Perennials: You can divide German bearded iris at this time through the end of September. Cut the leaves back about halfway so the plants are easier to handle. Also, I’ve been seeing a lot of botrytis on the leaves, which causes bullseye-like lesions and some yellowing. Remove those affected leaves. Yellowing can also be a result of infestation by iris borer larvae, and you may see whitish frass (larval feces) that are small roundish pellets. If you see these symptoms, dig up the rhizomes and check them for iris borers. The borers are mature at this time, and are pinkish and about 1½ inches long –yuck! Remove them from the rhizome and dispose of them. A fact sheet on iris borer is available at https://pddc.wisc.edu/. Look under the “fact sheets” tab for the title “Iris borer.” Often, bacterial soft rot may set in following the borer damage and further deteriorate the rhizome, leaving it mushy and foul-smelling. If there is unaffected tissue remaining, cut off the infected material and wipe off the cut end of the rhizome with rubbing alcohol or hand sanitizer. Also disinfect the cutting tool with rubbing alcohol. Discard the infected material. After the rhizome is cut back to healthy tissue, let it dry and callus off in your garage for a couple of days. Then, re-plant making sure the rhizome is horizontal in the soil and about half of it is above and half below the soil grade. Firm it in well so it doesn’t fall over. Some folks temporarily use landscape staples (also called sod staples) which are narrow U-shaped pieces of wire about six inches long to hold the rhizomes in place until they re-root. These are available in the garden center of most home improvement stores and garden centers. You could make your own out of wire coat hangers if you have a wire-cutter. Water the rhizomes in after planting.

Vegetables: Downy mildew of basil is a relatively new, destructive disease here in Wisconsin. Unfortunately it is not easy to recognize, because from the top side of the leaf, it looks like a bit of yellowing, maybe a nutritional problem, but nothing specific. However, leaf undersides show a grayish to black branched fungal growth, which is easy to recognize. The disease moves fast and kills plants fairly rapidly. Downy mildew can come in on infected seeds or plants, and is easily spread in the garden. Remove plants and destroy them if they are infected. You should not eat infected material. While sweet Italian varieties are the most susceptible, some of the other varieties including lemon basils, purple basils, cinnamon basil and “spice” type basils (“Blue Spice,” “Spice,” etc.) are less susceptible. Minimizing leaf wetness and reducing humidity may help as well. There are fungicides labeled for control, too. They need to be sprayed regularly, and before symptoms start. Organic fungicide products labeled for control are also available.

Lisa Johnson, Dane County UW-Extension horticulture educator

Angry
0
Sad
0
Funny
0
Wow
0
Love
0