Spatial distribution of Ataenius spretulus, Aphodius granarius (Coleoptera: Scarabaeidae), and predaceous insects across golf course fairways and roughs

In Michigan, scattered damage to fairway turf from Ataenius spretulus (Hald eman) or Aphodius granarius (L.) is reported Ly golf course superintendents every year. Yet, little is known about the distribution of these insects o n golf courses or why outbreaks occur. In 1992 and 1993, A. spretulus and A , granarius larvae were 10-fold more abundant on fairways compared with adj acent roughs of 3 Michigan golf courses. In 1994, glass vials were used as pitfall traps to sample adult A. spretulus and A. granarius and surface-dwe lling insects at 2 golf courses, A. spretulus adults were 4-fold more abund ant in the fairway, whereas staphylinids and formicids were 5- to 10-fold m ore abundant in the rough. At 1 location in 1995, and at a different locati on in 1996, pitfall traps were placed along replicated transects running in to the fairway and rough, In total, 112 pitfall traps were changed weekly f rom early May to early July. In 1995, 341 A. granarius, 1,131 A. spretulus, 4,703 Formicidae, 2,693 Carabidae, 2,304 Staphylinidae. and 579 Histeridae were captured in pitfall traps. Approximately 1/3 as many insects were tra pped in 1996. A. spretulus adults were again more abundant in the fairway, whereas the numbers of A.. granarius adults captured in the fairway and rou gh were similar. The numbers of predatory insects captured in pitfall traps declined sharply when crossing from the rough into the fairway. We found a strong inverse relationship (r = -0.62) between the distribution of A. spr etulus adults and predators caught in pitfall traps. and a weaker inverse r elationship between larvae and predators. At all 5 golf course sites, plots in the fairway and rough received a similar level of irrigation, fairways were mon ed at an average height of 13 mm and roughs at 51 mm, more fertili zer was applied to fairways (1.25 kg N/yr) than roughs (0.75 kg N) and no i nsecticides were applied, In 1996, grass species composition was the same i n the fairway and rough Potential causes of a high density of A. spretulus and a low density of surface predators in golf course fairways are discusse d.