Hello,

The grey mildew on your raspberries is likely caused by the fungus Botrytis cinerea, commonly known as gray mold. This is a common issue, especially in fall raspberries, due to the cooler and wetter conditions that favor the development of the fungus. More information at this link:

Management of botrytis gray mold in fall raspberries - MSU Extension

Here are some steps you can take to manage and treat the gray mold:

Cultural Control:

Ensure your planting site has good airflow to reduce humidity in the canopy.

Use low-density plantings, narrow rows, and trellising to minimize humidity buildup.

Maintain good weed control and use moderate fertilizer to prevent lush growth, which is more susceptible to mold.

During picking, avoid handling infected berries to prevent spreading spores to healthy berries.

Harvest timely and cool the berries rapidly after harvest to reduce post-harvest rots.

Fungicides:

There are several fungicides labeled for control of Botrytis in raspberries. For example, Switch (cyprodinil + fludioxonil) is a reduced-risk fungicide with excellent systemic and protectant activity against gray mold, and it has a 0-day pre-harvest interval (PHI), meaning you can apply it up until the day of harvest.

Remember to always read and follow the label instructions when using fungicides. It’s also beneficial to remove old, infected canes and plant debris, as the fungus overwinters in this material. More information at this link:

Management of botrytis gray mold in fall raspberries - MSU Extension

I hope this helps!

Could this be blight and how would I treat it if it is?

Could this be blight and how would I treat it if it is?

Hello Again,

For a confirmed and precise identification of the problem, I recommend you send all your images by e-mail to the MSU Plant & Pest Diagnostics Lab. The experts there can also provide you with the best treatment options. Their email is <personal data hidden> - Please include your name – The lab will let you know if they need a sample sent. FYI – The lab may also ask for additional images too.

Their website is at this link:

Plant & Pest Diagnostics (msu.edu)

Their Contact Information is at this link:

Contact Us - Plant & Pest Diagnostics (msu.edu)

This link will explain the details on submitting a sample to MSU Plant & Pest Diagnostics Lab:

Submit Samples - Plant & Pest Diagnostics (msu.edu)

I hope this helps!