ROSE MIDGE

Rose Midge


On Friday, August 23, 1996 I visited a rose nursery in Petaluma, Sonoma County, California that was heavily infested with the rose midge, Dasineura rhodophaga (Coquillett) [Diptera: Cecidomyiidae]. Nearly 100% of the new growth in a section of the field grown roses was affected. The infestation was first detected in early August by the nursery caretaker and confirmed as rose midge by Dr. Bill Chaney, University of California Cooperative Extension Farm Advisor for Monterey County (Salinas) and American Rose Society Consulting Rosarian.

While at the nursery, I also found scattered damage in the landscape roses and in the potted roses in the sales area of the nursery. Midge damage is very diagnostic. The tiny rose midge larvae feed on the tender new growth and immature buds and what they do not eat, turns black and withered. This type of damage can be confused very easily with foliar burn caused by some pesticides. In most affected area of the nursery, I saw a complete lack of healthy rose buds and flowers.

14cecidomyiid-adults

The rose midge are mosquito-like in shape and they are 1-2 mm in length. They emerge from pupae in the soil early in the spring in synchrony with the production of new plant growth and flower buds. There are several overlapping generations per year and a single generation, or life cycle, can be as short as two weeks. Populations of the midge build up until early fall and the last generation overwinters in the ground in cocoons and adult midges emerge the following spring. Females lay their eggs inside the sepals of flower buds or leafy tips. The larvae then hatch from the eggs and damage the buds and rose tips. The full-grown larvae may measure up to 1.8 mm long and are sometimes reddish in color. Pupation usually occurs in the soil but pupae have been observed in the damaged rose tips. They leave the damage tips after which the buds wither, blacken, and die.

14rosemidge-dam14rosemidge-dam114rosemidge-dam3



Rose midge appears to be a native insect to North America. It was first detected in 1886 in New Jersey by a greenhouse rose grower and since it has been recognized from many of the eastern and Midwestern states as well as in Oregon, Washington and Canada. It’s appearance in Oregon happened in the last 15 years. The present extent of the infestation in northern California is unknown. It is likely that the rose midge came into California from Oregon on its own. However, the infestation could have also been introduced into California via infested soil or plant materials either sent through the mail or carried from an infested area in North America.

Successful Control measures require repeated soil and foliar insecticidal applications. According to the literature repeated applications of Diazinon to infested soil as well as a foliar spray gave excellent degree of control to field grown roses (Smith and Webb, 1976. The Rose Midge 1976 ARS Rose Annual pp 57-73). In Petaluma, the infested rose nursery has taken preventative control measures against rose midge by spraying the infested soil around the roses with Diazinon and treating the foliage with Mavrik at a 10-day treatment schedule. This type of control is definitely needed in a nursery situation in order to for control of rose midge as well as prevent spread of rose midge in infested growing trips or in the soil of potted plants. Additionally, any blacken tips should be pruned off in potted roses in the sales area as added precaution against possible movement of the midge in these roses.

Home gardeners as well as commercial landscapes will need to follow a similar preventative control program consisting of repeated soil treatments and foliar insecticidal sprays. We are lucky to have many insecticides still available to commercial applicators and home gardeners.

In order to get a handle on the distribution of rose midge within California, please check your roses for midge damage, especially if you grow roses in a greenhouse. Please check the 1976 American Rose Society Rose Annual for additional information and pictures of the damage.

REFERENCES:

Smith and Webb, 1976. The Rose Midge. 1976 ARS Rose Annual pp 57-73.

Johnson, Warren T. and Howard H. Lyon. 1988. Insects that Feed on Trees and Shrubs, 2nd edition, Cornell University Press, Ithaca, NY., pp. 236-37.

 
 
 

ROSE ROSETTE

ROSE ROSETTE ON ROSE PLANT


CAUSAL ORGANISM:

This “disease” appears to be vectored by a blister mite but the causal agent has not been identified. Some plant pathologists think that it is a virus while others, incuding entomologists, think that the disease is the result of the blister mite feeding.

Mosaic is probably the most commonly found virus on roses but many other virus diseases also exist. While mosaic is transmitted by propagation other viruses can be transmitted by pollen, insect feeding or simply by mechanical contact. Symptoms of virus are usually dramatic manifestations of coloration, spotting or irregular distorted growth of leaves, flowers or growing points.

