Green Industry Resources
Hort Update- Seasonal Information for the Green Industry
Show Questions -- June 14, 2012
1. We have a picture to start the program. The viewer had insects that swarmed on a trumpet vine. They wondered what type of insects they were and if they are harmful.
a. This time of year we have a couple different species of what we call soldier beetles. They are beneficial insects. There are many of them congregating on the plant but don’t seem to be doing any damage, which they aren’t.
2. We have multiple viewers wanting to know when is the last day we can apply control for nutsedge?
a. You want to get the herbicide on before the longest day of the year, which is the 21st. You have another 10 days or so this year that you can apply that. Be sure to use a product that has the active ingredient sulfentrazone in it.
3. A viewer from Osmond has a May tree (Runus padus, European Birdcherry) that has brown bulges that look like knots in the trunk. They had to remove a Canadian cherry tree that had a fungal disease of some sort. They are wondering what this is, does it spread?
a. It is the notorious black knot that will attack any species that we have, Canadian cherry, plums. It’s a fungal infection that will enter into the bark through any openings, whether made by an insect, other animals, or hail injury and there isn’t much you can do. The best thing to do is prune out the affected stems. You will never be able to get rid of it so just practice good tree maintance.
4. Viewers are having beans that are just starting to flower. Is there anything they can do to insure a good bean crop?
a. Keep the soil moist and add some mulch. When the plant is flowering would be a good time to fertilize. Consistent good moisture is the best practice.
5. This is from a viewer in Omaha who has a peach tree that is six years old and has never produced peaches. It loses its leaves in the late spring and summer. The leaves had little brown spots. They have tried an antifungal treatment. They think there are insects in the trunk; they are finding sap at the base of the trunk. Is there any way to save this tree?
a. It is most likely peach tree borer which comes out as an adult in July and August, so that is the time to protect any peach trees you have. There is not much you can do about the borers that are in the tree now. Apply a bifenthrin product---not where the fruit is but at the base of the tree, that is where the problem is. That will help prevent re-infestation.
As for the leaf spots, that is a fungal infection. You have to treat this really early on. The leaf yellowing would be a sign of stress. With the fungus and the borers, you will need to be patient to see if the tree will come out of it. If the leaves have been yellowing for some time, you might need to look at planting depth and root health.
6. Lowell, you have the next photo. We have had this weed before but not one this vigorous. They were thinking it was knotweed.
a. The leaves on this plant are much more elliptical or oblong than knotweed. This is common pokeweed; it is a perennial. It is a poisonous plant and should be removed. It could be manually removed at this point of the growing season. The next year it will come up from the tap root. They may want to apply herbicide when the plant is smaller and younger---2,4-D plus Roundup. It may take a couple applications to get it under control.
7. We have a viewer in Panama who has an American elm, 30 years old, 30 feet tall. It lost most of its leaves. They were seeing flagging in the top of the tree.
a. It is probably Dutch elm disease. The tree will eventually succumb to the disease. Consider planting something new into your landscape and incorporate some diversity.
8. We have a viewer from Fremont who has seven double Knockout roses that were planted a few weeks ago on the south side of their house. The one on the end of the row, east side, it’s leaves are beginning to turn brown and dry up. This is the only one showing this. Is this disease-based or location-based?
a. It is probably more location based. Is it planted the same depth as the rest? Is there a downspout at the end of the house that would prevent root establishment? Look at what is different with this plant than the others planted. If they were just planted two weeks ago, it would be ok to shift that plant at this time. It sounds like a site location issue.
9. This is a viewer that has a 56 year old white pine. It didn’t really look good this spring or summer. Fewer needles and slowly dropping needles. It hasn't had its environment disturbed and they are wondering about aphids or insects in the white pine.
The springtime is when we have most of our aphid issues. There is a giant conifer aphid, which are blackish, but rarely do they cause any stress. White pine aphids are fuzzy and easy to recognize because they look like lint in and among the needles. There might be a larger issue going on here. Check the base of the tree for any borer exit holes. That could be treated but make sure that is the cause.
Kim: We have also had a lot of issues with white pines that involve environmental issues. The tree is 56 years old so that could be the issue also, that is pretty old for a white pine in Nebraska
10. This is a viewer in Richardson county. They have spurge in their newly planted buffalograss.
a. It is probably spotted spurge. It grows really flat on the ground, with a purple mark on the leaves. We are very warm to be applying a 2,4-D product so that’s really not an option. Some of the other growth regulator products are OK, as long as it does not contain 2,4-D. Spotted spurge is relatively sensitive to other growth regulator herbicides. Good cultural practices next year to get the buffalograss to thicken up and the spotted spurge should go away.
11. This is an Aurora viewer with a compact American Cranberrybush hedge. They began to see some dead areas four to six years ago. They are wondering if it could be fireblight?
a. Typically we don’t see a lot of fireblight in viburnums. You should look at the stem and see if there is any breakage in the bark andsunken areas. In these types of compact shrubs if there is canker formation you will see braches dying out. The only thing to do is prune out these areas. There could be insect issues.
