What should I do about the white fungus growing in my raised bed?

Asked November 3, 2018, 5:35 PM EDT

Over the summer, the soil in my raised bed inside a hoop house began to clump up with a white fungus (?) and seedlings stopped growing well. Also, the zucchini plant in the ground beside the raised bed behaved strangely, with each fruit rotting from the tip. (Not sure if that is related.) In the raised bed soil, the fungus is especially clumped around the roots. Do I need to remove all the soil before I plant anything again? Thank you.

Benton County Oregon

1 Response

Hello. It is difficult to diagnose a problem after the fact. Fungi grow in a moisture rich environment and can thrive in areas where air circulation is restricted such as in a hoop house. Not sure why you were using a hoop house in the summer especially for lettuces as they would not do well in a hot environment such as inside a hoop house and that could have been the reason for their decline. At this point it can’t be determined if the fungi shown in your photo was the cause of the decline in your lettuces. Lettuce prefers cooler temperatures than we typically receive in midsummer and would do better with some shade during the heat of our summer. Most importantly I don’t know what the symptoms of your lettuce problem were. Did they wilt, rot or just not grow as fast? Next growing season I would be sure to alternate crops in those beds affected. I would also carefully monitor the moisture levels in the soils to keep them from getting overly wet as this will encourage fungal growth. If you experience the same issues next summer call the Master Gardener Information desk as soon as the problem occurs and let us help you walk through the conditions of the weather, watering, fertilizing, what your crop is doing that is not normal and any other cultural practices that you have taken to try and avoid the problem.

On the other hand, two things could be causing the rotting on your zucchinis. One is the same physiological problem that is often seen in tomatoes and is called blossom end rot. This occurs when the blossom end of the vegetable is rapidly expanding during growth and not enough calcium is being supplied to the cells during this rapid growth. Causes of this are either Calcium deficiency in you soil OR irregular watering. Alternating between moist and dry soils causing the starting and stopping of the water moving through the fruit could result in the tissue dying on the ends of the fruit. You can see this in tomatoes, peppers, squashes and in some cases watermelons. Keeping the soil evenly moist is best. You also should get a soil test before you plant next year to determine if there is enough Calcium in your soil to rule out that as an issue. Be sure to also get a pH test when you test the soil. Calcium needs a soil pH of between 6 and 6.5 to be able to move freely. Our native soils can get quite acidic. Depending on the source of your soil in your hoop house this could be an issue. If the pH is lower than these numbers, you may want to lime the soil this fall. The other thing that could be happening with the zucchini is poor pollination. If your zucchini was inside the hoop house it is possible that pollinators were not able to get inside in large enough numbers to fully fertilize the flowers. Zucchinis do like hot environments but do just fine planted outside during our summers. You can put protection around them if you want to get a jump start on the season and plant them outside early. A wall of water or a row cover can help the plant get a jump on the season. Just be sure to uncover and allow pollinators in as soon as they start to flower.