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The Gardener’s Dirt July 2009

JULY 2009

The Gardener’s


Information you can dig into.

North Carolina State University
College of Agriculture and Life Sciences
North Carolina Cooperative Extension Service
Johnston County Center
2736 NC 210 Highway * Smithfield, NC 27577
919 989-5380
Shawn Banks
Extension Agent
Agriculture—Consumer Horticulture

In this Issue
Feature Article
Spotlight Plant
Insect Investigator
Gardening To-Do
This newsletter offers timely information for your outdoor living spaces.  Addressing the most common questions ranging from container gardening, tree pruning, wildlife management, to fire ant control, insect identification and lawn establishment.

Feature Story Banner

Controlling Black Spot on Roses

By Shawn Banks

According to several references, black spot on roses is the number one disease on roses worldwide.  The disease is cause by a fungal pathogen with the name Diplocarpon rosae, but most often seen in the imperfect stage named Marssonina rose.  Whatever name you use, this disease is the bane of many rose growers.
Rose leaf with Black spot symptoms
Black spot of roses gets its common name from the small black spots that appear on the leaves and stems of the rose plants.  They range in size from 1/16th of an inch to ½ of an inch.  The edge of these spots is feathery and the spot is usually surrounded by a yellow halo. 

The fungus will over winter on fallen leaves and in severe cases on the stems of roses.  The splashing rain propels the spores up onto the new leaves in the spring.  The foliage needs to stay wet for more than 7 hours while the weather is at a temperature between 71 and 79OF in order for the spores to germinate.

Now that we know a little about our enemy, here are some of the ways to control this disease.

  1. Sanitation:  Start with plants that do not have the disease.  Check the leaves and the canes for any symptoms of the disease.  Clean up any leaves that fall from the plants especially in the fall to prevent any carry over of the inoculum from one year to the next.  Prune out any infected canes in the winter before new foliage emerges.
  2. Culture:  Give the plants enough space to prevent splashing water from transfering the disease from one plant to the next.  Spacing also allows for better air circulation and light penetration which aids in drying of the leaves to reduce the chance of infection.  Watering should be done at the base of the plant to reduce splashing, and if overhead irrigation is used, it should be done in the morning to reduce the length of time water is on the leaf before it evaporates.
  3. Chemical:  Chemicals such as chlorothalonil (Daconil), myclobutinol (Immunox), tebuconazole (All-in-One Rose and Flower Care), and neem oil (Fungicide 3) may be used to control black spot.  Most of these should be sprayed at a 7 to 10 day interval.  For best control, rotate two or more chemicals to prevent the fungus from building up a resistance to one chemical.  Spraying should start as soon as leaves appear in the spring and continue into the fall until frost.

There are also several rose cultivars that have shown varying degrees of resistance to this disease in field trials.  Knock Out roses are only one of those varieties.  For a more complete list contact the Extension Master Gardener in Johnston County at 919-989-5380 or jcemastergardener@gmail.com.

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Spotlight Plant banner

The Knock Out® Roses

Knock out rose flower
Knock Out Rose Flower
When first introduced in 2000, the Knock Out® rose was a single flowered, red rose.  Now, there is a whole family of roses called Knock Out® roses.  Additions include a double red, a single pink, a double pink, a light pink, a yellow, and one called rainbow that has a yellow center turning pink toward the middle and outer edge of the petals. 

The Knock Out® roses are special because they are quite vigorous, while being drought tolerant, and disease resistant.  Disease resistance is a big plus in our climate where many roses succumb to black spot or powdery mildew.  Now, breeders only need to find a gene that makes them resistant to damage by Japanese beetles and flower thrips to have the perfect plant.

The Knock Out® roses are either patented or have a patent pending and should not be propagated by the homeowner.  The best way to get one of these wonderfully easy to grow roses is to visit your local garden center.

