Some effects of a white grub infestation on northern mixed-grass prairie.

Abstract

Graminoid standing crop in June 1985 on areas infested with white grubs (Phyllophaga anxia Leconte) (average density = 47 grubs m-2) was 92% less than on uninfested rangeland (average density < 2 grubs m-2). Study area was the Central Grasslands Research Center in south-central North Dakota. Infestations were noticeably associated with communities dominated by western snowberry (Symphoricarpos occidentalis Hook.) with an understory subdominance of Kentucky bluegrass (Poa pratensis L.). The objective of our study was to assess the initial impact and subsequent recovery of infestation on community standing crops and plant densities. Mid and late summer standing crops of Kentucky bluegrass and other grasses were significantly less (P < 0.05) on infested than uninfested sites between 1985 and 1987. Graminoid density was less (P < 0.05) on infested than uninfested sites during 1985 and 1986. Post-infested standing crop and density of forbs increased (P < 0.05) on infested sites. Infestation of sites subsequently provided habitat for establishment of noxious weeds such as wormwood sage (Artemisia absinthium L.). Management techniques to enhance the recovery of grasses and eliminate establishment of noxious weeds may be necessary.