Re: Cold weather & pests
This is the most comprehensive article I found so far.
It's over 10 years old, but gives a good idea of what to
expect and what not.....
Greetings from Belgium!!
Wim Van Loock
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A Realistic Look at Mycorrhizae
R. M. Augé
UT Ornamental Horticulture
Tennessee Flower Growers Newsletter 4(5): 2-3. 1990.
Over the past few years there has been interest in using beneficial soil
microorganisms in horticulture. This interest continues to grow, as there is
no doubt that certain soil fungi and bacteria can help plants scavenge
nutrients and possible water when these elements are in short supply.
Mycorrhizal fungi have been investigated as growth and quality enhancers on
a number of horticultural crops. Reported benefits to plants include larger
size and enhanced foliar quality, more profuse and earlier flowering, and
greater resistance to disease and drought and salt stress.
What are Mycorrhizal fungi?
Mycorrhiza literally means "fungus root". The term was coined a century ago
to describe the association of plant roots and certain fungi. This
association is referred to as symbiotic, which means both the plant and the
fungus benefit from the relationship.
There are several types of mycorrhizal fungi. Orchids and plants such as
azaleas and rhododendrons have their own particular types, but those which
colonize most floricultural commodities are referred to as
vesicular-arbuscular (VA) fungi (which are the kind described in this
article).
Mycorrhizal fungi have been colonizing the root systems of plants
essentially ever since plants have grown on land. The fungus extends from
the root like tiny pipes into the soil or potting medium, greatly enhancing
the absorptive surface area of root systems. Because of the use of
fungicides, high rates of fertilization and pasteurized, soilless,
"fungus-less" media, many of our important greenhouse crops do not have the
opportunity to form this symbiotic association in the greenhouse. Scientists
are now studying the effects of reintroducing this beneficial soil organism
to greenhouse cropping situations. Reports range from lukewarm to fantastic.
Plant benefits
What is the "mycorrhizal advantage" to a plant? The most consistent and
dramatic improvement in host plant growth results from the ability of the
fungus to increase phosphorus uptake. This effect is most conspicuous in
situations where the soil phosphorus level is low enough to limit growth.
Increases in growth on the order of five-to-10-and even 40-fold are possible
in these situations.
Specific studies using mycorrhizal fungi found:
In greenhouse trials, heliotrope and fuchsia inoculated with
mycorrhizal fungi produced more flowers and bloomed earlier than
non-inoculated plants. Inoculated unrooted cuttings of chrysanthemum,
fuchsia and benjamin fig produced more roots that noninoculated cuttings.
Inoculation of poinsettia cuttings in the mist bed increased cutting
survival, leaf retention and subsequent plant growth. In another study,
mycorrhizal fungi slightly reduced the incidence of Pythium root rot in
poinsettia.
Growth has been increased by mycorrhizal symbiosis in several
studies. Examples include the following: Easter lily, marigold, geranium,
bell pepper, rose, petunias and chrysanthemum.
'Samantha' rose plants inoculated with mycorrhizal fungi were more
resistant to drought that noninoculated plants. Plants appeared to maximize
soil water extraction and harden to drought more effectively when their
roots were colonized by mycorrhizal fungi. Leaf conductance (a measure of
stomatal openness and thus of a plant's ability to photosynthesize) was
about twice as great during drought in those roses colonized by the
mycorrhizal fungus Glomus intraradices. Leaf water potential (a measure of
plant water stress) also indicated this fungus was helping the plant during
drought.
In most (but not all) cases, these benefits are the result of improved plant
nutrition; mycorrhizal plants performed much better when compared with
undernourished nonmycorrhizal plants.
Free benefits?
Mycorrhizal fungi do come with a price tag, though it is usually not a large
one. In exchange for possible positive effects on host plant growth, the
fungus takes from the plant the carbon compounds (food) it requires. It has
been estimated that approximately 10 to 25 percent of the carbohydrates made
by the plant's foliage ultimately wind up nourishing the mycorrhizae. In
some instances, particularly during the fungal establishment phase in young
seedlings or cuttings, growth of mycorrhizal plants may lag slightly behind
that of plants which do not have to "feed" a fungal partner. This reduction
of growth by mycorrhizal fungi does not always occur, however, and is
usually short-lived when it does occur. Growth of mycorrhizal plants in
phosphorus-deficient media typically rapidly matches and then usually
greatly exceeds that of nonmycorrhizal plants.
Should I use them?
Would a grower notice an effect from using mycorrhizal fungi? If you were
late in watering, it's possible that those plants with mycorrhizae might not
wilt as soon. Definitely, if phosphorus levels in your medium became
deficient for any length of time, the mycorrhizal plants would fare much
better. Since these "ifs" seldom occur in a well-managed greenhouse, it
would probably not be worth the effort to most growers at this time to
inoculate plants.
Would a consumer realize any extra benefit from possessing a mycorrhizal
product? Maybe. During shipping and marketing, most plants do not receive
the ideal conditions they received in the greenhouse. Under stress, a
mycorrhizal product is likely to outperform its nonmycorrhizal counterpart
and will often look better longer when fertilization and regular water
cease. However, as many of our greenhouse crops are annuals, this
competitive "mycorrhizal edge" may not become evident in a single season.
