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Dahlia Biosecurity at RainySunday


  • Dahlia biosecurity: how we keep and share healthy dahlias

  • Labeling/records: knowing which plant/from where we are handling/testing/culling

  • Clean cuts/tools: one sanitized tool per plant, clean between plants/clumps, disposable gloves

  • Testing: cull all positives, useful when possible, but expensive

  • Visual inspection: When in doubt, throw it out!

Dahlia biosecurity? What’s that? For us, dahlia biosecurity is the broad category of “how we handle our tubers and plants to maintain their health and vigor.” Dahlias are a gorgeous and rewarding plant, but a lot of work goes into keeping them that way. Our dahlia biosecurity processes span the full year: ordering and planting, growing and flower harvest, tuber digging, dividing, and storage. We label, keep records, ensure clean cuts and tools, and cull based on testing and visual inspection.

Vivosun 12 Pack Clippers are great to be able to rotate through several pairs before having to stop and sanitize. Great size for harvesting cut flowers.

Labeling is a key focus throughout the year, to both ensure accurate identification, and to track down problems if they arise. Tubers are stored in containers separated by variety, one variety per container and beginning this year, are also individually labelled on the tuber itself. Labels are both on the box and in the box, so if one label is compromised, identification is still possible. Varieties with no surplus stock (I am keeping and growing all for the season) may be combined in storage together but are labelled individually to ensure they can’t get mixed up (they are then also double checked during the growing season to confirm identification). Records are kept of tuber source when we bring in new varieties. In the field, plants are marked with an identifying stake, and once they have bloomed, id is confirmed and they are marked with a flag tape label that also lists their variety.

Artline Garden Markers worked great for writing on garden tags and flag tape labels that didn't smear, run or fade all season long!

Clean cuts, clean tools, every plant, every time. Cuts/wounds in the plant are the most likely place for disease transmission to happen; as such, we fastidiously make sure our tools, and our cuts, are clean. When we are harvesting flowers, I have a several clippers that I rotate through. They are all immersed in Virkon-S solution, then moved to the “clean side” of my work box or tool belt. The clipper is used on one plant only, then moved to the “dirty side” of my box/belt. Once they are all dirty, I stop and reclean them in the Virkon-S solution. This repeats through all the rows/beds. The same one clean tool per plant process is followed for taking cuttings in the spring, for pinching back the central growing tip, for cutting plants back in the fall and for tuber dividing. When we are digging dahlias in the fall, I use disposable nitrile gloves, and each clump is dug, brushed off and visually inspected for signs of crown and leafy gall. If symptoms are found, that clump is disposed of, the gloves are disposed of and the tool is cleaned with either bleach or Virkon-S solution before moving on to any more digging.

Virkon-S Disinfectant and Virucide Tablets have been studied as effective against viruses and I much preferred working with it instead of bleach.

Testing for virus is a fabulous tool we have available to us as dahlia growers, however, due to the extremely cost prohibitive nature of testing every plant all season long (plants could be infected by a dirty cut or a pesky insect right after you sample), visual inspection is even more important for most dahlia growers. We tested several plants though the virus testing program made available by ADS and we tested many others after a virus problem was found to exist in some cuttings we had brought in last spring using commercially available tests.Any of those plants that tested positive for anything were disposed of (in garbage, not the compost) including the new cuttings. We will continue to avail ourselves of any testing options we can, when we can access them.

This Garden/Tool belt was awesome this year! I could designate clean and dirty sides, carry all my tools, have my markers, flag tape and extra gloves with me and throw it in the wash!

Visual inspection-when in doubt, throw it out! As I mentioned, testing every plant multiple times would be cost prohibitive for us (and most growers), so we test what we can and watch the rest very carefully. I have done a lot of research about the signs of dahlia viruses and anything I am not sure of is culled (pulled out, disposed of in the trash, gloves thrown away, tools sanitized). This will help reduce the chance of spreading viruses and improve overall plant health (ie, even if it isn’t virus causing odd/less than growth), I’d rather continue growing and sharing only the healthiest, most vigorous, plants.

Felco Pruning Shears; I LOVE mine for bigger cuts, taking the plants down in the fall, and lots of other uses all over the garden. I have small hands and these work well for me. They get dipped in the Virkon solution after every cut and wiped dry when I am done with them. You can get replacement parts too!

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