July 26 Pest Alert Message

July

July 26, 2022

Now that the weather is hot and dry, disease problems should be at a minimum. I have been seeing several species of blight on apples, it also affects pears, crabapples, hawthorns and other species in the rosacea family.  Prune out Fireblight strikes on a hot, dry day. Sterilize pruners in between cuts. Keep plants well-watered, but keep irrigation water off of branches and leaves to avoid disease infection.  If it is a severe infection a copper spray next spring should be planed.

Powdery mildew is being seen on trees now, try to keep water off leaves, or water mid morning to give the foliage time to dry. Most cases are not severe enough to spray a fungicide.

Cedar-apple rust is causing yellow to orange spots on hawthorn trees now. It is too late to spray, instead spray sulfur next spring when leaves emerge.

We are catching Codling moths now and finding codling moth worms inside developing apples in some sample sites and a few new Codling moth stings. Plan on applying another spray to your trees. 

Fall webworm caterpillars are forming silken webs in apple, cherry and chokecherry trees now. Cut out limb or spray with Bt (bacillus thuringensis) to control them.

Grasshopper populations are increasing a bit in some locations. If they are still a serious problem, you can apply quicker-acting carbaryl-treated bran baits to affected plants. These insecticide-laced baits can injure birds if they eat them.  

Aphid populations are decreasing. You may still see curled leaves from earlier aphid infestation, but few aphids are present inside curled leaves at most locations. There is no need to spray for aphids now at most sites.

Eriophyid mites are responsible for yellow to brown to red spots and blisters on maple, boxelder, apple, pear, and mountain ash leaves. These spots may coalesce and cause leaves to fall at this time of year. It is too late to spray for blister and rust mites now. The damage is mostly cosmetic and should not injure trees.

Spider mite populations are still prevalent in the landscape. Spray with insecticidal soap plus 1 Tbsp sulfur per gallon (spray in the early morning or late evening when it’s not so hot).

Wilting spruce tree terminals (top branches) can mean White Pine Weevil larvae are feeding inside the tip branch. Remove and destroy wilted, browning spruce tips as soon as you see them.

Knapweed is at full- bloom to seed setting. Mow knapweed to diminish seed dispersal ASAP.

Keep water off of vegetable garden plant foliage to avoid disease, or water early in the day so the water evaporates off the foliage.

Slugs and earwigs are very active in our flowers and gardens right now, try to water alittle longer but not as often so soils can dry out a bit. 


The Missoula Iris Society will host the Annual Iris Rhizome Sale on Saturday July 30th  at the Fort Missoula Iris Gardens from 9:00 a.m. to 1:00 p.m. unless sold out earlier. This is a great opportunity to pick and choose from a selection of colors and varieties of iris for your garden at a very reasonable price. The rhizomes are grown locally in member gardens and at the display gardens. Proceeds from this sale allow the Missoula Iris Society to maintain the public display gardens and sponsor iris shows at no cost to visitors. From South Avenue west of Reserve Street, follow the signage to the Historical Museum at Fort Missoula from the round-a-bout. The sales tables will be located just west of the museum.