Tips to Diagnose and Treat Pear Rust Mite and Disease

The Missouri Department of Conservation released a plea to the public in 2019 and urged homeowners to not plant pear trees because they are problematic. They are beautiful in the spring when their white flowers are in bloom but sadly, these trees are known to have poor branch structure, they smell horrible and there’s a problem with cross pollination.

While the MDC has asked folks to avoid planting new pear trees and remove any existing ones on their properties, some homeowners simply can’t (or don’t want to) do it. In these instances, it would be in your best interest to know how to diagnose and treat pear rust mites and pear rust disease. This is really important if you’re thinking about selling and you’re interested in selling your house as is – you don’t want buyers to inherit diseased trees!

What are pear rust mites?

The pear rust mite doesn’t attack pear trees each year, but when they do, they are a big problem – especially in an orchard where miticide hasn’t been used properly. These mites are incredibly tiny, so tiny you’d need a lens as much as 20x magnification!

When you do see them, the head of the insect will be wide and it’ll taper into a wedge shape and they’ll be hiding in the cracks in the bark or near new buds, leaves, and fruit to eat. The female mites are a pale brown (both male and female mites will be white or cream colored when they reach adulthood.

What is pear rust disease?

Pear rust disease is what causes pear leaves to have brown, rust or yellow spots. The disease is caused by a fungus which is passed from juniper tree to the pear during the spring and vice versa in the summer.

Pear rust disease doesn’t cause serious damage to the tree, but it does damage the aesthetics of the tree. You don’t have to treat (nor is it recommended) the pear rust disease, but you may want to treat the disease if there is a significant loss of foliage.

What can I do to treat the pear rust mites and disease?

Although pear rust mites are the sworn enemy of green lacewings and other predatory mites, they can’t be controlled by those alone. You can bring those pests under control by using sulfur spray when used properly.  You’ll want to look for sprays that are designed to treat insect and mites infestations.

Treatment for pear rust disease can only be done as a preventative measure. If you see rust spots on the leaves, it’s too late to do anything. As a preventative, you’ll want to use a fungicide that contains the active ingredient, myclobutanil. There are other alternatives but sprays with this ingredient tend to work the best because it kills the rust spore within four days of germination.

When using the spray, you’ll want to spray the trees during the summer when leaves begin to fall, but ideally after the autumn harvest. You should also be sure to use the spray on a calm day so that the spray isn’t flying all over the place. You’ll want to apply the spray every 7 to 10 days from the beginning of April to the end of May. Remember, if you see the rust spots after May, you’re out of luck this year – you’ll have to wait until the next season to begin using the spray.

If you have pear trees, you’ll want to be mindful of pear rust mites and disease. It’s recommended that you take the preventative measures in early April through to the end of May so that you can be sure your pear trees look healthy before you begin interviewing real estate agents to help sell your house!