Crown gall symptoms on roses caused by the bacterium Agrobacterium tumefaciens (Rhizobium radiobacter) – Photo credits: Kamil Duman
A plant with a mature gall that is potentially releasing the crown gall bacterium into the potting media. Photo credits: Susannah Wright
For gardeners, rose enthusiasts and rosarians, each of the many rose diseases is as important as the others. But we can say for sure Crown Gall is one of the most unsightly of the many rose diseases that can been seen currently.
The disease got this name from the large tumor-like swellings (galls) that typically occur at the crown of the plant, just above the soil level. The cause of crown gall disease is a bacterium that resides in the soil, Agrobacterium tumefaciens (updated scientific name Rhizobium radiobacter).
Galls or overgrowth (1/4 inch to several inches in diameter) of host plant tissue typically form at the soil line but also can form on branches or roots. Galls are initially white, spherical, and soft but darken with age as outer cells die. It can either be almost entirely on the surface of the plant and easily detached or can be almost indistinguishable from normal plant tissue except for its greatly enlarged appearance.
The bacterium that causes Crown Gall disease survives and persists in the soil for up to 3 years. It can invade recent wounds on the branches or roots. Swelling can be seen as early as 14 days following entry of the bacterium into the plant. The tissue near the gall can be crushed due to rapid cell enlargement. If vascular tissue is crushed, wilting can result from the restricted water movement.
Early stage symptom of Crown Gall on roses can be noticed as the small white galls. Photo credits: Susannah Wright
The galls can enlarge to a quarter size in a short period of time from the initial small galls. Photo credits: Mathews Paret
ABOUT THE BACTERIUM
Agrobacterium uses its genes as a weapon to attack plants. It enters the plant mostly from the soil through wounds on the roots or lower stem or from the branches during plant pruning. Symptoms are caused by the insertion of a small segment of DNA (known as the T-DNA), from a plasmid, into the host plant cell, which is incorporated into the plant genome. When the plasmid links up with the plants own DNA, the altered plant cells start dividing rapidly and uncontrollably, and the root or stem develops a tumor-like swelling.
Galls can range from pea size to softball size. Tiny cracks from freezing temperatures or wound sites can be the site of gall formation. Once the wound compounds are generated, the bacteria detach from the xylem cell walls and are carried upward with water during evapotranspiration to the wound site where they initiate galls. One of the common ways of the spread of the disease is by pruning infected plants and moving the bacterium accidentally while pruning nearby healthy plants.
The crown gall bacterium is a soil pathogen, which means main inoculum source is soil. The bacterium can overwinter in infested soils, where it can live as a saprophyte for several years. The bacterium can easily during field preparation, pruning and irrigation. Insects, nematodes and grafting materials, can also transfer the bacterium.
The galls will turn dark in color as they age. Photo credits: Kamil Duman
HOW CAN YOU MANAGE ROSE CROWN GALL DISEASE
- Plant only disease-free roses. Check very carefully before you buy plants for any kind of galls in the crown or branches. Use good sanitation practices in handling roses.
- Plant in clean soil. Avoid areas with a history of crown gall infestation.
- Avoid fields with heavy infestations of root-attacking insects and nematodes.
- Select well-drained soil and irrigate from clean water sources.
- Keep grafts and buds well above the soil line.
- Destroy diseased plants as soon as you notice them to avoid cross-contaminating other plants, or pruning equipment. Also, do not keep infected plants with healthy plants, as the likelihood of accidental transmission through pruning is high.
- Avoid mechanical injury to plants from tillage and hoeing. Provide winter protection so that the bark does not crack.
- Disinfect pruning tools between plants. disinfect budding/grafting tools before and after use. Bleach (10%; equivalent to 0.6% sodium hypochlorite), or quaternary ammonium-based sanitizer are effective as disinfectants. Make sure to prepare fresh stock routinely.
- If crown gall plants are noted, please let your local county extension agent know about it and they will be able to contact us for additional site-specific management plans if needed.
Gall formation at pruning sites indicating contamination of the plant during pruning. Photo credits: Kamil Duman
Authors: Kamil Duman, Susannah Wright, Fanny Iriarte, Barron Riddle, Gary Knox and Mathews Paret, University of Florida – NFREC, Quincy, FL
Photo courtesy: Gary Knox
Cupheas are perennials that produce bright orange, red, yellow or purple flowers all summer and fall. Some species are called cigar plants due to their tubular, cigar shaped flowers tipped in red or yellow (like a lit cigar). Others are sometimes called firecracker plants because their cylindrical flowers are bright red or orange (looking like a firecracker). By any name, their nectar-filled, tubular flowers are widely known for attracting large numbers of hummingbirds, butterflies and bees. In addition, young stems of some species are reddish, further adding color and contrast to the usually narrow, lance-shaped green foliage.
