Hort Update for the week of 7/13/2009
1. Nimblewill is a warm season perennial grass. It is a fine bladed, wiry, pale green grass. The leaf blades are short and emerge at 45 degrees angles from the stems, which are slender, smooth and tend to lie flat on the ground. It spreads by short stolons, or above ground stems, that root at the nodes. Nimblewill forms circular patches as a result of its stoloniferous growth pattern, which grow larger each year, often a foot or more in diameter. It goes dormant from mid fall through mid to late spring. When it goes dormant, the brownish patches may be confused for disease or insect damage. It has fibrous roots, making the plants easy to pull. Maintaining a dense, healthy lawn through proper turf selection, establishment, and maintenance is the recommended non-chemical control.
Commercial applicators can apply the herbicide Tenacity for selective control of nimblewill in Kentucky bluegrass lawns. As of summer 2009, Tenacity is not available to homeowners. Homeowners may use glyphosate (RoundUp), a nonselective herbicide, to kill green, actively growing mats of nimblewill from late spring through early autumn. Spray at least twelve inches beyond the visible edge of the weed to make sure you get all of the plants killed. Reseed or resod areas with desirable turfgrasses. Applications of glyphosate to nimblewill when dormant will not provide control.
Nimbleweed, Purdue University
2. Mushrooms and Slime Mold grow on organic matter such as dead tree roots, turfgrass thatch, and wood mulch. They are the spore producing bodies of decay fungi which are decomposing the organic matter. They do not infect and cause diseases in turfgrass. Fungicide applications will not control mushrooms and slime mold. They will disappear in dryer weather and stop appearing once the organic matter they are growing on decomposes. Where a slime mold is shading turfgrass and causing yellowing, remove it by mechanical means such as raking.
Slime mold on Turfgrass, Ohio State University
3. Brown Patch causes roughly circular patches of dead and dying grass, intermixed with green leaf blades. Patch centers may be less affected and remain green. Tan colored, irregularly shaped leaf spots with reddish margins are found on leaf blades. Fungicide applications are often not recommended after August 1. Preventive applications of Prostar (commercial use), Bayleton, and chlorothalonil (Daconil) do a fairly good job of suppressing the disease when applied at monthly intervals (June, July, August). Curative applications of chlorothalonil beginning a few days after symptoms of brown patch develop may do an adequate job of suppressing injury. In many cases, lawns damaged by brown patch will recover in two to three weeks, provided the outbreak is not sustained by continuous hot, humid weather; and treatment may not be necessary.
Brown Patch, Kansas State University
4. Chinch Bugs in Buffalograss and Zoysiagrass feed by sucking juices from leaves and stems. They inject a toxin while feeding which disrupts translocation of water and nutrients. Damage appears as patchy areas which turn yellow, then dry out and turn brown. Damage is usually heaviest in sunny locations during hot, dry periods. Chinch bug nymphs are red with a white band, then orange-ish, and finally brown to black. Adults are 1/10th of an inch long and black and white. Control thatch to reduce chinch bugs. If bugs exceed 20 per square foot, an insecticide treatment is justified. Bifenthrin still best for chinch bug control.
Chinch Bugs in Turfgrass, Ohio State University
5. Chiggers are the tiny, reddish, six-legged larval stage of a mite that torments people each summer by causing intensely itchy welts. Only the larval stage attacks humans and animals. Chiggers can be found in highest numbers in tall grass or weedy areas of the landscape. Eliminating weeds and regular mowing of turf areas will reduce chigger populations. Protect yourself by using insect repellents containing DEET
Chiggers, Ohio State University
6. Peach Tree Borers- Boring insects that feed under the bark is one of the most serious insects of fruit trees, including peaches, plums, nectarines, apricots, and cherries. The greater and lesser peach tree borers are two of the most common borers in stone fruits. Adults for both insects are day-flying, clearwing moths. The greater peach tree borer attacks healthy bark near, or slightly below the soil line. The lesser peach tree borer attacks the upper portions trees. Larval tunneling through the tree's cambium kills vascular tissue and reduces water and nutrient movement. A gummy mass of dried sap mixed with sawdust is usually found on the outer bark when the tunneling insects are active. Spray the trunks of affected trees with permethrin (Eight) in late June and early August.
Peachtree Borers, Ohio State University
7. Fruit Tree Cankers- Several diseases can infect the bark of fruit trees, causing the bark to die. Areas of bark infected by a canker disease often become discolored, rough, sunken or raised, and may crack around the edges of the dead section. When the canker girdles the branch, all tissue beyond the canker will die. Infected branches may be pruned out back to healthy tissue, but little can be done for infections on a tree's main trunk. No chemical control is available once a canker has formed.
Brown Rot, Cornell University
White Rot of Apple, West Virginia University
Nectria Canker, University of Nebraska- Lincoln Extension
Fireblight, University of Missouri Extension
8. Herbicide Injury- Herbicides such as 2, 4-D and dicamba can volatilize and drift to ornamental trees, shrubs and vegetables if applied when air temperatures are above 80 degrees Fahrenheit. Use caution when making applications to avoid unintended damage to non-target plants.
