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Hort Update for September 15, 2015

Lawns Major Symptom:

1. Leaf spot diseases

General browning or patches; leaf spots on blades

2. Zoysia stem rust

Rusty orange powder on shoes, plants, mower

3. Seeding - is it too late?

Early September ideal for cool season turfgrass

4. Sodding - is it time?

Early spring or early fall are optimum times to sod

5. Do not lower mowing height

Maintain high mowing height all season, even into late fall

6. No insecticides for mole control      

Attempting to control food source will not control moles

   
Trees & Shrubs  
7. Rust on Hawthorn, pears, apple Yellowing leaves with reddish-orange leaf spots
8. Little white winged insects Woolly aphids swarming
9. New EAB confirmation Montgomery  County, IA; 30 miles from Nebraska border
10. Avoid extensive pruning now On both deciduous and evergreen plants
11. Tree planting Avoid the top 10 tree planting mistakes commonly made
   
Landscape Ornamentals  
12. Bulb fertilization in fall Maintain bulb vigor with fall fertilization
13. Perennial division Fall is ideal time to divide and transplant
14. Digging tender plants Dig and store for winter
   
Fruits & Vegetables  
15. Basil downy mildew Remove infected plants
16. Bumble flower beetle Brown beetles feed on overripe or damaged tomatoes
17. Spider mites Yellow stippling on the leaves of tomato, watermelon & muskmelon
18. Storing fruits & vegetables Harvest at proper time and store at correct temperature/humidity
19. Fruit cultivar identification Very difficult from fruit alone, some tools available
20. Pruning brambles Maintenance pruning for best production and disease control
21. Protect fruits & vegetables from freeze damage  Guidelines for predicting fruit or vegetable damage
22. Compost pile success Maintain moisture; avoid adding diseased plants
   
Miscellaneous  
23. Fall invaders  Lady beetles, spiders, boxelder bugs, wood roaches & more

 

1. Leaf spot diseases on residential turf - Frequent rains and cloudy weather promote foliar turf diseases. Three common diseases, Leaf Spot, Dollar Spot and Brown Patch, are being identified in lawns. On residential turf, fungicide treatments are not recommended this late in the season. Infected turf areas will recover. All three diseases can be identified by leaf lesions. Bipolaris leaf spot are small, round to oval and buff-colored centers with a dark margin. Dollar spot lesions encircle the grass blade and are light tan in color with red margins. Brown patch leaf lesions are irregular in shape, dark tan or brown with reddish margins. Overseeding with resistant cultivars is one key to disease control. For information on cultural and chemical management of these foliar diseases, see the following NebGuides.

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2. Zoysia rust - An orangish-red powder accumulating on lawn mowers, pant legs or shoes is a sign of rust disease. The ‘powder’ are thousands of fungal spores. Rust fungi can infect different types of turfgrass. The fungi that infects Kentucky bluegrass is different than the fungi that infects Zoysia. Rust fungi typically do not overwinter in Nebraska. Spores blow up from the south in mid to late summer. Rust is mainly a problem on slow growing turf. The best way to address rust is to use cultural practices that maintain vigorous, but healthy turfgrass growth. At this time of year, fertilization of Kentucky bluegrass is recommended for rust management. It is too late in the season to fertilize warm season grasses, like Zoysia.

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3. Seeding – is it too late?  The optimum time to seed cool season grasses in Nebraska is between August 15 and September15. Later seeding can be done, but the risk of cold temperature injury increases. The answer to the “Is it too late?” question depends on when the first hard freeze occurs and fall weather conditions. Seeding can be successful later in September as long as cold weather holds off. It is too late to seed warm season grasses such as Buffalo or Zoysia.

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4. Laying sod – Is it too late? While turf areas can be sodded almost any time the soil is not frozen and when irrigation is available, sodding in early spring or early fall is preferred, and most successful, since irrigation is available and soil temperatures are conducive to root growth and establishment. Sodding can take place well into October as long as irrigation is available.

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5. Do not lower mowing height - Turfgrass should be mowed at the same height all season long. Despite this research based recommendation, it is still fairly common practice to lower the mowing height during fall. Using a tall mowing height, 3 to 3.5” for Kentucky bluegrass and Tall Fescue, all season long leads to vigorous roots, dense turf, fewer weeds and less environmental stress. The recommendation to “set it and forget it” should be promoted to homeowners; along with following the one-third rule of not removing more than 30 percent of the grass blade during any one mowing. If the turf is mowed at a 3” height, it should be mowed when it reaches 4.5” to stay within the one-third rule. Removing more than one-third is considered scalping and stresses the root system and overall turf vigor.

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6. No insecticides for mole control - Mole tunneling increases at this time of year as moles prepare for winter. While moles are feeding on earthworms and soil insects, the application of insecticides will not control earthworms or reduce the soil insect population enough to control moles.  With pollinator protection an important consideration whenever insecticides are used, applying insecticides to attempt mole control is not only not effective, it is not a responsible use of a pesticide. Trapping, the use of labeled products containing Talpirid, or a mole repellant containing castor oil remain the recommendations for mole control.

