Southwestern Entomologist (1998) 23, 183-188

S.M. Greenberg, K.R. Summy, J.R. Raulston and D.A. Nordlund (1998)
Parasitism of beet armyworm by T. pretiosum and T. minutum under laboratory and field conditions
Southwestern Entomologist 23 (2), 183-188
Abstract: Studies were conducted to assess the ability of Trichogramma pretiosum Riley and Trichogramma minutum Riley to parasitize eggs of beet armyworm, Spodoptera exigua (Hubner). In the laboratory, beet armyworm egg masses were exposed at a ratio of 1 parasitoid female per host egg for 24 h. Bollworm, Helicoverpa zea (Boddie), eggs were used as a control host. In small field plots, beet armyworm egg masses were exposed at a rate of 5 parasitoid females per host egg for 24 h. The control consisted of egg masses that were not exposed to parasitoids. The laboratory results showed that T. pretiosum parasitized 44.8% of beet armyworm eggs compared to 51.6% parasitism by T. minutum. When beet armyworm eggs were attacked by T. pretiosum or T. minutum , 24.9% or 29.3% of the eggs desiccated, respectively, compared with 5.8% in the control group, which were not exposed to parasitoids. Development time, emergence rate, sex ratios of progeny, body length, and the percentage of deformed females of T. pretiosum and T. minutum reared on beet armyworm were not significantly different from those reared on bollworm eggs. However, the longevity of both parasitoid species reared on beet armyworm was significantly higher than counterparts reared on bollworm. In small plot experiments where T. pretiosum were released, total mortality of beet armyworm eggs was 60.9% (36.8% parasitized + 24.1% desiccated) and 53.2% (32.5% parasitized + 20.7% desiccated) in release sites of T. minutum. These results demonstrate the ability of both parasitoids to attack and develop on beet armyworm eggs and suggest a potential for use in augmentation efforts.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Shoil M. Greenberg

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
evaluation - screening - selection

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Spodoptera exigua		U.S.A. (mid S)
Trichogramma pretiosum (parasitoid)	Spodoptera exigua		U.S.A. (mid S)
Trichogramma minutum (parasitoid)	Spodoptera exigua		U.S.A. (mid S)