Friday, August 5, 2016

Blossom End Rot in Tomatoes by Carol King

Photo by Carol King

It seems that all the tomato conversation lately has been about blossom end rot. The Plant Clinic reports that numerous examples have come in concerning it in tomatoes, squash, eggplant, and peppers. The gardening hotline at the Extension Office is buzzing with rot questions. There’s obviously a lot of rot going around.

So what is this nasty sounding ailment? It starts at the end where the blossom was and begins turning tan, then a dry sunken decay sets in. The lesion enlarges, turns to dark brown to black and becomes leathery. Thus the blossom end begins to rot.

It shows up especially in the first fruit of the season and after the fruit is well on its way to development. In severe cases, it may completely cover the lower half of the fruit. Both green and red fruit develop it. It’s not a pest, parasite or disease process but is a physiological problem caused by a low level of calcium in the fruit itself. In other words, dear gardener, IT’S ALL YOUR FAULT!

Why? Several factors may have been at work.

1. You rushed the season. Transplants should be set out only when soil temperature is above 55 degrees Fahrenheit. If you put your plants in, in early May and didn’t warm the soil that helped to create conditions for poor root development predisposing plants to blossom end rot.
2. You damaged the roots. If roots are damaged during transplanting or by hoeing later in the season that will increase the chance for blossom end rot. Don’t till within 1 foot of the plant, and when you do cultivate make sure not to go deeper than approximately one inch into the soil.
3. You inconsistently watered. You watered too much, watered too little, did not water deeply. Plant roots take up calcium and other needed nutrients only when dissolved in water, so irregular watering is often the culprit with blossom-end rot. All the water we've had from rain this spring and early summer hasn't helped the problem!
4. You didn’t mulch. If the soil is allowed to become too dry, calcium uptake is interrupted. Keeping the soil mulched is a good remedy to prevent blossom end rot
5. You used the wrong fertilizer. Fertilizing with ammonium nitrate can create conditions ideal for blossom end rot. This type of fertilizer (and that includes large amounts of manure) can compete with calcium for uptake by the plant. It also causes excess soil salts around the plants.

All right, so you know now that you messed up. What can you do this season to salvage some vegetables? Improve the soil quality around your plants by maintaining adequate, consistent soil moisture through mulching and watering properly. Avoid high nitrogen fertilizer using instead, a slow- release organic fertilizer high in phosphorus. A mixed fertilizer with a ratio of one part nitrogen: three parts phosphate: one part potassium is ideal. Many fertilizers marketed for vegetables come with this ratio. Cut the spots off the affected veggies and eat what you can salvage. No you can’t catch blossom end rot from your produce.

And so, enjoy what you can this season. Next season, I know you will do the right thing and avoid all this rot!