If you live in a hot and dry climate, as I do in the mountains of northern California, now is the time to start protecting your roses from spider mite infestation.
Hot and dry weather conditions are the perfect climate for spider mites to attack your plants and start a breeding program that spreads like fire. Every leaf they attack is the source of a loss of both food through photosynthesis and hydration which protects the plant from heat.
I have a rose in my garden that I call my canary-in-the-mine, De Vink’s ‘Cinderella’, because it is always the first rose to show symptoms of spider mite damage. When I see any damage on that plant, I go into prevention mode. I wash down my plants at least every other day and when temperatures are in the triple digits, I wash them daily, always careful to wash the undersides of the leaves. This breaks the breeding cycle of the mites.
If you do have a severe infestation on a rose, washing the rose daily for three days in a row will also break the breeding cycle and save the rose from complete defoliation. Of course, you can continue to wash the roses for a longer period of time, but three days is the bare minimum to halt the breeding cycle of this pest.
Note: You can also save a rose severely infested with spider mites by washing the rose every day for three days. The rose may lose all of its foliage and need to be shaded as it re-foliates, but, in my experience, it will come back.
A strong spray is often recommended, but it’s really not necessary if you follow a regular routine of washing your roses. If you do feel like you really need to hose a rose down with a hard spray, you can put your hand behind the cane you are washing to protect the plant from losing leaves while you spray.
In a garden with over one hundred roses on four levels in a perfect spider mite climate that goes on for months at a time, I have never had to purchase expensive miticides to deal with these pests.
It takes me about fifteen minutes to wash all of the roses in the garden and I usually am out there in the late afternoon because washing the leaves when temperatures are high also helps hydrate the roses to make them more heat resistant. The plants can only bring up so much moisture from the root zone. Even if the roots are moist, you may find the top growth wilting. Roses absorb moisture through their leaves, so you are helping your roses in two ways when you wash your roses later in the day. The only caveat is to make sure that you give your roses enough time to dry off before the temperatures drop for the night.
Good luck with your roses.