SYMPTOMS:

Rose mosaic usually appears in spring as a distortion of growing tips or expanding leaves. Later the leaves can appear to be wavy and have yellow lightening patterns, oak leaf patterns or simply gold to yellow veins. Plants infected with virus usually are slower to develop in spring than healthy plants and usually produce fewer good quality blooms. During the warm summer typical symptoms can disappear only to come back as fall and cooler temperatures arrive.

CONTROL:

Since there is no cure for the virus diseases it is important to purchase only quality materials which have no symptoms of the disease. Some pathologists suspect that mosaic may be pollen transmitted which could prompt removal if other roses in the garden are valuable and not already infected. In some exhibition gardens the disease can actually be very common. Propagation of buds from infected roses will probably result in transmission of the disease if the buds actually take.

ACKNOWLEDGEMENTS:

I would like to thank the following plant pathologists with the California Department of Food and Agriculture’s Plant Pests Diagnostic Centre: Dan Opgenorth and Dennis Mayhew. They have given me invaluable advice in preparing this article. All the above pictures were taken by Baldo Villegas.

rosette 1rosette 2

REFERENCES:

Horst, R. K. 1983. Compendium of Rose Diseases. The American Phytopathological Society, St. Paul, Minnesota. Pp. 26-27.

ROSE SPRING DWARF DISEASE

ROSE SPRING DWARF DISEASE


CAUSAL ORGANISM:

A virus is suspected in causing this disease.

SYMPTOMS:

Rose mosaic usually appears in spring as a distortion of growing tips or expanding leaves. Later the leaves can appear to be wavy and have yellow lightening patterns, oak leaf patterns or simply gold to yellow veins. Plants infected with virus usually are slower to develop in spring than healthy plants and usually produce fewer good quality blooms. During the warm summer typical symptoms can disappear only to come back as fall and cooler temperatures arrive.

CONTROL:

Since there is no cure for the virus diseases it is important to purchase only quality materials which have no symptoms of the disease. Some pathologists suspect that mosaic may be pollen transmitted which could prompt removal if other roses in the garden are valuable and not already infected. In some exhibition gardens the disease can actually be very common. Propagation of buds from infected roses will probably result in transmission of the disease if the buds actually take.

ACKNOWLEDGEMENTS:

I would like to thank the following plant pathologists with the California Department of Food and Agriculture’s Plant Pests Diagnostic Centre: Dan Opgenorth and Dennis Mayhew. They have given me invaluable advice in preparing this article. All the above pictures were taken by Baldo Villegas.

spring dwarf 1spring dwarf 3

REFERENCES:

Horst, R. K. 1983. Compendium of Rose Diseases. The American Phytopathological Society, St. Paul, Minnesota. Pp. 26-27.

ROSE MOSAIC

ROSE MOSAIC ON ROSE PLANT


CAUSAL ORGANISM:

Prunus Necrotic Ringspot Virus: Mosaic is probably the most commonly found virus on roses but many other virus diseases also exist. While mosaic is transmitted by propagation other viruses can be transmitted by pollen, insect feeding or simply by mechanical contact. Symptoms of virus are usually dramatic manifestations of coloration, spotting or irregular distorted growth of leaves, flowers or growing points.

SYMPTOMS:

Rose mosaic usually appears in spring as a distortion of growing tips or expanding leaves. Later the leaves can appear to be wavy and have yellow lightening patterns, oak leaf patterns or simply gold to yellow veins. Plants infected with virus usually are slower to develop in spring than healthy plants and usually produce fewer good quality blooms. During the warm summer typical symptoms can disappear only to come back as fall and cooler temperatures arrive.

CONTROL:

Since there is no cure for the virus diseases it is important to purchase only quality materials which have no symptoms of the disease. Some pathologists suspect that mosaic may be pollen transmitted which could prompt removal if other roses in the garden are valuable and not already infected. In some exhibition gardens the disease can actually be very common. Propagation of buds from infected roses will probably result in transmission of the disease if the buds actually take.

ACKNOWLEDGEMENTS: I would like to thank the following plant pathologists with the California Department of Food and Agriculture’s Plant Pests Diagnostic Centre: Dan Opgenorth and Dennis Mayhew. They have given me invaluable advice in preparing this article. All the above pictures were taken by Baldo Villegas.

mosaic virus 2mosaic virus 3mosaic virus 4mosaic virus 5mosaic virus 6mosaic virus 7

REFERENCES:

Horst, R. K. 1983. Compendium of Rose Diseases. The American Phytopathological Society, St. Paul, Minnesota. Pp. 26-27.

