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Strawberry Plasticulture – August 27, 2003
Situation Report on Diseased Plants
Vol 4, No. 39 August 27, 2003
Barclay Poling and Frank Louws, NC State
In brief: Over the last 3 days we have diagnosed anthracnose in several
strawberry plug-production facilities. The problem does not appear
to be restricted to one or a few operations but may be more widespread.
To date, we have characterized what appears to be the Colletotrichum
acutatum strain. This strain is typically associated with the anthracnose
fruit rot and less commonly with plant collapse. In a plug production
facility, the problem appears to start as hot spots. Plants in such
hot spots show a general unthriftiness, remain stunted and are slightly
discolored compared to neighboring symptomless plants. Such plants
may resemble symptoms due to lack of water or high salts injury. As
the disease progresses, one or more leaves wilt and the base of the
leaf (petiole) becomes brown and wet. Advanced stages of the disease
result in plant collapse. Botrytis crown rot and Pythium or Rhizoctonia
crown rot may have similar symptoms. Therefore, it is essential diseased
plants be properly diagnosed. For the diagnostician, incubate infected
tissue for 24 hrs and observe for characteristic spores and fungal
structures such as sterile setae. In some cases, we have isolated the
pathogen.
If a grower has such a hotspot in the greenhouse, contact your local
Cooperative Extension Agent and send samples to the Plant Disease and
Insect Clinic according to the clinic instructions (http://www.ces.ncsu.edu/depts/ent/clinic/Submit/submit.htm).
This is very discouraging: There is nothing an
individual grower could have done or should have done to prevent
it - it is a plant source
problem. A similar problem was encountered last year with plant material
propagated in Ontario from California stock plants in the spring
and summer of 2002. Apparently, one of the main nursery suppliers
in Ontario
to the North Carolina industry was unable to secure adequate micropropagated-certified
planting stocks for planting this past spring, and California purple
tags were (regrettably) utilized once again this season.
One difference from last year is the earliness of these outbreaks
in Virginia and North Carolina plug propagation facilities - the
earliest
symptoms of anthracnose were observed at about the end of the 3rd
week in the plug trays in 2002, but this year we are seeing it in
the second
week.
The best solution is to find an alternative source of plants. Some
supplies of tips and fresh dug plants from sources that have no history
of anthracnose (e.g. nursery plants from NC Certified Program and
Prince Edward Isle, Canada) are available presently. See Jeff Harzog's
and
Ron Cottle's note below (under plant supply update - below). However,
it may be very difficult to locate an alternative supplier of tips
or plugs at this late date. Most of the NC Certified plants were
sold-out in late July.
Stick with planting dates: In many instances, growers who received
infected material elected to find alternative plant supplies last
year, but these efforts can also result in serious planting delays.
From
a recent report submitted to the US-EPA as part of the Southeastern
Strawberry Consortium’s CUE application for methyl bromide
extension, it was noted that a very significant yield reduction
occurred at Clayton
Central Crops in 2003 related to later plantings in October 2002
(Table 1). Thus, it is paramount for growers to stick with their
fumigation
and planting schedules.
Table 1. Plant-back trial with Telone C-35 and Iodomethane 98:2 at
2 rates. Clayton Central Crops Research Station (2002-2003), Clayton,
NC. Fumigation was on 20-Sep-02. (Poling and Louws, NC State unpublished)
| Planting date |
Plant-back |
Spring Marketable Yield (lb/A) |
| 27-Sep-02 |
1 week |
21,791 a |
| 4-Oct-02 |
2 weeks |
17,492 b |
| 11-Oct-02 |
3 weeks |
10,287 c |
Trip to Canada tomorrow: It
is unlikely that these remaining supplies of fresh dugs from anthracnose
free sources
will hold out very
long. Thus, the NC Strawberry Association, Inc., has elected this
week to support an immediate visit to fresh dug fields of Ghesquiere
Farms
in Ontario Canada (B. Poling is flying up 8/28 and working with
F. Louws on a fresh dug field sampling plan for plants that will
be
dug
from mid-Sept through early October). We will be looking for
the obvious anthracnose symptoms such as slightly stunted plants
and
petiole and
runner lesions. We will also attempt some sampling for the first
time of plants that do not have the obvious symptoms. We have
little research
information on how to best sample symptomless plants, and as
Frank has stated before, "A negative may not be a negative" -
meaning that we could literally test hundreds of plants and not
find the organism
at all. Yet, just one or two infected plants in the field can
set off a very serious problem. But, we will still try to gather
some
preliminary
data on sampling approaches from this visit. We will keep growers
and agents advised of our trip and sampling results.
It is quite possible that the potential for anthracnose infection
in a fresh dug field (planted with California stock) is less
than in tip
and plug material, or at least that was the experience of last
year. The disease does not seem to show up as easily in fresh
dug plants,
and this may be related to the cooler conditions that prevail
when these are dug in late Sept/Oct. in Canada. Tips are cut
in the
heat of summer, and then rooted in even warmer greenhouses here
in the
Southeast - ideal for anthracnose expression. It would definitely
be our preference
for growers to use fresh dug plants that are apparently free
of anthracnose infection vs. attempting to “make a go of it” with
infected plug plants.
Making a go of it with infected or potentially infected plugs: If
an alternative source of plants is not a realistic option (or,
in
the
case of Sep 2002, water resources didn’t exist for fresh
dugs), immediately remove all infected trays and 1-2 sets of
trays surrounding
the infected area(s). Cull hard. Do not handle plants when wet
and avoid touching healthy plants after handling suspected diseased
plants.
