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Garden Pests - OtherCurly top virus
Eliminating ivy
Goathead weeds
Lichen on pine
Lichen removal
Mint takes over garden
Moss, lichen on trees
Mushrooms in garden
Mushrooms taking over
Oleander Leaf Scorch
Puncture vine (goathead) control
Snail & slug control
Snails & slugs nationwide problem?
Snails killed with salt?
Toadstools in lawn
Weed control
Controlling weeds 8-98
Q. Since the monsoon rains have come to New Mexico, the weeds are taking over. What can I do?
A. It is too late now to use pre-emergence herbicides to control the warm season annual weeds, but you might plan for them next year. These are herbicides which do not injure established plants if they are used properly but will prevent new seed, weed seed, from germinating and creating new plants. Check with your local County Extension Agent or professional nurseryman for the proper products to use under your conditions.
Now that it is too late for these herbicides, mechanical control, mowing and weed removal, or use of post-emergence herbicides are your best options. If you choose the herbicides, be certain to use one which will affect the weeds you wish to kill without harming the desirable vegetation. Some weeds may be controlled by mowing, but others must be removed. The key is to prevent them from forming seeds if they are annuals. Perennial weeds present their own special problems. Consult with your County Extension Office or Garden Center experts to identify the weeds and determine your best options. Remember to plan ahead to next year to control the annual weeds which can return again only from seeds.
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Eliminating ivy takes persistence
Q. I was wondering if you could tell me the best way to get rid of ivy. I’d like to re-do the landscaping in my back yard but am afraid that the ivy will grow back.
A. There are two types of ivy - deciduous ivy and evergreen ivy, and you didn't indicate which type you are describing. This will have some effect on your options. If you prefer not to use chemicals (herbicides), you can dig the ivy to remove it. It doesn't matter which type of ivy in this case. It is a good idea to dig and screen the soil through a one-half or three-quarter-inch hardware cloth mesh to remove stems so that you do not get regrowth. If you prefer to use the chemicals rather than the digging, you can use any of several of the broad-leaf herbicides that translocate through the plant.
Be certain to choose which is labeled for the plant you are trying to remove. However, these may have residual soil activity and will require that you wait for a while before you can plant in the soil again. Glyphosate- based herbicide is also translocated and not specific to only broad-leafed plants. It does not have soil activity (it must be absorbed through the leaves to be effective), and you may plant again 10 days or so after treatment. If you choose to use herbicides, be sure to read and follow all directions. The waxy leaf surface of older leaves on some ivy may prevent absorption of the chemical, so plants with new tender growth are more likely to be affected. If the ivy you are trying to remove is Virginia Creeper or another deciduous ivy, you will need to wait until it has formed leaves.
Following use of the herbicide, it is a good idea to dig up much of what remains just to get it out of the way. Then water well and see if there is any regrowth. If there is regrowth, dig it or reapply the herbicide.
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Foliose lichen on pinon pine 9-01
Q. I was wondering if your could look at this picture and tell me what the two things are that are growing on the pinon pine tree. Are either harmful to the tree?
A. Your picture shows two forms of lichen, a symbiotic association of fungi and algae. The forms you show are a gray/silver foliose form and a duller silver/green foliose form. Foliose means that they look like they have leaves, when actually these are not true leaves. There are other forms that do not look like these, and there are many colors ranging from silvery, greenish, yellow, and even red-orange. In all cases they use trees, rocks, and in some instances even telephone lines as a substrate upon which to grow. They do not extract nutrition from the plant parasitically, thus they do not directly harm the tree. This is obvious if they can grow on rocks and telephone lines.
