What can we do to save these shrubs?
"Fielding Questions" columnist Don Kinzler offers advice on damaged arborvitaes, and also weighs in on using tires around tomatoes and a spray regimen to deal with insects on raspberries.
Q: We have three arborvitaes on the west side of our house, and two have damage. I’m wondering if it’s sunscald or something else. Is there anything we can do to save the shrubs? — Karen K.
A: When portions of arborvitae turn brown, there are two common causes. Winter injury is a possibility, either from winter winds that desiccate foliage, or from sun reflecting off the snow, burning foliage the same way that skiers get winter sunburn. From the photos, I’d say the damage is most likely winter-related injury.
Rabbit injury is a second possibility when entire branches turn brown. During winter, rabbits sometimes nibble the bark on branches inside arborvitaes. Tracing the damaged branch back to its point of origin sometimes reveals stripped bark, causing affected branches to die from the point of injury outward.
The browned foliage won’t revert to normal, of course, so the next step is to determine if the branches on which the damaged foliage is attached are living or dead. Test the twigs to see if they are live and pliable, or if they snap readily when bent, indicating death. There’s no other option than to prune out branches determined to be dead.
If the foliage is brown but the branch on which it’s attached is still alive, there’s a possibility new growth might arise, if the brown foliage is removed. New growth often does not regrow from these damaged areas, however.
After pruning out dead areas, decide whether there’s enough shrub left to salvage. Growth from the remaining branches can occasionally fill the gaps, but severely damaged arborvitae are often better replaced.
Q: When we plant our tomatoes, my husband has always believed in putting tires around the plants in addition to using cages. The plants start out looking great, but partway through the season, the leaves start turning yellow. I’ve tried an antifungal spray, and the tomatoes usually turn out okay, but not in great abundance. I’m wondering if using tires is a problem. What do you think? — June K.
A: Using tires or rubber mulch made from tires has been controversial, and I don't think all the data is in yet. Some sources believe toxic compounds used in tire manufacturing leach out of the tires and into the soil, while other sources say the leaching is minimal and plants don’t necessarily absorb the materials. The controversy is more substantial, though, when discussing edibles, versus landscape plants. I always believe in erring on the side of caution, especially with food crops.
What's causing the yellowing leaves? It could be a reaction to the tires. Are the tomato plants in full, all-day sunshine?
Disease is always a possibility. Tomato varieties vary greatly, and some are more disease-resistant and easier to grow. Two of the most popular and successful are Celebrity and Big Beef.
If fungicides are used, they should be applied as preventatives before the symptoms appear for effective disease control.
You might also try fertilizing around each tomato plant, if you haven't done so. You can use a special tomato fertilizer, water-soluble general-purpose types, or 10-10-10 granular all-purpose fertilizer, always following label directions.
Non-hardy shrubs might look nice, but they'll probably die back eventually
Gnats on houseplants, non-hardy evergreen, lawn thatch removal
Your lawn care calendar for 2021
Q: A while back you answered a question about what to use on raspberries for insects . I thought I kept the article but I can’t find it. Thanks. — Earl O.
A: Two insects that are common plagues of strawberries are the little black sap beetles, also known as picnic beetle, and the little white larvae of spotted winged drosophila flies.
Two products that are useful in rotation against these common pests are malathion and spinosad. The waiting period between time of application and time of harvest is less than many other insecticide types, meaning spinosad or malathion can be applied closer to the day you plan to pick berries. Check labels for the intervals between spraying and safe harvest.
If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at email@example.com. Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.