Tuesday, September 22, 2009

Can I Compost those Diseased Tomato Plants?

Yes. That’s the short and simple answer to a question that is on many gardeners minds. The disease that concerns most gardeners this year is late blight, Phytophthora infestans, which plagued so many gardens and farms this year. I have spoken to too many gardeners who are wasting time solarizing tomato vines, planning elaborate crop rotations or sending tomato debris out with the trash. Compost them. It’s also good to know that most diseased plants can be composted without the fear of aggravating the disease situation next year.

Let’s take late blight first because it is easiest. The late blight organism requires a living host to survive. Since tomatoes cannot survive our winters, any late blight fungus will die along with the plant. May as well compost the diseased plants. Or you could simply turn them into the soil. For that matter you could let the dead tomato skeletons hang out all winter on their stakes. Dead tomatoes = dead late blight. Late blight does not form overwintering spores in Pennsylvania that could cause new infections next year.

Potatoes are another story. Late blight infected potato foliage can be treated like tomato foliage. But infected tubers should not be put into the compost pile. Tubers may survive the winter and start up new infections next spring.

Most other tomato diseases do have the ability to survive and infect tomato again next year. Early blight, Septoria leaf spot and anthracnose can survive either on plant debris, in special fungal survival structures, on other plants and even on pots and containers. Crop rotation provides some small measure of control but you can expect these diseases to return each year regardless of crop rotation. And let’s face it, we often have limited ability to rotate crops in our small vegetable gardens. Do it, as a good general pest management strategy, but realize it will not eliminate re-occurrence of disease.

Back to that compost pile… since the environment in the compost pile is much more competitive for fungal pathogens than soil, and these disease organisms will survive thru other means, why not compost those diseased plants?
There are a few garden diseases that surely should not go into the compost pile. Fusarium and Verticillium wilt come to mind, but they are relatively rare these days because of good plant breeding. If you suspect that these are involved then trash them. Otherwise… everything into the compost pile.


Eben said...

You seem to have a good grip on this garden mess....tomatoes were great.. the plants, which were all over the place including the ground, looed bad. I put many pruned branches in the compost, for some reason I bagged up the pulled plants.
After the squash and cukes came on strong ...good fruit.... the plants started to look sick.
The potatoes still are green and grow'n. I've been wondered what to do as I'm gett'n ready to put the garden to rest for winter. As per your post I guess I'll compost the stuff and spreed it out to make sure everything freezes. WOW that presumes we get a frost this year.

Scott Guiser said...

Not sure where you live but if temperatures go below freezing (32 F)tomatoes will die. Sounds like your vine crops had late seson problems. Powdery and downey mildew are common late season diseases. Both can go into the compost pile. The larger question of how to put the garden to bed....after moving most debris to the compost pile, till up the garden. This is a good time to add lime if necessary. Incopporate any organic matter on hand such as finished compost, manure or fall leaves. Finally, if you'd like to put icing on the cake, seed a cover crop. In Pennsylvania, consider spring oats or rye. They germinate quickly. Rye will overwinter and make lots of biomass next spring. Spring oats will winter kill. Not always a bad thing, esp. if you want to work that ground early next spring. Rye can be seeded throughout the month of October and still make a stand.