Mystery disease in Farmington Hills plants

Asked June 16, 2018, 12:53 PM EDT

Hello,
A lot of our different plants, around my suburban home, seem to look rather diseased. Can you please advise me if i need to dig them up and get rid of them? Or if there is anything I can do to make them better? Thank you for your time and expertise.

Oakland County Michigan garden pests leaf spot flowers: annuals and herbaceous perennials

1 Response

Hello,

On the columbine in your first picture you have leaf miners. Control isn’t necessary unless all of the leaves are affected. Pick off the damaged leaves and place in sealed trash. This will help reduce the population of these insects. If you must use insecticides spray early morning or late evening to avoid spraying when bees are active. Insecticides for columbine are pyrethroid-based and useful against the adults leafminers: Permethrin, bifenthrin, cyfluthrin.; spinosad is somewhat effective on the larvae, but clipping off the leaves is best.

Your mums in the second photo have some sort of leaf spot, though they are so far gone I am not sure which. You may submit sample stalks with as many still live leaves as possible and showing the start of the spots to MSU Diagnostic lab, who may identify the exact fungi. A small fee is charged:

https://pestid.msu.edu

Chrysanthemums are subject to several leaf spot fungi including Septoria chrysanthemi, S. chrysanthemella, Alternaria species, and Cercospora chrysanthemi . Symptoms first appear as yellow spots which turn brown to black. Fter defoliation, and most will come back next year. Spots often occur on lower leaves first and can coalesce into large necrotic areas and finally death of the entire leaf. Regularly clean up and destroy infected plant debris and hand pick symptomatic leaves from lightly infested plants. Avoid splashing water onto plant foliage and water early in the day to allow foliage to dry quickly. In severe cases, applications of fungicides with the active ingredients with the active ingredients azoxystrobin, chlorothalonil, fludioxonil, iprodione, mancozeb, myclobutanil, propiconazole, pyraclostrobin, or thiophanate methyl may be applied according to label instructions.

Your last photo looks like four-lined plant bug damage. Small amounts of damage are tolerable and require no action. Here is an article describing controls-

https://www.extension.umn.edu/garden/insects/find/fourlined-plant-bugs/

Most well established perennials will push out new leaves after losing leaves. For all these issues keeping damaged leaves clipped off and cleaning up debris under plants is helpful. Also, keeping foliage as dry as possible when watering reduces most fungal diseases. As always, please follow all directions and precautions when using chemicals. The fewer chemicals you use the lower the impact on bees and other beneficials.

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