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The Weekly News Source for Wyoming's Ranchers, Farmers and AgriBusiness Community

Interesting Discovery for the Leaf Cutter Bee Lab

by Wyoming Livestock Roundup

Some of you may not know that the Wyoming Department of Agriculture (WDA) wears many hats in the regulatory arena. 

One of our “hats” includes enforcing the Wyoming Alfalfa Leafcutter Bee (LCB) Law and Regulations.   The WDA LCB lab, located in Powell, interacts with alfalfa seed growers using leaf cutter bees for pollination of their seed crop.

By law, these LCB larvae must be officially sampled, x-rayed and certified yearly and meet specific standards to be allowed to remain in Wyoming for the next year’s pollination season. Often, during the course of the analysis season, we receive questions from our growers as to interesting finds, while punching their bee boards for analysis. 

This season was no exception. 

Shortly before the holidays, we received an interesting question from one of our alfalfa seed growers. They had some rather large cocoons starting to show up when they were punching their bee larvae out of the polystyrene bee boards for testing and asked if we could identify them. After a quick look, it was obvious that we had never seen them before, so we snapped a quick picture and e-mailed the identification question to the USDA Agricultural Research Service Pollinating Insects Research Unit in Logan, Utah.   

After a flurry of e-mails, we had the panel stumped, so they asked us to send samples. Thinking that we may have discovered a new parasite or scavenger of the leaf cutter bee that had shown up in our state caused us grief.  Within a few days the cocoon was identified and, to our relief, will not harm the leaf cutter bee larvae. 

The Logan Bee Lab is confident that our little bee-board dweller is the grass wasp Isodontia. The grass wasp performs important services, pollinating the plants in our landscape and preying on foliage-eating insects like crickets and katydids, in particular. It is a solitary wasp that sometimes utilizes alfalfa leaf cutter bee nest holes. They stuff the entrance with wisps of dried grass and stock their provisions with tree crickets. 

Then the question was posed, why are we seeing so many cocoons all of the sudden?

The Logan lab had asked if there had been an infestation of crickets near these fields, so we asked the grower.  We then found out there had been a five-inch rain event in the area in September, which was followed shortly thereafter by a cricket outbreak.  The infestation was so bad that the grower called pest control for help in their extermination efforts.   The crickets had invaded their shop, office and were covering the sides of their house. The fields where these cocoons have shown up are all within one mile of the shop.

Evidently the grass wasp took advantage of the crickets and a warm place to nest, so its next generation could prosper. The rain event and the cricket outbreak may have had nothing to do with the grass wasp showing up this year, but thankfully the alfalfa leaf cutter bee will have nothing to worry about with this species, except the space it takes up in the living quarters normally used for rearing its own young.

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