The University of California has just published trapping guidelines for the walnut twig beetle, which carries the fungus responsible for thousand cankers disease in walnuts.
A group of entomologists from UC Davis and the U.S. Department of Agriculture's Forest Service Pacific Southwest Research Station in Davis developed the trapping methods and guidelines, according to a news release.
In 2011 field trials in Tennessee, Virginia and Utah, they showed that a small plastic funnel trap baited with a beetle aggregation pheromone could pick up new populations.
They extended the trials to Pennsylvania this year.
The trap was developed in conjunction with Contech Enterprises Inc., Victoria, British Columbia, Canada.
Early beetle detection is key to local eradication or effective management.
Thousand cankers disease is caused by the fungus Geosmithia morbida and infects both black walnut and the commercial English walnut.
The fungus enters walnut trees through the feeding and reproductive habits of the walnut twig beetle.
It then colonizes and kills the phloem and cambium of the branches and main stem.
Initial symptoms include flagging and branch dieback.
If you look closer, you will find pinhole-sized entrance holes, which are frequently near cankers.
Staining may occur around the holes.
As the disease progresses, the cankers with coalesce, girdling branches and stems.