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.
This is the Q&A for the Yard and Garden show for July 14, 2017. 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 28, 2017. 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: Steve Karloff, District Forester from the Nebraska Forest Service
If you enjoy reading my Q&A from the show each week, take my quick survey at: http://go.unl.edu/44qr and be entered to win a free plant book or some free UNL gifts.
1.The first caller of the day has overgrown Forsythia and Yellow Dogwood plants. What can be done for pruning to reduce the unproductive plant materials and when can it be done?
A. Because these plants are overgrown, it would be most beneficial to do a rejuvenation cutting on them. A rejuvenation cutting is when you prune a shrub back to about 6-8 inches from ground level and remove the majority of the top growth. This will get rid of all the old, unproductive wood to bring in all new, younger wood that will be more productive to leaf out better throughout the entire shrub, will lead to more flowering, and will be healthier and free of insects and diseases that were problematic on the shrub. It is best to prune forsythia immediately after they flowered, but it could be done in the fall. Remember with a rejuvenation cutting that the plants will not flower for at least 2 years following the heavy pruning.
2. A caller has blue spruce trees planted in an area near a lake. Some of the spruces are 60 years old and some are 15 years old, all are dying from the bottom up. What is wrong with these trees?
A. Too much moisture can cause blue spruces to die from the bottom up, since they are planted close to a lake, they may be getting too much watering. When replacing the trees, choose a species more adapted to wet locations such as white pine, cedars, or bald cypress.
3. This caller has a green apple tree that was planted before he moved in and the apples are falling so they are ripe. The apples are not juicy and are quite porous and pithy. What is wrong with the apples?
A. After discussions on this with Paul Hay, this is just the variety of apple that is growing there. This is an apple that is used more for processing to be used in pies and sauces and not for fresh eating.
4. A caller has rabbits that are eating her hostas and lilies. What can be done to control them?
A. The only effective management for rabbits in a garden is to put up a fence that is at least 2 feet high.
5. This caller has a bur oak that was planted in the spring. The old leaves on the tree are turning brown but the new growth is green and healthy looking.
A. Be careful to not overwater a tree, especially with newly planted trees. These young trees have a small root system and do not need to be watered as heavily as an older, established tree. It is beneficial to allow the roots to dry out a little between waterings.
6. A caller has white pines that were planted too close to the driveway and now the branches hit cars when they come to park in the drive. Can the branches be trimmed back so they don’t hit cars and when can that be done?
A. Yes, these branches can be removed. Take the branch all the way back to the trunk so that they don’t regrow causing pruning to be necessary every couple of years. You can prune evergreens most any time of the year.
7. This caller has a bur oak that was planted last fall. It didn’t come out of dormancy this spring and has not grown. However, there are suckers coming up at the base of the tree, can the main tree be pruned out and the suckers allowed to grow into a new tree?
A. Yes, remove the main tree and allow one of the larger more upright suckers to grow into a new tree. However, sucker growth is not always as strong as the tree itself, so it may not perform how the tree was supposed to.
8. Can lilacs be pruned now?
A. No, it is best to prune lilacs within a couple of weeks after they are done blooming. Lilacs produce their flower buds in the summer and fall of the year before they bloom, so pruning now would cut off the flower buds for next spring. To ensure flowering for next year, wait until after it blooms next year and then prune it back at that time.
9. A caller has cypress trees that were planted 5 years ago. One of the 2 trees is in great condition with good color. However, the other one is smaller and yellow in color. The trees are only a few feet apart. What is wrong with it and can it be fixed?
A. The yellow and shorter tree may have just been a bad tree out of the gate. Sometimes our trees develop a problem in a nursery or from the seed source and never really overcome that. Also, with Bald Cypress trees, it is hard for them to overcome iron chlorosis. When these trees get iron chlorosis, they become stressed and no matter how many trunk injections, which also harm the tree, they never come out of the chlorosis. At this point, it would be best to remove and replace the bad tree.
10. This caller is having problems with their lawn. He fertilized it in May but now it has brown patches throughout. How much water does a lawn need and how can he improve his lawn?
A. Our lawns need 1-1.5 inches of water per week on average to stay green and out of dormancy. The patches could be the lawn going dormant or they could be from a fungal disease. There are a lot of summer fungal diseases such as brown patch, summer patch, and dollar spot. They are common in the hot and humid days in late summer but as soon as that weather fades, the brown spots will turn green again. For more information on these diseases, see this TurfiNfo from UNL.
