVay 1991). Moreover, imbalance of 02 and C02 or release of acetaldehyde, ethylene, and other volatile toxic compounds were also reported as accounting for weed death (Rubin and Benjamin 1984 Gamliel et al. 2000). 

Sauerbom J, Linke KH, Saxena MC, Koch W (1989) Solarization a physical control method for weeds and parasitic plants (Orobanche spp.) in Mediterranean agriculture. Weed Res 29 391-397... 

Allelopathy found hopeful utilization in plant protection against parasite weeds. The main world parasitic species are the witchweeds (Striga spp.), broomrapes (Orobanche spp.), and eventually dodder (Cuscuta spp.). Witchweeds and broom-rapes attack many economically important crops especially throughout the semi-arid regions. Early detection of parasitic weed infestation and protection is difficult because of the growth habit of a root parasite and huge production of dust-like seeds viable up to 20 years (Kebreab and Murdoch 1999). 

A chemical stimulant, a root exudate, is required to break seed dormancy of a parasitic weed and initiate seed germination. Upon receiving a signal for germination, a radicle emerges from the seed coat. However, an additional chemical signal is needed for the radicle to penetrate host roots and form a haustorium. Therefore several plants can serve as catch crops or trap crops for the reduction of the parasitic weed seed bank in infested soil. 

Table 14.3 Examples of effective parasitic weed control...

These days, allelopathic plants as catch crops or trap crops found utilization in plant protection of tropical regions against parasitic weeds. They do not eliminate the parasite completely but decrease the seed bank in the soil. Other applications of allelopathy for weed control include the use of plant residues as a natural herbicide agent, e.g., water extracts, pellets, flours, by-products of crop processing, etc. The strategies for use of volatile compounds as soil fumigants are developed. 

Dawson JH (1987) Cuscuta (Convolvulaceae) and its control. In Weber HC, Forstreuter W (eds) Parasitic flowering plants, Philipps-Universitat, Marburg, Germany, pp 137-149 De Almeida FS (1985) Effect of some winter mulches on the soil weed infestation. In Proceedings of 2nd Brighton Crop Protection Conference - Weeds, British Crop Protection Council, London, pp 651-659... 

What to do Control weeds in susceptible crops remove or mow weedy areas adjacent to garden beds. Attract native parasitic wasps and flies by planting small-flowered plants. 

MacQueen, M. "Proceedings of the Third Sympos1 urn on Parasitic Weeds" Parker, C. Musselman, L. J. Polhill, R. 

It has been established that DXS catalyzes the first step in a novel biosynthetic pathway leading to isoprenoids in bacteria, algae, plant chloroplasts, and in the malaria parasite, Plasmodium falciparum. DXS is therefore a novel target for antibiotics, herbicides, or anti-malarials. Our work has contributed to an understanding of the novel biosynthetic pathway and could further open new perspectives on how to inhibit the pathway in pathogenic bacteria, protists, or weeds. 

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