Tomatoes and Spider Mites
Question: I have a raised bed garden and have battled spider
mites to no avail. They have ruined my tomatoes. I use cypress
mulch in my garden as well as a weed block. Do I need to get rid
of these things to start the garden this year, spray my soil with
Kelthane or something else? Please help I want my garden back.
Answer: Spider mites do over winter in mulches and plant debris
left over from the previous summer. But if you think that you
will avoid mites by burning, scorching, "poisoning",
or otherwise sterilizing your garden soil, you are mistaken. Spider
mites have an admirable capacity to find tomatoes even if the
tomatoes are planted on virgin soil. They apparently do this via
wind transport, or some other means we haven't quite figured out.
Unfortunately, there are not many magic bullets on the market
for spider mite control on vegetables. I recommend an integrated
approach.
(1) Do not compost mite infested plant material (There's no use
giving mites a head start. Unless your compost pile is uniformly
hot enough to kill mites, I'm convinced this is another way mites
can infest a garden.)
(2) Inspect your tomato seedlings for mites and choose only mite
free plants (Again, let's not help the mites by giving them an
early start). With a hand lens, check the undersides of a few
leaves of every plant you purchase.
(3) At the first sign of infestation (assuming you do check your
plants a couple of times a week for the first signs of spider
mites on leaf undersides), do one of the following: try blasting
mites off with a stiff stream of water directed at leaf undersides
(this can significantly delay mite population buildups, if done
thoroughly); apply horticultural oil or insecticide soap sprays;
pick off and destroy any leaflets you find mites on.
(4) Apply Kelthane, if you have it. Kelthane is the last good
miticide labeled for use on vegetables. It is difficult to find
in stores any more, but old stocks can still be used for this
purpose.
(5) Get your spring tomatoes started early, and remove plants
when they become mite infested. Instead of battling the mites,
give in and focus on a late summer planting of tomatoes. Sometimes
the fall tomato crop is easier to grow without spider mites. Check
with your local county recommendations for the best time to start
a fall tomato garden. Michael Merchant, PhD, BCE; Urban Entomologist;
Texas Cooperative Extension
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