New Discovery for Grape Crown Gall Biological Control
By John Hartman

Crown gall is especially devastating to grapes in Kentucky and some vineyards have been lost due to the disease.  In grapes, Vitis vinifera cultivars are more susceptible to crown gall than V. labrusca cultivars.

Symptoms.  The disease is characterized by galls or knobby overgrowths that form on susceptible planttissues, generally on grape trunks (photo 1) at or above the graft unions.  Galls are rarely observed on the roots, but roots may develop necrosis.  New galls first appear in early summer as white, fleshy, callus growth.  Galls turn brown by late summer and in the fall become dry and corky.  The woody tumors may be gnarled with rough surfaces (photo 2).  When galls are numerous they disrupt the translocation of water and mineral elements, leading to poor growth, gradual dieback, and sometimes death of vines.  In general,affected plants are more susceptible to adverse environmental conditions, especially winter injury.

Cause and biology of the disease.  Crown gall is caused by the soil-borne bacterium, Agrobacterium vitis, formerly thought to be a strain of Agrobacterium tumefaciens.  The bacterium survives at low levels for long periods of time in soil, and also in galls and in diseased plants.  The crown gall bacterium is widely present in Kentucky soils and may be systemically present in many grape vines, but the bacterium seldom causes disease unless the vine is injured.  Galls develop following an injury to grape cells permitting entrance of the pathogen and systemic movement in the plant.  Such injuries may occur during intermittent freezing and thawing weather common to Kentucky each winter.  Overwintering bacteria may be spread to wound sites by splashing rain, running water, on cultivation implements or on pruning tools.  Contaminated nursery stock may be another source of the disease.
Biological control of crown gall (A. tumefaciens) on other crops has been achieved through application of antagonistic strains of related bacteria (A. rhizogenes, strain K84) which prevent the crown gall bacteria from causing disease.  Recently researchers A. Kawaguchi, K. Inoue, and Y. Ichinose in Japan have expanded on this concept by using a non-pathogenic strain of A. vitis.  The report appeared in a recent paper entitled: Biological Control of Crown Gall of Grapevine, Rose, and Tomato by Nonpathogenic Agrobacterium vitis Strain VAR03-1.

A nonpathogenic strain of A. vitis VAR03-1 was tested as a biological control agent for crown gall of grapevine (Vitis vinifera).  When roots of grapevine were soaked in a cell suspension of antagonists before planting in soil infested with tumorigenic A. vitis, treatment with VAR03-1 significantly reduced the number of plants with tumors and disease severity.  Moreover, VAR03-1 greatly controlled crown gall of grapevine due to tumorigenic A. vitis in the field.  VAR03-1 established viable populations in the rhizosphere of grapevine and persisted on roots for 2 years.

This research is the first report that a nonpathogenic strain, VAR03-1, can effectively control crown gall caused by tumorigenic A. vitis.  Thus, there is hope that in the future, a biological control product effective against grape crown gall will be developed and made available to Kentucky grape growers.

Database on Cancer Risks of Turf Fungicides
By Paul Vincelli

The Cornell University Turfgrass Science program has partnered with Cornell’s Program on Breast Cancer and Environmental Risk Factors to create a database that provides information on the cancer-causing potential of the fungicidal active ingredients used for turf disease control.  This database reports the U.S. Environmental Protection Agency’s classification of cancer risk for turf fungicides, and thus, it can be considered as an authoritative source of such information .  The database can be found online at http://envirocancer.cornell.edu/turf/.   

Users can easily use this database to search for the active ingredient(s) or by searching product names.  The database only reports cancer risk classifications for the active ingredients, and not for the commercial products themselves, which also contain inert ingredients.  Inert ingredients are not required to be reported publicly, and so cancer risk assessments of these are not included in this public database. 

Keep in mind that cancer risk assessments don’t tell you whether you, your co-workers, or users of turfgrass treated with commercial fungicides will actually develop cancer from using commercial fungicides.  They only provide a reasoned scientific judgment of the expected cancer-causing potential of the active ingredients.  Nevertheless, that information still will be of value to many in considering your turfgrass management program.  More information on interpreting cancer risks is available at the website. 

Below is the cancer risk classification for selected turfgrass fungicidal active ingredients, along with trade names of commercial products that contain those fungicides.  I’ve only shown those fungicides for which the classification raises concern about potential carcinogenicity.  Many other turf fungicidal active ingredients are included in the database, so interested readers can access the website directly to see cancer risk classifications of most fungicides in use in Kentucky. 

