A common question I get is when is the best time to apply the MCH anti-aggregating pheromone to protect Douglas-fir trees from Doug fir Beetles. My first reaction is to say that it's hard to apply too early but it's easy to apply too late. In the grand scheme of bark beetles, the Douglas-fir beetle is the early riser. Often times these beetles can be seen flying while there are still patches of snow on the ground.

As a rule of thumb, my advice is to get your MCH out early. Put on your boots and apply the bubble caps to the north sides of your trees as early as you are able. Cooler temperatures will prevent the bubble caps from emitting the MCH pheromone too rapidly but they will be in place in the event that warm temps spur an early beetle hatch and flight.

Once the beetles have flown the coop and found their new host, it is generally thought the games over until next year.  Research indicates that beetles that emerge in early spring are capable of making a second attack in June, July and August but this is thought to account for only 20% of the total flight.

If your area experienced a mild winter and warm spring, or if there is evidence there may have been an early beetle flight, it might be prudent to consider a second application of MCH in early July.