GDD Update May 20, 2019

Well, this is different – sun and heat!  Based on the weather alerts popping up on my radio, some people got lots of rain this weekend, which continues to make everything difficult.

Most reports are ‘missed that window for weed/insect management, planting, etc…’.  Peter Brooks wondered what the effect of all the rain on GDD based insect models is.  I suspect the effect is less on their development and more on our ability to deal with them.  Now, for something that pupates or overwinters in the soil, there might be an effect.  Harder to escape muddy soils?

On the disease side, there is definitely an effect of a wet spring.  We’ve seen too much Phytophthora in the past to not know it is exacerbated by waterlogged soils.  And George Hudler is noted in the Branching Out newsletter for May 17 as saying that leaf, needle and rust diseases are expected to be at high levels in 2019.  He thinks Rhabdocline and Swiss needle cast are as high as he has seen in many years.  (I have heard comments about Rhabdocline this year after not hearing any for quite a while.)

So this is a year to make sure you get good coverage for your needlecast sprays.  Remember Brian has seen good results treating for the first time at 1.5 – 2 inch elongation of shoots for Swiss needlecast, later than the traditional recommendation.

Growing degree days for the farms I am following range from 85-345.  Where do you fall?  Find out at NEWA:


Things to be scouting for now or soon:

Douglas fir needle midge – adults emerge 200-400

Gypsy moth  – eggs hatch 90-448

Pine needle scale – first generation crawlers emerge 298-448

I don’t get many requests for information on sawflies, but if you have them (and there are several species), they may be emerging now (78-220 for European pine sawfly).  Treatment is usually spot treatment only and often only in the last few years before sale.  Unfortunately, Bt doesn’t work on sawflies.

Have a great week!