Hort Update for the week of 9/18/2009
1. White Clover is often a sign of low nitrogen. To control white clover, begin with lawn management practices. If needed, make changes in practices to those that promote a dense turf better able to compete with weeds. The preferred time to control white clover and all other broadleaf perennial weeds with herbicides is late summer through early fall. Spray applications after a hard frost, while slightly less effective, can still result in up to 80% control as long as the weed is actively growing and daytime temperatures exceed 65 F. Herbicide products containing carfentrazone, mecoprop or quinclorac as an active ingredient provide good control. For troublesome weeds like violet and ground ivy several applications may be necessary.
2. Kentucky bluegrass stem rust symptoms are an orangish-yellow powder (fungal spores) on grass blades in late summer. The turfgrass may develop a yellow or brown appearance. Rust typically occurs on lawns with slow growth. Sound fall care practices, including proper fertilization and correct irrigation, along with cooler fall weather promotes turfgrass growth and rust disappears. Control with fungicides is rarely suggested for home lawns.
Kentucky Bluegrass Stem rust, University of Illinois Extension
Note for Sports Turf: If stem rust occurs on sports fields, the fungal spores can present problems for allergy/asthma sufferers. Control of stem rust is recommended on sports turfs using a combination of sound turf management and correctly timed fungicide applications in July and August.
Sports Turf Internet Rust Resource, The Ohio State University
3. Brown Patch causes roughly circular patches of dead and dying grass. 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 Extension
4. Dollar Spot Small (three to six inch diameter), roughly circular patches in lawns. Spots may coalesce into a larger patch. Grass blades have tan lesions with red margins that encircle the grass blade. Damage is usually most severe where nitrogen is deficient. With timely rains this year, nitrogen may have been leached out of the root zone. The best control may be nitrogen fertilization. Turfgrass can be treated with products containing benomyl, mancozeb, propiconazole, thiophanate-methyl.
Dollar Spot, University of Nebraska- Lincoln Extension
5. Re-Tree Nebraska: Fall Tree Planting- Fall is a great time to plant trees in Nebraska. When properly planted, fall’s cooler temperatures, combined with increased moisture and reduced humidity, allow trees to quickly establish their root system, giving them a jump start on spring growth. If you weren’t able to celebrate Arbor Day with a tree planting, now’s your chance! Celebrate ReTree Nebraska Week 2009 during September 19-26. For a list ways to help promote fall tree planting in your community or for a list of 'Nine for 2009' tree species to plant.
Most trees and shrubs can be fall planted, though a few trees do better if planted in spring including magnolia, dogwood, tuliptree, red maple, birch, hawthorn, poplars, cherries, plum, ginkgo, willow, many oaks, bald cypress, fir and yews. While these trees are best saved for spring planting, if an exceptional bargain is found, go ahead and fall plant them. As a general rule, container grown and balled & burlapped trees can be planted from September well into October as they already have a developed root system. Plant bare root trees in spring. When transplanting large trees, wait until after the first frost to move these trees.
ReTree Nebraska
6. Iron Chlorosis causes leaves of trees to be light green to yellow with darker green leaf veins. It is often due to a high or alkaline pH soil which reduces availability of iron or manganese to some plants. It is most common in pin oak and silver maple. Reports of a possible increase in chlorosis in plants other than pin oak and silver maple are being made. These plants include spirea, roses, red maple, and others. For trees, apply iron via soil treatment or trunk injection. For smaller plants, promote a healthy rooting environment and soil apply iron. For information on a newer soil treatment using pvc pipe, see link below.
Whitcomb Iron Chlorosis Treatment
7. Bagworms numbers did seem to decrease this year, but some evergreens still sustained severe damage. At this time of year, up to 2 inch long bagworms are now attached to twigs. Larvae have pupated and insecticide applications will not be effective. Remove and destroy bags to reduce the number of overwintering eggs. Insecticides, such as Bifenthrin, are best applied after eggs hatch in early to mid June.
Bagworms, University of Nebraska- Lincoln Extension
8. Ash and Walnut Anthracnose disease has been active this year due to frequent rains providing the moist environment needed for infection. Leaves are still showing blighted areas with leaf browning, curling and leaf drop. Damage to these trees from this disease is seldom severe enough to justify a treatment. Now is too late to apply fungicides. If control is needed, apply fungicides in early spring at budbreak and repeat two to three times with fungicides such as Thiophanate-methyl, chlorothalanil, or Mancozeb. Follow label directions.
