Courtesy Meredith Seaver, USU Extension

I’m finally planting my beets in a few days, but I don’t want to have the same problem I had last year. I don’t know what you call the disease, but the leaves got large brown patches on them and dried out. I still got lots of nice beets, but I want to avoid that problem this year. Should I plant a special variety or spray a fungicide or something like that?

Your description sounds more like an insect problem than a disease problem. There are small, gray flies called leafminers that like to lay their eggs on spinach and beet leaves. Take a look at today’s photos and see if the plant damage looks like what you saw last year.

When leafminer eggs hatch on beet, chard or spinach leaves, the larvae enter the leaf and feed on the tissues between the upper and lower surfaces of the leaf. Their feeding leaves trails and patches of tissue that turn brown and die. At first glance, the leaves often look diseased. Once the larvae are ready to pupate, they drop out of the leaves and into the soil. Adult flies will emerge from the soil after pupation and lay eggs for a new generation of leafminers.

Leafminer damage doesn’t affect the quality of the beets, but if you want to eat the beet greens, their damage is a problem. There are a few things you can do to reduce leafminer damage in your garden.

The most important thing you can do is to give your beets good care. Water deeply during the summer between once and twice a week, depending on your soil and the weather. Keep your garden weeded and watch for other insect pests.

Courtesy Meredith Seaver, USU Extension

Get in the habit of inspecting your beets frequently. Look for eggs and leaf mines. Take a look at this week’s photos for examples. Eggs can be crushed by rubbing them between your thumb and finger. Leaves with leaf mines should be removed and disposed of; don’t just drop them in the garden.

You can also shallowly and carefully cultivate the soil around your beets during the growing season to find and destroy any pupae. In the fall after you’ve cleaned out your garden, cultivate the soil again to expose any pupae to predators and winter weather.

Another method to try is excluding leafminers from your beets this year by planting them in a different part of the garden and completely covering that planting area with lightweight floating row cover (with room to grow) for the first few weeks. That will temporarily exclude leafminer adults that emerge from the old planting area.

Insecticides to target the egg-laying adults and the hatching larva may be helpful, but larvae that are already feeding inside the leaves will be protected from the sprays. Choose a “soft” insecticide, like the active ingredient Spinosad, to reduce harm to beneficial insects.

Is it true that I can’t plant my tomatoes in the same place where I grew my potatoes last year? Why won’t they grow if I do?

Courtesy Meredith Seaver, USU Extension

Your tomatoes will grow, but you could have disease problems if you’ve grown potatoes or tomatoes in that spot for a few years already. Potatoes and tomatoes are members of the same plant family and are susceptible to the same diseases and pests. When vegetables or annual flowers from the same family are grown in the same place year after year, pathogens or pest populations can build up in the soil. If you alternate your plantings with completely different vegetables or flowers in each part of your garden from season to season, those pathogens won’t have the hosts they need and won’t have a chance to increase year over year.

If you have enough room in your garden, don’t plant the same plants or related plants in that part of your garden this year. For example, if you’ve been growing petunias in your flower garden, choose geraniums or dahlias this summer instead of petunias, or their close cousin nicotiana, or plant corn or onions instead of potatoes where you grew tomatoes last summer.

Planting unrelated flowers and vegetables in a three-year rotation, removing diseased plants promptly and cleaning up dead plant material every fall can make a difference in the health and productivity of your garden plants. Good sanitation for your tools is also important so you don’t carry disease organisms from one place to another in the soil on your tiller, shovel, hoe or trowel.

It’s easy to lose track of where things were planted from year to year. Keep notes about what you planted and where you planted and save the notes in a calendar or similar location so you can check what you’ve done in the past before you plant each year.