|
Less than 3 years ago, researchers
in South America discovered a new alternative to controlling
powdery mildew. Wagner Bettiol, a scientist from Brazil, found
that weekly sprays of milk controlled powdery mildew in zucchini
just as effectively as synthetic fungicides such as fenarimol
or benomyl. Not only was milk found to be effective at controlling
the disease, it also acted as a foliar fertilizer, boosting the
plant's immune system.
Powdery mildew in the cucurbit
family is caused by the organism Sphaerotheca fuliginea. It is
a serious disease that occurs worldwide. For decades, organic
gardeners had to rely on making a spray from baking soda to control
the disease. Now, instead of measuring out the baking soda and
combining it with a surfactant (a "sticking" substance)
of either oil or soap, gardeners need only head for their refrigerators.
|
In his experiments with zucchini
plants, Bettiol found that a weekly spray of milk at a concentration
of at least 10% (1 part milk to 9 parts water) significantly
reduced the severity of powdery mildew infection on the plants
by 90%. While some gardeners may be tempted to increase the concentration
of milk for more control, Bettiol found that once concentrations
rose above 30%, an innoccuous fungus began to grow on the plants. |
|
How does milk control powdery
mildew?
Scientist aren't 100% sure how
milk works to control this disease. It seems that milk is a natural
germicide. In addition, it contains several naturally occurring
salts and amino acids that are taken up by the plant. From previous
experiments using sodium bicarbonate, potassium phosphate, and
other salts, researchers have found that the disease is sensitive
to these salts. It is possible then, that milk boosts the plant's
immune system to prevent the disease.
Milk used around the world
The benefits of using milk to
control powdery mildew haven't been isolated to Brazil. Melon
growers in New Zealand are saving thousands of dollars every
year by spraying their crops with milk instead of synthetic fungicides.
The melon growers in New Zealand have been so successful that
the wine industry is taking notice and beginning experiments
using milk to control powdery mildew in grapes.
What kind of milk should be
used?
In Bettiol's original experiment,
fresh milk was used, straight from the cow. However, this is
obviously not feasible to most home gardeners. The research work
in New Zealand actually found that using skim milk was just as
effective. Not only was it cheaper, but the fact that the milk
had no fat content meant that there was less chance of any odours.
Wagner Bettiol's original article
was published in the journal Crop Science (Vol. 18, 1999, pp.
489-92). It can be found on-line at:
http://147.46.94.112/journal/sej/full/c12_199908_180801.pdf |