9. Oak Galls are numerous and varied in type and appearance. Extension staff have been seeing an increase in oak galls. Oaks are susceptible to a number of galls which range in appearance from pink fuzzy balls or tan fuzz growing on leaves to green or brown galls growing around leaf petioles and twigs. Most galls form in response to insect feeding, often a very small wasp. Oak galls are interesting, but usually harmless, and control is often not needed nor is it easy to achieve. In a few cases, on young trees, woody galls encircling small stems might lead to dieback of the stem. In these cases, prune out the infested branch.
Gall Wasps, University of Nebraska- Lincoln Extension
10. Aphids feeding on trees and shrubs have most likely come and gone. They may have left behind some leaf curling, stickiness, and a black sooty mold growing on the honeydew they exude out of their bodies. Damage to trees is usually not severe enough to warrant treatment. Before any control is attempted, it is important to look for the insect itself to determine they are still present. In many cases, they have moved on or natural predators, such as lady beetles and lacewing larvae, have been effective in controlling them.
Aphids on Shade Trees & Ornamentals, Colorado State University
12. Early Fall Coloration in some trees is being reported. This is most likely due to shorter day length and weather conditions of cooler than average nights and warm, sunny days. Other environmental conditions or stresses may also lead to early coloration.
13. Tobacco (Geranium) budworm feeds on flower buds and may cause petunias, geraniums and other annual flowers to stop blooming. Tobacco budworm can also be found on ageratum, bird of paradise, chrysanthemum, gardenia, mallow, marigold, snapdragon, strawflower, verbena, and zinnia. Oftentimes droppings, sometimes described as small black seeds, are seen before the worms are noticed. On close inspection, small green-to-brown colored worms can be found nibbling small holes in flower buds and leaves. If left alone, the plant can be thoroughly eaten. Treat with a Bt product (Bacillus thuringiensis) such as Dipel or Thuricide, carbaryl (Sevin) or permethrin (Eight).
14. Late Blight of Potatoes and Tomatoes has been promoted by cooler than average and moist conditions. Once plants are infected, late blight can kill leaves in two to three days and cause tomato fruit and potato tubers to rot after harvest in storage. Late blight begins as dark green water-soaked lesions on leaves. As it continues to grow, leaf edges turn brown and lesions dry up. On tomato fruit, a dark, greasy-looking lesion appears that quickly, within two days, expands to a soft rot of the whole fruit. On potatoes, tubers may look fine at harvest but rot in storage. Fungicides are available to treat the disease, but must be applied immediately after symptoms are spotted according to label direction. Gardeners with infected plants this year should remove them immediately and discard them. Do not place them in compost piles.
Potato and Tomato Late Blight, University of Nebraska- Lincoln
Late Blight of Potato and Tomato, The Ohio State University
15. Tobacco budworm- As mentioned in #13 above tobacco budworm feeds on the flower buds of many ornamental plants, but it is pricipally a pest of field crops, such as alfalfa, clover, cotton, flax, soybean, and tobacco. It sometimes attacks vegetables such as cabbage, cantaloupe, lettuce, pea, pepper, pigeon pea, squash, and tomato, especially when other favored crops are abundant. It generally only overwinters successfully in southern states, although in colder climates it may occassionally overwinter in a greenhouse or other sheltered locations.
Tobacco Budworm, University of Florida
| Current Problems: | Major Symptom: |
| Lawns | |
| 1. White clover | Fall ideal time to control; newer herbicides effective |
| 2. Kentucky bluegrass stem rust | Orange powder (fungal spores) appear on shoes and mowers |
| 3. Brown patch | Roughly circular patches of brown and dying grass |
| 4. Dollar spot | Small brown patches, tan lesions with red margins |
| Trees & Shrubs | |
| 5. What not to fall plant | Fall is a good time to plant; but wait until spring for some plants |
| 6. Iron chlorosis- newer treatment | Tree and shrub leaves light green to yellow with darker green veins |
| 7. Bagworms | Too late to control with insecticide; hand-pick and destroy |
| 8. Ash & walnut anthracnose | Leaves blighted, some curling and leaf drop |
| 9. Oak galls increasing | Numerous types of galls on oak leaves and twigs |
| 10. Aphids | Curled leaves. Sticky foliage. Black sooty mold. |
| 11. Lacebugs | Yellowish discoloration of a variety of trees |
| 12. Early fall coloration | Reported in many areas; most likely due to environment |
| Landscape Ornamentals | |
| 13. Tobacco (Geranium ) budworm | Small caterpillar; attacks flowers of many annuals including petunias |
| Vegetables & Fruits | |
| 14. Late blight- potato & tomato | Browning, blighted leaves; fruit and tuber rot; rapid plant death |
| 15. Tobacco budworm | Feed on flower buds of tomato, pepper and other vegetables |
1. White Clover is often a sign of low nitrogen. To control white clover, begin with lawn management practices. If needed, make changes in practices to those that promote a dense turf better able to compete with weeds. The preferred time to control white clover and all other broadleaf perennial weeds with herbicides is late summer through early fall. Spray applications after a hard frost, while slightly less effective, can still result in up to 80% control as long as the weed is actively growing and daytime temperatures exceed 65 F. Herbicide products containing carfentrazone, mecoprop or quinclorac as an active ingredient provide good control. For troublesome weeds like violet and ground ivy several applications may be necessary.
