Organic Pest & Disease Control
|By Carol Yaw
Using organic controls in the greenhouse is much
easier than in the great outdoors. With regular care and a bit of patience,
your rewards include healthier, chemical-free plants, more change in your
pocket, and the satisfaction of knowing that you're doing something great
for your environment.
|Make time for preventative hygiene
The best way to prevent future problems is to inspect all your plants
carefully before you bring them into the greenhouse. Look closely at their
leaves (especially the underside), stems and the soil they are potted
in. A quality, lighted
magnifier is an essential for this job. Check underneath pot rims
and on the bottom of containers for slugs and snails.
|Make it a regular habit to watch for all of the
above while you're caring for your greenhouse plants weekly.
Unwanted Insects & Controls
|Maria Rodale, in her beautifully written book,
Organic Gardening, wisely noted, "Pest bugs are actually our
messengers. Not only are they a concern, but they may point to a larger
problem in our greenhouse or garden - poor soil, drought stress, weak plants."
Look for the additional message pests may be pointing out to you as you
stomp out those pesky bugs!
- Ants -
Destroy with boiling water. Plant pennyroyal, spearmint or tansy
- Aphids -Tiny, pear-shaped, often light
green in color. Adults may be winged or wingless. Aphids suck sap, excreting
a honeydew, sticky substance. They cause wilting and curling of leaves
A For small infestations,
wipe with soapy water and use Whitefly
& Aphid Traps. For larger infestations, spray frequently with soapy water or a product such as 3-in-1
Safer's Garden Spray, or 70%
Neem Oil. Plant pennyroyal, spearmint, tansy or garlic to repel. Ladybugs
are also very effective.
- Mealy Bugs - These sapsuckers are often
confused with aphids and produce a wax-like cottony substance that looks
like cotton on your plant. They are white to tan and oval in shape.
Find them particularly near buds, on leaf bases, and leaf veins.
For small infestations, wipe with a Q-tip or cotton ball that has been
dipped in rubbing alcohol. For larger infestations, spray with a product
such as 3-in-1
Safer's Garden Spray, or 70%
Neem Oil. A good beneficial beetle control is the "mealybug
destroyer" -Cryptolaemus montrouzieri.
- Brown Scale - There are many different
species of scale that can inhabit a greenhouse, but Brown Scale is the
most common. These tiny, soft-shelled, flat insects attach themselves
to plant stems and leaves. They are pale yellow when immature but later
darken to brown. Find them often along the stem, leaf vein, and leaf
stem as well as the leaf. Notorious for multiplying FAST, they weaken
plants by sucking juices from the stem.
Wipe them off with a cotton swab or cotton ball dipped in rubbing alcohol.
Scrape them off carefully (so as to not damage plant) with your fingernail.
Alternately, for larger infestations, spray with 70%
- Slugs, Snails - Slugs are slimy, soft-bodied
pests. They are gray to brown to army green in color and up to 4"
long. Slugs leave a shiny trail of slime. They generally like to feed
at night and on cloudy days. They love moist environments. Find them
hidden under pots and trays, in rims of pots, on the ground, crawling
up bench legs, under debris. Snails are similar in looks and habitat
to slugs, however, they have a roundish shell. Both slugs and snails
eat holes in leaves. They enjoy feasting on seedlings, tender starts
and new young growth.
For a fun nighttime activity, take a flashlight into your greenhouse
and you'll find them feasting on your plants. Handpick them off, if
you dare, and put them in a jar with rubbing alcohol. Or alternately
get your kids or grandkids to do it
Slugs and snails are highly attracted to anything that is fermenting.
I have had excellent luck filling Slug
Hotels with cheap beer and placing them in strategic spots. They
come running (well crawling fast) enter, enjoy the beer and drown happily.
Or make your own beer traps.
