May 26, 2004
Christmas Tree Scouting Report -
Welcome to the Christmas Tree Scouting Report for the week ending Wednesday May 26, 2004. The next report will be available after 5 PM on Wednesday June 2nd. To receive a FAX of this week's message, please call (814) 865-1636.
Most growers in the more southern counties have completed their third spray for Rhabdocline needle cast and will be wondering if a fourth spray will be necessary. Samples examined the later part of last week showed that rhabdocline was still infectious in Adams, Franklin and Northumberland Counties. After the hot weekend that continued into the beginning of this week, I was finding that the rhabdocline fungal spores were beginning to blacken and the needles dropping in Dauphin, Lancaster and Lebanon Counties. This year's infectious period is almost over. However, if you have the other needlecast on Douglas fir known as, Swiss needle cast, you will want to apply a fourth spray since those fungal spores are infectious a little longer into the season than Rhabdocline.
With all this wet weather, signs of Sphaeropsis, or diplodia fungal blight were observed on the new growth of Douglas fir and Scotch pine in Dauphin, Lancaster, and Lebanon Counties. If you're seeing new growth that is hanging limp and discolored and the stem is dark and shriveled, you're looking at fungal blight. There is nothing that can be done to control this but less rain and more sunshine and removal of damaged stems later in the season during shearing.
Cooley spruce gall adelgids are out on the new growth in Franklin, Dauphin, Lancaster and Lebanon Counties. Growers who are wondering if this pest can be controlled at this time missed the boat for three reasons. First, most of the damage occurs when the growth is still tender. Second, the insects are at several different stages at this time of year and the sprays will not kill all of the stages. The third reason not to spray at this time of year is to preserve the naturally occurring predators of Cooley adelgid. Many fly larvae and lacewings feed on the adelgid and will be killed by the spray materials. The recommended time to spray for this pest is early spring when the forsythia is in bloom or again in the fall when the overwintering stem mothers are exposed and have not begun to produce their cottony protective cover.
Damage from the white pine weevil was evident in white pine in Lebanon County. When the discolored and stunted terminal was examined the bark was soft and pliable and easy to peel away, exposing the white grubs and their characteristic red-brown frass. Removing these infested terminals by cutting down as far as the healthy tissue is the best method of control at this time. Remember to remove the damaged terminals from the field and destroy them by burning.
Young bagworms about 1/8th inch long were found on white pine in Lancaster County. Feeding damage to the bark and surface of needles by the young larvae was observed. As the larvae get bigger they are capable of eating whole needles and can defoliate an entire tree. When sprays are directed to the young larvae, softer chemicals, such as Bt (Bacillus thuringiensis) can be an effective solution.
Female cryptomeria scale on Canaan and Fraser firs in Franklin, and Lancaster Counties are still laying eggs. These lemon colored eggs can be dislodged when an infested branch is tapped onto a white surface and observed with a hand lens. Crawler emergence is expected in the next week or so.
Damage from the Douglas fir needle midge was found on the new growth of Douglas fir in Bucks and York Counties. If you had damage from this pest last year and did not spray when adults were present about the time of bud break, chances are you can see kinked needles that resemble Cooley spruce gall adelgid damage. However, the difference of the two is that the Cooley spruce gall adelgid would be visible on the surface of the needle at this time whereas the larvae of the Douglas fir needle midge has already entered the needle. The only evidence of the midge is an entrance wound or "dimple" on the bottom of the needle at the kink. We will continue surveying for this new pest of Douglas fir this summer and evaluate fields that were sprayed this spring.
A few eggs and crawlers of the stripped pine scale were found underneath adult females in Lancaster County. No eggs were found underneath this scale in Dauphin and Lebanon Counties. The most effective time to spray for this soft scale is when the crawlers are out on the needles and well exposed to chemicals.
The next report will be issued Wednesday June 1st, after 5:00pm.