Page 17 - Griffin Gazette Issue 2 - 2021

NUTRITION | Some growers have been taught to significantly reduce or end fertilization late in
the crop as it begins to come into bloom. If you are liquid feeding only, you can reduce to 100 ppm N
constant feed as the crop approaches the sale date. Reducing fertilizer by more than that will almost
certainly result in yellow lower leaves and an undesirable purple/red pigment in the upper foliage.
Research conducted by Brian Whipker, NC State University, has shown this is due to a phosphorus
deficiency late in the crop. For growers utilizing CRFs for some or all of the nutrition, it is important to
beware of the possibility that it could run out before the end of the crop. Unseasonably warm weather
during the mum production season may accelerate the release of the nutrients and lead to end of
season deficiencies.

CATERPILLARS | The risk of a late season invasion can vary from year to year and by location, CHRYSANTHEMUM
PHOSPHORUS DEFICIENCY
but regular scouting is essential to head this problem off before it gets a foothold. Caterpillars can
consume a lot of mum foliage in a short amount of time and to make matters worse, some caterpillars
feed on buds and blooms. Bee safety is a major consideration at this stage of the crop so please
consult with GGSPro before making insecticide treatments. Anecdotally, we have had excellent
success drenching with Mainspring GNL at just 4 oz per 100 gals if the crop is within 30 days of
shipping. Longer control would likely require higher rates.
AERIAL RHIZOCTONIA AND BOTRYTIS | Growers work hard to develop a great
looking garden mum crop with a tight ball shaped foliage canopy. Unfortunately, this creates an
environment deep in the plant canopy where there is very little airflow, leading to a high humidity
environment. This can result in an outbreak of aerial Rhizoctonia which is often accompanied by CHRYSANTHEMUM
Botrytis taking advantage of the damaged tissue. Often, the outside of the plant canopy looks CATERPILLAR
good but pulling the plant open slightly reveals the meltdown taking place in the middle of the plant.
Frequent rains and overhead irrigation add to the trouble since the internal foliage is slow to dry. The
long term answers involve striving to avoid overhead sprinkler irrigation and allowing a little more room
between plants to maximize airflow. In the short term, there are very effective fungicides that control
Rhizoctonia and Botrytis at the same time. Mum bloom safe options include but are not limited to:
Affirm, Broadform, Medallion, Mural, Orkestra, Pageant, Palladium and Spirato GHN. Bacillus based
products such as: Cease, Stargus and Triathlon BA are effective as preventatives. It can be difficult
to penetrate the dense foliage effectively with a foliar spray. Most of the products mentioned will allow
for a sprench treatment, which may prove more effective at penetrating the plant canopy. Excess
fertilizer late in the crop can also make the crop more susceptible to foliar diseases. (See nutrition
section above.)
CHRYSANTHEMUM
RHIZOCTONIA WEB BLIGHT
CHRYSANTHEMUM WHITE RUST (CWR) | Through the hard work of the breeders,
propagators and garden mum growers, the incidence of CWR is significantly lower than when the
disease first became a threat to the garden mum market. This disease still has the potential to be a
very destructive problem for mum growers, and therefore, the USDA has kept the CWR quarantine
in place. High humidity, free moisture on plant surfaces and cool temperatures (50’s-70’s) are ideal
conditions for CWR to become active. This makes late season mum production a vulnerable time in
many parts of the country. Once garden mums begin to bloom, GGSPro recommends fungicides that
contain strobilurins as preventative treatments when weather forecasts indicate conditions favorable
for CWR are likely. Examples: Broadform, Heritage, Mural, Pageant and Orkestra. Eagle is the only
fungicide recommended by the USDA treatment plan to eradicate CWR so it should only be applied
if the disease is detected. GGSPro has a bulletin on CWR as well as the current USDA treatment
protocol available upon request or see the digital gazette on our website. CHRYSANTHEMUM
WHITE RUST
PLANT GROWTH REGULATORS (PGRS) | Generally, the earlier PGRs are applied in
garden mum production, the more effective they are. There are still times where in the later stages
of the crop that growers may feel the need to apply a PGR. Foliar sprays of B-Nine/Dazide should
be concluded before the flower buds are the size of a pea. Later applications run the risk of a flower BONUS CONTENT
cluster that is clubby in appearance. Lowering the rate from 5,000 to 2,500 ppm lowers that risk. In Chrysanthemum White
states where outdoor applications of Bonzi/ Paclo Pro/Pac O/Piccolo are allowed, drenches can be Rust Recognition and
very effective and have little or no impact on flowering when used as directed. The typical rate range Management
CLICK HERE
is 1-3 ppm, and GGSPro would be happy to advise you on the best rate for your situation. Some
growers have reported good results drenching Topflor as well. Chrysanthemum White
Rust Eradication Protocol
Pesticides other than those mentioned may be safe, legal, and effective. It is the grower’s responsibility to read and follow all CLICK HERE
label instructions.