Questions from this past week

Mystery mushroom — stinkhorns. iGrow photo

By David Graper
SDSU Extension Horticulture Specialist

Is it OK to eat rhubarb now?

Q I went to the Farmers Market in Aberdeen this week and several offered rhubarb. I thought you had to stop picking rhubarb by mid-July because the oxalates from the leaves moved into the stems and cause upset stomachs. We have had some rains so rhubarb looks good. Is it safe to pick it for pie?

A Yes, it is good as long as it looks good and the rain definitely prolongs the season. Enjoy your pie.

— Sue W White SDSU Master Gardener Lawrence County

Bug ID

City parks supervisor dropped off this bug sample. They are in the playground areas and he wonders what they are and what can be used to eliminate them. Parents are concerned about children being stung. Thanks!

Those are spider wasps (family Pompilidae). These wasps are solitary and nest in the ground, preferring sandy or bare areas (so playgrounds are a popular place for them). They are not known for being aggressive and do not work together to defend a nest like yellowjackets (a ground nesting, social wasp). This is not a wasp that needs to be controlled with an insecticide.

Amanda Bachmann, PhD

Pesticide Education and Urban Entomology Field Specialist

A question on wild mushrooms

Q I found an article you wrote on on wild mushrooms. I am wondering if you or anyone you know of could help me positively identify some wild mushrooms. I just found some chicken of the woods, I believe, but I don’t want to eat it until I have an expert look me in the eyes and tell me yes that’s right! If you could offer any assistance, I’d greatly appreciate it! Thank you!

A Yes, those certainly look like Chicken of the Woods. They are one of the fool-proof-five because they do not look like anything else. Be sure that the underside of the mushroom has pores, rather than gills, like some other kinds of mushrooms have. Even though I am pretty sure this is what you have, and most people find it delicious sautéed with a bit of butter, I would suggest you just eat a small amount to make sure that you personally do not have reaction to it. Hopefully you won’t and will be able to eat more. They are best eaten shortly after they grow since they can get dried out and a bit woody after a few days. Enjoy!

For more information on wild mushrooms see

Brown tomatoes on bottom

Q Some of my tomatoes are in containers on my deck. The two plants that are larger tomato varieties (one yellow and one red) are bearing much fruit; however, the tomatoes turn brown and become rotten from the bottom. What is the cause of this?

A The bottom rotting you are referring to is more commonly called blossom end rot because it occurs on the blossom end of the fruit. It is caused by a calcium deficiency in the tomato fruit, which results from the plant not being able to take up sufficient calcium from the soil. Generally there is adequate calcium in garden soil but uneven watering, excessively wet conditions or other environmental factors that limit water and calcium uptake that lead to the problem. However, in some cases, commercially available potting soil might be low in calcium. If you used purchased potting soil, this may be the problem. Try mixing in 3-4 TBS of bone meal or gypsum per pot with the potting soil before planting next year. There are also differences between tomato varieties, and determinate vs. indeterminate types of tomatoes. Often this is a more common problem for the first tomatoes that are harvested then it gets better later in the season.

The best treatments call for management of water to the plant. Do not let the plant go through water stress then followed by heavy watering, try to maintain even moisture content in the soil. Maintaining evenly moist soils in a container can be particularly difficult if you are growing large tomato plants in relatively small containers and that is coupled with very hot and dry conditions. An organic mulch can help to shade the soil and help it to retain water during hot and dry periods. Adding lime to garden soils, which is calcium carbonate, is not recommended because there is likely already enough calcium in the soil and the addition of lime will raise the pH of the soil, which can cause additional problems with the availability of other nutrients. Calcium applications to the leaves are not generally effective either. I have even heard of people applying milk to their tomato plants, or even ground-up Tums – this would not be a good idea in either case. The souring milk would likely attract insects, animals or various molds that could be harmful to the tomatoes and be a source of food-borne pathogens that could be dangerous to a person eating the fruit. For additional information go to:

Can we transplant my iris and hosta plants?

The best time to plant and transplant rhizomatous iris is late July through September. Iris loves the heat and drier weather of summer and the summer dividing will reduce the incidence of bacterial soft rot. Most rhizomatous iris should be divided every three to five years. If your iris patch is producing very few flowers, it’s time to divide and conquer.

The best time to transplant hostas is in the spring as they emerge. However, hostas can be dug and moved or divided this fall as they are going dormant. If you know you want to divide or move them, get it done this fall, and you will have stronger plants for next growing season.

— Sue W White SDSU Master Gardener Lawrence County

Strange things under a flagstone

Q Wondering if you can help or know who to send this picture to for identification. These were discovered when I noticed a slab of flagstone on our patio was lifting. I decided to dig into the dirt to re-fit the stone and these were just below the surface somewhat hidden in the dirt. Rather slimy. If you look closely there is a branch-like part connecting one part to another on the one in front. We thought it was some sort of animal or egg sac at first, but now are figuring it’s some sort of mushroom. Really creeped us out. Even the ants didn’t want anything to do with it.