2. Kentucky bluegrass stem rust symptoms are an orangish-yellow powder (fungal spores) on grass blades in late summer. The turfgrass may develop a yellow or brown appearance. Rust typically occurs on lawns with slow growth. Sound fall care practices, including proper fertilization and correct irrigation, along with cooler fall weather promotes turfgrass growth and rust disappears. Control with fungicides is rarely suggested for home lawns.
Kentucky Bluegrass Stem rust, University of Illinois Extension
Note for Sports Turf: If stem rust occurs on sports fields, the fungal spores can present problems for allergy/asthma sufferers. Control of stem rust is recommended on sports turfs using a combination of sound turf management and correctly timed fungicide applications in July and August.
Sports Turf Internet Rust Resource, The Ohio State University
3. Brown Patch causes roughly circular patches of dead and dying grass. 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 Extension
4. Dollar Spot Small (three to six inch diameter), roughly circular patches in lawns. Spots may coalesce into a larger patch. Grass blades have tan lesions with red margins that encircle the grass blade. Damage is usually most severe where nitrogen is deficient. With timely rains this year, nitrogen may have been leached out of the root zone. The best control may be nitrogen fertilization. Turfgrass can be treated with products containing benomyl, mancozeb, propiconazole, thiophanate-methyl.
Dollar Spot, University of Nebraska- Lincoln Extension
5. Re-Tree Nebraska: Fall Tree Planting- Fall is a great time to plant trees in Nebraska. When properly planted, fall’s cooler temperatures, combined with increased moisture and reduced humidity, allow trees to quickly establish their root system, giving them a jump start on spring growth. If you weren’t able to celebrate Arbor Day with a tree planting, now’s your chance! Celebrate ReTree Nebraska Week 2009 during September 19-26. For a list ways to help promote fall tree planting in your community or for a list of 'Nine for 2009' tree species to plant.
Most trees and shrubs can be fall planted, though a few trees do better if planted in spring including magnolia, dogwood, tuliptree, red maple, birch, hawthorn, poplars, cherries, plum, ginkgo, willow, many oaks, bald cypress, fir and yews. While these trees are best saved for spring planting, if an exceptional bargain is found, go ahead and fall plant them. As a general rule, container grown and balled & burlapped trees can be planted from September well into October as they already have a developed root system. Plant bare root trees in spring. When transplanting large trees, wait until after the first frost to move these trees.
ReTree Nebraska
6. Iron Chlorosis causes leaves of trees to be light green to yellow with darker green leaf veins. It is often due to a high or alkaline pH soil which reduces availability of iron or manganese to some plants. It is most common in pin oak and silver maple. Reports of a possible increase in chlorosis in plants other than pin oak and silver maple are being made. These plants include spirea, roses, red maple, and others. For trees, apply iron via soil treatment or trunk injection. For smaller plants, promote a healthy rooting environment and soil apply iron. For information on a newer soil treatment using pvc pipe, see link below.
Whitcomb Iron Chlorosis Treatment
7. Bagworms numbers did seem to decrease this year, but some evergreens still sustained severe damage. At this time of year, up to 2 inch long bagworms are now attached to twigs. Larvae have pupated and insecticide applications will not be effective. Remove and destroy bags to reduce the number of overwintering eggs. Insecticides, such as Bifenthrin, are best applied after eggs hatch in early to mid June.
Bagworms, University of Nebraska- Lincoln Extension
8. Ash and Walnut Anthracnose disease has been active this year due to frequent rains providing the moist environment needed for infection. Leaves are still showing blighted areas with leaf browning, curling and leaf drop. Damage to these trees from this disease is seldom severe enough to justify a treatment. Now is too late to apply fungicides. If control is needed, apply fungicides in early spring at budbreak and repeat two to three times with fungicides such as Thiophanate-methyl, chlorothalanil, or Mancozeb. Follow label directions.
9. Oak Galls are numerous and varied in type and appearance. Extension staff have been seeing an increase in oak galls. Oaks are susceptible to a number of galls which range in appearance from pink fuzzy balls or tan fuzz growing on leaves to green or brown galls growing around leaf petioles and twigs. Most galls form in response to insect feeding, often a very small wasp. Oak galls are interesting, but usually harmless, and control is often not needed nor is it easy to achieve. In a few cases, on young trees, woody galls encircling small stems might lead to dieback of the stem. In these cases, prune out the infested branch.