As a group, cupheas grow best in full to part sun (the brighter, the better) and well-drained, moderately fertile soil. Cupheas are drought tolerant once established, but grow faster and larger with regular moisture and occasional fertilization. Their origins in warm climates allow them to thrive in heat, but likewise make some species sensitive to cold winters. Those that are frost tender along the Gulf Coast are best placed in a sheltered location in the garden. Cupheas are pest and disease resistant and are not invasive in Florida. They are not truly deer resistant, yet reports suggest cupheas are not favored by deer.
Cupheas are great summer performers in bright, hot and dry locations. Flowering begins in summer and continues through fall until short days and cool weather reduce flowering or frosts cause dieback. Along the Gulf Coast, cool winter weather slows them down, so re-growth doesn’t occur until mid to late spring, and flowering usually doesn’t begin until days and nights are warm. Growth and appearance of many cupheas are improved if plants are pruned or cut to the ground in late winter.
Over 200 species of Cuphea are native to Mexico and the warm-temperate and tropical Americas. Of these and their hybrids, the cupheas listed below are great summer-flowering perennials for the northern Gulf Coast.
Photo courtesty: Gary Knox
Cigar Plant (Cuphea ignea)
This fine-textured plant produces red to orange tubular flowers about an inch long. This cigar plant is hardy to about 20°F. It grows about 2 feet tall and 3 feet wide along the Gulf Coast, though it would be a larger, evergreen shrub in warmer climates. This cuphea tends to have lanky growth, so occasional summer pruning will stimulate branching which results in more dense growth.
Cigar Plant or Candy Corn Plant (Cuphea micropetala)
Flowers are 1.5 inches long, emerge pale yellow and gradually turn orange from the base upwards, offering a colorful, two-tone effect. Foliage is hardy to 25-30°F and this cigar plant is root hardy to at least 15°F. Stems should be cut back to ground level in late winter to keep the plant tidy. Clumps spread slowly outward by rhizomes, and the plant will reach 3 feet tall and wide along the Gulf Coast.
Photo courtesy: Gary Knox
Orange Cigar Plant or Schumann’s Cuphea (Cuphea schumannii)
This sprawling, floriferous cigar plant prefers moist, well-drained soil to thrive. Barrel-shaped, 1- to 1½-inch blooms are orange and yellow and sometimes have small purple petals at the tips. Flowers cover the branch terminals in the heat of summer and into fall. This plant is hardy in Zones 8 to 9 (at least down to the mid 20s°F). Unlike many other cupheas, leaves of orange cigar plant are oval- to heart-shaped. Stems grow 2 to 3 feet tall and readily flop or fall over. Plan to give orange cigar plant lots of room to sprawl through the garden!
Cuphea ‘David Verity’
Photo courtesy: Gary Knox
‘David Verity’ Large Firecracker Plant (Cuphea ignea × micropetala ‘David Verity’)
This floriferous hybrid produces flowers that are dark orange with a short yellow-orange flared tip and purple filamentts. Well-adapted to the Gulf Coast, this plant is foliage hardy down to 25-30°F and root hardy to at least 15°F. In Zone 9 this plant will grow as an evergreen shrub up to 4 to 5 feet tall and wide, but it will be smaller in areas where frost or freezes occur. This selection is believed to be a hybrid between Cuphea ignea and C. micropetala that was given in the mid 1970s to David Verity, then the manager of the UCLA Mildred Mathias Botanic Garden. It was subsequently named for him when later brought into commercial production.
‘Vermillionaire®’ Large Firecracker Plant (Cuphea ‘Vermillionaire®’)
This new hybrid appears to be a superior cuphea because it grows as a naturally compact plant that produces more flowers than other selections. ‘Vermillionaire®’ grows about 24 inches or more tall and wide with a compact, mounding habit. Orange tubular flowers are produced continuously until late fall. This cuphea is too new to know the full extent of its hardiness, but it is expected to be a perennial in Zones 8 and higher.
Mexican Heather (Cuphea hyssopifolia)
Unlike the previous cupheas, this plant has small purple flowers, and some selections sport white flowers. Another difference is Mexican heather’s finely textured, bright green leaves. Gulf Coast Zone 8 plants are usually killed to the ground in winter, often recovering by summer but resulting in a compact plant growing less than 24 inches tall and wide. In Zones 9 and higher, Mexican heather is a larger-growing semi-evergreen tropical shrub. Reported pests are leaf-chewing beetles (Altica and Colaspis spp.) and the twig-dwelling lesser snow scale (Pinnaspis strachani). Mexican heather works well for edging beds or sidewalks, helping to define and soften pathways. Cultivars include Allyson, Lavender Lace, Purple Nurple™ and the white-flowered Monga (Itsy Bitsy° White) and ‘White Whispers’.
