Impact of No-till Cover Cropping of Italian Ryegrass on Above and Below Ground Faunal Communities Inhabiting a Soybean Field with Emphasis on Soybean Cyst Nematodes.

Two field trials were conducted between 2008 and 2010 in Maryland to evaluate the ability of an Italian ryegrass (IR) (Lolium multiflorum) cover crop to reduce populations of plant-parasitic nematodes while enhancing beneficial nematodes, soil mites and arthropods in the foliage of a no-till soybean (Glycine max) planting. Preplant treatments were: 1) previous year soybean stubble (SBS); and 2) herbicide-killed IR cover crop + previous year soybean stubble (referred to as IR). Heterodera glycines population densities were very low and no significant difference in population densities of H. glycines or Pratylenchus spp. were observed between IR and SBS. Planting of IR increased abundance of bacterivorous nematodes in 2009. A reverse trend was observed in 2010 where SBS had higher abundance of bacterivorous nematodes and nematode richness at the end of the cover cropping period. Italian ryegrass also did not affect insect pests on soybean foliage. However, greater populations of spiders were found on soybean foliage in IR treatments during both field trials. Potential causes of these findings are discussed.

Phylogeny of parasitiform mites (Acari) based on rRNA.

Acari (mites and ticks) form one the most diverse lineages of arthropods, but basal relationships in the group are still poorly understood. The current study addresses this issue for one of its two main lineages, the order Parasitiformes. Relationships are examined at the subordinal and infraordinal level using complete 18S and partial 28S nuclear rRNA sequence data. Most currently recognized lineages are recovered with good support, suggesting that nuclear rRNA, and specifically 18S rRNA, is very well suited for analyzing relationships at this level in this lineage. These results were found despite quite variable rates of sequence evolution, with rates "ratcheting up" from relatively low in most non-mite arachnid lineages, to intermediate in Pseudoscorpiones, the mite order Acariformes, and the parasitiform suborders Opilioacarida, Holothyrida, and Ixodida, to high in the parasitiform suborder Mesostigmata. The most species rich mesostigmatid infraorder, Dermanyssina, shows huge distances to the outgroups, but remarkably low within-group divergence in nuclear rRNA. This suggests the possibility of a relatively recent origin of this lineage.