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Symptom: Leaves curled, yellowed and distorted
Aphids feed on the leaves of and flowers of plants extracting the juices there within. The leaves turn yellow or brown, wilt under the sun and eventually curl and collapse. Melon aphids, green peach aphids, potato aphids and rose aphids are the most common species to attack the rose family. They feed on the underside of leaves. They're about about the size of a pinhead and have soft, pear-shaped bodies. Most of them are green but some are pink to reddish. They are most active in May and June and are rapid multipliers so an infestation can happen rather quickly.
To control them, spray with a fine misted garden hose early in the morning every other day. This will help with mild infestations. With heavier infestations spray with insecticidal soap every two to three days or until they are gone. If they become a serious problem you can spray them twice with pyrethrum three to five days apart.
Symptom: Holes in flowers, buds and leaves
Beetles will eat leaves and flowers and heavy infestations can strip the entire plant. Grubs of beetles can attack the roots making it difficult to notice immediate damage but a general weakening of the plant will occur.
Most common beetles to effect roses are the Japanese beetle, fuller rose beetles, rose chafer beetles, rose curculios and rose leaf beetles.
To control them you can pick them off by hand and drop them in a bucket of soapy water. This is only feasible with light infestations. With heavier infestations you can spray with a pyrethrum /isopropyl alcohol mixture every three to five days. A mixture of 1 tablespoon of alcohol to every pint of pyrethrum. You can also use pheromone traps to catch the beetle. Be sure to keep them 40 to 50 feet away from your plants. This will reduce the population if used over the course of 3 to 5 years.
To control the grubs or larvae you can use milky spore disease or Bacillus popilliae.
Symptom: Chewed leaves
Chewed leaves is a common occurrence when caterpillars are present. Some common to roses are the fall webworm, the bristly rose slug and the rose budworm.
Bristly rose slugs feed at night. They are about a half inch long and hairy and slimy. They are the larvae of the sawfly. If you hand pick them use gloves because they can irritate the skin.
Fall webworms are about an inch long and are pale yellow to green. The adult moth is white, often with brown spotted wings. They are most active in August when you will find webbed nest among chewed leaves. Remove the nests and or spray heavy infestation with Bt ( Bacillus thuringienus) two times every 3 to 5 days.
Rose budworms, two types, common to roses are green and about 3/4 inch long and can also be pale orange about an 1/8 of an inch long. They feed on leaves and buds. Control with handpicking or Bt as mention above.
Slugs and snails:
Symptoms: Large ragged holes in leaves.
Damage is usually noticed from the bottom of the plant to the top. Click here for further descriptions and treatments.
Symptoms: Chewed markings along the edges of leaves
Japanese weevils can be 1/4 inch long in brown to light brown in color with striated wing covers. They feed at night and hide during the day in soil and anywhere out of sunlight. Their larvae bore into roots and stems
Fuller rose beetles are greenish brown with tan strips along their sides and about a 1/3 inch long. They are mostly found in California and the Southern states. The feed at night and rest on twigs and stems during the day. Their larvae is yellow with brown heads and feed on roots.
To control them these weevils are pretty easy to remove. They play dead when they feel threatened so place a tarp below the plant and shake them off then collect them and dump them in a bucket of soapy water. Heavy infestations can be sprayed with a mixture of 1 tablespoon of isopropyl alcohol to 1 pint of pyrethrum once a week. They best time to do this is an hour or two after sunset.
Symptoms: Leaves rolled and secured with silky strands
Caterpillars of these pests roll themselves up in the leaves and bind them with silk to protect themselves as they feed. The leaves turn brown and die.
Common leaf rollers to the rose include fruit tree leaf rollers, oblique banded leaf rollers and red-banded leaf rollers. They can be green to light green or pale yellow.
To control them hand pick the rolled up leaves and discard them and then treat with Bt at the first sign of rose buds. This will kill any remaining young caterpillars.
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