Welcome to the first issue of the 1998 growing season. What a difference a year makes. The new year is off to a good start and the growing season appears to be way ahead of last year. However, it is but probably really not that far ahead of the average spring. The calls and samples have been coming in already as many gardeners have been out working in their yards and gardens, getting ready to get the vegetables planted and the flowers blooming. As in past issues, categories for topics are as follows, H - Herbaceous plants and flowers, W - Woody Plants, V - Vegetables, F - Fruit and L - Lawns.
DISEASES
While pest activity is low at present there are a number of tasks managers should be considering at this time. Each year we receive numerous calls regarding tree disease problems. Unfortunately, by the time people notice the symptoms it is usually too late to effectively provide treatments. The following is a list of problems that require spring preventative treatments.
W,F APPLE SCAB attacks apples and crabapples. Now is the time to begin your apple scab spray program. The first recommended spray for apple scab is when the buds have opened and the leaves are about 1/2 inch in length (referred to as "1/2 inch green tip"). Additional sprays should follow to maintain control during bloom and flower petal fall, as well as throughout the summer. Fungicides such as Captan and Benlate should be effective (read label for directions).
W ASH ANTHRACNOSE attacks ash. Treatment is rarely necessary. However, the best treatment is to apply Captan, beginning just after bud-break and continue at 10-day intervals as long as cool (below 55F), moist conditions persist.
W,F BLACK KNOT attacks chokecherry and plums. Many home owners have been hit very hard by this fungal disease. In many cases trees show the big black knots on almost every small branch. Prune out the knots that are black as well as any swollen portions of branches where new cankers will be appearing this spring. Best chemical treatment is to apply lime-sulfur at green tip, bloom and petal fall. Keep in mind that the knots that will appear this spring will still occur unless they are pruned out because they were caused by infection last spring.
W DIPLODIA TIP BLIGHT attacks Austrian and ponderosa pines. Best treatment is to use Thiophanate-methyl or Fungo Flo, applied at bud break and again in seven to ten days.
W,F RHIZOSPHAERA NEEDLE CAST attacks blue spruce. Best treatment is to use Chlorothalonil or Bravo, applied when new needles are half elongated (about 1/2 to 2" long) and again when needles have fully elongated (about 3 weeks later). Repeat this treatment for two consecutive years to control this disease. This disease has been very serious the last few years and is expected to continue to be a problem as long as we continue to have wet spring conditions.
F PLUM POCKETS attacks plums. Best treatment is to apply lime-sulfur at bud swell.
L DEAD SPOTS IN YOUR LAWN? Gray Snow Mold, Pink Snow Mold, or Dollar Spot may have left circular patches of dead turf in your lawn. If the patches are not too large, spreading turfgrasses, such as Kentucky bluegrass, may fill in the dead area without reseeding. Larger areas of dead turf will require a good raking to loosen up dead plant debris, thatch, and soil prior to reseeding. Good seed-to-soil contact is important, as well as keeping the seedbed constantly moist until seed has germinated. Avoid application of preemergence herbicides to areas you wish to reseed, as these herbicides will kill germinating turfgrass seed as well as weed seed.
INSECTS
L BILLBUGS. You may have noticed small, black insects about 1/4 inch long scurrying across your sidewalks or driveways recently. These insects are likely to be adult bluegrass billbugs that are headed for your turfgrass after overwintering in sites with taller vegetation. This "snout-nosed" weevil deposits eggs in bluegrass stems near the crown. Eggs hatch into larvae which eat their way downward, eventually moving into the soil and feeding on roots. Symptoms of bluegrass billbug damage include brown areas of turf with fine sawdust-like plant debris and excrement. For estimating infestation, apply 1 tablespoon of 1 to 2% pyrethrins in 1 gallon of water per 1 sq. ft. area and observe for 10 to 15 minutes. Numbers greater that one adult per 1 sq. ft. indicate the need for treatment. Use either traditional turf insecticides such as Diazinon, Dursban (chlorpyrifos), Oftanol (isofenphos), or Sevin (carbaryl), or the newer generation insecticides like Merit (imidacloprid) or Mach 2 (halofenozide).