Lichen absorbs nutrients from the surface of the substrate and from the air (dust). Moisture is obtained from moisture in the air. All forms of lichen need sunlight but can grow in quite shady places. Often it appears that they are damaging a tree because they grow better on a tree with declining health than on a healthy tree. However, they are not the cause of the tree’s decline - they only benefit from the tree’s bad fortune. An unhealthy tree allows more light to penetrate to the bark, and this is beneficial to the lichen. Sometimes a tree with declining health leaks nutrients and sugars which become available to the lichen once it is outside the tree. Consequently, the lichen on the unhealthy tree grows better and looks like the culprit. This is a clue that you should investigate other factors that can cause tree decline. Insufficient water, disease, and insect attack are likely causes of poor tree health. Last summer was a dry summer, and many trees are exhibiting symptoms of drought injury this year. This may be the cause of excess lichen growth in some natural and home landscape settings.
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Goathead weeds a big pain!
Q: Since the rains came, goathead weeds are appearing all over my garden and lawn. What can I do? Can I use a preemergent herbicide?
A: Like many other weeds, goathead (called bullhead by some in New Mexico and puncture vine by others) seeds may lie dormant in the soil for many years until just the right conditions stimulate its growth. Our recent rains have provided the perfect conditions and the goatheads are growing where they haven't been seen growing so densely for several years. You cannot use a preemergent herbicide to control weeds which have already germinated. Preemergent herbicides are to prevent the seeds from sprouting. Once the seeds have germinated you will need to use mechanical control, hoeing or pulling, or a postemergence herbicide labeled for controlling your target weeds.
It is important to know that there is no herbicide labeled for goathead weeds. The name you will see listed on the herbicide container is puncture vine. Look for a product labeled for post emergence control of puncture vine weeds. Be sure to read the instructions carefully and follow the directions. Misuse of the herbicide can cause results you do not intend. Be sure it is safe to use the product you purchase in the garden or lawn. It should identify the environment where it is intended to be used. Using the herbicide in the wrong place may result in the death of desirable plants or contamination of food crops. If you intend to use mechanical control techniques, be diligent and persistent. Learn to identify the weed in the seedling and more mature stages. Don't let seed form and mature. Remove the weed every time you see it. Don't delay. Though you may plan to return to the site, if you wait too long it will have made seed and you will have problems again next year.
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Lichen, removing from a fence 11-00
Q. Lichens fungus has gotten onto my fence boards and are rotting the fence. What can I do to prevent this? What will destroy the lichens fungus on the fence? Any help is greatly appreciated.
A. Copper solutions kill fungus and algae. Lichen is a symbiotic relationship of a fungus and an alga. So copper sulfate, or other such material, should help. I wonder if the lichen is a result, not a primary cause of what you are describing. It is likely that the lichen is growing in that location because the fence has begun to rot, releasing nutrients that benefit the lichen. The lichen will exude some weak acids which may enhance the rotting process but are probably secondary to the problem. Fortunately, the copper solution will probably help control the primary rot organisms. Contact your local Cooperative Extension Service office for more local recommendations on products that will help.
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Mint takes over garden
Q. How can I get rid of or stop the spread of mint in my garden? It’s taking it over and is very invasive.
A. Mint can be very invasive and somewhat difficult to manage. If it is in a grassy area and you do not wish to injure the grass, you may use a trans-located, post-emergent, broadleaf weed herbicide (Weed-B-Gone, Weed-out, or other such product labeled for use in controlling broadleaf weeds in grasses. Be sure it is labeled to be safe for your type of grass.) In areas with no other desirable vegetation you can use a "glyphosate" based herbicide (check the active ingredients for potassium based salt of glyphosate - Roundup TM, or other product with this ingredient - this is absorbed through the leaves and may kill any plant to which it is applied to green leaves). If the mint is in an area with other desirable plants, you may find it necessary to apply the herbicide to only the mint using a paint brush. This is tedious, but if you are careful and persistent, you should be able to remove the mint without doing too much damage to the surrounding plants. If you choose to use a herbicide be certain to read and follow the label directions carefully. Please read the label before purchasing the product to be sure you understand the directions. If you prefer not to use herbicides, the mint can be removed by frequent cultivation until the mint no longer develops from its extensive system of underground stems. This may take several years of cultivation every two weeks. This will take persistence regardless which method you select.
