Dealing with drought stressed lawns

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Farm Forum

Drought is a common concern across the region this summer affecting landscapes in many ways but probably most noticeably in its impact on lawns. Cool season grasses are particularly vulnerable to drought stress when it is accompanied by high temperatures, as we have often had since late spring and into the summer. Watering restrictions have already been imposed in many communities which limit some of the options that home owners have who want to keep their lawns green.

It is important to keep in mind that even though a lawn turns brown, it is often a temporary condition. Cool season grasses, like Kentucky blue grass, will routinely go into a dormant-like condition when water is lacking and temperatures are high. Often lawns are made up of several different cultivars or species of grass so a drought stressed lawn may also have a patchy appearance. Individual grass plants can recover and green up again, once the plants get sufficient water. The crown of the plant can remain alive for up to three weeks without any water. Then, as little as 0.2” of rainfall or irrigation can rehydrate the crowns and help to keep them alive. That amount of water will not turn your lawn green again, but it will allow it to survive until greater rainfall and cooler temperatures return later in the summer and fall.

If you decide that you are going to water your lawn, infrequent, deep watering is the most beneficial. This will help to allow deeper penetration of the water into the soil profile which will in turn encourage deeper rooting that will help to avoid further water stress. Frequent, shallow watering encourages roots to stay near the soil surface where they can dry out quickly. Generally cool season grasses need about 1” of water per week for best growth which is ideally applied in one or split between two applications per week.

Home owners have other cultural treatments to help their lawns survive heat and drought stress. One of those is to raise mowing height to at least 3.5”. While this may seem quite tall, plant grass height is often proportional to the depth of rooting. If grass plants have roots that penetrate more deeply into the soil, they are able to access water that is deeper in the soil. The roots will also have access to more nutrients in the soil profile as well. Avoid applying fertilizer to a drought stressed lawn – it will not cause the grass to green up and can actually increase overall stress. Wait until mid- to late-August to make that fall application. Ideally try to apply most of a lawn’s fertilizer in the fall of the year, right before a rain or irrigation.

Fall herbicide treatments for the control of broadleaf weeds should also be delayed until later in the fall, ideally after the first frost. An herbicide application now can cause additional stress to a lawn and cause significant damage to nearby garden and landscape plants. Some broadleaf herbicides will readily volatilize when temperatures are above 85°F which can then drift hundreds of feet, potentially causing damage to particularly sensitive plants like tomatoes, potatoes, peppers and eggplant.

Can I eat this fruit?

By John Ball

SDSUExtension Forestry Specialist

This is a common question right now. Wrong question. Sure you can eat it, the important question is should you! Seems South Dakotan are out trying to make jam out of fruit they are collecting. The two questions are; what is it and can I eat the berries? So let’s look at a few. The first is the Tatarian honeysuckle (Lonicera tatarica) and it can be easily identified by its opposite, ovate leaves that have a slight bluish-green color. The fruit is an orange-red berry, usually found in clusters of two’s, and occur at the axils of the leaves rather than on the terminal of the shoots. The plant, a native of Central Asia, was widely planted as a tough windbreak shrub and has become even more widely disseminated by the birds as they carry the seeds. The shrub has lost its value as a windbreak plant due to the introduction of the honeysuckle aphid in the early 1980s. This insect is responsible for the witches-brooming commonly seen on the tips of affected shrubs. The fruit is widely regarded as poisonous to humans, though there is not much documentation regarding this fact. Vomiting and abdominal pains are often given as the symptoms following eating the fruit. Europe is where most of the information on toxicity comes from, but no sense tempting fate. I would suggest avoid eating this fruit fresh or using it in jams or jellies. Interestingly, one paper from the United States points out a study where the fruit was found to be poisonous to rabbits so it’s not all bad news.

What about common chokecherry (Prunus virginiana). The fruit of chokecherry is edible, in fact in 2007 it was voted the state fruit of North Dakota (South Dakota does not have a state fruit, let’s get on it!). The fruit was also highly prized, and still is, by the native nations. Capa sapa wi, “black cherry moon” is the name the Lakota gave to the month of August, the time when the fruit ripens. The Lakota would grind the fruit, pit and flesh together, into cakes and dry them in the sun. This can be mixed with dried meat to form pemmican. The fruit can also be made into jams and jellies. Some folks, with few taste buds, can even eat them right off the tree but they do not get the name chokecherry for nothing!

Common chokecherry trees can sometimes be confused with common buckthorn and this is a serious mistake if you are planning on picking the fruit. While common chokecherry fruit is edible, common buckthorn (Rhamnus cathartica) is not and works as a very, very powerful laxative. The way to separate the two is chokecherry leaves are arranged alternately along the twig while common buckthorn (As seen in the picture to the left) are sub-opposite, where a leaf is almost opposite another leaf on the twig. The orange patches are from a rust disease. The margin or edge to buckthorn leaves usually have rounded teeth while the chokecherry has sharp teeth. Common buckthorn also has a single thorn at the tip of each branch. The fruit differs in that chokecherry has dark purple to black fruit and is about 1/3 inch in diameter and contains a single large seed while buckthorn’s glossy black fruit is about 1/4 inch in diameter and contains two to four small seeds. Also, each individual common buckthorn fruit is attached to the twig on its own little stem while the fruit of chokecherry is borne in small clusters that are attached to the main stem.

