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40 year old Ficus tree #843391

Asked July 31, 2023, 8:30 AM EDT

Hello- My 40 year old ficus tree has some type of disease or fungus. I've tried spraying with copper type treatment and neem oil, but end up having to completely cut the tree back to the branches. It then gets new leaves and thrives for a few months before going into this cycle with dropping leaves. The backs dropped leaves show some damage (see photo) and some of the leaves still on the tree have very tiny black dots on the back - not all leaves. I would very much appreciate your help!

Washtenaw County Michigan

Expert Response

Hi Laurie,

The damaged leaves in your photo look like they have damage from thrips.  The whitish marks are from the sucking mouth parts of the thrip as it feeds on the leaves and the black spots are the frass.  Thrips are a common houseplant pest, and are very small bodied, straw-colored insects with tiny feathery wings. They’re so small they can be tough to spot with the naked eye. Blotchy reddish brown discoloration can also be an indication that a thrips infestation is present. They can reproduce asexually, and with no natural predators found in human spaces (indoors), they can quickly multiply and cause significant damage. Of all the common houseplant pests, thrips are perhaps the most challenging to deal with.
Your plant may have been infected from a new plant in your home or if you place your plant outside in the summer.
To treat a plant for thrips, the first step is to hose the plant down under the sink or shower faucet, dislodging the bugs. Take care not to overwater the soil with the runoff. If it's not possible to move the plant to a water source, use a spray bottle and microfiber cloth and spray and wipe each leaf. Follow this with an insecticide, such as neem oil. Neem oil is a natural pesticide and leaf shine that’s been used for hundreds of years on crops and houseplants alike. Best of all, it’s non-toxic to birds, animals, and many beneficial insects. Mix the neem oil with water and apply it to the plant with a spray bottle, letting it rest for 5-10 minutes, and then wiping the leaves clean afterwards. For serious infestations that are undeterred by neem oil, an insecticidal soap is a stronger treatment option to consider. When the insects are present, apply thoroughly to all of the plant’s surfaces and repeat every 10 days until you no longer see any of the bugs. Please note insecticide should be applied in the evening, or when the plant is removed from the direct sun, as sunlight combined with the insecticide can burn a plant.  
No matter the treatment separate the affected plant from the rest of your collection while it recovers, taking special care to ensure that none of the plant’s leaves are touching another plant’s. For future prevention, try regularly wiping down the leaves with water to deter thrips from returning.

Hope this information helps.

Thank you for using Ask Extension.

Pam V.
MSUE Advanced Master Gardener



An Ask Extension Expert Replied August 07, 2023, 12:49 PM EDT
Thank you for this information! This is good to know. I’ll follow your directions.

~Laurie

On Aug 7, 2023, at 12:49 PM, Ask Extension <<personal data hidden>> wrote:


The Question Asker Replied August 07, 2023, 1:17 PM EDT

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