With spring coming soon, we will begin to get outdoors to improve our lawns, and just be outside. Make sure you know what weed you are dealing with in your landscape and know the best way to control it. There are times for controlling weeds, it may not be the best in spring for all. Spraying at the wrong time is a waste of money and can be harmful to our environment.
Crabgrass is one of the most problematic weeds in lawns. It is a summer annual weed. Summer annuals germinate in the spring, grow and produce seed throughout the summer and die with the first frost in the fall. Crabgrass germinates when the soil temperatures average 55-60 degrees Fahrenheit. So, crabgrass preventer should be applied when the soils reach that temperature. Typical preemergence herbicides include dithiopyr, prodiamine, or pendimethalin as the active ingredient. A second application should be made in late May to June for season-long control.
If you miss the window for preemergence products, you still have options. There are some great post-emergence products. Dithiopyr and mesotrione have pre- and postemergence activity on crabgrass. Quinclorac is a great postemergence herbicide that is often found in the product Drive. So any of these can be used if you miss the spring window for control.
Annual Broadleaf Weeds
Henbit is a winter annual. A winter annual is a plant that germinates in the fall and grows a bit before basically becoming dormant for the winter months. Very early in the spring, henbit will start to grow again, produce flowers and seed for the next year then it will die when the temperatures warm up. This is different from a summer annual which germinates in the spring and goes through its lifecycle through the summer months and dies with our fall frosts.
The problem with henbit is that by the time we see it, or rather see the purple flowers, it is too late to treat for the year. Once the flowers begin to show up, it is already producing seed for next year, so killing blooming henbit is unnecessary because it will die naturally and the chemicals won’t reduce production for next year. However, pulling the plant would be a fine management practice after blooming has begun. It can be sprayed with a 2,4-D product very early in the spring once it has greened up but before it blooms. If you know where it is you can spray it before it blooms. Otherwise, wait until this fall to spray those areas with a preemergence herbicide before it germinates in the fall.
We have a lot of perennial weeds in our lawn as well. Plants like dandelions, creeping Charlie, and clover are perennial broadleaf weeds. Perennial weeds are best controlled in the fall once the weeds have begun their preparations for winter. In the fall, these perennial weeds will move sugars that they use for energy from the above ground portions of the plant down into the roots to store them for next spring. If they are sprayed during this phase of their lifecycle, they are more likely to take that herbicide down into the roots to be more effective than if done in the spring. Spraying these weeds in the spring will knock them down, but likely not kill them outright.
Nimblewill is a perennial grassy weed. It is controlled through one of two methods. You can spray it with a product containing mesotrione that won’t harm the surrounding grass. Or you can spray it with a glyphosate product, such as Roundup, then overseed the area. The glyphosate will only be effective if sprayed on the nimblewill when it greens up, and this is a warm season grass so it will be later in the summer. It is best to do this in August then you can overseed 2-3 weeks later.
*Reference to commercial products or trade names does not imply endorsement by Nebraska Extension or bias against those not mentioned.
Weeds in the lawn will drive us crazy through the whole summer, but don’t forget about them yet. Fall is the best time to treat for broadleaf weeds, even though we don’t notice them as much now because they are done blooming for the year.
Perennial broadleaf weeds including dandelions, creeping Charlie or ground ivy, and clover are best controlled in the fall once the weeds have begun their preparations for winter. In the fall months, these perennial weeds will move sugars that they use for energy from the above ground portions of the plant down into the roots to store them for next spring. If they are sprayed during this phase of their lifecycle, they are more likely to take that herbicide down into the roots and kill the plants rather than just burn the tops off.
The cooler temperatures in the fall are better for turf and ornamental plants due to a reduction in volatilization. In the warm summer days, the herbicides we typically use on broadleaf weeds can turn into a gas and move to non-target plants, causing damage and in some cases even death. With the cooler temperatures, this is not a big concern because the common chemicals we use, such as 2,4-D and Dicamba, do not volatilize at temperatures below 80 degrees. Wind drift is still a concern, so always be sure to apply herbicides on days with little to no wind.
The fall is not the time to worry about or treat for summer annual weeds such as crabgrass. Those plants that are still alive will die with the first frost and the seed will not germinate until next spring when the weather warms back up again. However, you can treat now for winter annual weeds such as henbit, speedwell, and little barley. Once they have germinated this fall you can use a 2,4-D product, which can be achieved with a late October and into early November application for dandelions.
