RESUMEN
Plant-parasitic nematodes (PPNs) can cause substantial economic yield losses to many agronomic crops in the United States. A regional-scale survey was completed across 20 counties to determine PPNs prevalence in Michigan corn and how factors such as soil type, tillage, irrigation, and cropping systems influence their distribution. Ten different major genera of PPNs were identified in Michigan corn fields: Longidorus (needle), Helicotylenchus (spiral), Pratylenchus (lesion), Meloidogyne (root-knot), Heterodera (cyst), Hoplolaimus (lance), Tylenchorhynchus or Merlinius (stunt), Paratylenchus (pin), Criconemella (ring), and Xiphinema (dagger). No significant differences among different categories of tillage for lesion, stunt, or needle nematode prevalence was detected. Lesion nematodes were most prevalent in muck soil, while stunt nematode prevalence was significantly affected by the soil type. Needle nematodes were least abundant in irrigated soils and in contrast, stunt nematodes were higher in non-irrigated soils. Spiral nematodes were the most common PPNs in Michigan corn in all cropping systems. These findings will be helpful in planning future nematode studies in Michigan and in developing and evaluating corn nematode management strategies.
RESUMEN
The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive agricultural pest in the United States with the potential to become a serious economic threat to Michigan agriculture. As a novel pest in Michigan's agroecosystems, the potential for a biological control program that utilizes existing natural enemies for H. halys is currently unknown. The present study identified potential H. halys egg predators and determined their effectiveness as biological control agents through functional response testing. Four generalist predators were selected based on video surveillance of sentinel egg masses in the field and through preliminary experiments. The predators were Acheta domesticus (L.) (Orthoptera: Gryllidae), Melanoplus femurrubrum (DeGeer) (Orthoptera: Acrididae), Orius insidiosus (Say) (Hemiptera: Anthocoridae), and Conocephalus fasciatus (DeGeer) (Orthoptera: Tettigoniidae), and each was tested against four densities of H. halys eggs: 26, 52, 78, and 104 eggs. A. domesticus was the only predator tested that exhibited a Type II functional response with non-negative estimates of handling time and attack rate, suggesting the potential to be a density-dependent mortality factor when H. halys egg densities are low. The theoretical maximum predation rates for female A. domesticus were 189 eggs (±95), or roughly seven egg masses. For males, the theoretical maximum was 116 eggs (±35), or 4.5 egg masses. The remaining predators tested exhibited a Type I functional response and are unlikely to be a stabilizing force in H. halys population dynamics.