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7. Rust on hawthorn, pear, crabapple and apple - Fungal rust diseases can cause severe defoliation of infected trees during years with frequent rainfall. All rust diseases require two hosts to complete the life cycle. Junipers (cedars) are the alternate host for rusts found on Hawthorn, crabapple, apple and pear. While some growers consider removal of Juniper species as a control method, this is not feasible nor effective given the large numbers of windbreak cedars and landscape Junipers; and the fact the fungal spores can travel long distances via wind. While fungicides applied in early spring, just as trees are leafing out, will reduce infections on susceptible trees, the use of resistant cultivars is the most effective means of controlling rust diseases.  

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8. Little white insects - If tiny white-winged, flying insects were recently encountered, they were most likely swarming woolly aphids. Female woolly aphids hatch from overwintering eggs in spring and produce live offspring. After one to two generations on a primary host plant, new aphids develop wings and fly to a secondary host. While feeding, woolly aphids appear as white masses on plant stems or leaves. In late summer, another generation of winged females is produced. These white winged adults fly to primary host plants to lay eggs for overwintering. This is what was encountered as annoying, little white insects. Insecticide applications are not needed. Swarming will stop and the nuisance will end. If woolly aphid control is needed on a plant, this needs to be done next season once woolly aphids are identified on a plant in a high enough population to cause damage.

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9. New EAB confirmation in eastern Iowa - Emerald Ash Borer was confirmed in Montgomery County, Iowa in mid-August. Being about 30 miles from the Nebraska border, this is the closest confirmation to date. The recommendation to wait to begin treatment until EAB is found within 15 miles of an Ash tree remains.

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10. Avoid extensive pruning on woody plants now - This is one time of the year to avoid pruning shade and ornamental trees, evergreen trees and shrubs, and deciduous shrubs. Pruning now can trigger new growth that will not harden off before cold weather arrives. The large amount of browning that occurred on the ends of Japanese Yew branches last spring is an example of what can happen when plants are pruned after mid-August and cold temperatures arrive early in the season (i.e. our 5 degree F. weather in mid-November last year). If possible, wait until early November to begin pruning trees and shrubs.

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11. Tree planting is done in September and October. The key to a tree having a long life with less stress and fewer issues is to select the right tree for the site and then plant correctly. Incorrect planting methods such as planting too deep, amending the backfill soil, fertilizing with nitrogen at planting, pruning at planting, and more account for slow growth, reduced tree vigor, and tree failure. Before planting trees, read through and/or provide homeowners with the Nebraska Forest Service fact sheet on avoiding the Top 10 Mistakes of Tree Planting.

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12. Bulb fertilization in fall is an important practice to maintain bulb vigor. Apply 5 tablespoons of 10-10-10 water soluble fertilizer or an equivalent amount of bulb fertilizer, plus two cups of bone meal per 10 square feet. 

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13. Dividing perennials is an important management practice for many species, helping to encourage vigorous growth and optimum blooming. Many perennials benefit from division once every 3-5 years. Dividing is also a good way to propagate perennials.

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14. Digging tender plant - tender bulb-like plants such as cannas, tuberous begonias, and gladioli are not hardy enough to survive Nebraska winters in the ground. Once frost has killed the top growth in fall, especially in cannas, cut off the foliage and dig up the rhizomes. Brush soil off the canna rhizomes and store them at 45 to 50 degrees F. Do not allow the rhizomes to freeze. Dahlia tubers must be dug each fall and stored in damp sawdust or peat at 60 degrees F. Divide the tuber clump in spring leaving a part of the true stem attached to the tuber.

For more information on the correct temperature and humidity for storage, refer to the publication below.

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15. Basil Downy Mildew, a new destructive disease of basil first reported 2007 in Florida, is appearing in Nebraska gardens again this year. The fungal pathogen, Peronospora belbahrii, can be seed borne or distributed through air-borne spores. The most common symptom of infected plants is leaf yellowing, similar to a nutrient deficiency. Purplish-gray fungal spores develop on the undersides of infected leaves during the nighttime hours.  Inspect suspect plants in the morning to find the spores beneath the yellowed leaf sections. Many common sweet basil varieties, Ocimum basilicum, are susceptible. Fewer symptoms have been found on red leaf basil; Thai, lemon and lime basil. At this point in the growing season, removal of infected plants is the best method of control.

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16. Bumble bee beetles, also known as bumble flower beetles or brown fruit chafer, is a mottled yellow/brown beetle, with a thick layer of fine hairs on its thorax. Adults emerge in later summer and feed on rotting fruit, corn, sap, and other plant juices.  They sometimes cause damage to flowers and have been found feeding on overripe or damaged tomatoes in Platte County. Remove old damaged or rotting fruits to reduce population.  Handpick adults and drop into a bucket of soapy water.  Chemical control is not necessary.

