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Slow and consistent nutrient release by organic fertilizers can improve plant nutrient balance and defenses, leading to herbivore avoidance of organically managed crops in favor of conventional crops with weaker defenses. We propose that this relative attraction to conventional plants, coupled with the use of genetically modified, insecticidal crops (Bt), has created an unintentional attract-and-kill system. We sought to determine whether Bt and non- Bt corn Zea mays L. plants grown in soil collected from five paired organic and conventional fields differed in attractiveness to European corn borer [ Ostrinia nubilalis (Hübner)] moths, by conducting ovipositional choice and flight tunnel assays. We then examined the mechanisms driving the observed differences in attraction by comparing soil nutrient profiles, soil microbial activity, plant nutrition, and plant volatile profiles. Finally, we assessed whether European corn borer abundance near corn fields differed based on soil management. European corn borer preferred plants grown in conventional soil but did not discriminate between Bt and non- Bt corn. Organic management and more alkaline soil were associated with an increased soil magnesium:potassium ratio, which increased plant magnesium, and were linked to reduced European corn borer oviposition. There was an inconsistent trend for higher European corn borer moth activity near conventional fields. Our results extend the mineral balance hypothesis describing conventional plant preference by showing that it can also improve attraction to plants with genetically inserted toxins. Unintentional attract (to conventional) and (Bt) kill is a plausible scenario for pest declines in response to Bt corn adoption, but this effect may be obscured by variation in other management practices and landscape characteristics. [ABSTRACT FROM AUTHOR]

In this study, the utility of inoculative releases of local strains of Heterorhabditis bacteriophora and Steinernema feltiae isolated from northern New York (NY) State for managing soil-dwelling pests in sod (turfgrass production systems) was evaluated. The objectives of the project were to (a) quantify changes in biocontrol potential during the sod production process and (b) evaluate the potential for the nematodes to suppress populations of soil-dwelling turf pests following harvest and installation at a new site. A field study was conducted on four sod fields in central NY State on soils with varying texture and organic matter content, and a post-harvest sod installation study was performed in the greenhouse on a sandy loam soil. Nematode-induced mortality of Galleria mellonella was increased significantly one month following inoculation but differed between fields with different soil types, likely due to variation in soil organic matter content. In the following year, nematode persistence in sod fields was low, likely driven by moderate to severe drought conditions. In contrast, upon harvest and installation, significant nematode-induced mortality was observed in soil receiving an installation of muck-produced sod. Enhanced nematode-induced mortality was detected in both the greater wax moth and third instar Japanese beetle larvae. This study indicates that inoculation of sod with entomopathogenic nematodes can improve biocontrol potential during sod production and after harvest, however, the utility of this practice is sensitive to soil conditions, and likely most efficacious on coarse-textured soils with high organic matter. [ABSTRACT FROM AUTHOR]

Endophytic fungi are ubiquitous in nature and can play important roles in regulating plant– herbivore interactions. While some aboveground obligate symbionts are considered defensive mutualists of host plants, the importance of root endophytes in plant defense, especially against root-feeding insects, remains unclear. This study aimed to investigate the effects of root fungal endophytes on plant resistance against belowground herbivores and the recovery of host plants from damage. We grew the common grass Festuca arundinacea (tall fescue) semi-aeroponically in the laboratory and inoculated roots with one of five fungal endophytes isolated from field-collected tall fescue or meadow soil. Endophyte-inoculated and uninoculated control plants were subjected to feeding by larvae of the generalist root herbivore Rhizotrogus majalis (European chafer). Herbivory intensity was quantified after eight days, and regrowth of roots and shoots following root herbivory and mechanical shoot damage was measured thereafter for each treatment. Fungal identifications by DNA sequence analysis were conducted after completion of the herbivory experiments and revealed that the five endophytes included the decomposer fungi Trametes versicolor and Mortierella alpina, the entomopathogenic fungi Isaria fumosorosea and Beauveria bassiana, and a potential plant pathogen/entomopathogen Fusarium cf. equiseti. The effects of these root endophytes on plant defense against root-feeding insects were species-specific. While four endophytes had few effects on plant resistance, endophytic B. bassiana significantly reduced herbivore damage to roots. In comparison, plant tolerance to damage was impaired after colonization by all endophyte species except T. versicolor and M. alpina. The contrasting effects of endophytes on plant resistance and plant tolerance suggest that research solely evaluating plant resistance is likely to overestimate the benefits conferred by endophytes without accounting for potential negative effects on plant tolerance. We propose a conceptual framework to include both plant resistance and tolerance as two dimensions of a defensive strategy and show that plant associations with different root endophytes may shift the relative importance of resistance and tolerance for plant defense. [ABSTRACT FROM AUTHOR]