Tomato disease

Asked September 24, 2019, 8:35 AM EDT

Hi there,

Despite my sanitation efforts, my tomato plants become diseased every year.

Is this septoria leaf spot? It starts in July and affects the lower leaves first, even though I prune them from touching the soil and water with soaker hoses beneath straw mulch. Is there a prevention/treatment that will not harm my honeybees?

Thanks for your assistance,

Dickinson County Michigan tomato diseases

1 Response

Hello Stacy
I double checked with our state lab's plant pathologist, and she confirmed that it is Septoria. She has this to say, "

Yes, this looks like Septoria. Assuming that this is a home garden (not commercial production) there are relatively few chemical control options – including chlorothalonil and copper-based products. Some copper-based products are organic. I recommend that the user fully review the label for any pesticide to find application instructions, some of which may pertain to limiting off-target exposure.

It is especially important that the location where the tomatoes are planted be rotated. This allows time for the amount of the pathogen persisting in the soil to be reduced. Typically a layer of mulch that creates a barrier between the soil and the foliage is helpful in reducing disease severity.