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Pests and Diseases |
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I want to use an insecticide
to kill the bugs on my plants. What are my natural alternatives?
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Why are there webs appearing on
my plants?
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How do I control recurrent mite
infestations?
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What kind of predator mite
should I use in my garden? How many do I need?
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What are these little black
flies flying around the base of my plants?
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I think I have aphids. Now what?
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How do I get rid of whiteflies?
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I have a bug problem and I want to get rid of it
immediately. What are my alternatives to the pesticides I see at the
hardware store? |
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If you are concerned about environmental health or safety, you
will first want to take a look at botanical options. Botanicals
are pesticides which are derived from plants. They quickly degrade
and are considered to be safer than common synthetic chemicals.
However it is important to use them properly, just like any insecticide.
Two common botanicals that you might look into are neem and pyrethrins.
Neem is widely used in asia and india for a number of things including
brushing teeth! It contains a bitter chemical that bugs don't like
to eat, and it also acts as a growth regulator that interferes with
insect reproduction. It is effective on a wide range of insects.
It has very very very low toxicity to mammals.
Pyrethrins come from a chrysanthemum species, Dendranthema
grandi-flora found in Kenya and Ecuador. Pyrethrins ill insects
by interrupting their nerve impulses.
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There are some sort of webby looking things appearing
on my plants. Ive also noticed that my plants have polka-dotted
discoloration in some areas. Whats going on and how do I fix
it? |
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It sounds like you have spider mites. Spider mites are often found
on indoor plants, and in the right temperature and humidity, their
population can quickly explode out of control. If you look closely
you will see tiny spider-like creatures running over the webs. The
damage spider mites cause looks like needle puncture marks where
the mites have sucked the sap from the leaf. This damage may at
first appear silver in color, or yellow, but eventually it will
sink in and turn brown.
There are several alternatives to dealing with mites, and the choice
you make is up to you and the number of plants you are dealing with.
If you have only a few plants, you can control the mites by rinsing
the plant in water, paying extra attention to the undersides of
the leaves, where mites accumulate. The webs can also be broken
up with blasts of water.
You may choose to use a miticide, of which we carry several natural
based ones. Pyrethrum is an old stand by and it is effective against
numerous pests. Another good choice is Pest Out
which is 100% certified organic and is effective against spider
mites, thrips and aphids. Use caution when using any solution on
your plants, it is best to use a low dosage on a single plant first
to test for any ill side effects.
To maintain control after knocking down a heavy infestation, we
suggest introducing
beneficial insects to your garden. As a balance
of beneficals is achieved within a grow area, there is less fluctuations
of pest populations. Beneficals can be released two days after the
use of insecticidal soaps and horticultural oils, however residual
pesticides can stick around for up to a month and will kill beneficials
as well as pests.
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There are several places in my garden that get
mites without fail, every growing season. What do I do for long term
control? How do I prevent infestations? |
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You have hit on the key word, PREVENT. It is
much easier to prevent a pest infestation then to control one which
is already in progress. If I were you, I would do a three pronged
attack on the little buggers.
- When the plants are young, use a miticide on them such as Pest Out.
This will greatly lower the resting mite populations.
- About a week after using the miticide, introduce beneficial
insects, putting extra beneficials in the areas of your room which
are most prone to infestation.
- Monitor your plants regularly, looking under the leaves to see
if you can find any mites. (a 10x hand lens can help greatly!)
If you do find mite hot spots, you will find them early enough
that you can prevent serious damage. The best bet would be to
then introduce a second round of beneficials.
Some other factors to consider when dealing with a chronic mite
problem are that in general spider mites prefer high temperatures
and low humidity. Simply cooling the room a bit and allowing for
a bit of humidity buildup can slow down their reproduction. Another
bit of food for thought is that healthy plants have a better chance
of naturally defending themselves than do unhealthy, stressed plants.
You may find that supplementing your plants with
silicone helps prevent the mites from ever gaining a foothold.
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What kind of predator mite should I use in my garden?
How many do I need? |
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There are generally three kinds of
Predatory Mites that are available. Each is specific for use
against a certain kind of mite and a certain temperature and humidity.
We find the most effective control is found using the Triple Threat!
mix of all three species. To wipe out an infestation, we recommend
blasting them with 1000 predators to 50 square feet.
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There are lots of little tiny black flies around
the base of my plants. What are these?
Are they harmful? |
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Those little black critters are known as fungus gnats. The term
refers to a large group of insects, most of which have not been
extensively studied. They reproduce in moist, shaded areas in decaying
organic matter like leaves and algae. The life cycle is about four
weeks, with continuous reproduction when warm temperatures are maintained.