The main borer is the viburnum borer. It is a clear-winged moth that looks like a wasp. It comes out as an adult in June and July. That would be the time to be treating the crown area with an insecticide and bifenthrin is the best to use. You need to get good coverage with canes this dense.
12. We have several potato questions. A viewer thought they were told to cut the seed of their seed potatoes up seven days before planting.
a. You will see that recommendation but it doesn’t really make any difference.
Second, four rows of seed potatoes were planted, each in a separate row, but they were told that potatoes wouldn’t pollinate and they need short rows.
a.That sounds more like sweet corn. With potatoes, we eat the underground tuber, so they don’t need pollination.
13. Next is a viewer who wonders if there might be scale on her oak trees. They did have a bit of hail damage last week but think they have seen some scale. Is there a threshold they need to worry about and should they treat the trees?
a. On oak trees there is a very common scale called obscure scale and, unfortunately, it blends in with the bark. If you see a branch in the tree that is not growing very well and the leaves are stressed or yellowing, scratch the woody part of the twig and see if you can actually work up the scale insects. The undersides of their little shells are white so you will be able to see them. We are past the time that the eggs underneath hatch and the baby scales have moved out to colonize, so that window of opportunity is gone this year to treat them. You will want to treat late May to early June next year.
14. We have a viewer from Arlington who wants to know how to eradicate poison ivy and whether they have to wait until fall to do it.
a. Eradication and weeds never go hand in hand. It is just management of these because they always seem to return. Removing the poison ivy and doing a cut stump treatment with a brush killer or something that has triclopyr, or use a 2,4-D and diesel mix, applied immediately after you cut the woody stem. Always be careful and wear gloves and dispose of the poison ivy material in a safe place. Do not burn it.
Kim: There is no method that does not include a chemical control.
Lowell: It is a perennial and has a very hardy root stock. This is an area where applying a herbicide provides real benefit for control.
15. Amy, this is a viewer in Maxwell, Nebraska. They have a two-month-old pear tree, the leaves are black. They’ve used some Ferti-lome. They are wondering if this is a disease. Are they likely to lose the tree?
a. If the leaves are black, my first question would be whether the tree is getting adequate water. It could have been a real severe scorch, lack of water type of situation. There are a few fungal diseases that will start off as little black spots, but I haven't seen the whole leaf turn black. If the whole tree has black leaves, typically that isn't a good sign. Maybe a picture would be helpful here, or dropping it off at your local extension office and letting them take a look at that one to be on the safe side so you know if you can plant back in that spot.
16. Your turn for a picture. They got they think as a gift from their birds, growing and spreading on the north side of the house next to the hostas and the ferns. They want to know what it is.
a. This is lysimachia, I’ve never heard of a common name for it. It is a perennial that will grow here; it does spread by rhizomes, so once you plant it, you'll have more of it. But it is a pretty plant, it's a nice yellow bloom.
17. We've had several viewers who have sent us Asiatic or Oriental lilies with issues that begin with lesions on the stems. They're wondering if it is the stalk borer, and then we’re seeing this purpling or yellowing from the base up, and they’re wondering if this is environmental or disease-based.
a. I think we can safely rule out stem borers or stalk borers. The lily just doesn't seem to have issues with that. With that first image with the lesions on the base of the stem, to me it almost looks maybe like hail injury or maybe critter injury, something of that sort, causing injury there. On the purple leaves as a whole, typically this is an indication of a nutrient deficiency. With the weather the way it is, it may be a good time to add a little bit of fertilizer. That might help it as a whole. But, I would say it's probably more environmental.
I would agree, to be more environmental, and the same with the purplish on the leaves. Sometimes that purple indicates phosphorus deficiency. Yet, most of our soils have plenty of phosphorus, so it leads me to think maybe environmental stress or make sure that we're not over watering. It's so hot and so windy that people are watering a lot, and it is needed, we need a lot of water, but at the same time, don’t overwater. That could lead to phosphorus deficiency. It would be a little bit unusual, but something to consider. As our viewers know, we might know everything, but this year we pretty much don't know anything. It's the way we all feel. We keep saying, "well, we think.”
18. Lowell, let's talk about getting rid of locusts, probably honeylocusts, in pasture areas.
a. Locust trees can be a real nuisance in pastures, they have thorns, they keep coming up persistently, and the best thing to do is apply a product that has Picloram or Tordon about this time of year. We may be getting a little late for that. Once the honeylocust puts on good foliage, that's probably the best time to apply that. And, it is labor intensive. They'll have to do spot treatments more than likely, but that’s probably the best approach.
