A healthy apple harvest each growing season depends on a variety
of factors, not least of which is an effective program to combat
fungal diseases, such as powdery mildew. While powdery mildew
thrives in high humidity, it survives arid periods too and waits to
colonize and produce spores once environmental conditions are
more favorable. Present in all crop-producing regions in the world,
powdery mildew is one of the most common diseases affecting a
wide variety of crops.
In apples, powdery mildew, caused by the fungus Podosphaera
leucotricha, attacks not just the fruit but also the leaves, twigs,
and blossoms, making it a significant threat to overall tree health.1
Infected blossoms won’t produce fruit, and infected buds spread
the disease to the next year’s blossoms and leaves, making longterm
proactive management essential.1
If left untreated, powdery mildew can be a devastating disease
not only in the field but also on the wallet, because of its effect
on overall apple quality. Harold Schell works as the Horticultural
Manager of Chelan Fruit Company, a cooperative of more than 300
growers, and understands the importance of attacking this highpriority
disease in the orchard.
“If you have a young orchard and you’re growing young trees, it can
literally stop the growth,” Schell said. “If it’s a producing block, it
can adversely affect the fruit and create damage that, come harvest
time, is bad enough to make it a cull.”
In young, small orchards that are particularly susceptible to
powdery mildew damage, pruning infected flower and shoot
buds during winter and early spring can provide some protection.2
Chelan Fruit Company, however, consists of more than 12,000 acres
of tree fruit and produces roughly 350,000 bins of apples, making
pruning practices nearly impossible.
Foliar applications of fungicides throughout the season provide
the best protection against powdery mildew and can be combined
with existing spray rotations to treat other apple issues, including
botrytis and rots.
According to Schell, most growers begin their sprays early in the
spring, rotating chemistries through the course of the worst of
the mildew period, which is early spring to early summer.
“Once the heat in the summer crops up, then if we’ve done our job
earlier, mildew is less of a problem,” Schell said.
One solution that some of the Chelan Fruit Company’s growers have
used to combat this prevalent concern is Luna®
from Crop Science. Foliar fungicide programs that include
Luna Sensation have been broadly tested by university researchers
and crop advisors in the field since 2008. For example, research
trials conducted by Oregon State University have shown that the
use of Luna Sensation as part of an integrated powdery mildew
program along with DMIs and protectants results in a reduction in
the damages inflicted by powdery mildew.3
powdery mildew (%)
Sensation @ 5 fl. oz.alternated with DMI plus protectant
Chuck Cary, a Crop Science Pacific Northwest sales
representative, also recommends Luna Sensation fungicide
to growers in his region because of its unsurpassed efficacy
in fighting powdery mildew and storage diseases.
According to Cary, early-season and late-season applications of
fungicides are necessary to protect the crop from many of the postharvest
spots and rots. “Luna Sensation offers control of powdery
mildew at an early petal fall timing which is also an ideal timing for
many of the storage rot diseases like botrytis. A grower will also find
a second application close to harvest is an excellent timing for this
fungicide to reduce overwintering powdery mildew for next season
and will be a good timing to improve fruit quality going to market or
storage,” Cary said.
“One of the things that Luna Sensation offers over some of the other
products is that it has two unique active ingredients,” Cary said.
“From a performance and resistance management standpoint, these
particular active ingredients cross over, giving us control of powdery
mildew, scab, and botrytis.” Both actives work on stopping the
energy of the pathogens but from opposite sites in the fungus. Due
to this multiple-site activity, there is excellent reach back control of
disease that might be started. “Although these actives work in a
similar way and on similar pathogens, their physical characteristics
complement each other, as one is very mobile in the xylem (systemic
fungicide) and the other offers outstanding redistribution on the leaf
surface,” Cary added.
Schell recommends Luna Sensation to his growers for this same
“It’s not just a good mildewcide, but it’s also good for controlling
these storage rots,” he said. “In my life, working with a shipper
and a packer, that’s important because without quality fruit there
is no market.”
Learn more about powdery mildew and solutions offered by Crop Science.