This is the Q&A for the Yard and Garden show for June 12, 2020. 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 July 31, 2020. 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: No guest host due to COVID-19 and social distancing
1. The first caller of the show has tomatoes that only grew to about 1 foot tall and then they died back from the top. What is wrong with them?
A. It could be that they need to be watered more effectively. He has the plants mulched with grass and is watering, but just using a hose-end sprayer. When just watering with a hose like that the top couple inches of soil get wet then it spreads out rather than down, so the plants aren’t getting enough water to their roots. It could also be from a disease, but it is hard to tell from just a description.
2. A caller has watermelon radish plants that are going to seed. Can she cut the flower stalks off so they continue to grow? The radishes are not very large yet.
A. These plants are not going to grow much longer. When we get to hot weather the cool season crops will go to seed or bolt and will not live long, radishes are one of those plants. She said she had to replant later in the year due to frost damage in late April/early May, that is just too late to plant radishes for a good crop. She could try again in the fall or plant earlier next spring.
3. A caller has an American elm tree that has a few branches that are dying off. He has cages of rabbits underneath the tree and wondered if too much nitrogen was being applied to the roots or if the roots are reaching up to under the chicken coop with high nitrogen?
A. It is more likely that this tree has developed Dutch Elm Disease and will likely die. There is no control or prevention for this disease. American elms were mostly wiped out in the 1960’s due to this disease but a few have survived or came up naturally. The American elms that are still alive will eventually die due to the disease, it will get to them. He can send a sample into the UNL Plant Pest Diagnostic lab for confirmation, but if it is Dutch Elm disease, the tree should be removed.
4. This caller is actually from Oklahoma, but was doing work in the area to call in. He was wondering what we do for squash bugs?
A. Squash bugs can be difficult to control in a garden and most of the time once they are in your garden, they will always be there. For chemical controls, sevin, eight, or bifenthrin are all labeled for use in the vegetable garden. Be sure to watch the PHI, pre-harvest interval, or amount of days to wait from application until harvest. For squash bugs make sure you are spraying thoroughly on the underside of the leaves where the eggs are laid to kill larvae just as they emerge. You can also squash the copper-colored, football shaped eggs as you find them on the underside of the leaves. Be sure to clean up the garden in the fall to eliminate the overwintering site.
5. This caller had 3 questions. First, when and how short can a spirea be pruned?
A. It is a spring blooming spirea, so it should be pruned within a few weeks after blooming has completed for the year. Up to 1/3 of the plant can be removed in one season. So if it is 3 feet tall, you can remove 1 foot of the growth. Be sure to prune back to a side branch. Continual shearing will leave heavy growth at the base of the plant with spindly growth on top. Spireas can be renewed with a rejuvenation pruning where it is cut back to 6-8 inches above the ground. This should be done in the fall and not every year. You will not see blooms the year following a rejuvenation pruning.
How do you prune lilacs? It is overgrown.
A. If the lilac is overgrown, it can be pruned through a rejuvenation pruning in the fall, like suggested with spireas. Otherwise, it should be pruned within a few weeks after blooming has been completed in the spring.
His final question was about tree black walnut. The tree was pruned at a random location mid-way through the branch. It has now died back further than where it was pruned. What is wrong with it?
A. Be sure to make a good pruning cut. Branches either need to be pruned back to the trunk, just outside of the branch collar, or to a side branch. The side branch needs to be at least 1/2 the size of the branch being removed.
6. A caller has poppies that she received from the Yukon. These poppies are blooming now and she wants to dead head so they continue to bloom, but she also wants to save the seed to start some new plants. Can she cut the flower heads off before they fully dry to save the seed?
A. The seed needs to be allowed to fully mature on the plant. So, unfortunately, you will have to choose between dead heading and allowing the seed to mature on the plant. If they are picked too soon, some may germinate, but the rate will be low.
7. An emailed question regarding the listeners garden which was hit by herbicide drift. Will the produce from this garden be safe to consume?
A. There is no way to know for sure when or if the produce will be safe to eat. It is better to throw it out and start over when in doubt.
8. This caller was curious about collecting seed from winter onions, or walking onions. She tried last year but they didn’t grow at her house after she took the above ground bulbs from her sisters plants. What does she need to do differently to get these onions to grow?
A. These also need to be allowed to fully mature on the plant, like the poppies. The stems with the above ground bulblets on them will dry up and fall over. When they are falling over the bulblets are mature and can be picked up and planted in new locations. If the bulblets were picked off the plant prior to this, they were not fully mature and wouldn’t develop into new plants.
9. A caller has oak trees that the branches are dying from the bottom up. What can be done?
A. These are likely pin oak trees and it is very common in pin oak trees. The lower branches could be dying due to lack of sunlight. It could also be due to a few diseases. If the branches are dead with no leaves, they should be removed to keep them from falling. If this continues, a sample could be submitted either by photo to me or a sample to the diagnostic lab at UNL, linked above.
10. This caller has tomato plants that were cut off at the ground level but the plant was left behind. What caused that? How can this be stopped?
A. This was likely due to cutworms. They can be managed by using sevin or diatomaceous earth around the base of the plant when they are planted. You can also wrap the base of the plant with aluminum foil to prevent feeding. This caller took the plants inside the next day and placed them in water and in soil to try to re-root them, it worked for some. Great idea, if caught early enough!
She also wondered if diatomaceous earth is effective for squash bugs?
A. It would not be as effective for squash bug adults. It can be used for squash bug nymphs.
11. A caller sprayed his evergreen trees with Tempo to treat for bagworms and it rained just a few hours later. Will he need to respray?
A. The label states that it is rainfast after 24 hours, it is likely that this application was mostly washed off. The label also states that it can be reapplied every 7-10 days, so it would be best to wait about 7 days before reapplying. It would still be within the timeframe for spraying bagworms at that time.
12. This caller has been able to hand-pick bagworms off of her small tree through the year. Does she also need to spray?
A. If you are able to continue to pick the bagworms off as you see any new bags form, you wouldn’t have to. If you see a large amount of small, black caterpillars or if a large quantity of bags form on the tree, you can spray.
13. How often can you spray Eight to control squash bugs?
A. Remember to always read and follow the label when using pesticides. It would likely be fine to spray every 10-14 days through the season, but one label I looked at said every 3 days if necessary. Just be sure to follow what your label states and also follow the PHI, pre-harvest interval, or amount of days to wait from application until harvest.
14. A caller has an oak with old scars where limbs were removed by previous home owners. One of the wounds is weeping. What is causing this weeping? What can be done about it?
A. This is likely due to a bacterial infection of the heartwood, called wet wood disease. Those pruning scars did not fully seal over and it has allowed the bacteria to enter the tree. It is minimal damage to the tree and won’t kill the tree. There is nothing to do to stop the weeping, but again it doesn’t really hurt the tree.
15. The final question of the day was from a caller who has cucumber plants with leaves that are drying up and dying. What is causing the browning which starts on the outside edge of the leaves? Can anything be sprayed on the plants to stop the damage?
A. This is likely either environmental stress or a slight fungal disease. The environmental stress could be due to the heat or drought stress if they aren’t receiving sufficient irrigation through this hot, windy weather. It could also be from a fungus, there are many that affect cucumbers. A fungicide, such as copper, could be used to reduce the spread. Without a picture, it is hard to determine for sure what is affecting these plants.
*Reference to commercial products or trade names does not imply endorsement by Nebraska Extension or bias against those not mentioned.
Plants and Pests with Nicole 