What are these “eggs” on cereal heads in my field?

Quite a few people over the past week have sent in photos (as in Figure 1 below) asking what are these “eggs” on the cereal heads, and noticing that they can be quite abundant in some fields.

Parasitoid Pupal Cases

Figure 1. Pupal cases of a wasp parasitic to armyworms. Photo from Dean McCowan, Agree Ag Services.

These are not eggs, but are the pupal cases of parasitic wasps. These are being found in fields that contained armyworms, and it is likely that armyworms were hosts for the parasitoids. For some parasitoids it is common for dozens of parasitoid larvae to emerge at the same time from an individual armyworm, killing it in the process. This is because an initial egg laid in the armyworm starts dividing and can become dozens or at times hundreds of eggs, that results in multiple parasitoid larvae of the same general age feeding in the armyworm. When the parasitoids emerge form the armyworm, they all emerge at approximately the same time, and very soon after form these clusters of pupal case, which are together in a cluster on the plants. So each cluster would have been parasitoids form a single armyworm, and will result in multiple wasps looking for more caterpillars to parasitize.

Information by:  John Gavloski, Entomologist, MAFRD

This article was taken from the Manitoba Insect & Disease Update: July 14, 2015.  For the complete issue, please visit MAFRD’s website at http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-update-2015-07-14.html





Have a follow-up question?

A new season of Manitoba Insect and Disease Updates has started!

The purpose of the updates is to compile information on insects and diseases of current concern to those growing or monitoring crops in Manitoba, and present a summarized weekly report that can alert farmers and agronomists to concerns in their region. This relies on insect and disease observations and concerns being reported by those monitoring crops. So the cooperation of agronomists and farmers in providing information for these reports is greatly appreciated. Results of insect and disease monitoring programs will also be presented in these reports.

A Manitoba Insect and Disease Update for May 13, 2014 has been posted at: http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-report-2014-05-13.html


Agronomists, Farmers, Farm Production Advisors, and others scouting crops: Please remember to send in reports of insects or plant diseases over the growing season so we can make these updates as complete as possible, and alert farmers and agronomists where and to what degree insects and pathogens are of concern or being controlled.

Information can be sent to:

John Gavloski (MAFRD Entomologist):  [email protected]


Vikram Bisht (MAFRD Plant Pathologist): [email protected]

Have a follow-up question?