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Moss and lichen on tree branches
Q. I have gray, green, and yellow moss growing on dead branches of my pinon trees and am having a disagreement with my husband about it. He says it does no harm, but the trees it is in are all thin and look sick. Some of the living branches have the moss, so I think they are dying. I want to save my trees. A nursery suggested that I use a herbicide that they called Roundup. They said I should spray it on the branches to kill the moss. My husband still says that I shouldn’t do it. Can you suggest something better?
A: The "moss" on the branches of your tree is an interesting symbiotic combination of fungus and algae. Symbiotic means that they live closely together and help each other. The fungus creates a moist environment and catches nutrients for the algae which uses the water and nutrients to create sugar and other food for itself and for the fungus. If you will notice, there are lichen growing on rocks as well as the trees. The ones on the trees may be closely attached to the branches, or may be foliose, that is leafy-looking. The ones on the rocks will usually be just closely attached and not foliose. In climates with more moisture, they will even coat the telephone lines in some areas.
Lichen (the plural as well as singular spelling) do not take food from the plant on which they are growing. You noted that the trees with the most lichen were looking sick. These lichen are a "result" rather than the "cause." The lichen need sunlight and do better on the trees which are not healthy, so they are more apparent on the "sick" trees. A sick tree will also "leak" nutrients and sometimes sugars and other things which the lichens can use to grow. This causes increased growth of lichen on the "sick" trees.
As for the use of an herbicide on the trees, it may kill the lichen, but will also kill the trees. The best you can do is be sure that the trees receive extra water in the driest times. If there are many trees in the area, you can thin the weak trees by removing them so that the healthy trees can receive extra sunlight and less competition for soil nutrients and water.
Lichen are interesting but not harmful. Unfortunately, they prefer situations which make them look guilty of harming trees, when they are not the guilty culprit. They are only innocent bystanders taking advantage of the habitat provided by conditions which have harmed the trees.
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Mushrooms in the garden
Q. How can I get rid of mushrooms that are growing in my garden? They are almost taking over the garden.
A. It is interesting to receive a question from Canada that is relevant to New Mexico as well. Each year New Mexico County Extension Agents are asked this question - "How can I get rid of toadstools?" Unfortunately, or fortunately, the answer is that you cannot get rid of the fungi that produce the mushrooms’ however, we can do some things to limit mushroom production and manage the mushrooms themselves. The fact that there are mushrooms indicates that there is a high level of organic matter in the garden. This organic matter is decomposing, releasing nutrients to the soil.
This is good! The fungi producing the mushrooms are doing much of this decomposition and are a beneficial, and necessary, part of the environment. Once the organic matter has sufficiently decomposed (composted), the mushrooms will cease to appear. Be careful not to add too much uncomposted organic matter to the garden, rather compost this material before applying it to the garden. This will be of some help. The other critical factor for formation of mushrooms in the garden is adequate water. Here in New Mexico, by limiting our irrigation and targeting water by use of drip irrigation to the specific area where water is needed, we can slow the growth of fungi in the soil and reduce the production of mushrooms. For the existing mushrooms in your garden now, just rake them up and put them in the compost pile to decompose and produce good soil amendments for next year’s garden. As new mushrooms appear, rake and compost.
Oleander Leaf Scorch
Q. Our home was built in 1993 on a double lot in Las Cruces. It has an oleander hedge planted along the perimeters of the property adjacent to the rock walls as a privacy screen. This planting covers 320 linear feet. Over the years, it has filled in completely and is quite tall.
Late this spring we observed a great deal of leaf damage on at least half the plants. We assumed that we should have provided more water to these plants during the winter where, as you know, there has been essentially no rainfall. However, we are now reading information on the Internet from the University of California. There appears to be a problem with "oleander leaf scorch" caused by the bacterium Xylella fastidiosa. This bacterium is "vectored" by insects, primarily the "Glassy Winged Sharpshooter." We are informed that the problem first appeared in southern California but has since spread into Arizona and Texas. Someone apparently has not checked a map. The last time I looked, New Mexico lies between those last two named.