Knock Out Rose Bush
Knock Out Rose Bush
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Hand holding clipboard          Announcements banner heading            Hand holding clipboard

  • July 15, Farmscaping for Pest Management, 9:00am – 3:00pm at CEFS in Goldsboro, registration fee is $20.00 which includes lunch.  Learn how various landscapes can be managed to enhance beneficial insect populations.  More information and a registration form can be found at http://www.cefs.ncsu.edu/calendar2009.htm
  • July 25, Top Tomato Contest, at the Clayton Farm and Community Market.  Entries accepted between 8:00am and 9:30pm, judging to start at 10:00am.  Categories include Appearance, Taste, and Best in Show.  For more information contact Amie at 989-5380 or amie_newsome@ncsu.edu.
  • July 30, Rain Barrel Workshop, 6:30pm until 8:00pm at Johnston County Livestock Arena, registration is $35.00 which includes making a rain barrel to take home.  To sign up, get more information and direction contact Angie at 989-5380 or Shawn at shawn_banks@ncsu.edu.

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Insect Investigator banner  Bagworms on Leyland Cypress
Bagworms on
Leyland Cyparis


Thyridopteryx ephemeraeformis

Bagworm is somewhat of a misnomer.  These aren’t worms at all, but caterpillars that have found a way to camouflage themselves to look like part of the tree.  When these caterpillars start out at 1/8th of an inch or less they spin a web or bag of silk around themselves as a protection.  As the feed, they attach pieces of the plant they are feeding on to the silk bag as they increase its size. 

The bagworm feeds on a wide range of plant material, but tend to be most destructive on juniper, cyparis, and other similar plants.  They will usually feed June through August at which time they go through metamorphosis and turn into adults.  The females are wingless and never leave their bag.  The males have wings so they can fly to the females and mate.  The females then lay eggs inside their silk bags and die.  The next generation will survive the winter as eggs in the mothers bag.  They will hatch out the following May or June to start the cycle over again.

Picking off bags during the winter can control bagworms.  A sharp pair of scissors will be needed, as the silk they use to attach the bag to the limbs is very strong.  In the early growth stage, products containing Bacillus thuringiensis or spinosad, both of which are OMRI approved and the least toxic method are very effective.  Once the caterpillars have put on some size, more toxic products containing acephate, carbaryl, malathion, bifenthrin, and permethrin will be more effective.

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Gardening to-do Banner


  • Water deeply but infrequently, this will encourage deep rooting of plants for better drought resistance.
  • Control fungal diseases which flourish in hot and humid weather by keeping irrigation water off foliage.  The best time to water is early morning.  This allows the sun to dry water from foliage. Watering in early evening creates damp foliage all night, which encouraging the development of fungal diseases.
  • Help reduce the mosquito population by emptying any containers with standing water.  Mosquito larva can grow in shallow water, like plant saucers that do not dry completely.


  • When should you water your lawn?  When the grass blades  are just starting to curl and your footprints remain on the lawn when you walk on it.  Watering too often encourages a lawn with a shallow root system that cannot handle drought well.  Apply an inch of water, in the early morning.  Set your timer for 4 am if you can.  
  • Grasses vary in their needs. Check out the Lawn Maintenance Calendar for your grass and learn how best to care for it, month by month …
  • Keep fescue mowed at a height of 3 – 3 1/2 inches to help it survive hot, dry periods.  It is a cool season grass that slows down in the summer.  If it is cut it too short the tender roots will be exposed to extreme heat which will certainly damage, if not kill them.  It is also difficult for fescue to recover from cutting too short as it is not actively growing at this time.  
  • Repair Warm-Season Lawns: Bermuda, Zoysia, and centipede are growing strong by now, making it easy to see spots that are weak or weedy. Pull weeds and patch bare spots if you haven’t already.
  • Established fescue lawns naturally go semi-dormant in the heat of July. Established fescue can survive up to three weeks without water, but will need a drink if it doesn’t rain by then! Water only when grass shows sign of wilt (footprints show when grass is walked on). Fescue planted last fall will need watering every week. See the Fescue Lawn Maintenance Calendar (link above).


