This is the Q&A for the Yard and Garden show for June 10, 2016. Yard and Garden Live is a call-in radio show I do on KUTT 99.5 FM from 10-11:30 am and it will run through August 5, 2016. It can also be found on kutt995.com for online listening. If you missed a show or just want to read through the questions, I have written them all in my blog and will continue to do so throughout the season.
Guest Host: Paul Hay, Gage County Extension
1. The first caller of the day has a small Dwarf Alberta Spruce that is turning brown. What would cause this?
A. This would be from spider mites. This particular tree species is very susceptible to spider mites. They can be controlled with a strong spray of water or insecticidal soaps, horticultural oils, or a general insecticide such as a permethrin product.
2. This caller wanted to know if it was still ok to apply the second fertilizer application for the lawn?
A. Yes, you can do one around Memorial Day. I would suggest waiting until after this heat wave passes through and make sure the lawn is well-watered when you do fertilize, so you don’t fertilize to a drought-stressed plant which can cause leaf burn.
3. What would cause Clematis leaves to turn yellow, the plants still bloomed fine this year?
A. Clematis has a problem with Iron chlorosis. This could be iron chlorosis which can be treated with an iron fertilizer.
4. A caller wanted to know what the best control for squash bugs in the garden would be?
A. Squash bugs will become active soon. Look on the underside of the leaves of your cucurbit plants such as cucumber, zucchini, squash, pumpkins, and melons. Squash bugs lay their eggs on the underside of the leaves. If you find the eggs, squash the eggs or remove the leaves. You can also spray for them. Spray on a rotation of every 10-14 days throughout the growing season. Switch between at least 2 of the following: sevin, eight, or bifenthrin.
5. This caller has rocks near the lawn and near some trees. There are weeds growing up through the rocks. Can glyphosate, or Roundup, be used around these trees?
A. If the trees are not close enough to be spraying directly on the trunk or leaves, then it will be fine. Glyphosate is not mobile through the soil like some chemicals.
6. This caller wanted to know what to do about the gnats outside? He cannot go outside right now without being attacked by gnats.
A. There is no longterm cure for gnats, much like mosquitoes. Using bug sprays, especially those containing DEET, will help the most. If you have an outdoor event coming up, you can treat the lawn and surrounding plants with sevin or other general insecticide, but these will not last for more than 2-3 days.
7. Is it too late to plant sweet potatoes? What can you do about grasshoppers in the landscape?
A. No, it is not too late to plant sweet potatoes. This is a warm season crop that really doesn’t like the early spring planting. They will do fine if planted in late May to early June. For grasshoppers in the landscape, they can be sprayed with any general insecticide. If in or nearby the vegetable garden use sevin, eight, or bifenthrin for safety of the produce. Be sure to spray the insecticides in the ditch, roadside, and fence rows where grasshoppers are found in high numbers.
8. This caller has hemlock in the pasture. Is it poisonous? How can he control it so his cattle don’t eat it?
A. Yes, poison hemlock is poisonous if eaten, not if it is touched. Cattle can be poisoned by it, but they typically don’t eat the poison hemlock if there is an alternate food source. Use 2,4-D or Grazon in the pasture to control poison hemlock or dig it out.
*Don’t use 2,4-D this late in the season around landscape plants and never use Grazon or other products that contain Tordon in a landscape setting.
9. A caller has common mullein in his pasture. How can it be controlled?
A. Common mullein is best controlled with 2,4-D or Grazon. Make sure you spray down into the heart of the plant to get the chemical past the hairy leaves. It is best to spray the smaller plants, it would be too late to spray the larger plants that already have a flower stalk on them. Removal of the flower stalks will help reduce seed production from the full grown plants.
10. This caller has a 16 foot river birch that was planted last fall. Now the leaves have turned yellow and are beginning to fall off of the tree. Can it get too much water? What would cause this problem? She hasn’t been watering the tree much yet since it was planted in the fall.
A. Yes, plants can be overwatered to cause death. Newly planted trees need to be watered because they have no root system developed. A tree that was transplanted at this large of a size is going to have a great deal of transplant shock to overcome. Water was sitting in the hole when the tree was planted, so there may be an issue with water draining from the location. Use a probe or long screwdriver to see if the tree needs water. Push the probe into the soil 12-18 inches, if it goes in easy it doesn’t need water, if it is hard to push the probe in very far, the tree needs to be watered.
11. The final caller of the day wanted to install an electronic timer for watering his garden. What would be the best time to set his timer to water his garden?
A. 4 am-10 am is the best time to water any plants. This helps to water the plants while they are already wet from the dew period. It also helps to water early in the day so that the plants will dry out before night. Plants that are wet and cooler overnight introduce a great environment for diseases to occur. To reduce diseases, it is best to water early in the morning.