Farmers Weekly Review

We are entering those dog days of summer, and along with that comes heat, humidity and lumps and bumps on trees and shrubs.

There are fungus among us and bacteria (but nothing rhymes with bacteria, other than cafeteria, and let’s not go there.) Some look scary — and aren’t, and some are barely noticeable and deadly. It is important to know the difference.

Cool, moist springs — I know, we started with a very warm spring, but ended up cool and wet—well, this is the Barbie dreamhouse of some plant diseases — fungal cedar/apple/quince/hawthorn rust and bacterial fireblight. One looks strange and awful, and might make you want to kill your tree, but it is mostly cosmetic. The other starts out with a few dead leaves but can take out a tree quickly.

First the funky, fungal disease group of cedar/apple/quince/hawthorn rust. This one brings many unusual calls to the office. In mid spring, I get reports of bizarre “orange JELL-O bags with fingers” hanging on evergreens. And no, I don’t have to ask the caller what they have been imbibing, because it is an actual plant disease. But wasn’t this column about midsummer problems? Yes, it is.

This week, homeowners are sending photos or bringing in samples of their Washington hawthorn berries that should be a solid Granny Smith apple green color right now. But instead, those little, round berries have sprung whiskers covered with orange dust and look like sputniks (the first Russian satellites).

These may seem like two different issues, but they are one. A two-host disease. In the earlier spring, the infectious stage of the cedar/hawthorn rust has grown its fruiting structure (the orange JELL-O with the fingers) on the cedar (which is the juniper tree). Those spores are spreading to apple or hawthorn trees (Hawthorn are a member of the apple family) in that moist, cool spring.

Then, in mid- to late-summer, in the warm, moist environment, the hawthorn puts on its fungal show with infected berries and leaves. The berries take on that same strange structures — hairs instead of fingers this time, and the rust spores go flying back to the cedar. And the cycle begins again.

Fortunately, cedar/hawthorn rust affects berries and small twigs, and the JELL-O bag barely affects the cedar/junipers, even though it looks strange and awful.

Gardeners can help to slow the cycle by removing the cedar’s fruiting bodies in spring as soon as they are noticed. This would stop the first cycle of the disease, if you could eliminate every single one. Unfortunately, that would be having to wipe out every single one within quite a distance. University of Massachusetts reports that trees can spores can travel 15 miles. So, unless you own that property, you might find it difficult to do complete eradication.

You can also choose to do nothing. Or one step up is to practice good garden sanitation. Remove JELL-O bags from junipers in spring, and infected twigs and berries on hawthorns by pruning. But remember, I always talk about that Integrated Pest Management strategy. First properly identify, then make decisions based on your level of tolerance and satisfactory control.

If you do want to treat, you will use an appropriate fungicide (so on the label it will say treats for cedar/apple/hawthorn/quince rust.) But the product is only successful if the timing of application is right. The goal is to treat the “receiver” tree when the other “giver” tree is sporulating.

The other disease that I am getting a lot of calls about starts out as just a few affected clumps of leaves. This is fire blight, and we are having a terrible bout of it in Will County this year. Unlike the showy JELL-O and orange dust of the cedar/hawthorn rust family, fire blight is silent, but deadly.

First, you may notice a few very dark clumps of leaves, but within a short time, full branches are dead. The reason the disease is called fire, because sometimes (from afar-with bad eyesight) the branches looked as if someone torched them. This is a bacterial disease. And timing of control, which is quite brutal, is of the essence. Fire blight is the most destructive disease affecting plants in the rose family.

The causal bacteria is Erwinina amylovora. Fortunately, fire blight for us, so far, occurs more rarely. In 30 years, I have only seen three bad outbreaks, but unfortunately, this year is one of them. The symptoms include those brown clumps of leaves that stay adhered to the tree instead of falling. But the telltale sign is that at the ends of the branches, you will see a “shepherds crook” at the tip of the branch where it is crooked over 180 degrees.

Cankers develop on the branches and exude a sticky, bacterial ooze. The disease spreads to the blossoms and is spread by wind and insects.

Unfortunately, there is no treatment for fire blight except to remove the affected material and cut back deep into the healthy wood to stop the spread. Ideally, pruning during dormant season is recommended because it would cause less chance of spread. You would cut 6 to 8 inches beyond the affected area into clean wood.

But in the growing season, like the calls I am getting now, recommendations are to go deeper; cut a full 12 inches deep into healthy wood. Sterilize pruning tools between each cut (I like to use rubbing alcohol poured into a bowl. Swish your pruners around in the alcohol between cuts.)

The branches should be burned (which I know isn’t allowed in many areas now). The other option is to bury them.

When looking to buy new plants in the rose/apple family look for ones that have resistance to fire blight.