[compost_tea] phytopthora root ro

From: dloring3 <dloring3_at_cox.net>
Date: Mon, 20 Oct 2003 02:15:34 -0000

For anyone working on Phytopthora

Dave

http://www.citrusresearch.com/publications.asp

Suppressive Soils

Much has been written about suppressive soils with respect to avocado
root rot (Borst, 1983; Broadbent and Baker, 1974;

Downer, 1998; Halsall, 1982, Ko and Shiroma, 1989; Pegg et al., 1982;
Turner and Menge, 1994). Avocado root rot

suppressive soils occur naturally. For example, natural rainforest
habitats were suppressive to avocado root rot and a

complex method called the Ashburner method was created to duplicate
the suppressive rainforest soils (Broadbent and

Baker, 1974). The Ashburner method consisted of cover cropping,
applications of manure, dolomite, and super-phosphate,

and the addition of organic matter. Today the method has been
modified to provide only the key ingredients,

which are organic mulches and gypsum. High populations of bacteria
and actinomycetes (Broadbent and Baker, 1974) or

cellulose and lignin degraders (Downer, 1998) are naturally
stimulated to create the suppressive soils. As we learn more

about the factors that create suppressive soils, this term will lose
its mystique and we will speak of specific suppressive

factors. Certain bacteria, such as some species of Pseudomonas and
Chromobacterium violaceum, are required to stimu-late

sporangial production of P. cinnamomi, while other bacteria are
inhibitory (Erwin and Ribeiro, 1996; Zentmyer,

1980). Specifically, microorganisms such as Myrothecium roridum,
Trichoderma harzianum, Epiccocum purpurascens,

Catenaria anguillae, Humicola fuscoatra, Anguillospora
pseudolongissma, Hypochytrium catenoides, Myrothecium ver-rucaria,

Streptomyces griseoalbus, Micromonospora carbonacea, Streptomyces
violascens, and Ceraceomyces tessulatus

have been shown to be inhibitory to P. cinnamomi via competition,
antibiosis, or parasitism (Downer, 1998, Erwin and

Ribeiro, 1996). The complex community structure of microorganisms
like these is undoubtedly responsible for the fact

that some soils are suppressive while others are not. Zentmyer (1980)
draws attention to the fact that populations of P.

cinnamomi usually drop off dramatically after the first wave of root
rot occurs. He feels this may occur as parasites of P.

cinnamomi and other antagonistic microorganisms invade and make the
soil more suppressive.

 



------------------------ Yahoo! Groups Sponsor ---------------------~-->
Rent DVDs Online - Over 14,500 titles.
No Late Fees & Free Shipping.
Try Netflix for FREE!
http://us.click.yahoo.com/Tq9otC/XP.FAA/3jkFAA/0PSxlB/TM
---------------------------------------------------------------------~->

To unsubscribe from this group, send an email to:
compost_tea-unsubscribe_at_yahoogroups.com

 

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/




Received on Mon Oct 20 2003 - 00:16:49 EDT

This archive was generated by hypermail 2.3.0 : Tue Feb 07 2012 - 14:14:49 EST