Scout your Bougainvillea and Mandevilla now for spider mites
Greenhouses growers need to check their Bougainvillea and Mandevilla for spider mites and apply treatments if easily found.
Greenhouse growers who grow or buy-in Bougainvillea and Mandevilla need to be scouting them very carefully now for the presence of spider mites. In the past three years, I have noted an increasing number of these plants being shipped-in with an infestation of spider mites on the undersides of the leaves. Since many of these plants are grown in southern states, the risk of them having spider mites has increased and many times the mites have already developed resistance to the miticide you plan to use.
Michigan State University Extension suggests checking with the supplying greenhouse to see what their miticide applications were for the past month and if possible find out what has worked well for them and what has not. This may help you avoid spraying a miticide that the mites are resistant to.
Check the undersides of the leaves of these plants and look for the tiny, straw-colored mites that have the characteristic two red spots on their backs. Tap foliage over a white card or white paper and check to see if any of the tiny flecks on the paper start moving. If you find numbers that are high enough, you may even notice fine webbing and many eggs.
If mites are detected, you need to apply one of the following miticides as a foliar spray with good coverage to the undersides of the leaves: Akari, Avid, Floramite, Hexygon, Judo, Kontos, Ovation, ProMite, Pylon, Sanmite, Shuttle-O, Tetrasan or Ultiflora. Check the plants again one week later and spray a second time if mites are still present. If just as many mites are found then switch to another product from a different chemical group with a different mode of action.
Kontos is a systemic that has shown effectiveness in some cases on this mite issue. However, it takes a few weeks to be taken up into the plant and be fully effective. Foliar sprays will work faster.
Spider mites reproduce very rapidly at temperatures above 85 degrees and can complete a life cycle in eight to 12 days (egg to adult). An adult female can live for 30 days and lay on average between 100-200 eggs in her lifetime. Thus, you can see why spider mites can be very impactful on these crops.
Contact your MSU Extension greenhouse educator for more information.