March 11, 2005

Christmas Tree Scouting Report Pest Update For the 2005 Season -

In 2005, the scouting report will be updated every Wednesday after 5:00 PM beginning March 30th. New reports will be produced weekly through June 30th. This gives growers the opportunity to get into the field before the weekend.

As we all know, White Pine Weevil has been causing significant damage in many Christmas tree species across the state. This weevil is also a serious pest in timber production, reforestation and natural regeneration. The population may be building, in part, due to the large stands of host material in the field. Weevil populations build in response to food supply, sun and long thick terminals, which are optimum for larval survival. Recent loss of some effective weevil chemical controls may also be a contributing factor.

The best protection from damage by this pest is targeted chemical applications when adults are present. To achieve maximum control with least amount of damage, early detection of emergence is important. We have found over the last ten years of scouting that weevil emergence can be as early as mid- March. There are a few tools you can use to monitor for early emergence. Scouting for the weevil on the terminals of trees near those damaged the previous year is a good place to start. You may be lucky to see the weevil but symptoms of feeding damage can be recognized by small pin holes just below the new terminal bud cluster; some holes may be oozing with clear sap. On a sunny afternoon both the weevil and the feeding damage are easy to detect.

Trapping is another good way to monitor. Gempler's Supply is no longer selling the Tedder's traps we have used to monitor weevil emergence. However, Great Lakes IPM in Vestaburg, Michigan is selling a similar trap as pyramid trunk traps for $14.75 each. The top assembly only can be purchased for $1.75 each and you can build your own bottom out of a more durable material. To find plans for building the trap base (click here). These traps have to be baited and replenished with turpentine and 95% ethyl alcohol to attract weevils. However, I've been told a liquor license is now needed to purchase grain alcohol at your local state store. A liquor license cost $40 and is good for four years. Denatured alcohol is easily accessible at your local hardware store. However, we do not know how effective this grade of alcohol will be. We will be comparing denatured alcohol and 95% ethyl alcohol this spring at one of our trapping sites to see if one is more successful at catching weevils than the other. If you monitor with traps, spray the top 1/3 of the tree when the first weevil is caught in the trap.

Keeping track of the growing degree days (GDD) is also another way of monitoring weevil emergence. 7-58 GDD (base 50) is the range for WPW emergence. As of March 8th there were 5 GDD accumulated at sites in Chester and Delaware counties. GDD accumulation should begin March 1st. Calculate the average temperature for each day then subtract 50 to determine if any GDD's have accumulated for that day. Add each daily GDD to the accumulated total.

If you have any pest information in your area that would be helpful to other growers please send the information to Sandy Gardosik at to be included in the scouting report for that week. Please include the pest name, host plant, and county with a brief description of what you observed.

Look for the next scouting report after 5:00 PM March 30th.