Offer ends September 30, 2012.

By Matthew Krause, PhD, Product Development Manager, Plant Disease Management

Tank-mix applications of CEASE® and MilStop® can be very effective for preventive control of many foliar plant diseases including bacterial leaf spots and blights caused by Xanthomonas. The cyclic lipopeptides and competitive activity of Bacillus subtilis QST 713 in CEASE disrupt the growth and establishment of pathogenic bacteria on leaf surfaces. MilStop makes the leaf surface more adverse to pathogenic bacteria by stressing their cells with potassium bicarbonate and weakening their integrity with multiple surfactants. Together, CEASE and MilStop can create a very inhospitable leaf surface environment for bacterial pathogens that land on them.

 

CEASE and MilStop need to be applied at the start of a crop and frequently thereafter to treat new foliage and to overcome natural loss of their active ingredients due to irrigation and weather. Coverage, coverage and coverage are key, especially on the undersides of leaves where bacteria primarily reside and enter the plant. Neither of these products can be used to "sanitize" leaves or other surfaces, and neither is effective once pathogenic bacteria are in the plant. CEASE and MilStop used properly in rotation with registered copper-based products and antibiotics not only improve disease control with these products but also can help slow the build-up of pathogen resistance to them.

 

To get the best control of foliar bacterial diseases with any biological or conventional pesticide program, it is critical to follow these simple cultural practices:

• Start with "clean" plant material. Seed, cuttings and plugs frequently serve as sources of pathogens. Though it is virtually impossible to obtain plant material that is completely disease free, it is possible to purchase relatively "clean" plant material from reputable suppliers who maintain good disease management practices.
• Work with good sanitation practices. Maintaining clean and disinfested growing environments, equipment, pots, and benches greatly reduces accumulation and transfer of bacterial (as well as fungal) plant pathogens. Once plant material and other debris are physically removed, quaternary ammonium- and hydrogen peroxide-based products are ideal for disinfesting bacterial pathogens from building environments, bench surfaces, recycled pots, and tools.
• Minimize conditions favorable for bacterial growth and infection. For Xanthomonas (and Pseudomonas), this means keeping free water from remaining on the foliage. Pathogenic bacteria use water films or droplets to reproduce and swim into leaves through natural openings and wounds. The longer leaves remain wet, the greater the chances for bacterial growth, infection and disease. A standard rule for cultural control of bacterial diseases is to overhead irrigate only when leaves can dry in an hour or less. Obviously, this is a challenge in propagation on mist benches or in mist houses. Also, leaves that are in constant contact with water (e.g. persistent dripping, against wet plastic or wet walls, etc.) are ideal candidates for disease
• Rogue-out diseased plants as soon as they are seen and remove plant debris from floors and benches. These practices prevent bacterial inoculum from remaining in the growing area during and after production of a crop. Xanthomonas has been known to survive in dried leaf tissue in greenhouses for 3 years or more due to the sugary coating on its cells called exopolysaccharide (or EPS).

Early and regular tank-mix applications of CEASE and MilStop combined with simple cultural practices can provide effective preventive control of Xanthomonas bacterial leaf spots and blights on greenhouse crops. Contact a BioWorks representative to discuss your particular crops and growing system and to recommend programs with CEASE and MilStop that fit your needs.