Accordingly, should we assume that the "oleander leaf scorch" has invaded our area? It appears from what we are reading that there is nothing we can do about it. We would greatly appreciate your comment.
A. I think your first suspicion was correct. The dry winter is the most likely cause of the leaf dieback. Winter desiccation of oleander leaves is not uncommon in Las Cruces. The winter of 2004-2005 was wetter than normal. The previous winter, plants were much smaller and required less water. As plants become larger, their water requirements increase. Winter irrigation and mulch to conserve water in every season will help with this issue.
Dr. Natalie Goldberg, NMSU Extension Plant Pathologist reports that oleander leaf scorch has not been reported in New Mexico. She has recently tested some oleander samples from Las Cruces and says that oleander leaf scorch was not present. Dr. Carol Sutherland, NMSU Extension Entomologist, reports that one of its insect vectors, the smoke tree sharpshooter, has been reported in the state but not in Las Cruces. She says that the glassy winged sharpshooter has not yet been found in New Mexico. For these reasons, the best hypothesis is winter water deficit. The fact that New Mexico seems to be skipped over in the distribution of this disease is probably due to our lower population and reduced chance for importing the disease on infected plant material. The expanse of arid lands between us and the infested areas also provides some protection. The insects carrying the disease cannot easily cross the desert.
While it may be premature to assume that oleander leaf scorch is the cause, this hypothesis may be tested by sending a sample for analysis. If your plants have significantly different symptoms from other oleanders in your area, you may have them tested. Collect some stems that contain both healthy and dead leaves. Take those samples to your local Cooperative Extension Service office. The sample may then be delivered to the Extension Plant Pathologist for testing to determine the presence or absence of the disease organism if such testing is warranted. New Mexico gardeners hope that you will not be the first reported case of this disease in New Mexico. It will cause problems in plants other than oleander, and it will be a problem that is best avoided. If your plant samples are like those in many landscapes in Las Cruces, you won’t need to send them in. With current information, winter desiccation is the most likely cause of leaf scorch of your oleanders.
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Overrun with mushrooms!
Q. I live in Las Cruces. One section of my back yard is overrun with mushrooms. (An area of approx. 8x15) I have tried a solution of Weed-B-Gone™ but with no success. I hesitate to go to a stronger solution for fear of killing my grass (fescue), but my back is getting tired of bending over and picking them out one by one. Any suggestions?
A. Yours is a common complaint, and the answer is not what the gardener wants to hear. Mushrooms are fungi; weed killers, such as the one you used, will have little affect on them. Use of fungicides, however, is also not recommended. The fungi which produce the mushrooms are an important part of our environment, releasing the nutrients from dead grass, tree roots, and any other dead organism in the soil. Without them, we would have a very difficult time growing gardens and lawns. They compost dead debris such as old dead tree roots, lawn thatch - anything that dies. Most of these composting fungi are not pathogenic and should not cause you to worry that they will attack your healthy, well-cared-for lawn and garden plants. As long as the weather (moisture) and food source (decomposing organic matter) remain, the mushrooms will keep appearing.
So......enjoy them, just realize that you shouldn't eat them unless you are an expert at mushroom identification. Having said all of that, when the mushroom caps are very new, before they fully open and ripen their spores, you can use them for golf practice. This will remove the obvious mushroom caps from the lawn, but the fungus will still remain below. After the spores mature, you will just spread the fungus spores if you hit or kick the mushrooms. They can be attractive and interesting, especially if you learn to make spore prints by placing the mushroom cap right-side-up on a sheet of dark or light construction paper. Then, as the spores released, they will form a pretty pattern which is useful in identifying them and quite artistic as a side benefit.
