Article: Disease Control After Spring Freeze Injury in Grapes: What are the Options? By Annemiek Schilder, Michigan State University
It is unfortunate that the
Michigan grape
industry has been hit with widespread freeze injury once again. In
addition,
there was hail damage in the Lawton area. A more accurate estimate of
yield
will not be possible until after fruit set. However, based on the number
of
surviving flower clusters and proportion of secondary buds, an initial
assessment can probably be made. In previous years, the crop turned out
to be
harvestable in some vineyards that growers had given up on. One thing
that is
clear is that growers will need to reduce inputs, including fungicides.
There
are basically three different reduced cropping scenarios:
1) There is no crop worth harvesting and you
don’t care about inoculum build-up.
In this case, protecting the fruit from infection by black rot or
Phomopsis is
not necessary. If you’ve had good black rot control in previous years,
you
probably won’t have too much disease. If you’ve had black rot problems
in the
past, one more year of inoculum production won’t make much of a
difference
because you already have an “inoculum bank” in the vineyard. We have
shown that
even under conditions of high disease pressure, it is possible to
produce an
excellent crop with a standard spray program, which you would implement
next
year. As far as foliar diseases are concerned, vines with a low crop can
tolerate more disease than vines with a full crop. Powdery mildew may
infect
Concord and, to a lesser extent, Niagara leaves, but if there is no
crop, the
vine can tolerate quite a bit of disease without ill effects. However,
there is
a risk that a severe downy mildew outbreak may defoliate Niagara, which
may
predispose vines to winter injury, even if there is a low or no crop. If
downy
mildew comes in early in the season (based on scouting) and if it looks
like
the weather will continue to favor downy mildew, a fungicide spray may
be
needed to knock back the disease to the point that it does not lead to
serious
defoliation.
2.) There is no crop worth harvesting, but
you want to limit inoculum build-up.
In this case, we don’t want to protect the vine to preserve fruit
quality as
much as we aim to apply fungicides at a few critical times to knock back
diseases to prevent large amounts of overwintering inoculum production.
In this
case, we can also opt for less expensive fungicides that have good to
excellent
disease control efficacy. This would include at least one protectant
fungicide
application (e.g., before a rainy period) to protect the young shoots
and
exposed flower clusters from Phomopsis. An SI spray could be applied at
first
postbloom if you are concerned about black rot. Scouting-based
management of
downy mildew in Niagara would occur as described above. If powdery
mildew
becomes severe on Concord leaves, you may consider an eradicant spray
(e.g.,
JMS Stylet Oil) to knock down colonies and cleistothecium formation.
3.) There is a harvestable but reduced crop.
In this case, protecting the fruit from black rot and Phomopsis is the
most
important activity and will require a few more sprays than the two
scenarios
above, e.g., one or two pre-bloom protectant sprays to protect against
Phomopsis, one or two postbloom sprays to protect against black rot and
Phomopsis (while also controlling powdery and downy mildew), and
curative/protectant sprays against foliar powdery and downy mildew only
if
scouting indicates a need.
To cut input costs, you can use lower-cost fungicides (e.g., generics,
older
protectant fungicides, phosphites) and reduce the number of fungicide
applications only to critical times. Watching the weather and stretching
spray
intervals during dry periods also helps to lower the number of sprays.
It is
important to also take labor and fuel costs for applying fungicides into
account. The fewer times you have to drive through the vineyard, the
better. A
way to reduce the number of applications is to tank-mix fungicides with
insecticides (most growers are already doing this), apply products at
higher
rates, or apply products with longer-lasting residuals for extended
coverage.
Adding a sticker-extender (e.g., NuFilm) can be a low-cost way to make a
fungicide last longer and obtain better coverage. Ensuring thorough
coverage by
spraying every row at an appropriate spray volume (at least 50 gpa after
the
canopy fills in) will increase the “bang for your buck” of the
fungicides you
use. This is especially important for protectants like Ziram, Captan,
and
Manzate.
This article was published on the Integrated Pest Management Resouces, CAT Alert webpage. (follow the link below to view article tables) http://ipmnews.msu.edu/fruit/Fruit/tabid/123/articleType/ArticleView/articleId/2686/Disease-control-after-spring-freeze-injury-in-grapes-What-are-the-options.aspx.
This report evaluates biopesticides for control of black rot and Phomopsis in organic grape production in 2009. The experiment was conducted in a mature ‘Niagara’ vineyard at the Trevor Nichols Research Complex in Fennville, MI. Here is a summary of the report. Apply Serenade (+ Nu-film-P), Sonata (+Nu-Film-P), Kaligreen and JMS Stylet Oil for disease control, see attached report (put in WEB link of table after you put on our web site here Danielle). Everything on this list is organic except the blue-lettered treatments, which are conventional fungicides for comparison .Dr. Annemiek Schilder (Dept of Plant Path-MSU) would consider Serenade and Sonata to be the strongest of the bunch against most grape diseases (be sure to add Nu-Film-P as a spreader-sticker). JMS Stylet oil is most efficacious against powdery mildew (but does suppress the other diseases as well) and Kaligreen is good for powdery mildew and black rot (and provides some suppression of other diseases). (To read full report visit www.michiganorganic.msu.edu under the fruit production tab).
Row covers are used as a means to modify the microclimate around the crop. Attempts to modify the environment for enhanced crop production dates back to the 16th century. Since the early 1960s, the introduction of plastics in agriculture helped develop new and efficient row cover technologies for open field vegetable production. Row covers are used for a number of reasons such as, season extension (frost protection), insect exclusion, heavy rain and hail protection. Regardless of the primary goal of the row covers, their management should help avoid excessive heat that can injure the crop and also avoid poor pollination that may reduce yield.
Row covers and heat injury
When using row covers, always keep in mind that they are more efficient
at
increasing temperature, especially during a sunny day, than protecting
against
frost. Even in the absence of a frost risk, some growers may consider
using row
covers because most warm season vegetables stop growing at temperatures
below
40-50oF. A row cover may increase the temperature enough to promote the
growth
of these warm season vegetables.
When outside temperatures are high, it is recommended to remove row covers. Temperatures inside row covers can get extremely high and injure crops, especially when row covers without perforations or holes are used.
Under a sunny day with a calm wind, we have observed about 20 to 30 degree temperature increases inside row covers when compared to outside. Depending on the outside temperature, this extreme heat can easily damage certain crops like tomato. Under those conditions, it is recommended to open the row covers for ventilation.
Row covers and pollination
Many crops require insects, especially bees, for pollination. In
cucurbits for
example, there are separate male and female flowers. For adequate
pollination
and fruit set, the pollen needs to be moved from the male flower to the
female
flowers. Row covers present physical barriers for insects including
bees. Even
when the row covers are perforated, most insects normally stay outside.
In a
recent study conducted by our team, we observed a significant reduction
in
slicing cucumber yield when the row covers were removed two to three
days after
appearance of the first flowers. It is important to know that flowers of
most
cucurbit crops remain open for only 24 hours. It is therefore important
to
remove the rows covers before cucurbit flowers open to facilitate
pollination
and proper fruit set.
This article was published on the Integrated Pest Management Resouces, CAT Alert webpage http://ipmnews.msu.edu/vegetable/vegetable/tabid/151/articleType/ArticleView/articleId/2738/Managing-row-covers-to-avoid-heat-injury-and-poor-pollination.aspx.