9. Squirrel damage-In winter when other food sources are scarce squirrels may strip and eat bark from trees. In summer they may clip twigs and branches from tree and shrubs. Large trees seldom suffer serious damage from bark stripping or twig clipping. Squirrel damage in yards, gardens, forests, and orchards is often very difficult to control. During population highs, new squirrels arrive quickly to replace those shot or trapped.
Squirrel Damage to Trees, Colorado State University
10. Ash Rust- Yellow/orange, raised spots (pustules) on leaves. This fungal disease may cause some twisting of foliage and leaf drop. Ash rust is not a serious disease of trees. Fungicide control is not recommended or needed.
Ash Rust, Kansas State University Extension
11. Cedar-Apple Rust/ Cedar-Hawthorn Rust is causing leaves of some apples, crabapples and hawthorns to yellow and drop. Fungal infections occurred early this spring just as leaf buds were beginning to break. Fruits can be infected too, and display rough orange-yellow spots. While severe defoliation can occur, and this is a stress for the tree, few trees will die unless severe defoliation occurs year after year. Fungicide applications need to be applied just as tree leaves are breaking bud in early spring and repeated as recommended to be effective. In some cases, it is suspected leaves are dropping due to dry soils we experienced.
Cedar-Apple Rust, University of Nebraska- Lincoln Extension
12. Anthracnose is a common fungal disease on ash, maple, sycamore and oak. It causes irregular brown areas on leaves. Leaves may become distorted and minor to severe defoliation of a tree can occur. It is too late to treat trees effectively. Anthracnose is rarely a serious problem for otherwise healthy trees. Most trees will produce new leaves to replace lost leaves.
Anthracnose Diseases of Shade Trees, Kansas State University Extension
13. Oak Leaf Blister causes yellowish, blister-like, raised areas to form on leaves. It is a fungal disease. It does not cause serious damage to trees as they can still photosynthesize even though infected by the disease. Control is not needed and it is too late for control. Fungicides need to be applied just before bud break to be effective.
Oak Leaf Blister, Cornell University
14. Elm Flea Weevil first appeared in the Midwest in 2003 and may now be throughout Nebraska. The adult weevil is very tiny (1.6 mm long), dark brown to black, with a prominent “snout”. They can jump when disturbed. Adult feeding results in tiny shot holes in the leaves. At this time, it appears to feed mainly on Siberian elm (Ulmus pumila) which is commonly called Chinese elm in Nebraska. Morton Arboretum is reporting feeding on hybrids containing U. pumila, particularly “Homestead”. Most trees will recover with good plant health care practices. On high value trees or trees under stress, insecticides may be applied as soon adults appear and feeding is noticed. It is late now to apply insecticides.
Elm Flea Weevil, Michigan State University
15. Overwatering of Trees is a common problem in home landscapes. Overwatering occurs when soil is very wet for days or weeks at a time, mostly commonly a result of the overuse of home irrigation systems. In saturated soils, water replaces oxygen in the large soil pore spaces. Plant roots must pull in oxygen from the soil for normal chemical processes, such as respiration, to take place. Roots stop growing if oxygen is not available. Tree species vary in their tolerance of saturated soils, but extended periods without soil oxygen will cause root dieback. Other symptoms of saturated soil affecting plant growth include yellowing foliage, leaves dying and dropping especially from the interior of the tree.
For good growth trees require one inch of water per week throughout the growing season. Water should be applied slowly, so that ideally the water can all be applied at one time without excessive runoff. At most, applications can be broken up into two applications of one-half inch water each. Redirect the drainage of downspouts away from trees to avoid overwatering, if necessary.
Watering Trees, Warnell School of Forestry
16. Pine Wilt infects primarily Scotch and Austrian pine trees. Dead pines or those that begin to exhibiting rapid crown dieback may have pine wilt. Pine wilt is a fatal disease of exotic pine species, such as Scotch pine, and consequently Scotch pine should no longer be planted in Nebraska without homeowners being aware of this potentially lethal threat. The disease has already killed thousands of Scotch pines in southeastern Nebraska. Across the state, most infections have been found east of Grand Island, however, a few pine wilt cases have also been reported in western Nebraska.
Pine wilt is caused by a microscopic organism called a pinewood nematode, which is spread by pine sawyer beetles. Adult beetles can carry thousands of nematodes within their bodies as they fly from tree to tree in spring, feeding on young twigs in the upper tree canopy.
Trees infected with pine wilt cannot be saved, so must be cut down and burned, buried or chipped. During the summer months destroy trees suspected of Pine Wilt infection within one month of fading green color. Do not save the wood from these trees for firewood.
Diseases of Evergreen Trees, Nebraska Forest Service
17. Fall Webworms are appearing as webbed nests on the ends of branches in cottonwood, crabapple, walnut and other trees. Caterpillars hide in the webbed nests during the day and feed at night. The nests are unsightly, but caterpillars cause little harm to otherwise healthy trees. Tree health is usually not affected until more than 50 percent of the foliage is eaten. If there are enough nests, almost one on every branch, a tree could be completely defoliated. If you can safely reach the nest, use a broom to break up the bag of webworms. Follow up by spraying with a strong stream of water or an insecticide such as permethrin or Spinosad. Prune out the webbed nests when feasible. There are natural parasites and pathogens of fall webworm that often bring these infestations under control. Trees with lots of fall webworm this year may not have many next year. Outbreaks usually last two or three years.
