PEST AND DISEASE PROBLEMS ON THE GOLD COAST;

As indicated in the help and advice tab;  Regular Pest and Disease control is necessary to produce good roses here on the Gold Coast.   Throughout Australia, Rosarians encounter pests and diseases, however the climate on the Gold Coast (Sub-tropical ) influences the severity of these.   Pests proliferate quickly after winter pruning, because there is no long cold winter as in other parts of the country.   One could say that roses here do not really have a period of winter dormancy, and grow and flower all year round, producing some flowers even in July.   This also affects the incidence of diseases.

The main disease problem Black Spot as noted, is influenced by wet foliage and during dry spells the incidence means that less frequent foliar spraying is required.   Because of the long growth cycle pest populations have many generations a year, and require regular preventive treatment.  Suggested controls for Pests and Diseases are covered in regular Society newsletters, and discussed at Monthly meetings where members questions are answered.

Many Guest Speakers also advise on some of these aspects of rose culture.   Rose plants on the Gold Coast with some regular attention to controls, can produce  magnificent blooms during all parts of the calendar year. 

The following are the main pests and diseases encountered here.

PEST      
                       
APHIDS;                        Colour range from green to black and grey. Occur on young growth.

HIBISCUS BEETLES;     Small black beetles which attack flowers.  Present almost all year.  About 6mm. long.

MONO-LEPTA;             Yellow brown with reddish darker spots on the back. 
                                        Appear in late spring causing severe damage to buds and foliage.             

WEEVILS;                     Various sizes and colour - grey to blackish. They attack young buds. (ELEPHANT BEETLES)

CATERPILLARS;        Various species, some looper type. Some green in colour, some grey brown,   some striped etc. The native LBAM (Light brown apple moth) appears to be   the worst of these. It has many generations per year.  Caterpillars attack buds and foliage.

THRIPS;               Most thrips are about 1-2mm. long and about 0.5mm wide.   Colour yellow/brown to black. Attack flowers.

TWO SPOTTED MITES;           These mites are greenish yellow with two dark spots on the            body.  Outbreaks start in late spring, and occur sometimes two or three times, even after some control has been used.  They attack the lower foliage.   Rapid             population increase, may defoliate plants with leaves turning brown and then falling.   First symptoms are usually stippled leaves, low down on the plant. (A small hand lens is required to see them.)

ROSE FOLIAR DISEASES;

DISEASE      
           
BLACK SPOT           Disease symptoms are primarily circular black spots on the leaf surface,   appearing first on older and lower leaves. Spots may be small but the majority, up to one cm. in diameter with fringed margins.   Varying in number from one to twenty or more on a leaf.   This is soon followed by yellowing of part of the  leaf and then by defoliation.

ANTHRACNOSE    Black spots small and circular, later purplish and yellowing foliage. Controls for Black spot also control this disease.

POWDERY MILDEW;       Symptoms appear on young shoots and buds as a whitish grey fungal growth.  Severely infected leaves and buds may be  malformed.
 
ROSE RUST;   This is said to be a disease of cool moist weather.  Symptoms are bright orange spots on under-sides of foliage. It is not prevalent here.

DOWNY MILDEW;   Symptoms are purplish red to brown spots or blotches with a poorly defined border up to 12 mm. in diameter.   Usually on younger leaves and towards the edge of the leaf and angular in shape.  It starts at the top and moves downwards.  Foliage yellow and falls.
 
ROSE FLOWER DISEASE

BOTRYTIS   This diseases symptoms are pinkish spotted flower petals, or brownish decaying tissue of petals. In severe infestations flowers fail to open.  The disease is more prevalent in humid conditions.