A Yes, this is one of the more unusual things that people sometimes find in their gardens or yards this time of year. They do look like some weird kind of alien egg at first glance. These are stinkhorn mushrooms that have not quite emerged yet, but were uncovered when the paver stones were removed. They might have actually been responsible for the lifting of the flagstone that you observed. Nothing to worry about, just rather unusual. They are called stinkhorns because the caps do emit a smelly odor when they emerge from the soil, which attracts some kinds of flies and beetles that get the spores on their bodies and help to spread the fungus around. No treatment is needed or really possible, other than to just remove them from the soil and discard them. They may show up again sometime in the future.

A question on harvesting onions

Q Some of my onions are still growing nicely and getting larger while others have essentially stopped growing and the tops have kinked over, just above the bulb. Are those done growing? Should I harvest them now or wait? I heard that some people knock over the tops before harvesting, should I do that? I planted my onions from plants that I purchased from a local garden center. A friend of mine planted his onions from sets. Most of his were flowering a few weeks ago, now many of his have the tops kinked over too.

A The best way to grow onions and get the largest possible onion bulbs is to grow your onions from plants. You can start your own from seed, about 2 months before you expect to plant them outside. Some local greenhouses or garden centers may also carry the plants in small pots – those work well too. Other retailers may sell bundles of plants that can also be used. However, most gardeners still plant their onions by using sets. Onion sets are easier to plant but generally will not produce bulbs as large as you can get growing your onions from plants. The problem is that onions are biennial. This means that the plants grow one year, go dormant, then resume growth the second year with the “intent” of flowering and producing seed. A first year seedling’s main “intent” is to produce a bulb, so you tend to get larger bulbs by planting plants.

Usually, when onions have matured their leaves will kink over, just above the bulb. That means they are pretty much done growing for the season and can be harvested, cured and put into storage. They can be left in the garden for a few more weeks but you get wet weather for an extended period of time, they may become diseased or rot. As long as the leaves are upright and healthy, they are still producing carbohydrates to store in the onion bulb, causing it to grow larger. So, do not break over the tops. You can harvest them at any time though as needed. If you want to cure them for storage, pull the onions, remove excess soil clinging to the bulbs or roots and let them dry in the sun for a few hours. Then, twist the tops to remove them and place them in a dry, well-ventilated area to cure for at least several days, until the outer layer or two of the bulb scales turn brown. Then you can put them into storage for the winter.

Is this corn smut?

Q I was checking my sweet corn yesterday to see if it was getting ready to harvest when I found this ear of corn with most of it covered in this black mess. I think its corn smut, is that correct?

A Yes, you are correct. Smut is a fungal disease that can attack the leaves, stalks, tassels, silks and cobs. While many fungal diseases cause spots on the leaves or stems, smut is much more flamboyant. What might start out as small spots soon grow into a big mass that will weigh down a corn tassel or turn what was a nice big cob into a blackening grotesque mess. When smut occurs on a cob, it forms kernel-like tumors that can grow to an inch or more in size. The tumors contain spores that can be spread by rain or wind. Disease severity is often worse during dry years because the powdery spores are spread with blowing dust or soil particles. Infection can occur at any time but requires free moisture to be present on the plant for several hours. Corn silks, tassels and leaf axils often hold moisture so they are likely sites of initial infection.

Initially the tumors have a white covering that will eventually turn dry and split open, allowing the spores to be released. Once released, the spores can travel great distances. Removing and destroying the infected portions of sweet corn plants before the tumors break open can reduce the chance of spread but it must be done several times over the course of the growing season. Infection can still occur from old spores from last year of from a neighbor’s garden or corn field. Planting rotation can also help but since the spores spread so easily it may not help much. Using drip tape or ooze hoses for irrigation can help reduce disease problems since it keeps the foliage dry. Selecting smut resistant varieties is also helpful. Fungicidal treatments are generally not effective.

Brown spots in turf

Q I irrigate my lawn but have one area that has been developing brown spots over the past several years. It starts out nice and green in the spring but then about mid-summer, when it starts getting hot, these areas of turf turn brown. I don’t know what the problem is or what to do about it.

A Closer examination of the brown areas in this particular turf revealed that this was a white grub problem. White grubs feed on turf roots during the summer time. Then, when it gets hot and dry, plants that have missing roots cannot take up water as well as other plants can and turn brown, even if the lawn is irrigated. The best way to check for grubs is to take a hand trowel and dig down into the brown spots and surrounding areas. If you can easily lift up the sod, almost like a carpet, look for the white grubs, which are usually about the diameter of a pencil and about 1” long. They are creamy-tan colored with brown legs, a brown head and form a C-shape when disturbed. These are often the larval stage of the typical brown June bugs (beetles) that we see during early summer. However, they may be the grub of other beetles too. Lately Japanese beetles have become more numerous in some areas of South Dakota so the grubs could be from them too. Use a granular turf insecticide labeled for control of white grubs. It is important to follow the label instructions carefully. Timing can be important because these grubs will be burrowing deeper in the soil for the winter soon, making them more difficult to control with the insecticide.