Key to keeping your plants & tubers healthy
A thorough spraying program is the best method to prevent the spread of disease and viruses, as vectors (aphids, thrips, and other insects) are one of the main transporters.
We strongly recommend preventively spraying before issues arise and continue spraying throughout the season. In general, as with most plants, dahlias should be sprayed with an insecticide every two to three weeks (following the manufacturer’s recommendations) during the growing season. A good spraying program is the best preventative to stop infestations, virus transport, and create overall healthiness of your plants. Begin spraying once your plants have reached 12" or more and continue throughout the growing season and into the fall. The sprays listed here are just a few of the name brands available. Ortho, Bayer (BioAdvanced), and Monterey brands produce excellent all-around sprays. You may also check with your local garden center for other great products available in your area. When looking for a product to use on or around your dahlias, anything safe for vegetables, roses, or other flowering plants will work fabulously for your dahlias.We carry a wonderful line of products on our website or at our farm in our Pest & Disease Control section. Spraying is necessary to stay ahead of pest issues.
General Insects
Some general insects that attack dahlias are leaf miners, stem borers, aphids, and thrips. Recommended sprays: Bayer (BioAdvanced) 3 in 1, Monterey Garden Insect Spray, Orthene, Neem Oil, Sevin-5, Organocide, and Malathion. All organic sprays tend to work best for preventative care but are not as effective in treating a problem that already exists.
Snails & Slugs
Treating slugs and snails is critical during the first few weeks after planting in all areas untilsprouts are through the soil. Slugs/Snails will eat the sprouts off nightly before you ever seethem. Apply slug/snail bait after planting and continue applying throughout the season. Any slug or snail bait product at your local garden center will work. We recommend applying regardless of visible trails. We find many times there are no trails, as they can live up to 5' underground.
-Other Helpful links:
-managingslugssnails.pdf (oregonstate.edu)
Earwigs
These insects will crawl up your plants and most often are found hiding or chewing onyourblooms. They can be a nuisance especially when you cut your dahlias to bring the beautiful blooms inside. We recommend treating your plants with Sevin-5 dust or spray, malathion, or sprays containing pyrethrins.
Cucumber Beetles (similar to a ladybug, but green instead of red)
These insects fly in daily and are hard to control. They especially enjoy chewing on light colored blooms. We do not treat for them as we do not want to harm ladybugs and other beneficial insects. We recommend hand-picking them off your blooms.
Spider Mites
Spider Mites are the biggest and most common predators of dahlias. These pests will causeyourplants to look brown around the base with possible spots on the leaves. Spider mites feed on leaves during the summer and return to the soil for the winter and must be treated for toprevent future issues. Typically, your dahlia plant will look like it needs more water. Most plants will begin with yellow spots on the leaves and then the leaves will beginbrowning completely, working their way up from the bottom, and eventually killing the entire plant. Spider mites thrive in hot weather and can attack certain varieties, while not bothering others right next to it. If you take a leaf off the bottom of the plant and turn it over, it could look dusty/dirty and feel grainy. These are tiny pests that are hard to see with the naked eye. These pests will appear and thrive mostly when the temperature rises and you water more, as they love humidity and hot temperatures. We recommend preventively spraying beginning 60 days after planting and continuing through the entire growing season. We recommend spraying with a Miticide, Monterey Horticultural Oil, Bayer (BioAdvanced) 3-1, Malathion (good for prevention, but does not work as well on infested plants), or any spray that lists mites in its description.
Mildew
Most commonly shows up in the fall. The leaves will begin to get a white powdery mildew or spots on the leaves. We do not believe that this is caused from overhead watering, but rather weather temperatures and humidity. We recommend preventatively spraying before this issue arises, begin spraying in late July and continue through the fall. Recommended sprays: Daconil, Funginex, or Fung-onil, or any Oil-based sprays.