Fall Webworm Management, Ohio State University
18. Bagworms hatched in the early weeks of June and are now about 1/4-1/2 inch long. Tree with a history of infestation should be checked and treated. Smaller insects are easier to control and applications in mid to late June will reduce or prevent feeding damage. Recommended insecticides include Bt (Bacillus thuringiensis), Spinosad, Permethrin, Carbaryl and Acephate.
Bagworms, University of Nebraska-Lincoln Extension in Lancaster County
19. Rose Slugs & Rose Chafer- Brown, skeletonized leaves on roses are often caused by either rose slugs or rose chafer.
Rose slugs damage leaves by feeding on the green tissue and leaving behind the veins. Rose slug adults are sawflies- small, non-stinging wasps. The larvae are greenish, with a tan head and look much like butterfly or moth caterpillars. If they are not present there is no reason to treat. Most garden dusts or sprays will work. Insecticidal soaps must contact slugs to have an effect.
Rose Chafers are scarab beetles approximately 3/8 inch long, slender, and light tan. Adults feed on rose flowers and foliage. Inspect roses for skeletonized leaves and adult beetles. Rose chafers can be hand pick if the infestation is light. The insecticides carbaryl (Sevin) and acephate (Orthene) will control these beetles. However, the beetles are quite mobile and new beetles may replace those killed by insecticides.
Defoliaters/leaf feeders of roses, University of Minnesota
20. Septoria Leaf Spot on Rudbeckia- Fungal leaf spots have been appearing on Rudbeckia (Black-eyed Susans). This, and other leaf spot diseases, cause spots, or lesions, to form on leaves followed by yellowing and browning of foliage, usually near the bottom of the plant first. These diseases do not kill plants. Control with good sanitation and avoid overhead watering.
Rudbeckia Leaf Spots, University of Minnesota
21. Clematis Wilt is caused by the fungus Clematis ascochyta. Affected vines show wilting, browning and death of leaves along the entire stem. A red to brown lesion may be visible at the base of the affected stem. The disease overwinters in infected plant debris and is dispersed by rain throughout the growing season. Stems are infected at the soil line. Prune out and dispose of dead or dying stems, making sure to disinfect pruning tools between cuts. Plant clematis in well-drain soil and space plants adequately for good growth. Properly water, fertilize and mulch plants to maintain plant vigor. Early season, large flowered species seem to be most susceptible to infection.
Clematis, Clemson University
22. Blossom End Rot is a common problem of tomatoes, but is also found on peppers, eggplant, squash and watermelon. It occurs as a flat, dry, sunken, brown rot that is seen on the blossom end of the fruit, opposite the stem end. This problem is not an insect or disease. It is a physiological disorder associated with a calcium deficiency in the developing fruit.
Rarely is blossom end rot the result of a lack of calcium in the soil, but rather occurs when plants cannot pull up calcium quickly enough for developing tissues. Calcium is a nutrient that must be dissolved in water to move within a plant, so water deficits are contributing factors. Drought stress, low daytime humidity, high temperatures and rapid, vegetative plant growth caused by excess nitrogen favor blossom end rot development.
To reduce blossom end rot, use these cultural techniques:
23. Squash Bugs are one of the most common and troublesome pests attacking squash and pumpkin plants. Both nymphs and adults suck sap from plant leaves and stems. They also inject a toxic saliva which causes wilting known as Anasa wilt of Cucurbits. Vines wilt and leaves become black, crisp and brittle. Flat, brownish-black adults congregated on the underside of leaves and on fruits. Yellowish to brick red, oval shaped eggs are laid in groups, usually near veins, on the undersides of leaves. Nymphs are gray with black legs. Because of the extended egg laying period, all life stages occur together throughout the summer months.
Regularly inspect leaves for egg masses and crush or destroy them when found. Row covers can protect plants until blooming and pollination begins. Apply carbaryl (Sevin) according to label directions and safety precautions when bugs first appear. Rotenone is effective on younger bugs, but not the adults. Repeat applications as needed for best control.
Squash Bug, Ohio State University
24. Bacterial Wilt is spread on the mouthparts of striped and spotted cucumber beetles. It causes plants in the cucurbit family to quickly wilt and die. Diagnose bacterial wilt by cutting the stem near the soil line and squeezing the cut ends between your fingers. Place the tip of a knife blade on the bead of sap squeezed from the stem and slowly pull the knife blade away. If a slimy string develops between the blade and vine, the plant is likely infected with the bacteria. There is no cure for this wilt disease and most cucumbers and muskmelon are susceptible. Use crop rotation and control cucumber beetles to reduce the disease.
Options for Managing Bacterial Wilt, Cornell University
25. Anthracnose on Watermelon causes small, black spots on leaves and leaf yellowing. Sunken spots can appear on watermelons, but may not appear until after harvest. A combination of crop rotation and fungicide applications are necessary for controlling this disease on susceptible varieties. Protective spray applications should be made when vines start to run and should be continued at 7 to 10 day intervals during periods of humid or rainy weather.
