The Japanese Beetle appears to have become a resident of Colorado, and more specifically in the southern metro area. Through our monitoring program, we have already surpassed the captured population of 2012 up to early August. With the recent rainfall, and a surplus of susceptible plant material, it is reasonable to expect the population will be sustained through the end of this season.
Damage from the adult Japanese Beetle is evident in the skeletonizing of leaves and flowers. The top 10 plants that are palatable to the Japanese Beetle are: 1) Roses, 2) Virginia Creeper, 3) Grapes, 4) Lindens, 5) Plums, 6) Oaks, 7) Birch, 8) Cherries, 9) Rose of Sharon, and 10) the American Elm.
Adult beetles are strong fliers, which has greatly contributed to their spread from Centennial all the way west to Littleton. The beetle’s north to south distribution extends from 8th Avenue all the way south to just below Orchard Road. The movement of new plant material appears to be less impactful to the spread of the beetle than the ability of the adult to fly distances.
Achieving control over the Japanese Beetle population is very difficult. The insect’s ability to fly and their hard elytra (hardened outer wings) make control through insecticide treatments difficult. Treatments for controlling adult and larval stages include the following:
- Soap and/or Horticultural Oil (adult stage)
- Imidacloprid (adult or larva)
- Bifenthrin (adult)
- Milky Spore (larva)
- Parasitic Nematode (larva)
- Acelepryn (adult or larva)
- Acephate (adult)
Monitoring the adult population through the use of pheromone traps is very helpful in determining the peak of the adult stage and deciding the best time for treatments.
Contact us and we’ll send out an Arborist to recommend the appropriate treatment.