Contact: +84.933.067.033

BACTERIAL CROWN GALL

BACTERIAL CROWN GALL ON ROSE PLANT


CAUSAL ORGANISM:

Agrobacterium spp: This is really the only serious bacterial disease of Rose. The bacteria is found world wide wherever roses are grown and is especially severe in loose sandy or sandy loam soils.

SYMPTOMS:

On roses the symptoms of overgrowths can occur at the crown, bud union or on the roots. Galls are usually round to irregular in appearance and may have a rough exterior. Upon cutting across a gall, a disorganized callus type of tissue is commonly found. The portions closest to the exterior usually contain the actively growing bacteria. However, once the tumor inducing plasmid is introduced into a plant disease can occur without the presence of the vectoring bacteria.

DISEASE CYCLE:

The bacteria causing the disease are soil born and can survive in soils for many years. When roses are planted in infested soil any wound sites on the roots or crown offer points of entry for the bacteria. Once in the host the tumor inducing principle carried on a small circular portion of DNA is incorporated into the plant cell and a overgrowth begins to form. In some plants the bacteria can be systemic and galls may begin to form at many sites on the plant. As the galls develop callus tissue is laid down which is susceptible to other types of breakdown, decay or sloughing. In this way the soil around a plant can become infested with the bacteria. The bacteria survives many years in the soil and can be moved with water or other infected plant parts.

CONTROL:

Always inspect new plants thoroughly before placing them in your garden. Since wounds can be infected at the time of digging some plants may have latent infections which could become evident several years after they were planted. If crown gall is detected the plant may survive many years but could serve as a reservoir for the bacteria. Thus, removal of the plant as well as adjacent soil is recommended. In some cases soil fumigation is used to kill the bacteria in the soil, but this is only effective where relatively porous and dry soils are involved. Plant surgery is also an option on specimen roses but precautions should be taken to sterilize cutting equipment before and after use. These plants should probably be removed from the garden and watched closely for further development of disease. Any plants propagated from infected material should also be watched for the development of galls resulting from systemic contamination.

bacterial crown gall 1bacterial crown gall 2

REFERENCES:

Horst, R. K. 1983. Compendium of Rose Diseases. The American Phytopathological Society, St. Paul, Minnesota. Pp. 23-26 and Color Plates 39-42.

RUST ROSE

RUST ON ROSE PLANT


CAUSAL ORGANISM:

Phragmidium spp: The rust of rose is one of the most commonly found and easily identified diseases of rose. Severe outbreaks occur where cool temperatures and high moisture are found during the prime growing season. Where foliage is heavy, the first symptoms usually are found close to the ground and on the insides of plants. Nine species of the rust fungus are known to occur. The fungus is complex having up to five different spore stages in its life cycle. The resistance of various cultivars is usually well documented because rust is a very common disease in some parts of the country.

SYMPTOMS:

In early spring powdery pustules of light orange to yellow spores appear on the under side of leaves. Soon after these aecieospores can be found on the upper side of leaves where they are more obvious. As we move into summer the uredial stage usually is predominate forming the typical red brown to orange spores. This stage can repeat several times during the growing season usually in 10 to 14 day intervals. Finally as fall approaches and evenings become cool the over wintering telial stage develops black teliospores. Leaves, succulent canes and flower parts are all susceptible to the rust fungus.

DISEASE CYCLE:

The fungus over winters as teliospores on fallen leaves or on infected canes. The spores are wind borne and germinate to infect leaves through the stomata. Rust fungi are obligate parasites and can not be cultured. As the infection proceeds the various spore stages develop on rose, there is no alternate host for rose rust. Reinfection and spread occurs through aeciospores and urediospores. Spore germination requires cool summer temperatures and continuous moisture for at least two hours so the germ tubes can enter the leaf stomates. Teliospores serve as a means of over wintering on leaves and infected canes.

CONTROL:

In areas where Rust is severe, sanitation should be practiced to reduce inoculum and prevent early season infections. Infected canes should also be spring pruned to reduce the initial inoculum levels. Pruning very dense bushes will help to reduce the moisture levels inside of plants and prevent some infections. Preventative fungicidal sprays should be applied every 7 to 10 days when conditions are favorable for rust development.

rust rose 1

REFERENCES:

Horst, R. K. 1983. Compendium of Rose Diseases. The American Phytopathological Society, St. Paul, Minnesota. Pp 11-12 and Color Plates 12-19.