I want to collect the field strain of Trichogramma sp.and hymenopteran parasitoids of Plutella xylostella from the cabbage field. I need a method to collect field strain of these minute parasitoids.
I think you should collect eggs from Plutella and in the laboratory you can get the adults if they are parasited.
You have to collect Plutella eggs in the field and then if you obtain Trichogramma in the lab you will need a substitution host. See this paper for example:
http://www.nhm.ac.uk/resources/research-curation/projects/chalcidoids/pdf_Y/McGregHuLu998.pdf
Hi Qasim,
We find Trichogramma in suction samples taken from cotton fields. Unfortunately they are dead as our suction sampler is actually a leaf blower used in reverse and is far too rough for such a delicate insect. But you can sample a larger area that way. When we collected whiteflies in Arizona, staff there used a small modified electric vacuum cleaner with nylon stocking to capture live whiteflies which are also very fragile. The alternative is to use a manual aspirator and look for eggs with adult wasps that come to lay. This method is probably tedious and time consuming but I suggest it as an alternative if collection of possibly parasitised eggs does not work or takes longer.
Regards,
Simone
Try to collect eggs of host insects of Trichogramma sp. from the field OR mass release some fresh host eggs (attached in card or in a meshed pouch) in fields. Collect the released host eggs before they hatch out. You may get 20-60% of host eggs parasitized depending on your location, season, and host crop growth stage.
Trichogramma is attracted by Helicoverpa armigera under natural field conditions. Hence, Tagetes spp with H. armigera can be grown in field covered with mesh so as to prevent the dispersal of host but at the same time it should allow the entry of wasp. Observe for the presence of Trichogramma over a period.
You could either go to the field(s) in question, and collect parasitised egg clusters (parasitised eggs will appear darker in colouration) that you find there naturally and then rear the emerging adults. This can be done by punching a hole out of the leaf where the egg cluster is, as described here, as well as in many papers:
http://www.bioresources.com.au/pretiosum/PretiosumMonit.htm#steps for sampling
http://www.bioone.org/doi/pdf/10.1603/029.102.0321
http://www.nhm.ac.uk/resources/research-curation/projects/chalcidoids/pdf_Y/McGregHuLu998.pdf
Or you could set out your own egg cards or bait of irradiated eggs in the field, of either the host species you are interested in or a factitious host such as Sitotroga or Ephestia, as described in the following papers/articles:
https://www.researchgate.net/publication/230282411_Naturally_occurring_Trichogramma_species_in_olive_farms_in_Egypt
http://www.cabdirect.org/abstracts/20053186493.html;jsessionid=2B3BCD03A28C4FD5738CAF9CB47E045A
This is also a very useful piece of literature for the basics of working with Trichogramma
http://university.uog.edu/cals/people/pubs/insbene/b6071.pdf
Good luck!
Article Naturally occurring Trichogramma species in olive farms in Egypt
Leaving egg cards with alternative eggs in the fields, be sure to protect them against predators there like Chrysoperla larvae, stink bugs, ants and small spiders. Wrap the card bord (with attached fresh eggs) with some fine mash tissue (mosquito window net) letting pass Trichogramma but not bigger predators and place them under the leaf canopy to avoid the impact of direct sunlight. Recover them the latest after 3 days because the larvae hatching from unparasitized eggs can make the parasitized fall on the ground. Note that often, several Trichogramma species can coexist on the same hosts in the field. So it is desirable to offer several small distant egg patches in order to allow you to separate them in the lab after recovery. The technique: use a paper perforator (for archives) and a plastic sheet. Then you make a series of holes into the plastic sheet. Put it on a card board, apply glue , take the plastic sheet away and cover the glue points with eggs. Then wrap the card board in mesh tissue, fix a rubber band or circle and keep those dispositives in the fridge (in a thick brown envelope) until you bring them to the field. Put a long plastic band close to the place on the plant to find back your Trichogramma Trap three days later. Good luck!
Dear
You can collect these parasitoids by collecting the wild eggs and keep it in tubes or petri- dishes to emerging the egg parasitoids
Hello, to collect wasps, you can collect their hosts and collect wasps from other Trichogramma hosts on the same farm. Some insect eggs on weeds can be good examples for collecting parasitized eggs by Trichogramma. In addition, you can use trap eggs to collect wasps. These trap eggs can be either the eggs of the Trichogramma host on the farm or the eggs of other hosts such as Sitotroga and Ephestia eggs or Corcyra eggs
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