Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2012
Publication Date: 7/17/2012
Publication URL: http://www.tandfonline.com/doi/pdf/10.1080/09583157.2012.700695
Citation: Day, W.H., Hoelmer, K.A. 2012. Impact of the introduced parasitoid Peristenus digoneutis (Hymenoptera: Braconidae) on tarnished plant bug (Hemiptera: Miridae) infesting strawberries in northwestern New Jersey, USA. Biocontrol Science and Technology. 22:975-979. Interpretive Summary: The tarnished plant bug (TPB) is a native North American insect that is a serious pest of a wide variety of crops, especially fruits and vegetables. There are no effective natural enemies of the TPB in North America, so insecticides are the only practical control method. However, USDA scientists discovered two effective parasites of the European tarnished plant bug (a close relative) in Europe, and after safety (host-range) tests were favorable, the author established PERISTENUS DIGONEUTIS in the U.S. This was done in alfalfa, because it is a common crop (10 million acres in the NE U.S.), it is seldom treated with insecticides, and it is an important reservoir for the TPB. Subsequent research by the author showed that the parasite suppressed TPB numbers by 65% in NW NJ alfalfa, and likely also reduced TPB damage to apples in New Hampshire. By 2004, this parasitic wasp had spread into at least 11 states and 3 Canadian provinces. The present research was planned to determine if TPB damage to strawberries was reduced, by comparing the fruit in two areas--one with the introduced parasite and one with only the ineffective native parasite. As expected, TPB mortality by parasitism was much higher (20-46%) in strawberries where the introduced parasite is present, compared to where it is absent (4-11%). However, fruit damage with P. DIGONEUTIS (19-33%) was still more than desired, so further research will be necessary to adequately evaluate this biological control project.
Technical Abstract: Previous research has shown that the abundance of the tarnished plant bug, LYGUS LINEOLARIS (Palisot), has been markedly reduced in northwestern New Jersey alfalfa by the introduced parasite PERISTENUS DIGONEUTIS, and that damage to apples greatly decreased after this natural enemy became established throughout New Hampshire. The present study showed that parasitism of L. LINEOLARIS nymphs in organic strawberries (20-46%) was significantly higher where P. DIGONEUTIS is established, compared to where only the native P. PALLIPES complex is present (4-11%). However, strawberry damage by this pest with the two parasites (19-13%) was still more than desired. Some of the results were confounded by a fungus disease ("gray mold": BOTRYTIS) affecting the berries, so a fungicide should be used in future studies. Both tarnished plant bug numbers and the damage to strawberries were unexpectedly lower in the low parasitism/ "control" area where P. DIGONEUTIS is not present, so further research is warranted.