Fungal leaf spot a cause for thinning

Help! My sorrel plants suddenly have pinkish circles on their leaves, and I’m not sure what’s happening or what I need to do. I’m hoping to be able to save them and not use any chemicals.

— Becky (from Florida)

It sounds like your plant has some sort of fungal leaf spot. This is not an overly serious problem — leaf spot won’t kill the plant but, in severe cases it can cause defoliation and thinning.

Moist, humid conditions around the plant foster this issue. If possible, keep the foliage of the plant as dry as you can. Remove leaves that are affected the worst and see how the plant responds.

There are fungicides that can be used, but I’m assuming this plant is for culinary use, so I don’t recommend them.

There are some organic fungicides out there that would be safer, but they’re protective, not curative in nature. They won’t get rid of the existing infections, they will just prevent new lesions from forming.

You would have to use these products regularly to maintain the protective layer of fungicide — say, once or twice a week.

Generally, we try to modify the environment to make it less favorable to the disease and more favorable for the plant.

As I was raking leaves around my Cistena plum bushes, I noticed a gummy ooze around the base of the bushes, which indicates the presence of borers. I did drench them this summer with Permethrin, but obviously, not heavily enough.

Is it too late to fumigate with mothballs? I have searched in four different stores for mothballs made with paradichlorobenzene (PDB), and have been unable to find any.

Do you have any information about where I might find the PDB mothballs, or what else could I use to accomplish the purpose?

— Leah

I’d just sit tight until June. There’s no damage going on right now, and any additional damage next spring isn’t going to make or break the plant.

Just make sure you do the drenches late in the spring.

I’m not sure why PDB is so hard to find. I’ve always considered the PDB to be a very weak substitute for the drenches but better than nothing. Maybe we’re down to just doing the drenches.

 

We have three thriving spruce trees at our house that are at least 20 years old. Some branch tips are bent over and browning so that they look like cocoons. Is this budworm? If not, can you diagnose from my description? Can you suggest a treatment, then prevention we can do or does it call for an arborist?

— Betty

I think you may have Cooley Spruce Gall Adelgid in your tree. Go to forestryimages.org/images/768x512/1246053.jpg to see a picture of the damage this insect can cause on spruce.

The insect really doesn’t hurt the tree to any great extent; it’s mostly an aesthetic issue with dead brown cone-like tips on the branches. Their populations can vary a lot from year to year, depending on the weather. They also tend to be much more common and plentiful when Douglas fir trees are nearby.

Cooley Spruce Gall Adelgid have a fairly complex life cycle with the insect spending part of its time on spruce and part on the Douglas fir, though there are some indications that some of the insects may be able to live only on spruce.

If you want to treat for them, the best way to go about it is to spray the trees with a mixture of Sevin or Permethrin and Ultra Fine Oil. Spray the tree in the spring, probably sometime around the end of March to early April. You’ll need to do a good job spraying, working to completely and thoroughly cover the tree.

If the tree is big, you’ll probably have to hire a professional spray company to do it for you.

Dennis Hill is the nursery manager at Bookcliff Gardens, bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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