Watermelon Anthracnose, Kansas State University
26. Fusarium Wilt of Tomato and Cucurbits begins as yellowing of older leaves in tomato; watermelon typically begins with wilt symptoms. Plants can be infected at any stage. The fungus infects the plant's vascular system, which carries water from roots to leaves. To help confirm Fusarium, cut the lower main stem and look at the cross section of the stem for a pale brown discoloration. If found, pull and destroy infected plants. There are no fungicides are labeled for control of wilt diseases. Select varieties with resistance to Fusarium (they will have the initials VFN on their label) and use crop rotation. However, even resistant plants can become infected if disease pressure is high.
Fusarium and Verticillium Wilt,Ohio State University
27. Early Blight and Septoria Leaf Spot are the two most common diseases of tomatoes. Both are fungal and begin as leaf spots on lower leaves and work their way upward causing foliage to die; often leading to fruit sunscald. Use fall sanitation to reduce the amount of inoculum available for infection the following year. In the fall, gardens should be deep-plowed or tilled to bury tomato debris, or dead plants removed and destroyed. Avoid planting tomatoes in the same area year after year. Both diseases can be controlled effectively with fungicides labeled for use on tomatoes. For best results, applications should begin as soon as symptoms first appear, generally around the time of the first blossom set. Applications should be made every 7 to 10 days. Severely infested plants are best pulled and destroyed.
Early Blight and Septoria Leaf Spot of Tomatoes, Kansas State University
28. Two Spotted Spider Mites infest a large variety of plants. Mites and their webs can barely be seen with the naked eye. Mites feed by sucking plant juices with piercing-sucking mouth parts, causing white or yellow speckling on leaves; then off-green to bronze discoloration. Controls range from hosing down plants with a strong spray of water (syringing) to using insecticidal oils or soaps, or using miticides or insecticides when mites are active. Tap a branch over a white sheet of paper to monitor for active mites. They’ll appear as specks moving around on the paper if present. Mites can be in the egg stage so monitoring should continue for one to two weeks. NOTE: Carbaryl (Sevin) can increase mites by killing their predators such as lady beetles.
Spider Mites and Their Control,Ohio State University
Spider Mites, Colorado State University Extension
29. Squash Vine Borers bore into plant stems (mainly squash, pumpkins, and gourds) and their feeding restricts translocation of water and nutrients. The point where a borer enters a stem, usually at the plant base, may have a sawdust-like frass around it and be decayed. Infested plants are weakened or die; depending on the number of borers. Control the borers by practicing good sanitation, physically removing borers by slitting stems when borer activity is noticed, or applying insecticides labeled for vegetables during egg laying, usually from the time vines begin to run and re-applying every 7 to 10 days for 3 to 5 weeks.
Squash Vine Borer, Ohio State University
30. Grasshoppers have hatched but are still small. Now is the time for most effective control, by treating hatching areas (roadsides and weedy areas). Later in the summer grasshoppers can severely defoliate garden and landscape plants. Adult grasshoppers are difficult to control.
A Guide to Grasshopper Control in Yards and Gardens, University of Nebraska- Lincoln Extension
| Current Problems: | Major Symptom: |
| Lawns | |
| 1. Nimblewill | Dense mats of fine-bladed, lank grass that lies flat on the ground. |
| 2. Mushrooms & slime mold | Grow on organic matter. Nonpathogenic. Fungicides do not control. |
| 3. Brown patch | Roughly circular patches of brown and dying grass intermixed with green leaf blades. |
| 4. Chinch bugs in zoysiagrass & buffalograss | Patchy areas which turn yellow, then dry out and turn brown. |
| 5. Chiggers | Protect yourself with insect repellents containing DEET |
| Trees & Shrubs | |
| 6. Peach tree borers | Gummy sap mixed with sawdust on tree trunks; tunneling beneath bark. |
| 7. Fruit tree cankers | Discolored, raised or sunken, rough, dead areas of bark. |
| 8. Herbicide drift | Use caution with 2, 4-D and Dicamba when air temperatures are above 80°F. |
| 9. Squirrel damage | Stripping of bark and clipping of twigs. |
| 10. Ash rust | Raised orange spots on leaves; some leaf curling. |
| 11. Cedar-apple rust/ hawthorn rust | Leaf yellowing/browning and drop in apples and crabapples. |
| 12. Anthracnose | Irregular brown areas on leaves, often along leaf veins. Leaf drop. |
| 13. Oak blister gall | Raised, blister-like spots on oak leaves. |
| 14. Elm flea weevil | Tiny holes chewed in elm leaves; mild to severe leaf drop. |
| 15. Overwatering trees | Yellow and/or dropping leaves associated with wet soils. |
| 16. Pine wilt | Dead Scotch Pine trees or rapid crown dieback. |
| 17. Fall webworms | Webbed nests in deciduous trees containing caterpillars & frass |