11. A caller has Bradford pears that have branches coming out 1.5 feet above the ground, should those be removed or will they move up as the tree grows? The trees also have suckers, what should be done about that?
A. If these low branches are in the way for mowing and you don’t like how low they are, they should be removed. Remember not to remove more than 1/4 of the tree in one season, so you may have to remove one this year and another next year. Those branches will always be at that level, though, so if they are in your way they need to be removed. As for suckers, cut those off at ground level and don’t treat them with anything or the spray will kill the tree as well.
12. This caller has pumpkins in his garden that are wilted during the day but at night they look fine. What is wrong with the plants?
A. If a plant looks better in the evening or in the morning but is wilted during the hot part of the day, it is heat or water stress. Make sure your plants are properly watered through this hot and humid couple of weeks of the summer.
13. A caller has tomato plants with leaves that are drying up from the bottom of the plant. The tomatoes are also rotten on one end of the fruit. What is causing these two problems?
A. Ensure that the plants are being properly watered. Vegetable gardens need 1-1.5 inches of water per week. Hand watering at the base of the plant every night is not sufficient for the root system. The plant could also be exhibiting early blight which is common right now. Remove the infected leaves, the disease will fade soon. The rotten side of the fruit is blossom end rot. This is a calcium deficiency in the plant caused by uneven watering making the calcium unavailable to the plant. Adding calcium to the soil will not help the problem, just make sure your plants are well watered and mulched in. Blossom end rot will fade soon. You can eat the good side of the fruit and dispose of the rotten end.
14. This caller has round berries on the plants of her potatoes. What are these?
A. These are the fruits of a potato plant. We typically do not see the fruits because we are growing the plants for the tubers produced underground and we harvest before the fruits appear. Remove the fruits so the plant can build the tubers.
15. A caller has roses that have uniformly round holes on the edges of the leaves and brown spots. He sprayed with rose spray and it is not working. What is wrong with the plants and how can he fix it?
A. This is likely damage caused by the leafcutter bee which is a pollinator and beneficial insect. There is no need to control this insect. Here is a great article from Jonathan Larson, Nebraska Extension Entomologist, on Leafcutter Bees.
16. How do you control puncturevine in a lawn?
A. Use a 2,4-D product in the pre-bloom stage. Management will not be achieved this time of year because the plant is large and will be difficult to kill. Also, don’t use 2,4-D products in the heat and humidity of the summer or the product may move to non-target plants causing damage.
17. How do you control moss in a pond?
A. Copper sulfate crystals can be used for control. For more information on pond management, visit the Lakes, Ponds, and Streams section of the water.unl.edu website.
18. A caller has apple trees that get insects in the fruit every year. When and what should they be spraying for that?
A. It would be best to get on a spray schedule, spraying with an orchard fruit tree spray every 10-14 days throughout the growing season. For more information visit the Local Food Production page within the food.unl.edu website for spray guides.
19. The last caller of the day has vines with milkweed type pods growing in his fenceline. What can be done to control it?
A. The plant sounds like honeyvine milkweed. At this point of the year, pull it or spray it with roundup. In the spring or fall, 2,4-D could be used, but not now due to the heat and humidity.
April is finally here, which means spring should be bringing in warmer weather. April is a good time to get out and start working in the lawn and garden to prepare our yards. To help ensure that you have the best lawn on the block, here are few tips to improve your lawn this spring.
April is a great time to overseed your lawn. If you had some spots that were flooded out last spring, now is a great time to get some new seed planted. The beginning part of April is best for seeding lawns, but it can be done until the end of the month. Frequent, light irrigation is necessary to keep newly seeded lawns moist. It may be necessary to water twice a day to keep it from drying out and dying. Straw mulch can be applied to keep the seedbed moist, but it is not necessary and can bring problems with weed seed that is often a contaminant of straw. Do not apply any pesticides to newly seeded lawn until you have completed 2-3 mowings. Also, do not try to overseed right before or right after applying crabgrass preventer as this chemical will prevent the germination of your desired grasses as well.