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17. Spider mites on tomatoes can cause problems in the late summer garden, particularly on tomato, watermelon and muskmelon growing in light or sandy soil.  Damage symptoms progress from stippling to yellowing, wilting, browning, and eventually to death of the leaves or whole plant. Mites may move from soybean fields into vegetable gardens, as the soybean plants begin to turn yellow and dry out. To check for spider mites, place a white piece of paper beneath the branch or leaves and tap several times. The mites will appear as very small, bits of dust that are crawling across the page.

Controlling spider mites is difficult because they reproduce so rapidly. One method to try involves spraying the plant with a strong jet of water once or twice a day to dislodge some of the insects and to create an environment that is cooler, more humid and less favorable for spider mite reproduction. Several days or even weeks of this treatment will be required to make a noticeable difference in spider mite populations.

In the late summer garden chemical control may not be needed as plants near the end of their harvest season. Removal of infested plants may be the best option.  Refer to the publications below for additional chemical control options. Be sure any chemical you use is labeled for use in the vegetable garden.

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18. Storing fruits & vegetables is most successful if produce is harvested at the correct stage of maturity, cured or otherwise prepared properly for storage, and then stored at the temperature and relative humidity needed by each vegetable and fruit. For specifics on curing and best storage conditions for each fruit and vegetable, see:

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19. Fruit cultivar identification – In fall, a common question from gardeners with a favorite apple or pear tree is for identification of the cultivar from the color and shape of the fruit. This almost impossible to do, in fact, it’s really only realistic to give a general idea of possible cultivars.

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20. Pruning brambles - After harvest, remove all of this year's fruiting canes (floricanes) by pruning them out as close to the crown as possible. It is best to remove these canes during the dormant season before new growth begins in spring. Also remove any canes showing symptoms of raspberry anthracnose, which causes slightly raised spots with gray centers and purplish margins on raspberry canes. These eventually girdle and kill canes. Infection can occur throughout the season during wet periods. Sanitation, through removal of infected canes, during the dormant season will reduce the potential for disease next year.

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21. Protect fruits & vegetables from freeze damage - Average autumn freeze (32° F) dates are a measure of when the average first frost will occur in a region. They indicate that half of all autumn freezes will occur before the dates shown and half will occur after, based on 47 years of data from 1949-1995. In southeastern Nebraska that average autumn freeze date is approximately October 9 and September 21 in the northwest corner of Nebraska's panhandle. These dates are guidelines only. Freezing temperatures may occur before the dates listed below. Also remember that local microclimate conditions can significantly affect the occurrence of frost in your landscape.

These dates can be used as guidelines for gardeners growing late season vegetable crops. Frost sensitive vegetables will not tolerate freezing temperatures and must be protected to prevent damage. These temperature guidelines can serve as a guide when predicting potential flower bud damage to perennial fruit crops, such as fruit trees, brambles or strawberries.

Frost Resistance of Vegetables. From the Effects of Cold Weather on Horticultural Crops in Indiana, Purdue University.

  • Very hardy
    • Can withstand freezing temperatures and hard frost (less than 28° F) for short periods without injury.
    • Asparagus, collards, endive, kale, kohlrabi, lettuce, mustard, pea, potato, rhubarb, rutabaga, salsify, spinach, turnip

  • Frost tolerant
    • Can withstand light frosts (32-28° F) without injury.
    • Beet, broccoli, Brussels sprout, cabbage, carrot, cauliflower, celeriac, celery, chard, Chinese cabbage, Jerusalem artichoke, onion, parsnip, radish

  • Tender
    • Injury or killed by frost (32° F).
    • Snap bean, sweet corn, tomato

  • Warm loving
    • Cannot tolerate cold temperatures.
    • Lima bean, cucumber, eggplant, muskmelon, okra, pepper, pumpkin, summer squash, winter squash, sweet potato watermelon

Approximate Low Temperatures that Damage Dormant Plants and/or Flower Buds.

  • Apple, -30° F
  • Pear, -30° F
  • Peach and Nectarine, -15° F
  • Plum, -15° F
  • Cherry, -20° F
  • Apricot, -25° F
  • Strawberry, -10° F
  • Blueberry, -20° F
  • Blackberry (erect), -20° F
  • Blackberry (trailing thornless), -5° F
  • Raspberry (red), -30° F
  • Raspberry (black), -20° F
  • Grape, -15° F
  • Gooseberry, -30° F
  • Currant, -30° F

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22. Compost pile success begins with using the right combination of materials, called the carbon to nitrogen ratio (not too much green material and the right amount of brown material); chopping plant debris to increase surface area and speed decomposition; keeping the pile about as moist as a squeezed out sponge; and turning the pile frequently for aeration. It is also important to avoid adding pet feces since they may transmit disease. Meat, bones, grease, whole eggs, and dairy products should not be added because they attract rodents. Avoid adding diseased material and weed seeds to compost piles.

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23. Fall invaders are pests such as spiders, boxelder bugs, clover mites, wood roaches, and lady beetles that accidentally move indoors as they seek overwintering locations. Most are a nuisance. For crawling pests, a perimeter insecticide spray will help control them. For flying insects, use a silicone caulk to close openings.

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