| 18. Bagworms | Bagworms have hatched; scout and if necessary treat trees with a history of infestation. |
| Landscape Ornamentals | |
| 19. Rose slug & Rose chafer | Skeletonized rose leaves. |
| 20. Rudbeckia leaf spots | Leaf spots and browning of leaves from base of plant upward. |
| 21. Clematis wilt | Leaves & vines turn brown or blackish, wilt and dieback. |
| Vegetables & Fruits | |
| 22. Blossom end rot | Leathery to soft brown rot on bottom of tomatoes & other fruit. |
| 23. Squash bugs | Flat, brownish-black insects cause wilting and death of cucurbits |
| 24. Bacterial wilt & cucumber beetles- cucurbits | Vine crops suddenly wilt and do not recover. |
| 25. Anthracnose- cucurbits | Black spots on leaves. Sunken, brown spots on fruit. |
| 26. Fusarium wilt- tomatoes & cucurbits | Yellowing & wilting leaves, followed by collapse of the plant. |
| 27. Early blight/ Septoria leaf spot- tomato | Tomato leaves yellow and brown from bottom of plant upward. |
| 28. Spider mites | Speckling and yellowing of leaves, particularly in tomato and watermelon. |
| 29. Squash vine borers | Vines or entire plants wilt; base of main stem soft with frass evident. |
| 30. Grasshoppers | Chewing damage on fruits, vegetables & ornamentals. |
| Upcoming Programs | |
| 31. Late Blight and Other Important Diseases of Tomato in the Home Garden- recorded webinar | |
| 32. Cucurbit Diseases webinar will be held in late July by Rutgers New Jersey Agricultural Experiment Station- watch for announcement | |
| 33. Turfgrass Field Day, July 16 | |
| 34. Great Plains Summer Field Day (NNLA & NAA), July 24 | |
1. Nimblewill is a warm season perennial grass. It is a fine bladed, wiry, pale green grass. The leaf blades are short and emerge at 45 degrees angles from the stems, which are slender, smooth and tend to lie flat on the ground. It spreads by short stolons, or above ground stems, that root at the nodes. Nimblewill forms circular patches as a result of its stoloniferous growth pattern, which grow larger each year, often a foot or more in diameter. It goes dormant from mid fall through mid to late spring. When it goes dormant, the brownish patches may be confused for disease or insect damage. It has fibrous roots, making the plants easy to pull. Maintaining a dense, healthy lawn through proper turf selection, establishment, and maintenance is the recommended non-chemical control.
Commercial applicators can apply the herbicide Tenacity for selective control of nimblewill in Kentucky bluegrass lawns. As of summer 2009, Tenacity is not available to homeowners. Homeowners may use glyphosate (RoundUp), a nonselective herbicide, to kill green, actively growing mats of nimblewill from late spring through early autumn. Spray at least twelve inches beyond the visible edge of the weed to make sure you get all of the plants killed. Reseed or resod areas with desirable turfgrasses. Applications of glyphosate to nimblewill when dormant will not provide control.
Nimbleweed, Purdue University
2. Mushrooms and Slime Mold grow on organic matter such as dead tree roots, turfgrass thatch, and wood mulch. They are the spore producing bodies of decay fungi which are decomposing the organic matter. They do not infect and cause diseases in turfgrass. Fungicide applications will not control mushrooms and slime mold. They will disappear in dryer weather and stop appearing once the organic matter they are growing on decomposes. Where a slime mold is shading turfgrass and causing yellowing, remove it by mechanical means such as raking.
Slime mold on Turfgrass, Ohio State University
3. Brown Patch causes roughly circular patches of dead and dying grass, intermixed with green leaf blades. Patch centers may be less affected and remain green. Tan colored, irregularly shaped leaf spots with reddish margins are found on leaf blades. Fungicide applications are often not recommended after August 1. Preventive applications of Prostar (commercial use), Bayleton, and chlorothalonil (Daconil) do a fairly good job of suppressing the disease when applied at monthly intervals (June, July, August). Curative applications of chlorothalonil beginning a few days after symptoms of brown patch develop may do an adequate job of suppressing injury. In many cases, lawns damaged by brown patch will recover in two to three weeks, provided the outbreak is not sustained by continuous hot, humid weather; and treatment may not be necessary.
Brown Patch, Kansas State University
4. Chinch Bugs in Buffalograss and Zoysiagrass feed by sucking juices from leaves and stems. They inject a toxin while feeding which disrupts translocation of water and nutrients. Damage appears as patchy areas which turn yellow, then dry out and turn brown. Damage is usually heaviest in sunny locations during hot, dry periods. Chinch bug nymphs are red with a white band, then orange-ish, and finally brown to black. Adults are 1/10th of an inch long and black and white. Control thatch to reduce chinch bugs. If bugs exceed 20 per square foot, an insecticide treatment is justified. Bifenthrin still best for chinch bug control.