US-EPA Cancer Risk Classifications of Selected Turf Fungicides
Boscalid (also known as BAS 510) (Emerald®): Suggestive Evidence of Carcinogenicity but not Sufficient to Assess Human Carcinogenic Potential

Captan (Captan®): Likely to be carcinogenic to humans following prolonged, high-level exposures causing cytotoxicity and regenerative cell hyperplasia in the proximal region of the small intestine (oral exposure) or the respiratory tract (inhalation exposure), but not likely to be a human carcinogen at dose levels that do not cause cytotoxicity and regenerative cell hyperplasia.

Chlorothalonil (Daconil®, Echo®, Manicure®, Chlorostar®, Concorde SST®, Pegasus L®): Known/Likely carcinogen

Ethazole(also known as etridiazole) (Koban®, Terrazole®): Group B2-Probable Human Carcinogen-Sufficient Evidence from Animal Studies

Iprodione (Chipco 26019, Chipco 26GT®, Proturf Fungicide X®, Iprodione Pro, Raven®): Likely to be Carcinogenic to Humans

Mancozeb (Fore®, Manzate 200®, Protect T/O®, Mancozeb®, Dithane®, Formec®, Pentathlon®): Group B2-Probable Human Carcinogen-Sufficient Evidence from Animal Studies

PCNB (Also known as pentachloronitrobenzene) (Defend®, Penstar®, Terraclor®, Turfcide®, Revere®): Group C-Possible Human Carcinogen

Propiconazole (Banner MAXX®, Propiconazole Pro®, Spectator®, Savvi®): Group C-Possible Human Carcinogen

Thiophanate methyl (Cleary’s 3336 Plus®, Allban®, Fungo®, Proturf Systemic Fungicide®, Systec 1998®, Cavalier®, Absorb TM®, T-Storm®, Tee-Off®): Likely to be Carcinogenic in Humans

Triadimefon (Bayleton®, Proturf Fungicide VII®): Group C-Possible Human Carcinogen

Vinclozolin (Curalan®, Touché®, Vorlan®): Group C-Possible Human Carcinogen

The main message for Kentuckians this winter – buy local firewood and don’t bring firewood from other states. This is a major way that the emerald ash borer can be spread into new areas.

A variety of native creatures find Kentucky firewood a great place to live or hide for the winter. Consequently, it is easy to bring them indoors when stocking wood to burn. The warmth stirs them to activity and they can provide some temporary excitement but little in the way of problems. Firewood inhabitants usually belong to one of two groups: 1) shelter seekers and 2) wood-infesting insects.

Shelter Seekers
Many arthropods hide under loose bark or in cavities during the winter. Possibilities include beetles, wood cockroaches, and even overwintering wasp or hornet queens. Spiders and their egg sacks, praying mantid egg masses, and moth cocoons are part of the "life" that may be associated with trees or fallen logs. These creatures will become active after warming up indoors. They can be swatted and discarded as they appear. These insects are not able to survive for extended periods indoors and they will not multiply or become established in the home.

Wood Infesting Insects
Many insects attack stressed or dead trees. Their activities ensure that the resources in the wood are broken down and recycled. Beetles are the most common group found developing in firewood. These include roundheaded wood borers, flatheaded wood borers, and shothole borers, also called powderpost beetles. The legless, white larval stages of the first two types can be found while splitting logs. Piles of sawdust appear from small holes in logs infested by powderpost beetles. The potential for these insects to infest structural wood in the house is very low. Often these borers attack only certain types of wood and the moisture content must be much higher that than found in structural wood.

Sometimes adults emerge after logs are brought indoors. Roundheaded wood borers are brightly marked, fast beetles with long antennae. The elongate flatheaded woodborers often have a metallic sheen. Powderpost beetles are small, brown to black insects. Any of these may be seen crawling or flying in the room or accumulating at windows or light fixtures as they move to light. These insects are harmless. Carpenter ants and termites may also be found in firewood that has been wet or stacked in one place for a long time. Termite colonies are in the soil so only workers are found in the wood. Termites form mud tunnels and this mud can be found in wood that they are attacking. Carpenter ant galleries are very clean, with no mud or sawdust. Individuals brought into the house in logs will not start an infestation but a colony may exist in old wood piles outdoors.

Insect invasion of homes from firewood can be reduced by following these rules:

Inspect wood as you pick it up. Check surfaces that were on the ground or against other pieces. Brush off the creatures that you see and knock wood together to dislodge what you don't see.
Bring in small supplies that will be burned in a few days rather than large amounts that could stay in place for weeks.
Outdoors, avoid stacking the wood directly on the ground, especially right beside the foundation. This will keep it from getting too wet and reduce the chances for infestation by termites and ants.