Spring 2015 Scouting in NC Christmas Trees
Because of the issues that people had in 2014 with twig aphids (BTA), and the continued issues with elongate hemlock scale (EHS), this year I’m doing an intensive scouting project. I plan on visiting 2-4 farms in the main Christmas tree counties every two weeks through the spring and summer to observe how well natural predators are working at pest control. I’ve been visiting potential sites the last couple of weeks to set up the project and there are a few things I’ve already noticed.
Twig Aphids: I’m finding that most fields have high numbers of BTA eggs in them. Actually the fields with the lowest eggs counts are the ones that have the least amounts of pesticides last spring — such as organically grown trees or abandoned fields. That’s because the natural predators ate the aphids before they could lay any eggs. That’s one thing I hope to observe this year — what predators are most important and how early in the spring they show up.
Another thing we’ve observed already is that BTA eggs started to hatch the 2nd week in March which is actually earlier than normal. Typically it takes about 3 weeks for all the eggs to hatch. This may well mean that we have an early overall hatch this year. (I’ll keep you posted).
For scouting, that means that by around April 10, you should be able to go out into the field and beat the foliage over a plate to see if aphids are present or not. If you sprayed last fall with a synthetic pyrethroid, this would be the time to check to see if you can get away without treating this spring. Don’t look before that time as all the eggs haven’t hatched yet. And also evaluate other pests such as rust mites, which leads me to the next observation.
Rust Mites: There are already a few fields with active rust mites in them. It might be a good idea to go ahead and check fields where rust mites have been a problem in the past, or fields treated last spring with a pyrethroid, to see if they are making an appearance. If rust mites are a problem, you might need to treat this spring even if twig aphids have been controlled. Also keep an eye on the weather. Rust mites love long springs. I have a feeling that this year there will be good weather for them to be a factor in many fields.
Keep Posted and Thanks! In any case, thanks to the growers who are letting me work in their fields and to the county extension agents who are helping me to make these evaluations. I plan on posting observations here so stay tuned! This work is funded in part by the North Carolina Christmas Tree Association.