Hi Pat!

It was a pleasure having you attend the Extension Master Gardener Program, Houseplant Hero presentation at the Kimball Public Library Tuesday evening in Randolph. And you certainly gave me a head scratcher of a problem to solve. I’ve been researching (with the help of our Extension Master Gardener Program Manager and Program Assistant). And I am afraid my news is not great.

Here’s what I’ve found:

Cyclamen mites are microscopic mites (less than 0.02mm in length) that deform and distort the growing tips of plants which can result in stunted tips, curled leaves, and lack of flowering. No wonder we couldn't "see" any pests!

Symptoms and Diagnosis

The mites are generally not detected until after they have caused significant damage and then only with the aid of a dissecting microscope. Hand lenses are usually not powerful enough to see these small mites. Mites are closely related to spiders and likewise adults have 4 pairs of legs. Larvae, however, have only 3 pairs.

It's no wonder we couldn't "see" any pests!

Cyclamen mites are usually greenish and transparent and less than 1 mm in size. Their eggs are smooth and more apt to be found hidden in folds of plant tissue. They like to hide in buds or tips of new growth.

Cyclamen mites develop most rapidly with high humidity (80 to 90 percent) and cool temperatures at or near 60 ° F. To avoid light, they favor the plant crown or leaf folds located in the area where the petiole (stalk that attaches the leaf to the stem) joins the stem. As such, damage is usually seen there first. Mites feed by sucking sap from the plant. During feeding, they inject a toxic chemical that disrupts normal growth patterns. With heavy infestations, leaf and flower buds may die. If ignored, the entire plant or just the center of the plant may die. (Which is what we are seeing on your plants). Even after infestations are controlled, some symptoms will remain. A return to a normal appearance requires time and a gradual pruning of distorted leaves.

Prevention & Control:

Space plants so that they do not touch to prevent the spread of cyclamen mites. Also, be careful not to touch infested plants before working with non-infested plants. Isolate infested plants. Badly infested plants should be discarded. Pots of discarded plants should not be reused until they have been thoroughly scrubbed clean and then soaked for 30 minutes in a solution of 1 part household bleach to 9 parts water.

For valuable plants, spray with a miticide / insecticidal soap or horticultural oil that is labeled for use on houseplants. Take the plant outside during mild temperatures and spray with insecticidal soap or products containing sulfur or tau-fluvalinate. Two or three sprays at three-day intervals may be required for mite control. See Table 1 (from the Clemson link below) for examples of brands and products. Follow label directions for use and safety of all products.

To be effective the spray must completely cover the insects so apply liberally and make sure the spray reaches under leaves and into shoot tips where the mites hide.

Sanitation. Examine newly purchased plants and reject them if they have curled or deformed tips and shoots that may be signs of mites.

Cyclamen mites are heat sensitive and can be killed if immersed in 110^oF water for 30 minutes. These temperatures are generally low enough to cause little damage to most plants, but water temperature must be maintained properly and the whole plant, pot and all, needs to be immersed. Removing heavily infested shoots first may make this process easier.

I certainly wish I had better news for you, Pat.

Resources:

https://hgic.clemson.edu/factsheet/african-violet-diseases-insect-pests/  

https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/insects-pests-and-problems/insects/mites/cyclamen-and-broad-mites  

Check out the links above and let me/us know if you have additional questions. All my fingers and toes are crossed that you can save your African Violets! And thanks again for participating in our workshop!