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Puncture vine (Goathead) control 3-01
Q. I’m having a big problem with goatheads in the front and in the back yard. I have tried to use Weed-B-Gone™ but that seems not to help. Each year it seems to get worse, and I have young kids that play in the back yard and they’re forever getting the stickers in their feet. Is there something that I can use to get rid of the problem?
A. Goathead weeds, so called because of their spiny seeds, are more correctly called puncture vine. This is important to know because you will find no herbicides labeled for goathead, rather you will find them for puncture vine.
Pre-emergent herbicides labeled to control puncture vine can be applied in the spring before the puncture vine weeds begin to germinate. Such herbicides work by killing the seedling as it germinates. They will not kill existing plants, only those just germinating from seeds. Read and carefully follow the label directions to get the maximum benefit. Once the puncture vine has germinated and is growing, a "broad-leaf" (post-emergent herbicide) may be used. Again, follow the directions. You can supplement this with manual removal (digging or pulling the weeds). It is important to prevent the weeds from forming seeds, so diligence is required. If seeds do form successfully, that is the source of a problem for subsequent years. Even if a few plants do manage to form seeds, if you can limit the number formed you can reduce next year's problem. Since the seed can remain viable in the soil for several years, you must continue vigilant management until no live seeds remain in the soil to create problems.
For more detailed information and recommendations specifically for your area, contact your local Cooperative Extension Service Agent or Master Gardeners. Many nurseries and plant centers can also provide information and help you read and understand the herbicide labels so that you can select one appropriate for your location and conditions.
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Snail and slug control 5-01
Q. I can’t get rid of snails and slugs in my yard. It seems like when it rains, it must rain snails. Even when it’s not wet here, I still have them. I’ve tried a powder substance, granules, beer traps and I even poured beer on the plants. My poor plants are just constantly being eaten by those darn critters. Is there anything else I can use?
A. Snails and slugs are a problem in many landscapes, even here in New Mexico. They are often imported into the landscape with new plants. Snail and slug eggs, or the mollusks themselves (they are mollusks, related to oysters and clams - please don’t ask me to tell you how to make them into escargot), may be found in the soil around the roots of many ornamental plants. Once they have been introduced into a landscape, they are difficult to eradicate. It is even difficult to keep their populations low enough to minimize the damage that they do.
Many people don’t even know that they have snails and slugs in their landscape - they just find plants eaten by some secretive critter. As you have described, it is easiest to find them after a rain or irrigation. You may also recognize their presence by the silvery slime-trails that they leave on sidewalks or plant leaves. They lay down a layer of mucus (slime) as they travel across a surface. This slime protects them from sharp objects, even allowing them to crawl along the edge of a razor blade. There are some techniques that do work to a limited degree to help manage snails and slugs. Some people have had success with copper screen or copper bands surrounding areas they wanted to protect from snails. Others have used bands of fertilizer around some plants. The fertilizer salt dehydrates the snails and kills them (like table salt, but fertilizer salts aren’t harmful to plants if not over-used). If you wish, you can sprinkle a little granular fertilizer on the snails and slugs by hand, but this is time-consuming and only kills a few of them.
It seems everyone knows of the beer-filled traps into which the snails and slugs crawl and drown. It has been shown that non-alcoholic beer is also effective. A Master Gardener tells of snails being attracted to some mushrooms drying on her porch. She hand-collected and disposed of the snails. (The mushrooms didn’t kill the snails but were an effective attractant.) There are commercial snail bait products that may be used. Some products use chemicals which are quite toxic and should be used with caution where children, pets, and beneficial wildlife may potentially be affected. Another product uses iron phosphate. This is much safer to use and seems to be effective. A side benefit is the addition of both iron and phosphate plant nutrients to the soil.
There are also some predatory snails available through mail order insectaries (look for advertisements in gardening magazines). These snails eat other snails. They may also eat plants but are reputed to limit their damage through their cannibalistic nature (they eat their own kind, preventing damaging populations from developing). Finally, when all else has failed, hand-picking (yuck!) after rains and irrigation may be employed. This is not extremely effective in ridding a landscape of snails and slugs, but there is the vengeance factor that some gardeners appreciate. You may find it most beneficial to use several management methods in combination. However, if you use the predatory snails, do not use the other techniques at the same time as these techniques will kill the predators as well as the pest snails and slugs.