19. The foliage on potatoes is curling and turning yellow and then brown, no spots on the leaves, some are just blooming. The Stanton viewer’s potato leaves are yellowing and cupping. And, every 10th to 15th plant is dead.
a. There could be multiple things going on. Number one to consider with potatoes and tomatoes is if the leaves are curling, have you made any growth regulator applications nearby within the last week or so, especially with our temperatures getting way warm. And it's way too late to be applying 2,4-D at this point of time. If they're turning yellow and cupping, look at the base of the plant. We have a couple of root rot issues. There is a bacterial disease called blackleg and that would be black in color and move up the stem. That will cause the foliage to turn yellow and dieback because it can't get water, but blackleg will progress fairly quickly. There are other fungal diseases that will affect the base of the plant and the root system and that will cause that discoloration. The other thing to consider in that part of the state, it got really warm last week, up in the 90s.If you've done any recent tillage, trying to throw dirt up along those tubers a little more, there's the potential that it got too hot, affected the root system, and this overall stressed the plant. The other trick is if it's a lighter soil and you don't have a full canopy yet, maybe the soil just got too hot. If you haven't mulched your potatoes, do that real soon.
20. This viewer has Martha Washington geraniums that aren't blooming. They're on the east side of the house; they are fertilizing with a water-soluble once a month. They’re not saying what formula the fertilizer is.
a. Well, when something should be blooming and it isn’t, I just tell people to stress it. It should be blooming by now. You might want to cut back on fertilizer or be careful. If you’re fertilizing and have a lot of nitrogen, you’re promoting a lot vegetative growth. What I mean by stressis that you might want to let the soil dry out. Not for a long period but just a little bit between waterings and then water it again. That's what we mean by a slight stress. Watch the nitrogen. Make sure you're not applying too much. Wait a bit and, hopefully it will start to bloom.
1. We have a viewer who planted huckleberries, they water every day, but the leaves are still turning black.
a. Black. They’re watering every day. Cut back on the watering.
2. Any ideas on a six-foot tree that will grow in the shade?
a. I’m not aware of a six-foot-tall tree that will grow in the shade. Maybe go with a shrub.
3. A 40-foot tall Blue Spruce with a circling root, they wonder if they should cut that root to keep the circling from continuing.
a. If it's 60 feet tall, it’s too late to cut the root, and they could do more damage. Be careful. Sometimes a circling root can make that a hazardous tree.
4. Any ideas on a couple of shrubs for shade that people might be interested in?
a. Hydrangeas, some of the spireas, and the currants will tolerate shades.
5. Why aren't tomatoes setting fruit or ripening the fruit that sets?
a. I'll blame the weather!
1. We have a viewer who just planted roses and they’re seeing yellow leaves; not saying anything about black spots. Could that still be black spot?
a. You want to look to see if there are very distinct black spots on there. If not, it could be a planting depth issue or a nutrient issue going on.
2. A viewer a row of elms had one with Dutch Elm disease and they wonder how it could be transmitted to the trees next to it.
a. By insects. It’s insect control time, but typically it isn’t worth the time.
3. How do you avoid that brown spot that can occur in the middle of your potatoes?
a. That brown spot is actually from a potato growing too fast, so proper watering, and Mother Nature taking over there.
4. Is there a fungal leaf disease of tomatoes that would cause them to have light tissue with dark veins?
a. That would typically be a nutrient issue. You might want to add fertilizer to those tomatoes.
5. Are we seeing turf diseases yet?
a. Brown patch is starting to show up. We’re seeing the leaf spots because our turf is stressed, especially in western Nebraska in the drought areas. The best thing for that is to just try to add water if you can. If not, let it go dormant.
1. Thank you. Speaking of turf. Yes. A viewer wondered whether they should water their turf once a week very heavily, two to three times a week not quite so heavily, or every other day?
a. Every day is not the right answer. Infrequently in deep waterings are much better for turf this time of year.
2. There was a viewer who wants us to identify a plant that has a yellow flower that looks a little like a dandelion.
a. Possibly hawkweed. This is also something that people sometimes plant on purpose.
3. Is Tenacity a good grass and weed product for the homeowner?
a. It’s more of a professional product. The homeowner will have a much more difficult time getting it because it's sold in larger quantities and it's quite expensive. But it does an effective job on broadleaf and grass control.
4. How do you kill grass in a garden filled with the succulent called hen and chicks?
a. Hand removal but that can be quite laborious. Applying Grass-B-Gon is another way to selectively remove grass from those plants.
1. Yet again, phlox in Norfolk is turning yellow.
a. Phlox plant bug. It could also be spider mites, just the general yellowing, just use an insecticide, and knock them down.
2. The viewer has millipedes.
a. Clear everything away from the perimeter of the house, anything organic that retains moisture, then applying a barrier treatment, either a granular or liquid insecticide, and it doesn't last too long, maybe two weeks.
3. A Springfield viewer has square and triangular bugs on the ground around iris.
a. I think it could be stinkbugs because if you still have your iris up, you're getting developing ovaries or pistils, and they love to feed on that stuff.
4. Another viewer has Iris browning from the top down.
a. That would be iris borer; we’re pretty well into the stage. It’s too late to treat pretty much, so this fall you'll have to be selective and go through those irises, cull out those badly damaged rhizomes. Then kind of restore your bed, rework your bed, and next year prepare for the early onset of iris borer issues because it happens every year.