Fungal disease

1- Black spot

Causal organism Botryosphaera sp.

Symptoms

It is characterized by circular black spots with irregular margins on leaves. Mulching around plants can reduce disease occurrence. The leaf spots may increase in size and number with time. Infection will cause leaves to turn yellow and drop. Severely infected plants may be completely defoliated by midsummer.

The disease reduces leaf function, which weakens the entire plant. The result is a plant that grows very slowly and is more susceptible to other diseases and winter injury.

Control

                   COBOX               250g/100L.W
                   AMISTAR           40cm/100L.W

2-Powdery mildew

Causal organism Podosphaera clandestina

Symptoms

The disease stunts and distorts young, tender growth of buds, leaves and canes. Older leaves may also be diseased, but damage is not as severe. The fungus is a prolific spore producer. These spores form on the surface of the tissue, which gives it a “powdered” appearance - hence, its name. Fungicide application to new growth can reduce disease incidence and spread. Disease development requires damp, cool nights, which can occur any time during the growing season. Some varieties of climbing roses and small-flowering ramblers are most susceptible to this disease.

Control
                   BELLIS                        30g/100L.W
                   AMISATR                   40cm/100L.W
                   KUMULUS –S            250G/L.W

3- Botrytis blossom blight

Causal organism Botrytis sp.


Symptoms

This disease affects the buds and partially opened flowers. It is recognized by its grayish-brown fungus growth on the buds and petals under humid, wet conditions. The fungus over winters on infected plant parts, especially winter-killed stems. Pick off and destroy faded and infected blooms. Fungicides are effective in controlling the disease.

Control
                   BELLIS                        30g/100L.W

4-Crown gall

Causal organism Agrobacterium tumefaciens

Symptoms

severely damages roses. The bacterium usually gains entry into the plant via wounds or natural openings. This disease causes large, corky growths or galls to form on the crown or roots. Sometimes galls develop on above-ground portions of the plant. These galls first appear as small swellings that slowly increase in size. Diseased plants show a loss in vigor and produce smaller blossoms and leaves. This effect on the plant becomes evident only when the galls have reached a diameter of several inches. Do not confuse crown gall with normal enlargement of the graft union of plants. Infection may occur during grafting; therefore, inspect nursery stock before buying. Burn or destroy all infected plants. Chemical control of this disease is not effective.

Insects and Mites

Aphids

several species of aphid's damage roses by removing large quantities of plant juices and by secreting a sticky substance over the surface of infested plant parts. Heavy infestation can cause abnormal growth of plants.

Aphids are small, approximately 1.5 cm. long, and vary in color from yellow to green to black. Their life cycle is completed in as few as four days under favorable environmental conditions. Remove and destroy heavily infested plant parts. Then treat plants with an insecticide registered for aphid control on roses. Inspect roses for aphids two to three days after application. Due to their short life cycle, aphids can rapidly build back up in number; therefore, several applications of insecticide may be necessary to bring the population under control.

Control
                   APHOX               50g/100L.W
                   NUDRIN            75g/100L.W
                   MOSPILAN       25g/100L.W


Thrip

Thrips are another troublesome pest on perssimon. Thrips enter developing flower buds to feed and cause petals to become flecked and discolored. Heavy infestations cause deformities in new growth and can be responsible for buds not opening properly. Adult thrips are tiny, slender, and brown to yellow insects with feather-like wings. They are most easily seen by shaking new growth or flower buds over a white cloth.

Thrips have repeated generations during spring through fall. In hot, dry weather they complete a life cycle in less than two weeks. Cutting off and disposing of old blooms lessens infestation. Do not leave old blooms on the ground or thrips will quickly leave them and reinfest plants.

Control

Treat infested plants with an insecticide registered for thrips control on roses. Complete coverage of infested plants with the insecticide is important to your control program.

Control
                   NUDRIN                       75g/100L.W
                   MOSPILAN                  25g/100L.W

Spider Mites

Mites are such small pests that they often cause damage before they are noticed. Mites are found on the underside of leaves; there they feed by sucking plant juices. Infested leaves will have many tiny chlorotic spots. Heavy infestations cause leaves to turn brown and die.
Mites have a very rapid life cycle and can complete development in less than a week under hot, dry conditions. A control program for mites begins with the removal of weeds and other plants serving as alternate hosts for mites. Frequently inspect roses for the presence of mites. A magnifying glass is useful for seeing mites. When mites are found, treat plants with a registered miticide and reinspect plants for mites three to four days later

Control
                   MOSPILAN                  25g/100L.W
                   ORTUS                         50cm/100L.W