Agriculture Reference
In-Depth Information
while lighter-weight oils (summer oils or superior oils) can be applied to fo-
liage and fruit during the growing season.
In general, oils smother pests and eggs and have been especially valuable
in controlling mites and scales. Oils have also proven effective in controlling
aphids, caterpillars, leafminers, and psyllids. Highly refined petroleum oil
has proven very effective in controlling powdery mildew on cherries and
peaches. Be sure that the product you use is certified for organic production
and labeled for your crop.
Oils can be phytotoxic, particularly when applied with sulfur. Avoid ap-
plying oils when the humidity is high and temperatures are above 80°F
(27°C). Use large volumes of water (200 gallons per acre or more), and set
your sprayer equipment to produce fine droplets. Make sure the oil has an
emulsifier to allow it to mix with water, use constant agitation when spray-
ing, and follow label directions very carefully.
Horticultural oils are generally safe for mammals and birds when used
carefully and according to label directions. They can be toxic to beneficial
mites and result in pest mite outbreaks when used incorrectly. In an orchard,
an application of dormant crop oil just as buds swell in spring is very effect-
ive in controlling mites and scales when the beneficial organisms are not yet
in the trees. To avoid phytotoxicity, be careful not to apply too soon before
or after sulfur sprays.
Insecticidal Soaps
Insecticidal soaps are made from potassium or ammonium salts of fatty
acids and are applied to plants to control insect and mite pests. The soaps
act by smothering pests or damaging their cuticles (outer layers) and allow-
ing the pests to dry up and die.
Insecticidal soaps work best against small, soft-bodied insects like aphids,
mealybugs, thrips, whiteflies, and mites. Soaps are also toxic to caterpillars
and leafhoppers but generally do not provide an effective level of control
against them, especially against older, larger larvae. These products have
little impact on hard-bodied insects, including pest and beneficial beetles