W ELM BARK BEETLES will be emerging soon. The beetles, which carries the Dutch elm disease fungi, are attracted to fresh pruning cuts so all elm pruning should be completed by April. If an elm branch must be pruned during May - September, the cut should be covered with a light coating of a commercial tree paint. The paint will prevent the odor of the fresh cut from being released. This is one of the few instances where pruning paint is beneficial to the tree.
W HONEYSUCKLE APHIDS will soon begin feeding. These are the insects responsible for the malformed "witches broom" type appearance of the new shoots. A preventative treatment of Orthene can be applied once the new growth emerges in early May.
W MAPLE BLADDER GALL MITES will soon begin feeding on the newly emerged and expanding maple leaves, particularly on Silver Maple. The tiny mites feed on the developing leaves which induces the leaf to produce the characteristic yellow to orange-red nodule or gall on the leaf. These galls do not damage the tree and no treatment is needed. However, many people find the galls unsightly and want to get rid of them. If a tree has been infested in the past, chances are good that the tree will be reinfested again this year. Once the galls appear, it is too late to treat. Treatment must be applied as the new leaves are emerging and are less than ½ their full size. Kelthane is the best miticide to use but Dursban and Sevin are also labeled for this pest.
W SCALE CRAWLERS will be emerging soon. The crawlers are the newly hatched nymphs of the adult scale insects. Crawlers are quite easy to control since they have not yet developed the tough waxy body covering characteristic of the adults. Pine needle scale and oyster shell scale are the two most common scale insects found in South Dakota. While a dormant oil spray can do a pretty good job of controlling scale, it is probably too late to apply now since most shrubs and trees have already leafed out. Check for crawler emergence by doing a tap test as is done with spider mites. Once the crawlers emerge use malathion, diazinon or orthene to control them. In severe infestation on deciduous shrubs, heavily infested branches may need to be pruned out to help the plant recover. Also, check the plants for other types of site-related stresses like as water, temperature, light or nutrient extremes which may be contributing to poor plant health. Remember, heavy scale infestations are often a symptom of other problems.
W SPRUCE SPIDER MITES have become active in many areas. These tiny reddish mites prefer cooler and moister conditions than the red and two-spotted spider mites which become more active later in the season. They prefer to feed on spruce, juniper and some other evergreens. Infested trees will exhibit needles that have a blotchy yellow and green appearance. Do a tap test over a piece of paper to check for the mites. They may also be seen with a good hand lens. Treat with a miticide like Kelthane, Cygon or Isotox. Treatment will be most effective if two applications are made 7 to 14 days apart to kill the adults and then get any newly hatched individuals. Dimethoate may be used by commercial applications. DO NOT use malathion, diazinon, or sevin since these are poor miticides and may actually increase the problem by killing mite predators.
W TENT CATERPILLARS are out and feeding in many areas of the state. These caterpillars make a web in the crotch of a tree and then go outside the web to feed, usually at night when the larvae are still small. In most cases, the larvae are still very small and very easy to kill at this stage. The best recommendation at this point would be to use a B. t. (Bacillus thuringiensis) containing product. This is a very safe product to use and is quite effective on these young caterpillars. Of course, other products like sevin, malathion or diazinon can also be used.
WEEDS
L APPLY PREEMERGENCE TURF HERBICIDES NOW. Yearly infestations of annual grasses such as crabgrass, goosegrass, and foxtail in established turf are best controlled preemergence before weed seeds germinate. Crabgrass seed germinates when soil temperatures of 50 to 55F are sustained for several days. Germination of goosegrass and foxtail generally follows crabgrass by about 2 weeks. Products using pendimethalin, dithiopyr, prodiamine, oxadiazon, or trifluralin + benefin are effective. Be sure to follow preemergence applications with about 1 inch of irrigation (or rainfall) in order to move the herbicide into the top 1/2 inch of soil where weed seeds germinate.