Remember, all of these chemical controls are pesticides and therefore need to be carefully considered and applied according to the label. Any material used to maintain a landscape, including fertilizer, sand, or pesticides, can end up in the storm sewer and lead to pollution of lakes, rivers, and streams. In the same manner, even our grass clippings and leaves can pollute our water supply. There are ways to manage our landscapes while reducing water pollution. The following will help when managing our lawns this fall:
Any fertilizers, pesticides, and grass clippings should be swept back onto the landscape. Using a leaf blower will work as well. The idea is to keep these items on the greenscape rather than on the hardscape that leads easily to the storm sewer. Raking up leaves in the fall will also help reduce the amount of leaf debris that ends up in the water.
Check your sprayers before using to ensure they are properly calibrated and the nozzles are not clogged.
Compacted soils and thin turf do not allow fertilizers and pesticides to infiltrate the soil surface. Aerate and add organic matter to improve the composition of the soil to ensure these products do not run off of hard, compacted soils. Reseed bare areas of the lawn to catch lawn products.
Thatch layers in the lawn can become a natural barrier to prevent infiltration. Aerate the lawn to reduce the thatch layer to allow lawn products to infiltrate their intended areas.
This is the Q&A for the Yard and Garden show for June 26, 2015. 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, 2015. 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: Sarah Browning from Nebraska Extension in Lancaster County
1. A caller has a pine tree with needles that are turning brown at the bottom of the tree. What would cause this?
A: There are a couple of common fungal diseases on pine trees, needle blight and tip blight. Both of these diseases will start from the base of the tree and move upward. Depending on the species of tree, it could also be pine wilt, but this disease progresses rapidly, causing death in only a few months. There are fungicides to be used for needle and tip blight, but they are best used in May and June. Neither of these fungal diseases should kill the tree in one growing season. This publication from the Nebraska Forest Service, Diseases of Evergreen Trees, shows pictures of both diseases and pine wilt and goes over treatment methods.
2. This caller has tomatoes that have black specks on the leaves which eventually turn yellow and die, but there are no specks on the tomatoes themselves. She was also curious why it makes a difference to water from below rather than above?
A: This would be a fungal disease called black speck or black spot. It is best controlled through good sanitation practices such as watering from below the plant, removing infected leaves as they are first seen on the plant, removing plants in the fall after the growing season, avoid crowding plants, rotating plants each year in the garden, etc. There is a great NebGuide on Leaf and Fruit Diseases of Tomatoes that will be helpful with many of our tomatoes this year with all of the rains as we are seeing many more leaf diseases. Watering from below the plant helps reduce spores splashing from plant to plant and from the soil to the plant. Watering from below also helps to keep the leaves dry throughout the day and into the night to reduce leaf wetness and humidity in the plant which is conducive to disease development.
3. A caller has a bur oak that is 15 feet tall with leaves that are curled under. What would cause that?
A: This could be herbicide damage from a 2,4-D product. It could also be from aphids or lacebugs. To determine if it is due to insect feeding, look on the underside of the leaves for tiny, green bugs, lace-like bugs, or frass. If it is aphids, they can be controlled with many general insecticides. Lacebugs rarely warrant insecticides as their damage is minimal to the tree. If it is herbicide drift, the tree should grow out of it, depending on severity of damage.
4. Is it time to spray for bagworms yet?
A: They have not yet begun to emerge in Southeast Nebraska. They are behind in their development this year due to the cool spring. They should be emerging in the next week or two. Ensure that the immature bagworms are active on your tree before treating to get best control from your pesticide.
5. Another caller wanted to know if it is illegal to use rainwater in Nebraska?
A: No, Nebraska does not have a law to prohibit the catching and use of rainwater, as some other states do. Rainwater is a good use of extra water to avoid so much runoff and contamination to the water supply. Be careful to not use rainwater on vegetable crops to avoid contamination from non-potable water.
6. This caller has a Kentucky coffeetree that was planted in the right-of-way by the city within the last 2 years. The bottom of the tree has leaves and new growth, but the top of the tree does not. Will it survive?
A: This tree probably is having troubles with establishment or may have been planted incorrectly. Due to this, the top of the tree is not receiving water and nutrients from the roots. It can be pruned back to the growth with possible success. Be sure to watch for a new leader to develop or you may have to start a new one to help it grow taller as the central leader will be pruned off of the tree.
7. How can nutsedge be controlled in lawns?
A: A product that is specific for use on sedges can be used in the lawn with no harm to the turfgrass. The most commonly used product for yellow nutsedge is Sedgehammer, it should be applied multiple times throughout the growing season, as new plants come up. It is better to spray with Sedgehammer early in the life of the new plant to reduce nutlet production and reduce the size of the plant.
8. A caller wondered when the best time is to prune an oak tree?
A: It is not advisable to prune oak trees during the summer months to avoid chances of getting oak wilt in the tree. The best time to prune oaks, and many of our deciduous trees, would be in the dormant season, such as November.