Chinch Bugs in Turfgrass, Ohio State University
5. Chiggers are the tiny, reddish, six-legged larval stage of a mite that torments people each summer by causing intensely itchy welts. Only the larval stage attacks humans and animals. Chiggers can be found in highest numbers in tall grass or weedy areas of the landscape. Eliminating weeds and regular mowing of turf areas will reduce chigger populations. Protect yourself by using insect repellents containing DEET
Chiggers, Ohio State University
6. Peach Tree Borers- Boring insects that feed under the bark is one of the most serious insects of fruit trees, including peaches, plums, nectarines, apricots, and cherries. The greater and lesser peach tree borers are two of the most common borers in stone fruits. Adults for both insects are day-flying, clearwing moths. The greater peach tree borer attacks healthy bark near, or slightly below the soil line. The lesser peach tree borer attacks the upper portions trees. Larval tunneling through the tree's cambium kills vascular tissue and reduces water and nutrient movement. A gummy mass of dried sap mixed with sawdust is usually found on the outer bark when the tunneling insects are active. Spray the trunks of affected trees with permethrin (Eight) in late June and early August.
Peachtree Borers, Ohio State University
7. Fruit Tree Cankers- Several diseases can infect the bark of fruit trees, causing the bark to die. Areas of bark infected by a canker disease often become discolored, rough, sunken or raised, and may crack around the edges of the dead section. When the canker girdles the branch, all tissue beyond the canker will die. Infected branches may be pruned out back to healthy tissue, but little can be done for infections on a tree's main trunk. No chemical control is available once a canker has formed.
Brown Rot, Cornell University
White Rot of Apple, West Virginia University
Nectria Canker, University of Nebraska- Lincoln Extension
Fireblight, University of Missouri Extension
8. Herbicide Injury- Herbicides such as 2, 4-D and dicamba can volatilize and drift to ornamental trees, shrubs and vegetables if applied when air temperatures are above 80 degrees Fahrenheit. Use caution when making applications to avoid unintended damage to non-target plants.
9. Squirrel damage-In winter when other food sources are scarce squirrels may strip and eat bark from trees. In summer they may clip twigs and branches from tree and shrubs. Large trees seldom suffer serious damage from bark stripping or twig clipping. Squirrel damage in yards, gardens, forests, and orchards is often very difficult to control. During population highs, new squirrels arrive quickly to replace those shot or trapped.
Squirrel Damage to Trees, Colorado State University
10. Ash Rust- Yellow/orange, raised spots (pustules) on leaves. This fungal disease may cause some twisting of foliage and leaf drop. Ash rust is not a serious disease of trees. Fungicide control is not recommended or needed.
Ash Rust, Kansas State University Extension
11. Cedar-Apple Rust/ Cedar-Hawthorn Rust is causing leaves of some apples, crabapples and hawthorns to yellow and drop. Fungal infections occurred early this spring just as leaf buds were beginning to break. Fruits can be infected too, and display rough orange-yellow spots. While severe defoliation can occur, and this is a stress for the tree, few trees will die unless severe defoliation occurs year after year. Fungicide applications need to be applied just as tree leaves are breaking bud in early spring and repeated as recommended to be effective. In some cases, it is suspected leaves are dropping due to dry soils we experienced.
Cedar-Apple Rust, University of Nebraska- Lincoln Extension
12. Anthracnose is a common fungal disease on ash, maple, sycamore and oak. It causes irregular brown areas on leaves. Leaves may become distorted and minor to severe defoliation of a tree can occur. It is too late to treat trees effectively. Anthracnose is rarely a serious problem for otherwise healthy trees. Most trees will produce new leaves to replace lost leaves.
Anthracnose Diseases of Shade Trees, Kansas State University Extension
13. Oak Leaf Blister causes yellowish, blister-like, raised areas to form on leaves. It is a fungal disease. It does not cause serious damage to trees as they can still photosynthesize even though infected by the disease. Control is not needed and it is too late for control. Fungicides need to be applied just before bud break to be effective.
Oak Leaf Blister, Cornell University
14. Elm Flea Weevil first appeared in the Midwest in 2003 and may now be throughout Nebraska. The adult weevil is very tiny (1.6 mm long), dark brown to black, with a prominent “snout”. They can jump when disturbed. Adult feeding results in tiny shot holes in the leaves. At this time, it appears to feed mainly on Siberian elm (Ulmus pumila) which is commonly called Chinese elm in Nebraska. Morton Arboretum is reporting feeding on hybrids containing U. pumila, particularly “Homestead”. Most trees will recover with good plant health care practices. On high value trees or trees under stress, insecticides may be applied as soon adults appear and feeding is noticed. It is late now to apply insecticides.
Elm Flea Weevil, Michigan State University
15. Overwatering of Trees is a common problem in home landscapes. Overwatering occurs when soil is very wet for days or weeks at a time, mostly commonly a result of the overuse of home irrigation systems. In saturated soils, water replaces oxygen in the large soil pore spaces. Plant roots must pull in oxygen from the soil for normal chemical processes, such as respiration, to take place. Roots stop growing if oxygen is not available. Tree species vary in their tolerance of saturated soils, but extended periods without soil oxygen will cause root dieback. Other symptoms of saturated soil affecting plant growth include yellowing foliage, leaves dying and dropping especially from the interior of the tree.
For good growth trees require one inch of water per week throughout the growing season. Water should be applied slowly, so that ideally the water can all be applied at one time without excessive runoff. At most, applications can be broken up into two applications of one-half inch water each. Redirect the drainage of downspouts away from trees to avoid overwatering, if necessary.
