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Recommended Larch Casebearer Treatment in Greenhouses

Posted: Wed Apr 13, 2016 11:17 am
by akelsey
Larch casebearer larvae recently emerged on western larch scion material used for this year's grafting in our greenhouse. This is the first time we've grafted western larch and I've been scrambling to find out how best to treat for larch casebearers. Several professionals I've contacted have dealt with casebearers in an orchard setting, but I have not been able to find anyone with experience in greenhouse treatment.

Our main treatment to date has involved hand-removing the larvae, which is time-intensive but appears to be fairly successful (still too early to make a definitive conclusion however). I'm interested in hearing from anyone else who has had experience with other treatments for casebearer larvae in greenhouses or nurseries.

Re: Recommended Larch Casebearer Treatment in Greenhouses

Posted: Wed Apr 13, 2016 1:05 pm
by FabienneColas
In a nursery I work with, they still had a problem with this casebearer in a greenhouse. It is quite difficult to eliminate due to the case. If your "invasion" is not too important, manually is good. You can use chemical products such malathion or carbaryl (Sevin XLR), see the tag for the suggested dose.

Re: Recommended Larch Casebearer Treatment in Greenhouses

Posted: Wed Apr 13, 2016 4:24 pm
by akelsey
Thank you for the feedback, especially the pesticides that you've tried. I am currently working with my supervisor and our forest entomologist to explore which options we as an agency can use. One good thing about our situation is that we do not have larch trees in the greenhouse every year or in our orchards, so the casebearers will not get established here long-term. I do hope to make recommendations to the partner organization receiving the trees. My understanding, based on recent conversations with people who've grown western larch in orchards, is that casebearer has not been a significant problem once the trees are established in the field. If anyone has information related to casebearers in orchards, I'd be interested in hearing about your experiences.

Successful Larch Casebearer Treatment

Posted: Thu Apr 21, 2016 1:42 pm
by akelsey
We conducted two systematic hand-removals of the larch casebearers and it appears to have been effective. We have not found any additional live casebearers on our grafted seedlings. This is a time- and energy-intensive effort, but is environmentally friendly!

We will continue to monitor the larch seedlings to catch possible late emerging individuals or casebearers we previously missed.