9. A caller has a fescue lawn that is getting yellow in spots. What would be the cause of that?
A: This year we have faced many days of cool, wet, cloudy weather which is favorable to many turfgrass diseases. This sounds like it is either brown patch or dollar spot disease. Brown patch has tan colored lesions on the leaf blades that have a dark margin around the tan spot. Dollar spot would just be tan spots in the lawn that are typically half-dollar sized but you can see many dollar spots coalesce into one larger spot. As the weather dries out and warms up, the fungus should fade in the lawn, or you can use fungicides in the lawn if necessary.
10. A caller has bindweed in the lawn. What can be done to control it?
A: A herbicide that is just for broadleaf weeds will work on the bindweed and not harm the lawn. Triclopyr is a great choice to use. This is commonly found in brush killer, poison ivy killer, and clover killer in the stores. Make sure that the temperature on the day of application is below 85 degrees Fahrenheit to reduce the risk of harm to non-target plants.
11. A lady has cucumbers that are flowering with no fruits developing. What would cause that?
A: Cucumbers have both male and female flowers on the same plant. Early in the season you may see development in only male flowers with no female flowers to produce no fruit. The female flowers will have a tiny cucumber structure at the base of the flower. This also could be due to low pollinator presence in the garden. Rainy days and hot days discourage pollinators. Give the plants more time, they should begin to produce female flowers and fruits soon. Hand-pollination may also be necessary if it is due to low pollinator presence. To hand-pollinate, take a Q-tip and touch the pollen of all of the flowers.
12. A caller has a clematis plant that is dying back, causing all of the leaves to turn brown.
A: Clematis commonly gets a fungal root and crown rot. If this plant was in a location where water sat this year with all of the heavy rains, it may have caused this fungal disease to occur. Cut the plant back to the ground and see if it will grow back, if not, you will need to replant.
13. This caller has Iris plants that have completed their blooming period for the year. Can these be cut back now?
A: No, all spring blooming plants need to be left, without being cut off, for the remainder of the summer until their foliage turns brown in the fall. This allows the plants to make sugar throughout the summer months to have a starting supply for early spring blooming next year. The flower stalks can be removed after the flowers are done.
14. A caller has patches of clover in the lawn. What can be done for management for the clover?
A: The best time for treatment of clover is in the fall with a Triclopyr or 2,4-D product. At this point, the temperatures are too high for herbicide control without possible harm to non-target plants. Both of these products can turn into a gas and move to non-target plants if temperatures are above 80-85 degrees Fahrenheit, the 2,4-D can volatilize for up to 72 hours. Be sure to mow the clover prior to herbicide treatment to mow off the flower blooms and cause less harm to bees.
15. A caller has grass planted in late March and added more seed later in the spring. She used a starter fertilizer and covered the areas with straw, and now there are brown spots appearing in the lawn. What would be causing that?
A: Brown patch disease is common on young seedlings of tall fescue. Look for irregular shaped tan spots with a dark margin to know if it is brown patch. Bayleton is a good fungicide that may still be effective on this lawn. Also, remove the excess straw to reduce disease problems.
16. That same caller has crabgrass coming up around her trees. Can she use roundup to control it?
A: Roundup can be used around the base of trees with minimal damage to the trees. A better option would be to use a post-emergent crabgrass herbicide such as Dimension or Fusilade.
17. A caller wanted to know if it was allowable to use Grass-B-Gone in their sweetcorn?
A: No. Grass-B-Gone kills all types of grasses, including sweetcorn. Also, Grass-B-Gone is not labeled for use in a vegetable garden.
18. A gentleman has mock orange and bridal wreath spirea. When can these plants be pruned?
A: Both of these plants have just finished blooming for the year so they can be pruned now. Remove no more than 1/4 of the plant in a growing season. This can be done by removing the largest canes at the base of the plant. If it is too tall, you can remove 1/4 of the height, if it is a 4 foot tall shrub you can prune it back to 3 feet tall.
19. A caller wanted to know what to do for management of dandelions in their lawn?
A: Dandelions are best controlled in the fall with a 2,4-D product.
This is the Q&A for the Yard and Garden show for April 17, 2015. 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, 2015. 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: Dr. Paul Read, Professor of Horticulture, Viticulture Specialist
1. A Caller wanted to know if this was a good time to transplant rhubarb?
A: Now would be a fine time to transplant rhubarb. If you wanted to harvest from it yet this year, it would be best to wait until the fall to transplant it. Rhubarb should not be harvested from within the first 1-2 years after transplanting to allow the plant to build a good root system before harvesting begins. Make sure that rhubarb is planted in a well-drained location to avoid getting crown rot, a disease that will eventually kill the plant.
