Dormant and Delayed Dormant Fungicide Applications
by Aaron Cato - February 9, 2021
Looking to get ahead of diseases in your fruit crops? Here’s a few options for dormant
and delayed dormant fungicide applications that can help to decrease spore load and
lower incidence of some diseases.
We’re already through a good portion of the dormant period and likely coming up to
some of the last intense freezes here in Arkansas. This means we need to start thinking
about what dormant and delayed dormant fungicide applications may be necessary in
many of our fruit crops. We usually get a lot of questions about lime sulfur towards
the end of a disease-ridden growing year, but these applications should be considered
as a normal part of a fungicide spray program.
Outlined below are dormant and delayed dormant disease management options for blackberry,
blueberry, grape, and peach using lime sulfur, Sulforix®, or copper. Please consult
the following guides for more specific recommendations and spray schedules:
Small Fruit IPM Guide
SE Peach, Nectarine, and Plum IPM Guide
Blackberry Blackberry delayed dormant applications are a necessary tool for anthracnose, cane
blight, and spur blight management. These applications should especially be considered
if anthracnose cane lesions are observed during winter pruning, or if leaf or berry
damage was prevalent during the previous year. This is likely the most important application
each year for suppressing anthracnose in commercial blackberry plantings.
Applications of lime sulfur or Sulforix® should be after bud break (green tip) and before shoots are 3/4 inch long . Early applications will offer less protection and applications beyond 3/4 inch shoots
can cause damage to exposed tissue. Applications should aim for 200 gallons of diluted
spray per acre (200 GPA). See labels for rate.
Anthracnose lesions on a 1-year old blackberry cane.
Blueberry Delayed dormant applications before flower or leaf buds break is a great timing in
blueberry to manage Exobasidium leaf and fruit spot using either lime sulfur or Sulforix®.
This disease isn’t a known issue here in Arkansas, but our neighbors in Mississippi
do deal with this disease. These products are labeled for Phomopsis cane and twig
blight, but do provide suppression of Exobasidium leaf and fruit spot when made at
this timing. Consider a delayed dormant application only if you have confirmed cases
of this disease in your plantings in the previous year.
Applications of lime sulfur products or Sulforix® should be made in the delayed dormant period , 1-2 weeks before flower of leaf buds break . Lime sulfur applications should include 5 gallons of formulated product and 50-70
gallons of water per acre. Sulforix® applications should include 1-2 gallons of formulated
product and 100-150 gallons of water per acre.
Exobasidium fruit spot on blueberries. Photo by Bill Cline, North Carolina State
University Extension.
Exobasidium leaf spot on blueberry leaves. Photo by Bill Cline, North Carolina State
University Extension.
Grape Dormant lime sulfur or Sulforix® applications can be a great tool for fields that
experience intense problems with anthracnose or Phomopsis. Some enhanced management
of black rot and powdery mildew management could possibly be observed as well. Consider
this dormant application if anthracnose is beginning to become a common occurrence
in your plantings.
An application of lime sulfur or Sulforix® should be sprayed in the dormant period,
before bud break and after winter pruning has occurred. A rate of 10 gallons of lime sulfur or 1 gallon of Sulforix® should
be used in solution with at least 100 gallons of water per acre.
Phomopsis cane spot. Photo by Turner Sutton, North Carolina State University.
Peach Dormant and delayed dormant applications of copper are a great management strategy
for bacterial spot and leaf curl in peaches. In plantings with known bacterial spot
and leaf curl issues, or when using highly susceptible cultivars, these dormant and
delayed dormant applications are required to prevent infection from bacterial spot.
In areas where disease prevalence is lower, bacterial spot sprays can begin at 1-5%
bud swell. Most Arkansas growers likely need to consider starting their copper spray
program in the dormant season, based on the high occurrence of bacterial spot issues
in Arkansas peaches.
If bacterial spot or leaf curl is known to be an issue in your peach plantings, begin
applying 2.0-2.5 lb of MCE from late dormant-early budbreak every two weeks or if a major rain event occurs. MCE is the “metallic copper equivalent,”
or the pounds of actual copper active ingredient you need per acre from products that
range from 8%-75% copper per pound of formulated product. Begin applying 1-1.25 lb
MCE at 1-5% budswell. Apply in a solution that achieves at least 60 GPA.
If bacterial spot and leaf curl is not a major issue, copper sprays containing 1-1.25 lb MCE should begin at 1-5% budswell . See the SE Peach, Nectarine, and Plum IPM Guide for information regarding the full bacterial spot spray rates and MCE recommendations
at later growth stages. Always inspect trees for copper injury before making additional
copper sprays.
Bacterial leaf and fruit spot. Photo by Dr. Dario Chavez, University of Georgia.
Remember to stay safe using products like lime sulfur which can be hazardous to our
health when not used considering the labeled safety requirements. Additionally, many
growers should consider adding these early fungicide options into their normal spray
programs. Commercial plantings of blackberry and peaches will almost always require
an early start to disease management. Other crops such as grapes and blueberry may
not necessitate these applications and should be considered on a case-by-case basis.
Lastly, be sure to find a source for Lime Sulfur or Sulforix® ahead of your application
timing, as many co-ops or chemical suppliers may not carry them. Not having this product
ahead of time can really complicate delayed dormant application timings, which are
already hard to predict due to the nature of plants breaking bud.