Watering Trees, Warnell School of Forestry
16. Pine Wilt infects primarily Scotch and Austrian pine trees. Dead pines or those that begin to exhibiting rapid crown dieback may have pine wilt. Pine wilt is a fatal disease of exotic pine species, such as Scotch pine, and consequently Scotch pine should no longer be planted in Nebraska without homeowners being aware of this potentially lethal threat. The disease has already killed thousands of Scotch pines in southeastern Nebraska. Across the state, most infections have been found east of Grand Island, however, a few pine wilt cases have also been reported in western Nebraska.
Pine wilt is caused by a microscopic organism called a pinewood nematode, which is spread by pine sawyer beetles. Adult beetles can carry thousands of nematodes within their bodies as they fly from tree to tree in spring, feeding on young twigs in the upper tree canopy.
Trees infected with pine wilt cannot be saved, so must be cut down and burned, buried or chipped. During the summer months destroy trees suspected of Pine Wilt infection within one month of fading green color. Do not save the wood from these trees for firewood.
Diseases of Evergreen Trees, Nebraska Forest Service
17. Fall Webworms are appearing as webbed nests on the ends of branches in cottonwood, crabapple, walnut and other trees. Caterpillars hide in the webbed nests during the day and feed at night. The nests are unsightly, but caterpillars cause little harm to otherwise healthy trees. Tree health is usually not affected until more than 50 percent of the foliage is eaten. If there are enough nests, almost one on every branch, a tree could be completely defoliated. If you can safely reach the nest, use a broom to break up the bag of webworms. Follow up by spraying with a strong stream of water or an insecticide such as permethrin or Spinosad. Prune out the webbed nests when feasible. There are natural parasites and pathogens of fall webworm that often bring these infestations under control. Trees with lots of fall webworm this year may not have many next year. Outbreaks usually last two or three years.
Fall Webworm Management, Ohio State University
18. Bagworms hatched in the early weeks of June and are now about 1/4-1/2 inch long. Tree with a history of infestation should be checked and treated. Smaller insects are easier to control and applications in mid to late June will reduce or prevent feeding damage. Recommended insecticides include Bt (Bacillus thuringiensis), Spinosad, Permethrin, Carbaryl and Acephate.
Bagworms, University of Nebraska-Lincoln Extension in Lancaster County
19. Rose Slugs & Rose Chafer- Brown, skeletonized leaves on roses are often caused by either rose slugs or rose chafer.
Rose slugs damage leaves by feeding on the green tissue and leaving behind the veins. Rose slug adults are sawflies- small, non-stinging wasps. The larvae are greenish, with a tan head and look much like butterfly or moth caterpillars. If they are not present there is no reason to treat. Most garden dusts or sprays will work. Insecticidal soaps must contact slugs to have an effect.
Rose Chafers are scarab beetles approximately 3/8 inch long, slender, and light tan. Adults feed on rose flowers and foliage. Inspect roses for skeletonized leaves and adult beetles. Rose chafers can be hand pick if the infestation is light. The insecticides carbaryl (Sevin) and acephate (Orthene) will control these beetles. However, the beetles are quite mobile and new beetles may replace those killed by insecticides.
Defoliaters/leaf feeders of roses, University of Minnesota
20. Septoria Leaf Spot on Rudbeckia- Fungal leaf spots have been appearing on Rudbeckia (Black-eyed Susans). This, and other leaf spot diseases, cause spots, or lesions, to form on leaves followed by yellowing and browning of foliage, usually near the bottom of the plant first. These diseases do not kill plants. Control with good sanitation and avoid overhead watering.
Rudbeckia Leaf Spots, University of Minnesota
21. Clematis Wilt is caused by the fungus Clematis ascochyta. Affected vines show wilting, browning and death of leaves along the entire stem. A red to brown lesion may be visible at the base of the affected stem. The disease overwinters in infected plant debris and is dispersed by rain throughout the growing season. Stems are infected at the soil line. Prune out and dispose of dead or dying stems, making sure to disinfect pruning tools between cuts. Plant clematis in well-drain soil and space plants adequately for good growth. Properly water, fertilize and mulch plants to maintain plant vigor. Early season, large flowered species seem to be most susceptible to infection.
Clematis, Clemson University
22. Blossom End Rot is a common problem of tomatoes, but is also found on peppers, eggplant, squash and watermelon. It occurs as a flat, dry, sunken, brown rot that is seen on the blossom end of the fruit, opposite the stem end. This problem is not an insect or disease. It is a physiological disorder associated with a calcium deficiency in the developing fruit.
Rarely is blossom end rot the result of a lack of calcium in the soil, but rather occurs when plants cannot pull up calcium quickly enough for developing tissues. Calcium is a nutrient that must be dissolved in water to move within a plant, so water deficits are contributing factors. Drought stress, low daytime humidity, high temperatures and rapid, vegetative plant growth caused by excess nitrogen favor blossom end rot development.
To reduce blossom end rot, use these cultural techniques:
- Prevent drought stress on plants by providing at least 1 inch of water per week, and greater amounts for plants in sandy soils or during very hot, dry conditions.
- Use organic mulch like wood chips, clean straw, pine straw, peat moss, compost, or herbicide-free grass clippings to conserve soil moisture.