2. An email listener wanted identification and control strategies on her plant with purple flowers that is blooming now.
A: This is henbit, a winter annual that is flowering to complete its lifecycle. Because henbit is basically done growing for its lifecycle, it is best to leave it alone and let it die naturally in the next few weeks. The seeds are already in the soil for next year. Henbit is best controlled with a 2,4-D product in the fall. Mark the areas where henbit is found in your lawn this year and spray those areas in the fall. Management also can be achieved by overseeding turf into those areas where henbit is found or planting something else to compete with the henbit.
3. This caller wanted to know how to control clover
A: The best time to control clover would be in the fall with a couple of applications of a 2,4-D product. Applications of this product now can be useful, but will not eliminate the problem altogether. Be sure that when you apply 2,4-D to your landscape to not allow it to drift to any other broadleaf plant, including our trees, shrubs, and perennials. Also, only spray when the temperatures are below 80 degrees Fahrenheit.
4. A gentleman has a lawn that has been neglected for a while that he is struggling to keep turf alive in a full-shade location with poor soil. What can he do to get the turf to live there? Also, in another area of full sun, would dwarf fescue be a good turfgrass choice?
A: Because it is poor soil that had subsoil put on top of the existing soil, it would be best to aerate and add organic matter to try to improve the soil conditions. Full shade is difficult to grow turf in, so it would be best to choose a full shade perennial or groundcover or somehow prune the trees to improve the sunlight for the turf. Dwarf fescue is not a good choice because the root systems are not as deep as the turf-type tall fescues or Kentucky bluegrass.
5. What would be the fruit tree spray schedules for cherry and apple trees?
A: Orchard fruit tree sprays can be applied to both of these types of trees on a 10-14 day interval, while avoiding the blooming period to avoid damage to the pollinators. There are guides to spray schedules from many Universities including one for homeowners from Missouri Extension
6. A caller wanted to know what are some good varieties for pear trees in Nebraska? Does he need multiple species for pollination? How does he mulch these trees?
A: Pear trees are not self-pollinated so you will need to plant 2 different varieties to get fruit. Some good choices for Nebraska would include Luscious, Harrow Delight, Harvest Queen, and Seckel. A mulch ring is necessary to help the tree survive, it should be only 2-3 inches deep.
7. This caller used crabgrass preventer with fertilizer in it a couple of weeks ago and wants to know when he should use his weed and feed? Also, what type of care would he need for shrub roses he just planted this spring?
A: It would be best to just use a 2,4-D product anytime now and wait until the end of May to do another application of straight fertilizer to get through the summer, since he already applied fertilizer with his crabgrass control. The best thing for the roses would be to ensure that they are kept well-watered but not overwatered.
8. A gentleman has Philodendrons and Crotons as houseplants that he has moved outside for the summer. Now the leaves on the Philodendrons are curling up, why is that? Also, what kind of care should be given to the Croton, is misting a good practice for them?
A: These plants are tropical plants that we can grow indoors in our homes. The nights are still too cool for those, which is why the Philodendrons may be having leaf rolling issues. If the weather is predicted to get to the low 40’s to 30’s for the overnight hours, it would be best to bring these plants indoors. The Crotons should be watered properly from the base of the plant to ensure survival. Misting plants leaves the leaves wet which can lead to diseases.
9. What can be done to control ants found in the kitchen?
A: Terro ant baits work the best with the odorous house ant. Also, seal up all cracks and crevices in the foundation and around doors and windows. Clean up plant debris outside the home near where ants are found inside the home to reduce locations where ants may be hiding outdoors.
10. A lady has blackberries that are overgrown. How can she clean them up?
A: Cut out the old stems that are existing and continue to do this at the end of every growing season.
11. This caller has a 30 year-old pear tree that has never produced fruit. She has one pear in her landscape. Why would it not produce fruit?
A: Pears are not self-pollinated. Plant another variety and it should begin to produce fruit.
12. When is the best time to prune a snowball bush?
A: This is a spring blooming shrub, so it is best to prune it immediately after it has finished blooming for the year.
13. This caller wanted to know how to control Dandelions in her yard?
A: 2,4-D products can be used now but will have the best efficacy in the fall. If applied now, ensure that the wind is not blowing and the temperatures are at or below 80 degrees Fahrenheit for the day of application and the 2 days following.
14. This caller has started tomatoes and peppers from seed indoors and they are now becoming tall and spindly. What would cause that and when can they be placed outdoors?
A: They will need more light to avoid becoming tall and spindly. Also, be sure to buy clean and sterile soils for seedling production to avoid problems with Damping Off, a disease common to seedlings. Summer crops can be planted outdoors in the beginning of May, typically Mother’s Day is a good date to plant summer vegetable gardens.