Fall and Winter to-do List for Blackberry
by Aaron Cato - October 27, 2023
Many pests of blackberry require special attention in the Fall and Winter months
to achieve season long control. See below for information on what you can do in the
next few months to maximize yields next year.
After blackberries are harvested there are still many pests that need to be managed
throughout the fall and winter months to ensure that yields can be maximized in the
following year. First, utilize cultural control tactics to reduce insects, pathogens,
and weeds. In my experience, the growers that emphasize cultural control on their
operations are those that achieve the highest levels of suppression of insect pests
and disease. Next, use the recommendations below for management of raspberry crown
borer, raspberry cane borer, and several diseases during the fall-winter months, and
consult the Southeast Regional Caneberry Integrated Management Guide
Cultural Control Tactics
Remove all harvested floricanes (second-year canes) and burn them outside of the planting.
This will lower disease inoculum within plantings significantly.
Maximize efforts in weed management to help increase airflow between rows of blackberries.
It’s important to get rows cleaned up prior to the dormancy to maximize airflow in
the fall and help with penetration of fungicide applications. Growers should be shooting
for 3 ft of bare ground adjacent to plants and mowed row middles (Picture 1) .
Clean up field edges and hedgerows to maximize airflow into plantings and remove all
nearby wild blackberries where possible.
Prune canopies to maximize airflow and plant production. It is best to wait until
cold days when plants are dormant to fully prune plants. This helps to lower the amount
of injury you can cause to plants and helps to prevent pathogens from infecting canes.
Remove all damaged, diseased, or galled canes. Prioritize keeping healthy canes when
pruning, as damaged canes will have reduced yield and possibly harbor insects such
as raspberry cane borer or many pathogens.
Picture 1 – Blackberry planting in the fall with successful weed control. Note how a weed free
strip is being maintained beyond the weed fabric to obtain at least 3ft from the center
of plants without weeds.
Insect Management We normally observe damage from raspberry crown borer in the spring (Picture 2) , but effective control can be achieved in the fall using a soil drench of Brigade
or Altacor in a 50-to-100-gal solution. This application should be applied late October-early
November and should contact the bottom 6 inches of cane and the soil around the crown.
This application will control newly hatched larvae as they move down to the base of
plants to bore into the crown of the plant. You can likely achieve control with an
application in the very early spring prior to larvae boring into the crown, but this
timing will vary year-to-year based on accumulated degree days, which is a risky business.
Picture 2 . Primocanes with a “shepherd’s hook” appearance after raspberry crown borers have
fed on the crown at the base of these canes. These primocanes will die back but the
majority of the damage will be to the crown itself.
Next, all first-year canes that have galls from red-necked cane borer (Picture 3) should be removed during winter pruning. If greater than 5% of canes are galled,
weekly foliar applications may be warranted during May-June to suppress the population.
Blackberry plants generally produce many more canes than the 4-6 canes per plant that
are optimal for good fruit size and quality, so winter pruning generally necessitates
removal of several canes. This is the main reason we use a threshold of 5% for galled
canes, as it is unlikely you will incur economic damage from choosing those canes
to be removed. This may not be true for all cultivars as some, such as ‘Caddo’, don’t
produce nearly as many canes.
Picture 3 – Cane infested with red-necked cane borer. Canes will have galls within 18 inches
from the base of crowns, as seen on one cane in this picture, and will not be productive
and should be removed.
Disease Management Maximizing cultural control tactics is necessary to prevent serious disease issues.
Early-Fall disease risk can be lowered by immediately removing floricanes after harvest
to reduce disease inoculum. This should be combined with heavy winter pruning to remove
all diseased canes, such as those with anthracnose lesions that have begun to crack
(Picture 4) . All pruned canes should be removed from the planting and burned. Any additional
measures that can be done to increase airflow and decrease the amount of inoculum
present should be prioritized during the Fall and Winter months before susceptible
plant material emerges in the Spring.
In addition to these cultural practices, regular fungicide applications should continue
after harvest to lower the amount of inoculum present. Captan every 10-14 days (depending
on rainfall) should be used as a baseline protectant program post-harvest until temperatures
drop. An addition of Quilt Xcel with Captan should be considered to enhance prevention
of Anthracnose issues and cleanup both leaf spot diseases and cane and leaf rust when
they are present. After dormancy is reached, fungicides will not be necessary until
the delayed-dormant application of Lime-Sulfur or Sulforix once the green tip growth
stage is reached. This fungicide is very important for cleaning up Anthracnose and
growers should source product for this application now. The window for spraying is
very small and often suppliers need to order these fungicides. If diseases from nematodes
are suspected, samples should be taken in the fall with county agents to determine
the scale of the potential problem.
Picture 4 – Blackberry cane with excessive anthracnose lesions. Lesions begin as white/purplish
scars as seen on the edge of this cane but can join and completely split the cane
open as seen in the center of this cane. This will lead to lowered yield and fruit
quality on this cane, and spores can move to leaves and eventually fruit which will
further lower quality.
As always, give me a call if you have any questions. Aaron Cato – 479-249-7352