How to inoculate?
Ease in application is of course important to growers. Because mycorrhizal
fungi are alive, there is a bit more involved than simply adding it to the
medium at potting time, but not much more. We are pretty much in the
"grow-your-own" phase right now with mycorrhizal fungi. However, a Utah firm
(NPI Nutri-link, 417 Wakara Way, Salt Lake City, Utah 84108) markets a
commercially available inoculum (a batch of mycorrhizal fungi propagules
which gets the symbiosis going). This inoculum can simply be measured out
and worked into a potting mix. Thus, it is easy to inoculate plants at
seeding. At transplanting, the fungus moves into the new container or plug
along with the colonized roots. Those conditions which promote good root
growth generally encourage growth of the mycorrhizal fungi, with the
exception of phosphorus fertilization. For many, if not most crops, the
amount of phosphorus applied to plants must be limited to about one-third to
one-tenth of that normally applied. Higher rates of phosphorus often
discourage colonization of the fungi.
Future use
Is it likely that growers of the future will realize significant economic
benefits from these fungi? There is probably no compelling reason for the
greenhouse manager of today to worry about mycorrhizal symbiosis, but as our
resources diminish in the future and the costs of fertilizers escalate, it
is likely that these soil fungi will prove to be of economic advantage. An
additional consideration may be environmental quality. As restrictions
tighten concerning the contamination of runoff water, for instance, a soil
amendment which allows growers to apply less fertilizer would result in
cleaner leachate. Even right now, though, to a grower who is concerned about
survival and quality of his/her product after it leaves the greenhouse,
mycorrhizal fungi might give a competitive edge to some plants.
More research is required, but the indications are that certain mycorrhizal
fungi can assist plants growing under saline conditions. The amount of salt
a plant can tolerate is limited, and mycorrhizal fungi may extend somewhat
the range a plant can endure. As water quality becomes more an more of a
concern to growers, both because clean water is getting harder to find and
because we are becoming increasingly aware of the effects our irrigation
water has on our crops, growers may begin to use this benefit of mycorrhizal
symbiosis.
In summary
Many benefits of mycorrhizal symbiosis in horticultural production systems
have been suggested and researched: reduced time to flowering, enhanced
rooting of cuttings, resistance to water and salt stress, resilience to
heavy metal and other pollutant toxicity, reduction of transplant shock and
incidence of disease. Yet a real, calculable, economic advantage remains
elusive, especially when plants are pampered as they are in most
greenhouses.
The future, though, may likely see a typical grower incorporating a
mycorrhizal inoculum into greenhouse media. As is becomes increasingly vital
that production be both in equilibrium with our resources and
environmentally compatible, mycorrhizal fungi may very well find significant
roles. For now, at least, they continue to be an interesting and hopeful
target of horticultural research.
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----- Oorspronkelijk bericht -----
Van: "andy wolf" <farm@eznet.net>
Aan: <pumpkins@mallorn.com>
Verzonden: maandag 8 januari 2001 5:40
Onderwerp: Re: Cold weather & pests
> well, I'll add what I can. I tried it this past season, and wasn't
> overwhelmed with results. Could have been many things, such as the
weather,
> genetics, soil, ect... I'm waiting to hear from a few other growers out
> there I know have tried it, maybe we can figure some things out. I'm
> planning on trying it again next season on only one plant, just to see
what
> happens again. Word of caution, if you want the good stuff, it's
expensive.
> Most should stick with the everyday good gardening practices until we see
> significant results from this stuff. I did do a lot of research on this
> mycorrhizal fungi on the internet before buying, and it's possibilities
are
> impressive, but not tested on competition AG's extensively enough by us.
If
> you want to check it out, here are some links:
>
> http://mycorrhiza.ag.utk.edu/
> http://dmsylvia.ifas.ufl.edu/
> http://www.cof.orst.edu/cof/teach/for442/sec8/more3.htm
> http://www.treemail.nl/eurobio/inform/mycart.htm
> http://www.soilfoodweb.com/index.html
>
> These were just what i had bookmarked, I'm sure there's a lot of new ones
> since i started looking.
>
> Andy Wolf
> best: 535* uow
> farm@eznet.net
> http://home.eznet.net/~farm
>
>
>
>
> -----Original Message-----
> From: BILL J. SADOWSKI <BSADOWSKI@CompuServe.COM>
> To: INTERNET:pumpkins@mallorn.com <pumpkins@mallorn.com>
> Date: Sunday, January 07, 2001 10:49 PM
> Subject: Re: Cold weather & pests
>
>
> >Message text written by INTERNET:pumpkins@mallorn.com
> >>on the subject of Endomycorrhizal fungi. Fascinating subject....<
> >
> >I deal with another person on another garden chat line. She is a PhD
from
> >Berkley University and speaks highly of the fungi.........which is a
growth
> >stimulant for the roots? I have some info on this, but I have to find
it.
> > It is something worth trying. Let me research my files.
> >
> >Bill Sadowski......finally hit over 30 degrees in Ohio
> >
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> >
>
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