- Avoid excess fertilization, especially with ammoniacal nitrogen sources.
- Foliar applications of calcium have little effect on blossom end rot due to poor absorption and movement of calcium from the leaves to fruits.
23. Squash Bugs are one of the most common and troublesome pests attacking squash and pumpkin plants. Both nymphs and adults suck sap from plant leaves and stems. They also inject a toxic saliva which causes wilting known as Anasa wilt of Cucurbits. Vines wilt and leaves become black, crisp and brittle. Flat, brownish-black adults congregated on the underside of leaves and on fruits. Yellowish to brick red, oval shaped eggs are laid in groups, usually near veins, on the undersides of leaves. Nymphs are gray with black legs. Because of the extended egg laying period, all life stages occur together throughout the summer months.
Regularly inspect leaves for egg masses and crush or destroy them when found. Row covers can protect plants until blooming and pollination begins. Apply carbaryl (Sevin) according to label directions and safety precautions when bugs first appear. Rotenone is effective on younger bugs, but not the adults. Repeat applications as needed for best control.
Squash Bug, Ohio State University
24. Bacterial Wilt is spread on the mouthparts of striped and spotted cucumber beetles. It causes plants in the cucurbit family to quickly wilt and die. Diagnose bacterial wilt by cutting the stem near the soil line and squeezing the cut ends between your fingers. Place the tip of a knife blade on the bead of sap squeezed from the stem and slowly pull the knife blade away. If a slimy string develops between the blade and vine, the plant is likely infected with the bacteria. There is no cure for this wilt disease and most cucumbers and muskmelon are susceptible. Use crop rotation and control cucumber beetles to reduce the disease.
Options for Managing Bacterial Wilt, Cornell University
25. Anthracnose on Watermelon causes small, black spots on leaves and leaf yellowing. Sunken spots can appear on watermelons, but may not appear until after harvest. A combination of crop rotation and fungicide applications are necessary for controlling this disease on susceptible varieties. Protective spray applications should be made when vines start to run and should be continued at 7 to 10 day intervals during periods of humid or rainy weather.
Watermelon Anthracnose, Kansas State University
26. Fusarium Wilt of Tomato and Cucurbits begins as yellowing of older leaves in tomato; watermelon typically begins with wilt symptoms. Plants can be infected at any stage. The fungus infects the plant's vascular system, which carries water from roots to leaves. To help confirm Fusarium, cut the lower main stem and look at the cross section of the stem for a pale brown discoloration. If found, pull and destroy infected plants. There are no fungicides are labeled for control of wilt diseases. Select varieties with resistance to Fusarium (they will have the initials VFN on their label) and use crop rotation. However, even resistant plants can become infected if disease pressure is high.
Fusarium and Verticillium Wilt,Ohio State University
27. Early Blight and Septoria Leaf Spot are the two most common diseases of tomatoes. Both are fungal and begin as leaf spots on lower leaves and work their way upward causing foliage to die; often leading to fruit sunscald. Use fall sanitation to reduce the amount of inoculum available for infection the following year. In the fall, gardens should be deep-plowed or tilled to bury tomato debris, or dead plants removed and destroyed. Avoid planting tomatoes in the same area year after year. Both diseases can be controlled effectively with fungicides labeled for use on tomatoes. For best results, applications should begin as soon as symptoms first appear, generally around the time of the first blossom set. Applications should be made every 7 to 10 days. Severely infested plants are best pulled and destroyed.
Early Blight and Septoria Leaf Spot of Tomatoes, Kansas State University
28. Two Spotted Spider Mites infest a large variety of plants. Mites and their webs can barely be seen with the naked eye. Mites feed by sucking plant juices with piercing-sucking mouth parts, causing white or yellow speckling on leaves; then off-green to bronze discoloration. Controls range from hosing down plants with a strong spray of water (syringing) to using insecticidal oils or soaps, or using miticides or insecticides when mites are active. Tap a branch over a white sheet of paper to monitor for active mites. They’ll appear as specks moving around on the paper if present. Mites can be in the egg stage so monitoring should continue for one to two weeks. NOTE: Carbaryl (Sevin) can increase mites by killing their predators such as lady beetles.
Spider Mites and Their Control,Ohio State University
Spider Mites, Colorado State University Extension
29. Squash Vine Borers bore into plant stems (mainly squash, pumpkins, and gourds) and their feeding restricts translocation of water and nutrients. The point where a borer enters a stem, usually at the plant base, may have a sawdust-like frass around it and be decayed. Infested plants are weakened or die; depending on the number of borers. Control the borers by practicing good sanitation, physically removing borers by slitting stems when borer activity is noticed, or applying insecticides labeled for vegetables during egg laying, usually from the time vines begin to run and re-applying every 7 to 10 days for 3 to 5 weeks.
Squash Vine Borer, Ohio State University
30. Grasshoppers have hatched but are still small. Now is the time for most effective control, by treating hatching areas (roadsides and weedy areas). Later in the summer grasshoppers can severely defoliate garden and landscape plants. Adult grasshoppers are difficult to control.
A Guide to Grasshopper Control in Yards and Gardens, University of Nebraska- Lincoln Extension