Plus is also an attractive bait that causes them to quit eating
and crawl away to die.
and Snail Copper Barrier Tape on the door threshold and around the
base of bench legs stops them quickly from going further. Keep any debris
picked up so they have no place to hide.
- Spider Mites - These very tiny arachnids
(8 legs) are impossible to see without a magnifier. They range from
yellow to brown to reddish. Look for their telltale webs on the underside
of leaves and at growing tips. They puncture leaves and suck the contents.
Leaves become yellow and mottled.
Spray strong blasts of water on the underside of leaves to knock them
off. They are encouraged by hot, dry conditions. Spray water in the
greenhouse regularly to create a more humid atmosphere. Use 3-in1
Safer's Garden Spray, 70%
Neem Oil or a similar product for larger infestations. Also there
are a number of effective beneficial predatory mites available depending
on your greenhouse temperature range and time of year. Check with Charley's
staff about your particular needs and we'll be happy to help you.
- Thrips - Very tiny, yellow to brown insects
with a cigar-like shape. Find them on the underside of
leaves, in flower buds and flowers. They begin their life in the soil
and then surface and become winged. They can multiply and do
much damage quickly! They feed on plant tissue through their mouths
like little needles, resulting in silvery discoloration of leaves.
They are also known for transmitting diseases including TSWV - tomato
Controls: Spray with 3-in-1
Garden Spray, or 70%
Destroy badly infected plants.
- Whitefly - Small, flying, translucent
(maturing to become white) insects. All stages - eggs, immature crawlers
and adults - suck sap from the underside of leaves. They can cause wilting,
yellowing, spotty marks, deformation, and curling of leaves and flowers.
Often they secrete a honeydew sticky substance on leaves and fruit;
which in turn attracts a black, sooty mold.
Gently sweep them up with a small vacuum cleaner. Spray with 70%
Neem Oil, or 3-in-1
Garden Spray. Use Whitefly
& Aphid Traps to control adults. Encarsia Formosa, a
small parasitic wasp, is a good beneficial insect control.
Diseases and Controls
There are no quick cures for plants having disease. The best choices
include taking preventative measures to keep your greenhouse clean
and growing plant varieties that are resistant to any particular disease
you are concerned about. Changing any of the climate factors - temperature,
light and humidity, moisture level and plant location are all excellent
ways to reduce and control disease.
- Blossom End Rot - A tomato disease in
which dark brown patch develops on the base of the tomatoes. Generally
caused by uneven watering.
Keep the growing medium wet but not soggy. Avoid splashing water on
the leaves and fruit. Increase air circulation and lower the humidity
- Appears as
a fluffy gray or brown mold on leaves and stems of soft-leaved plants.
Associated with humid, cool weather conditions.
Remove all diseased areas, reduce watering and increase air movement.
Spray with GreenCure
- Damping Off - Destructive fungi attack
the roots and stems of seedlings causing rot. Seeds may decay in the
soil and never germinate. Stems can rot at the surface and seedlings
wilt and die. Roots can rot after the seedling has germinated and stunts
it, then the plant dies. No cure.
Use only sterile germination medium.
Sow seeds thinly.
Do not over water.
Keep medium at recommended propagation temperature.
- Mildews -
Downy Mildew - A gray, downy substance that generally appears
on the underside of leaves of seedlings, lettuce and cinerarias.
Powdery Mildew - A white downy coating that appears on leaves
Remove badly affected plant parts.
Spray with bicarbonate of soda (2 tsp. to 1 liter of water).
Spray larger infestations with GreenCure
- Rust - Appears as small, raised spots
on the underside of leaves. Spots can range from dark brown to light
Remove affected leaves and destroy them.
Spray with GreenCure
- Sooty Mold - A fungus that grows on the
sticky honeydew excretions of many sap-sucking insects. Appears as black,
sticky substance on leaves.
Spray with soapy water. Wipe with a damp cloth. Spray with GreenCure
Eliminate the cause - sucking insects such as aphids, mealybug, whiteflies.