Down the Garden Path: More on apple and crabapple diseases and insects

Last week, I wrote about what I feel is the most damaging fungal disease for apples and flowering crabapples – apple scab. Treatments may seem like a lot of work, but control measures for apple scab will help with other diseases and pests, too.

Cedar apple rust

Cedar apple rust vacations on cedar and juniper evergreens from late summer through the winter and travels back to apples and crabapples during the same weather as apple scab – cool and wet. That sneaky foliar fungal disease is out there right now, waiting for the right weather conditions and stage of development of our crabapples and apples. When it comes to CAR, preventing the infection and spread is up to us, the gardeners. Spray treatments need to start when the apple and crab buds are just swelling and we can see the very tiniest amount of green tissue showing. Protection is name of the game with this disease.

Fungus on apple fruit

There are two superficial diseases that also go together: sooty blotch and flyspeck. These appear on the surface of the fruit skin and go no further. They will show up in mid-to late summer. So if cover sprays are being applied, these two diseases are taken care of.

Fruit insects on apple

The two main insects of concern on fruiting apples are codling moth and apple maggot. Codling moth is the proverbial worm in the apple. The female moth lays an egg on the calyx end of the apple where the hatching worm then invades and travels and eats into the center area. You do not notice until the apple is cut open or that first bite is taken. Apple maggot is easily spotted as the female fly lays a number of eggs. Hatching maggots tunnel into the meat, causing a lumpy looking fruit. Multipurpose fruit tree sprays include both fungicides and insecticides, so they will prevent damage if cover sprays are appropriately applied.

Volunteer Master Gardeners for your seasonal gardening questions

Our Master Gardener e-Help Desks are open again for the 2021 growing season. Residents can get gardening and growing advice for a variety of topics. To connect with your county’s Master Gardener Help Desk, email your question, pictures and any additional information to uiemg-dupage@illinois.edu, uiemg-kane@illinois.edu or uiemg-kendall@illinois.edu.

• Richard Hentschel is a Horticulture Extension educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. This column originates on his blog at go.illinois.edu/overthegardenfence. To get more tips from Hentschel, watch his “This Week in the Garden” videos on Facebook and YouTube.