We often face difficulties with weeds in our lawns. The key to weed management is to keep your lawn healthy to avoid weed infestations and to identify the weed before chemical controls are used. Many of our herbicides are specific to either a grass weed or a broadleaf weed and won’t work on the other weed type. Also, you need to know the weed to know the lifecycle for when the best time is to manage that weed with a chemical. As I stated in my previous news column, henbit is a winter annual and should only be chemically controlled in the lawn in the fall, the spring is too late.
Crabgrass pre-emergent herbicides need to be applied before crabgrass germinates, which is when the soil temperature is 55-60 degrees Fahrenheit. This typically occurs toward the end of April. Applying this chemical too soon may cause the chemical to stop working earlier in the season when crabgrass may still be germinating. In this case an additional application may be necessary later in the spring, so it is best to wait until the correct time to only have to apply this one time per season. Broadleaf weeds, such as dandelions, clover, and ground ivy should be controlled in the fall for best control but can be managed in the spring with 2,4-D products.
Fertilizing turf can be done up to 4 times per growing season. Apply fertilizers at a rate of 1 pound of nitrogen per 1,000 square feet for each application. A good trick for remembering when to apply fertilizers is to fertilize with the holidays: Arbor Day, Memorial Day, Labor Day, and Halloween.
We are now getting to the time of year when we will have to start mowing our lawns. Prepare your lawn mower for the season before you start mowing. Start by sharpening the blades. Dull mowing blades can cause tearing to occur on the grass blades rather than a smooth cut. These tears can lead to more insect and disease problems. Change the oil in your lawn mower, if you didn’t do that in the fall. Check your spark plugs and tire pressure. Finally, make sure you clean under the deck for any grass that may still be stuck under there from last season. You can start mowing as soon as the grass starts growing. Remember to mow at a height of 2.5-3.5 inches and only cut off 1/3 of the grass blade each time you mow.
Now that gardening has fully begun, it brings to mind the fact that so many of our fruit and vegetable crops are pollinated by insects. According to the Crops & Soils Magazine for certified crop advisers, agronomists, and soil scientists; more than a third of the food we eat depends on pollinators. Because of this, we need to make sure we are doing what we can to protect and reduce the damage to bees and other pollinator insects.
Bee populations have decreased in the past few years due to a problem called Colony Collapse Disorder, which is still being researched. The scientists are calling the reduced bee populations Colony Collapse Disorder and are attributing it to pesticides, a mite, and poor bee nutrition due to a lower diversity of flowers for the bees to forage. There are things we can do to help the bee populations, including planting a wider variety of plants for the bees to forage for pollen.
Integrated Pest Management, or IPM, is a good way to help reduce pesticides in the environment and help our bee populations. IPM is a method of managing weeds, insects, or diseases by using multiple techniques. Control methods for IPM would include mechanical such as hand pulling, cultural such as tillage, biological such as allowing natural predator insects to survive and chemical such as using pesticides.
IPM practices for insects would include
Tilling the garden after the growing season
Hand removal of the insects
Inspection for eggs to remove prior to emergence
Utilizing row covers to protect the plants from damage
Scout your gardens often to reduce an insect pest problem while the population is small
Try to avoid killing all the predator insects such as ladybugs, praying mantis’, and ground beetles.
The main idea behind managing weeds in your lawn or in your garden is to reduce locations where they grow and have healthy plants that can out-compete the weed species. IPM practices for weeds would include:
Mowing grass at the recommended 2.5-3 inches
Mulching around trees and gardens
Fertilizing correctly to ensure all plants are healthy
Planting the right plant in the right place
For a disease to occur there must be a susceptible plant host, a disease causing organism, and the proper environment. IPM practices for diseases would include:
Watering plants early in the morning
Avoiding watering over the top of the leaves
Spacing garden plants and trees correctly
Planting resistant cultivars
Removing exhausted plant material in the fall to reduce possible diseases to overwinter where the plants will be next spring.
Chemicals are often a good way to manage pests in our lawns and gardens, however if we use an IPM program we may not develop a pest problem in the first place. If a pest problem does occur and chemicals are necessary, just make sure that you are applying the pesticides correctly. Use pesticides only as prescribed on the label, in the correct environmental conditions, and using the correct personal protective equipment. Also, if insecticides are necessary for an insect pest, be sure to apply them later in the evening when bees are no longer active for the night to avoid harming the bee population. It is also best to avoid spraying insecticides on plants that are blooming, so bees cannot be harmed when foraging that flower for pollen.