Pest and ID samples from early August

By John Ball

SDSU Extension Forestry Specialist

Black blister beetle (Epicauta pennsylvanica) picture was sent in from Kadoka, SD. These beetles are about 1-inch long with a long, cylindrical black body. They also have long legs and antennae. There is also a striped blister beetle (Epicauta vittata) that looks very similar but is dark tan with dark stripes. The name blister beetle comes from the toxin cantharidin that the beetles exude from their leg joints when disturbed. This toxin can result in skin blisters. The insect in the larval stage is beneficial, feeding on grasshopper egg pods (and unfortunately the larvae of the solitary bee) but in the summer the adults can become a problem on legumes. The adults are common in alfalfa fields and also can be found defoliating honeylocust trees and Siberian peashrubs. These beetles, especially the stripped blister beetles, may also be found feeding on various vegetable garden plants including carrots and beans. While the defoliation can be a concern, the greater concern is the toxicity of the crushed adults in alfalfa bales. The adults tend to congregate so you might find 100 or so crushed adults in a flake and none in the rest of the small bale. If a horse is fed the flake, it might ingest several hundred of these insects. It takes about 350 to 500 to kill a horse.

Groundcherry (Physalis) was an identification e-sample this week. There are several groundcherry species found in the state. The smooth groundcherry (P. subglabrata) is the more common, but there is also the clammy (P. heterophylla) and Virginia (P. virginiana). Groundcherries have an interesting fruit, a round, berry-like, yellow fruit enclosed in a papery calyx. The cooked, ripened fruit is considered edible. Note the terms, cooked, ripened and considered, before deciding to make a pie from this fruit. Unripen (green) or raw fruit is poisonous.

Pear scab is showing up across the state. The disease caused by the pathogen Venturia pyrina is related to the similar disease that occurs on apples known as apple scab. Pear scab results in the infected leaves developing a blackened margin, sometimes covering most of the leaf. These leaves will hang for a short time then fall. There will also be lesions on the twigs and the fruit. The symptoms differ from fireblight in that the blackened leaves will still be moist to the touch while the leaves on blighted branches will often be curled, shriveled and dry.

Walnut caterpillar (Datana integerrima) is an unusual insect in South Dakota but we do see them from time to time. The full-grown larvae are about 2 inches long, black with thin yellow strips and the body is covered with long dirty-white hairs. The adults are out in the spring and early summer with the eggs deposited on the undersides of leaves. The eggs hatch and the larvae feed in masses on the foliage. Now they are dropping to the ground to look for a site for pupation. There is one-generation per year in South Dakota but farther south there can be two. The larvae feed on walnuts and hickories (including pecan) and if a tree is defoliated for two years in a row, the stress can result in dieback and decline. Fortunately this pest is often a one-year phenomena, appearing in large numbers one year and not seeing them again (at least in large numbers) for a decade or more. This appears to be a ‘bad’ year with some tree being completely defoliated and the ground (as in the picture) covered in frass.

I have received number pictures and questions regarding willow scab (Venturia saliciperda). This is a very common foliage disease that appears in late summer on willow trees across the state. The disease is closely related to apple and pear scab and the typical symptoms are discolored and falling leaves as well as tip dieback. This disease has similar symptoms to black canker (Glomerella miyabeana), a willow twig disease that can also cause the leaves to wilt and the shoot tips to die back. The two diseases are difficult to separate, but the willow scab infected leaves will usually have “tufts” of spores on the underside of the leaf, generally along the mid-vein. Separating them is not all that critical as these two diseases often occur together and the disease is simply called willow blight. There two disease are common problems when the spring weather is moist, a condition typicall of much of the state this year.

Raccoons in sweet corn

By David F. Graper

SDSU Extension Horticulturalist

Most gardeners are pretty generous with their excess produce – who hasn’t been the recipient of someone’s extra zucchini from time to time? The problem with raccoons though is that they are pretty greedy. Not only that, by the time a few of these nighttime foragers get done, there is often very little edible sweet corn left to harvest. They tend to knock lots of it down, rip open ears, take a few bites, shred the rest of the cob a bit then move on to the next stalk. It can be a pretty discouraging site after you have been tending your sweet corn patch all summer long, and now, waiting with mouth-watering anticipation find that the day or two before you were going to start harvesting that the ‘coons got to the corn first.

So what is a gardener to do? If you ask around, or check online you can find lots of different suggestions. In my experience the best option is an electric fence around the perimeter of the sweet corn patch. If you have a building with electricity close to your garden, you can purchase an inexpensive fencer starting at about $60. If that is not an option, a solar powered fencer can be installed just about anywhere. Those units can be picked up starting at about $150. Battery-powered fencers are also available. Keep in mind you can buy a lot of sweet corn for $150 but for many, the taste of freshly harvested sweet corn from your own garden is worth it.

If you are not familiar with how electric fencers work, be sure to read the instructions. You will also need the wire or fencing tape, posts, insulating buttons of clips and a grounding rod. I use 6’ T-posts and fencing tape. It is wider than regular fencing wire, somewhat easier to work with for a small installation like this but is more expensive. I install four layers of wire. The first one is about 6” above the ground with a second one 6” higher. I then add one more in the middle of the post followed by a final one at the very top. The bottom two are for the ‘coons while the top two help to deter deer that also love to eat sweet corn and knock it down. You should also have a way to easily turn off the fencer to allow you easy access to the sweet corn, or you can add a fence gate with an insulated handle that you clip onto the fence to close it or unhook it to open it. The solar powered fencer that I have has a simple switch right on the front so I can turn it off. Believe me, grabbing on to or bumping into the wire while it is on is a mistake that you will likely try to avoid repeating. Just remember to turn the fence back on after you are done or the ‘coons will likely find a free meal.