Minimize overhead watering.
Chemical control in late summer/fall not shown to be effective
in trials: In recent research we have not been able to confirm
any benefit from
late summer/fall applications of Quadris or Cabrio for controlling
this disease in plug plants. Both of these products have been
found effective for spring anthracnose fruit rot control, and
it is likely
that most or all sprays of these products should be reserved
for the spring season. Again, our research did not show that
Quadris
or Cabrio
sprays or drenches were effective treatments in the late summer/fall.
Growers who may wish to still apply these products at this
time: growers should know that the labels for Quadris and
Cabrio would permit spray
applications to plug plants in an outdoor setting, but not in
a greenhouse. Don’t apply sprays until after all infected
trays and 1-2 sets of the trays surrounding the infected areas
have been
removed.
It is advisable to tank mix Quadris or Cabrio with captan as
a resistance management strategy.
Captan should be used at 2 lbs per acre of active ingredient
(e.g. 4lbs Captan 50WP per acre) with Quadris (12.4 fl oz per
acre), OR
Cabrio (14 oz per acre).
Example calculation. If the producer has a plug propagation area
that occupies a 0.2 acre area (1/5th Acre), he or she would need
to apply:
----------------------------------------------------------------
Captan 50 W: 0.20 x 4 lb/A = 0.8 lb (12.8 oz)
12.8 oz = 362 g
Quadris: 0.20 x 12.4 oz/A = 2.48 fluid oz.
-----------------------------------------------------------------
OR
------------------------------------------------------------------
Captan 50 W: 0.20 x 4 lb/A = 0.8 lb (12.8 oz)
12.8 oz = 362 g
Cabrio 0.20 x 14.0 oz/A = 2.8 fluid oz. (the Cabrio label allows
up to oz/Acre)
-------------------------------------------------------------------
Calculation for 2000 sq ft area:
Quadris at the rate of 0.56 oz/2000 sq ft area + 3.7 oz captan
(you need both)
Cabrio at the rate of 0.64 oz/2000 sq ft area + 3.7 oz captan
(you need both)
Also, see http://intra.ces.ncsu.edu/depts/hort/berrydoc/sept18/index.htm
Plant supplier updates and questions from the field today (Aug.
27):
Plant supplier updates (2): (we welcome similar updates from
other nurseries)
1) Dr. Poling
I should still have about 16,000 Camarosa and 10,000 Bish plants
and maybe even a few more than that once they are dug and separated.
However I know I would
be able to safely sell this amount and have enough to fill the order.
If someone needs plants badly and I have sold the amount above
I
will take their name
and be happy to call them with whatever I have left.
Thank you,
Jeffrey Hartzog
2) Dr. Poling
We still have a few tips that would be available >from Sept. 10
to the 15th of Sept., other than that, there is still Chandler and
Camarosa bare
root available....
Thank for the update on the plant situation. I will pass the info on
the insect control to Sunny tomorrow.
thanks, Ron Cottle
Que. From Rockingham County
“ It looks like Rockingham County got some of the tips with
anthracnose. They are all switching to bareroot. Do you think you can do
a demonstration on how to plant bareroots somewhere in this area? Most
of them have not planted bareroot in years or never have. Thanks.
Kathryn
Kathryn A Holmes, Agriculture Extension Agent
North Carolina State University
North Carolina Cooperative Extension, Rockingham County Center
525 NC 65, Suite 200, Reidsville, NC 27320
E-Mail : kathryn_holmes@ncsu.edu
Ans. (Poling) Kathryn, we are definitely planning to do this. I have already
committed to a working in Caswell County at the Lunsford place in Prospect
Hill on Sept. 19. They are taking a shipment of fresh dug Chandlers
from Cottle Nursery
on Sept 18 and I will be there 7am on Friday Sept. 19 to work with
the planting crew. When I get back from Canada this weekend we can lock in
a
date for Rockingham.
Also, I was planning to put some photos up on both the SESFC web site
and Berry Agent next week on step-by-step fresh dug planting practices. I
might mention
that this approach is radically different in terms of water usage and
I
suggest that everyone make sure that their irrigation system can handle
at least 7-10
days of non-stop overhead irrigation from early morning (8-9am) until
about 5 5:30 pm. Some growers are having to stick with plugs as they cannot
handle
this
kind of watering schedule.
Nursery suppliers
1. Cottle Strawberry Nursery - 910-267-4531; theberryspot@intrstar.net,
westech.nora@pei.sympatico.ca
2. Hatzog, Jeffrey (B&H Nursery) - 336-982-8155, 336-982-9585;
jdhfarmer@hotmail.com
3. Lewis Strawberry Nursery - 910-675-2394: clewis@bizec.rr.com
4. McConnell, Danny (McConnell Farms) - 828-692-2819; mcconnell@brinet.com
5. McNeill Farms - 919-499-9706; skmcneill@alltel.net
6. Norton Creek Farm - 828-743-3674, 828-507-4869 (no email)
7. Sawyer's Strawberries - 336-685-9645, 336-215-1215; asawyer3@bellsouth.net
8. Shingleton Farms - 252-238-2155, 252-323-5287; T.shingleton@cocentral.com
Keep sending those questions and plant supply updates
E. Barclay Poling, Small Fruit Specialist
Campus Box 7609
Kilgore Hall - Office 252
NC State University
Raleigh, North Carolina 27695-7609
919.515.1195
919.515.2505 (fax)
919.418.9687 (mobile)
web site:
http://intra.ces.ncsu.edu/depts/hort/berrydoc/
click HERE
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