Influence of Turfgrass Parameters on the Abundance of Arthropods in Sod Farms

Sod farms, where turfgrass is commercially produced, have a unique system, in which sod is harvested within 2 yr after planting. Understanding the turfgrass factors that influence the abundance of predators, herbivores, detritivores, and parasitoids that inhabit turfgrass paves the foundation for developing effective pest management programs. However, little is known about those factors in sod farms. The objective of the study was to determine the influence of turfgrass height, density, and thatch thickness on abundance of arthropod taxa in sod farms. The study was conducted at 18 and 10 sod field sites in 2019 and 2020, respectively. Four pitfall traps were deployed at each site. In 2019, each site was sampled in May, June, and July, whereas in 2020, each site was sampled in June and August. In 2019, the numbers of predatory heteropterans were two times greater in bermudagrass (Cynodon dactylon L.) than in zoysiagrass (Zoysia spp.). The numbers of predatory mirids, Spanogonicus albofasciatus (Reuter), and carabids significantly decreased with increases in turfgrass height. In 2020, the abundance of staphylinids increased as the thatch thickness increased. The abundance of Sphenophorus spp. adults were significantly greater in bermudagrass than in zoysiagrass in 2020 and were more abundant in the denser turfgrasses in both years. The predatory arthropods were positively correlated with increased densities of cicadellids, whereas predatory mirids were positively associated with cicadellids, delphacids, and chrysomelids. These results have implications on management of arthropod pests in sod farms as abundance of beneficial arthropods are influenced by turfgrass factors.

Natural Enemy Community Composition and Impact on Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) Eggs in Minnesota Apple Orchards

Halyomorpha halys is an invasive, polyphagous insect that feeds on many major crops, including apple. Statewide monitoring in Minnesota has shown continued increase of H. halys populations and occurrence of this pest in apple orchards. Potential arthropod natural enemies of H. halys and other pests have not been studied in Minnesota apple orchards. The purpose of this study was to characterize the composition of natural enemy communities; compare their abundances, richness and diversities between apple cultivars using different sampling methods; and assess the impact of natural enemies on sentinel eggs of H. halys in Minnesota apple orchards. Sampling occurred during the summers of 2017 and 2018 on Zestar! and Honeycrisp cultivars in four different apple orchards. In vacuum samples, arachnids, neuropterans, and coccinellids had the highest relative abundances. On yellow sticky traps, anthocorids were the most abundant. The total predator abundance differed between the cultivars sampled across years, with more predators found on Zestar! compared with Honeycrisp. No differences were observed in richness or diversity between cultivars with the exception of yellow sticky traps in 2017, which showed a greater diversity of predators in Zestar!. Despite the abundance of natural enemies sampled, sentinel egg masses deployed in the orchards each summer suffered on average <2% predation and no parasitism across years. Knowledge of differences in predator abundance between cultivars could inform management decisions; however, with current management practices, the potential for biological control of H. halys in conventional apple orchards appears low.

Genetic diversity in aspen and its relation to arthropod abundance

The ecological consequences of biodiversity have become a prominent public issue. Little is known on the effect of genetic diversity on ecosystem services. Here, a diversity experiment was established with European and North American aspen (Populus tremula, P. tremuloides) planted in plots representing either a single deme only or combinations of two, four and eight demes. The goals of this study were to explore the complex inter- and intraspecific genetic diversity of aspen and to then relate three measures for diversity (deme diversity, genetic diversity determined as Shannon index or as expected heterozygosity) to arthropod abundance. Microsatellite and AFLP markers were used to analyze the genetic variation patterns within and between the aspen demes and deme mixtures. Large differences were observed regarding the genetic diversity within demes. An analysis of molecular variance revealed that most of the total genetic diversity was found within demes, but the genetic differentiation among demes was also high. The complex patterns of genetic diversity and differentiation resulted in large differences of the genetic variation within plots. The average diversity increased from plots with only one deme to plots with two, four, and eight demes, respectively and separated plots with and without American aspen. To test whether intra- and interspecific diversity impacts on ecosystem services, arthropod abundance was determined. Increasing genetic diversity of aspen was related to increasing abundance of arthropods. However, the relationship was mainly driven by the presence of American aspen suggesting that species identity overrode the effect of intraspecific variation of European aspen.