L ALTHOUGH AUTUMN IS THE OPTIMUM TIME to control perennial broadleaf weeds in turf, early May is probably second best. Dandelions, ground ivy, white clover, curly dock, mouseear chickweed, plantain, common yarrow, red sorrel, and wild violet may be treated with a broad spectrum postemergence product containing 2 or more of the following growth regulator herbicides: 2,4-D, 2,4-DP, MCPA, MCPP, dicamba, triclopyr, and clopyralid. Avoid mowing several days before and after application. Some weed species may require 2 applications 10 to 14 days apart. Don't apply these herbicides if rain appears imminent within 24 hours.
L CREEPING CHARLIE CONTROL OPTION. Every year we get lots of calls about how to control Creeping Charlie or ground Ivy. Our usual recommendation is to make two applications of a broadleaf herbicide in the fall after the first frost. However, Iowa State University has come up with another treatment using Borax. This is something that you may want to try on a small area to see if it works for you.
Here 's the formula suggested by researchers at Iowa State University. You can spray in spring as soon as the creeping charlie leaves are fully developed. To cover 1,000 square feet (adjust as needed for smaller areas): * dissolve 10 ounces of Twenty Mule Team Borax into 4 ounces of warm water, * dilute your mix into 2 1/2 gallons of water (mix it well), * spray it EVENLY over 1,000 square feet of lawn with creeping charlie interspersed in it.
OTHER NOTES
L HOLD OFF ON THAT TURF FERTILIZER until mid-to-late May! Cool-season turfgrass naturally responds to warming soil temperatures in Spring with "green-up" and a flush of new growth. Applications of nitrogen too early may cause excessive shoot growth at the expense of root growth, and you may find that you're time spent mowing has doubled. Application of a complete fertilizer at the rate of 1 lb. nitrogen per 1000 sq.ft., will prepare your turf for summer's stress. Use a product that has at least 10% of the fertilizer in a slow release form.
H SPRING FLOWERING BULBS - You can help your bulbs to come back year after year by fertilizing the bulbs after flowering. Use a nitrogen fertilizer while their foliage is still green and be sure to keep that foliage alive and actively growing as long as possible this spring. DO NOT cut the foliage off after flowering, wait until it turns yellow and dies down naturally. Otherwise, dig up the bulbs and plant large new ones next fall to make it more likely that you'll have a nice display in 1999.
V RHUBARB & ASPARAGUS should be transplanted now. Each season we get lots of calls about transplanting these spring vegetables, typically right after gardeners have enjoyed that year's crop. Unfortunately, that is not a good time to transplant or establish these plants. It is best to try to get them transplanted as early as possible, before the plants have much new growth on them. Remember if you are starting a new bed, it is best to start with new plants from a local nursery, garden center or catalog to reduce the chances of bringing a plant into your garden that has a virus or other disease. See ExEx 6009 - Growing Asparagus for additional information.
W PRUNING - Remember most of the major pruning on trees should be completed in the next week or so. Bud-break and leaf formation require much stored energy from the tree. Pruning wounds created at this time do not compartmentalize properly due to a lack of available energy. Poor compartmentalization could result in increased decay. Also, delay livewood pruning of elms until later this summer to reduce attraction to the elm bark beetles which can spread Dutch Elm Disease.
Some trees may have experienced branch and limb breakage from the weight of the snow and ice this winter. Some trees may have only suffered minor damage and lost a few branches while others may have been nearly demolished from the excess weight and wind. The first step in dealing with this damage is to assess how much damage was done and clean up the loose debris. Carefully prune out broken and damaged branches at their base, removing them at the branch collar without damaging the trunk. If bark was stripped down the side of the tree with branches, cut off the loose bark but do not trace the wound. Branches that are only partially broken should be removed. If major damage has occurred to large trees, we recommend you contact a professional arborist for additional treatment. Do not use pruning paints or sealers on the broken or cut surfaces. Research has shown that these do not help the tree recover from the injury and may actually reduce the tree's ability to wall-off the wounded areas.
W,F PLANTING TREES & SHRUBS - The number one killer of transplanted trees is planting too deep. When planting be sure to keep the bud union (graft) about 2-3 inches above the soil surface. See the Extension Extras 6018, 6019, 6020 and 6021 for more information on tree planting.
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Most recent revision Thursday, July 16, 1998 by David F. Graper