I have a lemon tree that was started from a seed 54 years ago. I keep it in the sun room of my house. This winter it got spider mites and nearly killed the tree. How can I keep it safe from the mites? What can I use to kill the mites indoors? No malathion... I got poisoned by that once so I never use it anymore.
Wow! Fifty-four years ago from seed? That is incredible! So here are some things you can do to prevent spider mites:
When bringing new plants into the house, isolate them for a month or two to observe them for insect infestations.
Give you lemon tree a bath now and then with a soft cloth and mild soapy water. Or, stick it under your shower occasionally.
Spider mites prefer dry air, so keeping humidity levels up around your plant can be helpful in preventing further attacks.
Keep it in good health with proper food, water, and fresh air (in other words, do whatever has worked for the past 54 years!) In addition, should the little devils decide to return:
Remove and bag any heavily infested leaves.
Isolate the tree immediately. If possible, take it outside and spray it with pressurized water (as much pressure as it can stand) for three days in a row.
You might try using a small, hand-held vacuum cleaner. After vacuuming, place the vacuum bag contents into a plastic bag and put it in the freezer for a few hours before discarding.
I would try using either organic dormant oil or an insecticidal soap the next time mites return. Spider mites are not true insects, so they don't respond well to normal insecticides, but these may work to smother the mites and their eggs. Re-apply the treatment at one to two week intervals as long as the pest persists. I haven't tried this, but read about this home remedy:
CANOLA OIL SPRAY RECIPE
Mix 1 part canola oil into 50 parts water (approximately 1 tablespoon oil to 1 liter water). Add a few drops of dish detergent and shake well. Spray tops and bottoms of leaves and stems generously. Test in a small area first.
Other homemade sprays you could try (again, I haven't used these myself) include garlic, basil, coriander, chive spray, feverfew, or dill spray (make a strong tea with the leaves (or crushed garlic, and use within a few days). Please, please, please test in a small area first before covering your whole tree.
You can also try a pyrethrum dust. Keep in mind that all of these chemical solutions (although the least toxic of your options) should not be used indoors. They are also better when applied in cooler weather or they may cause leaf scorching.
As always, keep all chemicals and home remedies away from pets and children.
Pepper Spray is an organic and safe insecticide which will take care of spider mites very well. Sold in the home gardening section of your home improvement stores. Or try making your own with water, dish soap and cayenne pepper.