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Snails and slugs nationwide problem?
Q. Are snails and slugs a problem throughout the U.S.?
A. The answer depends on the context of your question. Snails and slugs are a problem in landscapes and gardens in much of the U.S. In the natural environment, they are not as great a problem. Here in New Mexico, they cause problems only where we irrigate and have imported them in the soil of our landscape and garden plants. I don't remember any problems with snails and slugs when I lived in Montana. Perhaps that was due to the cold winters, but the lack of any problems may have been because fewer imported plants from snail- and slug-infested areas were used in landscapes. So, I can answer from the context of New Mexico. They are a problem in our irrigated landscapes and gardens. In the desert, they are not a problem. Perhaps Extension Service people in other states could answer for their states.
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Snails killed with salt? 6-02
Q. I have seen snails killed when salt was sprinkled on them. Can I use salt to kill snails in my garden?
A. Snails do die when salted, but so do plants. Sodium is another plant nutrient used in very low concentrations by plants and toxic to plants at slightly higher levels. Fertilizer will do the same thing to snails and slugs as table salt will do. You can sprinkle a little fertilizer on them and they will die. The fertilizer won’t hurt plants unless you overdo the snail treatments. Too much of any salt (and fertilizers are salts of plant nutrients) will harm plants. Fertilizers are nutrients that don’t become toxic as quickly as boron or sodium. A band of fertilizer placed several inches from tender plants after irrigation will help protect from snails following irrigation. For severe snail and slug infestations, it is better to use other methods to control snails to avoid over-fertilizing the garden and harming the plants. Other methods include the stale beer snail/slug traps and chemicals labeled to kill snails and slugs.
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Toadstools: what causes them? 10-00
Q. The morning after a night of thunder, lightning and rain often produces toadstools on the lawn. What causes the toadstools to grow overnight? Is it the lightning or the rain?
A. It is important to understand that a toadstool (mushroom) is the fruiting structure of a large mass of fungus growing in the soil. When conditions are right for this (pre-existing) fungus to reproduce, it quickly produces the mushroom. The mushroom, the fruiting structure, then produces spores to reproduce the fungus. The moisture provided by the rain storm is the factor for which the fungus waits.
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Curly Top Virus 3-03
Q. What is curly top virus and is there a cure for it? I have received about 15 different varieties of heirloom tomatoes, and I do not want to expose them to this virus.
A. Curly top virus is a plant disease that affects many garden crops, especially tomatoes and chile. While this virus is harmful to plants, it does not harm people, so the concern is exclusively for our plants.
The virus cannot overwinter in the soil; it must remain in a living plant. Plants cannot be infected by planting them in soil where infected plants grew last year or by use of compost from infected plants. Infection involves transfer of the virus from plant to plant by insects. Some perennial weeds, some landscape ornamentals, and especially the London rocket (mustard weed) carry the virus through the winter. The most common method of disease transmission is by an insect called the beet leafhopper. As the insect feeds on the weeds, it takes in some of the virus. When the insect feeds on a tomato or chile (after picking up the virus), it may then transmit it to the vegetable.
Symptoms of curly top include yellowing of the new growth, curling or twisting of the leaves, and often development of a purplish cast on the mid-rib on the underside of the tomato leaf. Perhaps the least desirable symptom is that crop yield is greatly reduced.
There is no cure, only prevention. Good weed management during the spring is essential. Removal of weeds that carry the disease should be accomplished before the susceptible vegetables are planted. Insect control is not effective. Treatment with insecticides will usually not stop spread of the disease. Row cover fabric surrounding tomatoes and chiles will provide protection from the spread of curly top virus. This may be a reasonable solution for limited numbers of plants. The row cover material will also provide some wind and sunscreen protection.
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