Gall Wasps, University of Nebraska- Lincoln Extension
10. Aphids feeding on trees and shrubs have most likely come and gone. They may have left behind some leaf curling, stickiness, and a black sooty mold growing on the honeydew they exude out of their bodies. Damage to trees is usually not severe enough to warrant treatment. Before any control is attempted, it is important to look for the insect itself to determine they are still present. In many cases, they have moved on or natural predators, such as lady beetles and lacewing larvae, have been effective in controlling them.
Aphids on Shade Trees & Ornamentals, Colorado State University
11. Lacebugs are tiny, flat, square-shaped insects with white lacy wings. They feed on leaf undersides by sucking sap from the plant. This feeding causes leaves to discolor, usually turning a dirty yellow color. Lacebugs are found most commonly on oak, sycamore, hawthorn, hackberry, American linden and azalea. Each species of lacebugs has specific host plants and will not feed on other plants.
Control of lacebugs, or other sapsucking insects such as aphids, is usually not necessary when damage occurs so late in the season. Most lacebugs have completed feeding and insecticide applications at this time of year are not effective in controlling them.
LaceBUGS are not the same as LaceWINGS. Lacewings are beneficial insects since their larvae are voracious predators of aphids and other pest insects. They may also be found on plants infested with lacebugs, especially if aphids are present too. In fact, if you have lacewings on your plants you should not reach for chemical pesticide to kill them unless the damage to your plants from lacebugs is severe.
12. Early Fall Coloration in some trees is being reported. This is most likely due to shorter day length and weather conditions of cooler than average nights and warm, sunny days. Other environmental conditions or stresses may also lead to early coloration.
13. Tobacco (Geranium) budworm feeds on flower buds and may cause petunias, geraniums and other annual flowers to stop blooming. Tobacco budworm can also be found on ageratum, bird of paradise, chrysanthemum, gardenia, mallow, marigold, snapdragon, strawflower, verbena, and zinnia. Oftentimes droppings, sometimes described as small black seeds, are seen before the worms are noticed. On close inspection, small green-to-brown colored worms can be found nibbling small holes in flower buds and leaves. If left alone, the plant can be thoroughly eaten. Treat with a Bt product (Bacillus thuringiensis) such as Dipel or Thuricide, carbaryl (Sevin) or permethrin (Eight).
14. Late Blight of Potatoes and Tomatoes has been promoted by cooler than average and moist conditions. Once plants are infected, late blight can kill leaves in two to three days and cause tomato fruit and potato tubers to rot after harvest in storage. Late blight begins as dark green water-soaked lesions on leaves. As it continues to grow, leaf edges turn brown and lesions dry up. On tomato fruit, a dark, greasy-looking lesion appears that quickly, within two days, expands to a soft rot of the whole fruit. On potatoes, tubers may look fine at harvest but rot in storage. Fungicides are available to treat the disease, but must be applied immediately after symptoms are spotted according to label direction. Gardeners with infected plants this year should remove them immediately and discard them. Do not place them in compost piles.
Potato and Tomato Late Blight, University of Nebraska- Lincoln
Late Blight of Potato and Tomato, The Ohio State University
15. Tobacco budworm- As mentioned in #13 above tobacco budworm feeds on the flower buds of many ornamental plants, but it is pricipally a pest of field crops, such as alfalfa, clover, cotton, flax, soybean, and tobacco. It sometimes attacks vegetables such as cabbage, cantaloupe, lettuce, pea, pepper, pigeon pea, squash, and tomato, especially when other favored crops are abundant. It generally only overwinters successfully in southern states, although in colder climates it may occassionally overwinter in a greenhouse or other sheltered locations.
Cultural Control- Early season destruction of weeds with herbicide or mowing, or destruction of larvae on the weeds by treatment with insecticides, can reduce tobacco budworm population size later in the year.
Biological Control- The microbial insecticide Bacillus thuringiensis is effective against budworm. Heliothis nuclear polyhedrosis virus has been used effectively to suppress tobacco budworm on field crops and on early season weed hosts. Tobacco budworm also is susceptible to nuclear polyhedrosis virus from alfalfa looper, Autographa californica. Release of Trichogramma egg parasitoids has been shown to be beneficial in some vegetable crops.
Insecticidal Control- Foliar insecticides are commonly used in crops where tobacco budworm damage is likely to occur. However, destruction of beneficial organisms often results, and this is thought to exacerbate budworm damage. Also, resistance to insecticides is widespread, particularly in crops where pyrethroid use is frequent. Larvae will also consume bait formulated from cornmeal and insecticide.Tobacco Budworm, University of Florida