  • When you visit your roses, clip off leaves that show early evidence of blackspot – a common fungal disease that causes black spots on leaves. Put the spotted leaves in the garbage (not in the compost pile.)
  • When gathering cut flowers to bring indoors, cut stems early in the day.  Bring them indoors and recut the ends while they are submerged in a sink of water.Japanese Beetle close up
  • Don’t use Japanese beetle traps.  The pheromones in the traps often attract beetles that would not otherwise visit the area.  To control a particularly pesky group of beetles, go hunting for them in early morning and shake them into a bowl of soapy water to get rid of them.
  • Keep potted plants watered! Plants in pots outside may need daily watering in the heat of summer.
  • Pinch out the tips of garden mums to encourage lower, compact plants with many flowers.
  • Start stem cuttings of geraniums and leaf cuttings of succulents to be potted for use as house plants this winter.
  • Propagate shrubs by rooting cuttings. Semi-hardwood cuttings of Azalea, Camellia, and Holly can be taken this month. The wood should be hardened enough that the stem breaks when bent. https://www.ces.ncsu.edu/depts/hort/hil/hil-8702.html
  • Prune spent crape myrtle blossoms to prolong the flowering period.  
  • Sooty Mold on the crape myrtles will make the leaves appear dark and sooty or almost uniformly charcoal gray. Sooty mold grows on honeydew (the sticky leftovers) from aphids. Control the aphids, and the mold will wash off.
  • Bagworms on Leyland CypressPowdery Mildew makes leaves appear gray and powdery. It’s a common problem which disfigures the foliage, but doesn’t kill the tree.
  • Hand-pick bagworms off evergreens. Pesticides are not effective once the caterpillars are safe in their bags.
  • Remove vigorous upright sprouts growing from tree roots (“suckers”), or from the upper surfaces of tree branches (“water sprouts”).  Pruning the sprouts out directs the tree’s energy into desirable growth.
  • Weed when it’s easy. Weeds are easier to pull when the soil is moist, so wait until after a soaking rain or irrigate the area first. The roots of desirable plants can be injured by pulling large weeds nearby so pull those weeds in late afternoon or on cloudy days, and water the area afterward to help injured plants recover.
  • Start seeds for cool-weather annuals indoors in July/August for fall planting. Try foxglove, pansy, alyssum, snapdragons, ornamental cabbage (kale), and primroses.  Pansy seeds germinate well when stored in the refrigerator (not freezer) for 10-14 days before planting.    


  • Pinch out the tips of blackberry shoots when they reach about 4 feet tall.  This helps form a tidier hedgerow for easy picking.
  • Soon after tomatoes begin to set fruit, give them a boost of fertilizer to keep them vigorous and productive. Most of the new varieties are heavy producers if provided with good nutrition and adequate soil moisture.  


  • Deckscape: Play with colors, textures, and the placement of furniture on your deck or patio. Use container-grown plants, windsocks and sculptures to change or fine-tune your color scheme and overall feel.
  • Think strategy. Now that deciduous trees and shrubs are in leaf, survey your landscape critically. Do you have too much? too little? are plants too low where screening is needed? So tall a view is blocked? Take photographs and make plans to add or move shrubs this fall. Don’t do it now.

WILDLIFEEastern Tiger Swallowtail butterfly caterpillarEastern Tiger Swallowtail butterfly

  • Put out a bird-bath.  Keep it filled with fresh water.  Change it once a week to minimize mosquitoes. Birds will pay you back by eating lots of insects!  
  • Think twice about squashing caterpillars; many turn into butterflies.  This is just one example of what swallowtail caterpillars look like.  This is a swallowtail butterfly(right).  Swallowtail caterpillars (left) love parsley, so set out a few extra plants to share with them. A pan of moistened pebbles or sand will attract butterflies.

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Got Questions? We’ve got answers!

If you have a gardening issue you would like to see addressed in this newsletter please let me know I will do what I can to get you the information you need.  Contact me by e-mail at shawn_banks@ncsu.edu or by phone at (919) 989-5380.

The Johnston County Master Gardener Volunteers are available Monday, Wednesday, or Friday from 1 to 4 pm to answer questions as well.  They can also be contacted by phone at (919) 989-5380 or by e-mail at jcemastergardener@gmail.com

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