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Strawberry Plasticulture – September 4,
2003
Vol 4, No. 42
A. In brief:
-1. Importance of excellent water drainage in plug beds!
-2. Crown rot caused by Phytophthora cactorum found in some Sweet Charlies
-3. Visit to Aarons Creek Farms on Sept. 3
A.1. Importance of excellent water drainage in plug beds!
Having gravel just beneath the black nursery cloth is an excellent
means of preventing a standing water problem in plug beds. The gravel
will also help to keep water from moving from one tray to the next.
If the pathogen Phytophthora cactorum (this pathogen causes a serious
crown rot of strawberries) is present in any of the trays, the movement
of surface water from one tray to the next can cause widespread infection
crown rot infection.
Fig. 1. In this outdoor plug bed there is no gravel beneath the nursery
cloth and in periods of wet weather problems with standing water can
be a problem - the grower cut a small drainage ditch to drain off the
surface water.
A.2. Crown rot caused by Phytophthora cactorum found in some Sweet
Charlies
In a phone conversation with Dr. Louws on Tuesday (Sept. 2) I learned
that he positively diagnosed Phytophthora cactorum in some Sweet Charlie
plug trays. In the event that you have plug trays of Sweet Charlie
that are not performing well, you may wish to submit a sample to the
Plant Disease and Insect Clinic as soon as possible to check this out.
It is important to have excellent water drainage (A.1) to minimize
the spread of this disease from tray to tray. It will also be important
to make an injection through the drip irrigation system of mefenoxam
(Ridomil Gold) EC at the rate of 1 pint/acre BEFORE PLANTING. At the
summer pre-plant meetings Dr. Louws was advising a broadcast spray
application of Ridomil Gold before fumigation, but now that most farmers
have completed bed-making and fumigation, the next best option is to
have the fungicide injected into the beds with the drip system several
days before planting.
Fig. 2. If you have Sweet Charlie plugs that look similar to these – send
them in for diagnosis.
A3. Visit to Aarons Creek Farms on Sept. 3
Late yesterday afternoon I was able to visit Aarons Creek Farms and
I had a chance to visually compare the performance of several groups
of plugs at varying stages of rooting. In Figure 3 you can see a five
week old group of Sweet Charlies – these are looking quite healthy
and ready for delivery today (Sept. 4). Sweet Charlie is one of Gregg
Gordon’s favorites – it is resistant anthracnose and this
is a major plus for propagating this variety in the Southeast. In Figure
4 is shown what appears to be a healthy group of Chandler plugs that
came off of Load 2 (rooted 8/7/03), but in another propagation area
we could identify diseased plants from the same load (2) that are headed
for the dumpster. In Figure 6 you can see open areas on the black nursery
cloth where Aarons Creek Farms has culled out trays of Chandler that
visible symptoms of anthracnose. I was somewhat encouraged by my walk-through
yesterday as there are still a number of plug tray groups that are
not exhibiting visible anthracnose symptoms at this time. Nonetheless,
Gregg Gordon is directing his customers to Strawberry Hill and Mitchell
Wrenn for replacement of plug plants with fresh dugs. For growers who
absolutely cannot manage a fresh dug planting process, I would suggest
that you stay in close touch with Gregg over this next week.
Fig. 3.
Sweet Charlie plugs at Aarons Creek Farms, Buffalo Jct., VA (photo
9-3-03).
Fig. 4. Chandler plugs from Ontario Load 2 (rooted 8/7/03)
Figure. 5.
This group of Chandler plugs has been heavily culled in the front section
of the photo.
Figure 6. Plugs exhibiting these symptoms are being culled
out. These plugs were positively identified to be infected with anthracnose
last week.
Western NC on Friday – please call on the mobile if you
need to reach me on Friday, Sept. 5.
Thanks!
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
to return to strawberry advisories page
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