Photo courtesy: Gary Knox
Bat Face Cuphea (Cuphea llavea)
Each 1-inch flower consists of a purple tube lipped with two red, upright lobes. By viewing the flower with its tip facing you, it takes only a little imagination to see the two red lobes resemble large “ears” above the purple “face” of a bat, hence the name. Along the Gulf Coast, bat face cuphea grows mound-shaped 8 to 24 inches tall and wide, depending upon the selection. It is very heat and drought tolerant but requires better drainage than the other cupheas. Bat face cuphea is evergreen down to the upper 20s°F and root hardy into the lower 20s°F. Improved forms of bat face cuphea include the cultivars, Flamenco Samba, Georgia Scarlet, Mellow Yellow, Miss Priss, Tiny Mice®, Sriracha™ Pink, Sriracha™ Violet, Torpedo, Vienco° Lavender and Vienco° Red.
IPM for Shrubs in Southeastern US Nursery Production Volume II is the third book released by the Southern Nursery Integrated Pest Management Working Group (SNIPM) and includes chapters on hydrangea, loropetalum, holly, rhododendron (including azalea), Indian hawthorn, and weed management. Each chapter covers history, culture and management of the major species and cultivars in production, as well as arthropod pest management and disease management. Within the discussion of these topics, each chapter includes strategies for developing effective IPM programs for key pests and plant pathogens, including tables of fungicides and insecticides for use with these key organisms. While developed for nursery producers, this information also may be useful to landscapers, students, arborists and others.
This free book is downloadable as pdf chapters at
The first book, IPM of Select Deciduous Trees in Southeastern U.S. Nursery Production, was released in May 2012 and is available for free download as chapter .pdf files at http://wiki.bugwood.org/SNIPM and as an eBook from the iTunes Bookstore https://itunes.apple.com/us/book/ipm-for-select-deciduous-trees/id541182125?mt=11.
The second book, IPM for Shrubs in Southeastern US Nursery Production Volume I, was released in June 2014 and can also be downloaded as chapter .pdf files at http://wiki.bugwood.org/SNIPM or from the iTunes Bookstore at https://itunes.apple.com/us/book/ipm-for-shrubs-in-southeastern/id903114207?mt=11.
The SNIPM Working Group is a multi-disciplinary group of Extension professionals formed to more efficiently and effectively develop and deliver educational programming to the southern U.S. nursery and landscape industry.
Come to this free workshop to learn about the latest results of University of Florida and national research on roses. Receive hands-on training on symptoms and management of rose rosette disease, rose mosaic disease, crown gall, and rose pests.
FL Pesticide CEUs, FNGLA CEUs and GA Pesticide CEUs have been applied for!
This program is geared for nursery and greenhouse growers, landscapers, municipal maintenance personnel, Extension personnel, Rosarians, rose enthusiasts and science teachers. Sponsored by Farm Credit of Northwest Florida and Harrell’s.
To register for this FREE event, please go to: https://rose-diseases-pests.eventbrite.com
A “Gardening for Pollinator Conservation” Workshop will take place Thursday, October 13, at the UF/IFAS North Florida Research and Education Center (NFREC) in Quincy. Pollinators are important in conserving native plants, ensuring a plentiful food supply, encouraging biodiversity and helping maintain a healthier ecological environment – – – the so-called “balance of nature.” Come learn how you can conserve and promote pollinators in your own garden, all while beautifying your own little piece of Nature.
As in previous years, nursery vendors will be selling pollinator plants at the Oct. 13 workshop, making it convenient for you to put into practice what you learn at the workshop! Registration is just $15 per person and includes lunch, refreshments, and handouts.
Check out the workshop details and register at: https://gardeningforpollinatorconservation.eventbrite.com/
What: Gardening for Pollinator Conservation
When: Thursday, October 13, 8:30 am to 5:00 pm EDT
Where: University of Florida/IFAS North Florida Research and Education Center, 155 Research Road, Quincy, FL. Located just north of I-10 Exit 181, 3 miles south of Quincy, off Pat Thomas Highway, SR 267.
Cost: $15 per person (includes lunch, refreshments and handouts)
For more information, contact: Gary Knox, email@example.com; 850.875.7105
For a printable Flyer click here: Gardening for Pollinators Workshop
Our workshop builds on previous successful pollinator workshops held at Leon Co. Extension last year and in Marianna in 2012. This workshop was developed as a collaboration of county faculty from several extension offices with folks from the Florida Fish & Wildlife Conservation Commission as well as UF/IFAS NFREC. Sponsors helping defray costs include Florida Native Plant Society – Magnolia Chapter, Gardening Friends of the Big Bend, Inc., Mail-Order Natives, and University of Florida/IFAS North Florida Research and Education Center.
We look forward to seeing you at the workshop!