Management of European red mites is a continual process. Decisions made throughout the growing season will affect your mite populations. Outlined here are steps that can help with mite management. For a more complete explanation, please see the following publication: https://extension.entm.purdue.edu/publications/E-258.pdf.
- Put on a timely Superior oil spray. See the article above.
- Conserver predator mites. If properly conserved, the predator mites, primarily Amblyseius fallacis, will usually control about 90% of the mite population. The best way to conserve those predators is to avoid using insecticides that are toxic to them. The most highly toxic pesticides that should be avoided include Asana, Baythroid, Danitol, Decis, Permethrin (Ambush/Pounce), Proaxis, Warrior, Carzol, Lannate, Vydate, Dicofol, and Nexter. Sevin is also toxic to predators so it should only be used as a thinning agent. As the brown marmorated stink bug becomes more damaging, it may become necessary to use one of pyrethroid insecticides to protect your crop. If you do so, be aware that you may create a mite outbreak because of the toxicity to the predator mites. Fortunately, we now have a number of excellent rescue miticides available to choose from.
- Preventive miticides. Some miticides such as Agri-Mek, Apollo, Savey, and Zeal can be used early in the season before you know if you are going to have a problem this year. Only use these products if you had a serious mite problem last year. This is a change from previous years when I recommended using these products every other year as part of a rotation. We now have enough rescue miticides available and overall mite populations have diminished enough that we no longer need to use these products on a regular schedule.
- Scout. You should begin scouting shortly after petal fall. Most growers will know where they usually see mite problems first and scouting efforts should begin there. Often that will be in Red Delicious trees or along a gravel road. Pick four leaves from each of five trees and select the leaves from different parts of the tree, high, low, inside, outside, etc. Use a 10X hand lens to look for mites. Also, notice any predators that you might see. The treatment threshold varies during the season, 2.5 mites per leaf before June 15, 5 mites per leaf in the remainder of June, 7.5 mites per leaf from July 1 – 15, and 10 mites per leaf from July 16 – 31. After August 1, you can stop sampling whenever the population falls below 10 mites per leaf. My observations over the years has been that populations will usually start to decline after about July 20.
- Rescue treatments. Treatments should be made when the threshold is exceeded. There are a number of good to excellent rescue miticides available. Check page 32 of the Midwest Fruit Pest Management Guide (ID-465) (https://ag.purdue.edu/hla/Hort/Pages/sfg_sprayguide.aspx). Notice the column that lists the MOA or mode of action. To avoid the development of resistance and to keep this valuable tools available, rotate between modes of action. For example, if you use Nexter (MOA group 21), don’t follow that up with an application of Portal (also MOA group 21).