Larvae not only feed on fungi and decaying organic matter, but on
living plant tissue, particularly root hairs and small feeder roots.
Usually, there are very few ill effects from these flies, but control
is advised. After the roots have been injured, root rots may attack
the plant. Entire crops have been lost in this manner. The plant
symptoms may appear as sudden wilting, loss of vigor, poor growth,
yellowing and foliage loss.
Fungus gnats can be easily controlled with a pyrethrin spray. They
can also be physically captured with yellow sticky cards. A Cooperative
Extension pamphlet written by A.L. Antonelli of Washinton State
University suggests that since fungus gnats are attracted to sprouted
wheat grain, that a pot of sprouted wheat could be used as a trap
crop. Antonelli recommends setting the pot in the problem area and
leaving it for a few days. Female gnats will lay there eggs on this
moist material and then the pot can be submerged in boiling water
to kill the eggs and larvae. Alternatively the contents of this
pot could be discarded outdoors. This procedure would need to be
repeated every two weeks until the flies are no longer a problem.
Perhaps the most important weapon you have against fungus gnats
(and all pests) is good grow room sanitation. Dont allow decaying
plant material to buildup. Always remove fallen leaves, algae, or
any sort of organic material that collects around the base of plants.
This material is a breeding ground for pests and diseases.
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I think I have aphids. Now what?
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There are so many Aphid species that just about every plant has
at least one species that likes it. The first thing you might notice
when you have aphids is that the plants arent thriving or
are even wilting. If you look at the growing tips of your plants
or underneath young leaves,ryoull see dense colonies of tiny
(I - 3 mm), soft bodied, pear-shaped insects. Aphids feed by inserting
their piercing-sucking mouthparts into the vascular system (phloem)
of the plant and sucking out the sap. This causes discoloration,
curling, crinkling and wilting of leaves, malformation and distortion
of buds and shoots, leading to plant stunting and deformities, reducing
the vigor of the plant. The worst thing about aphids though, is
the viruses they often transmit . The cotton aphid is known to transmit
over 50 plant viruses and the green peach aphid, over 100 (Kennedy
et al. 1962). They also produce honeydew which is like a Petri dish
for growing potentially fatal, sooty black mold.
Aphids reach adulthood in only a week, and they can quickly multiply
into a giant problem. One adult can produce 50 to 250 young during
her lifetime, depending on the host plant and its nutritional status.
The nymphs can mature and begin reproducing in 7 to 10 days. The
life expectancy of the adult can be from 7 to 21 days, making possible
more that 30 generations a year in the greenhouse.
Aphids can be washed off with water, or sprayed with horticultural
soaps and oils. To great organic alternatives are Neem
Oil and Pest Out.
Pyrethrins are also highly effective. After knocking down a pest
population, it is often a good idea to introduce beneficial insects,
or predators into the growing environment. Green
Lacewings are great choice as are Aphid predators. You may want
to use yellow sticky traps as a monitoring device for future
infestations, although you may find that you catch more beneficials
than aphids!
Kennedy, J. S., M. F. Day, V. F. Eastop. 1962. A Conspectus
of Aphids as Vectors of Plant Viruses.
Commonwealth Institute of Entomology. London, 114 pp.
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How do I get rid of whiteflies? |
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Whiteflies can be difficult to get rid of, as they are highly prolific
reproducers . The species is usually parthenogenetic, meaning that
the birth of young can occur without mating. The adult females lay
200 to 400 eggs on the undersides of leaves, and these young mature
within 18-25 days.
You may choose to handle your infestation in several ways, and
they will all work so long as you are persistant. There are several
products on the market that are all organic and safe for humans.
Safer's Insecticide soap will do the trick, as will Neem Oil. A
Pyrethrum based insecticide would work as well. All of the above
products are organic and can be applied up to the day of harvest.
The most important thing to remember is that the treatment is a
contact killer so it needs to be done once a week for three to five
weeks, otherwise new bugs will hatch out and the problem returns.
By applying the insecticide 3 to 5 weeks it will break the entire
life cycle of the pests.
For maximum effectiveness, attack your infestation in three stages.
- Use a vacuum to suck up adults early in the morning (as soon
as the lights go on). Low temperatures make them slow moving and
easy to catch.
- Use an insecticidal soap or oil in areas where the populations
are very high.
- Order Encarsia Formosa (Whitefly Parasites), releasing one to
five per plant or one for every 10 square yards of plant area.
You should aim for no more than one adult whitefly per leaf at
time of parasite release
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