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Abstract: Plant secondary chemicals can alter herbivores’ susceptibility to pathogens by weakening the host, by affecting exposure through feeding, or by synergizing or deactivating pathogenic microbes in the gut. This study examined how feeding on perennial ryegrass (Lolium perenne) with (E+) or without (E−) its alkaloid-producing fungal endophyte, Neotyphodium lolii, affects susceptibility of a grass-feeding caterpillar to a baculovirus. In separate experiments, black cutworms (Agrotis ipsilon) were reared on E+ or E− grass that had been sprayed with different rates of A. ipsilon multiple nucleopolyhedrovirus (AgipMNPV), or were droplet-fed a single dose of the virus while developing on those grasses. Larvae grew more quickly on E− than on E+ grass, and mortality from virus increased at higher doses, but there was no endophyte×virus interaction in either trial. Despite larger size, larvae that fed ad libitum on virus-sprayed E− grass died more quickly than counterparts feeding on virus-sprayed E+ ryegrass, but such an effect was not seen when the virus was consumed as a single dose. Together, the results suggest that feeding on E+ grass neither compromises nor synergizes infectivity of AgipMNPV in the A. ipsilon midgut. Reduced consumption or avoidance of less-palatable E+ grass could, however, decrease ingestion of virus and rates of subsequent mortality in the field. Net benefits of integrating endophytic grasses and baculoviruses for managing A. ipsilon may depend on the extent to which reduced intake of virus on E+ grass is counterbalanced by slower growth and increased mortality from other natural enemies. [Copyright &y& Elsevier]

The efficacy of biological control agents is affected by numerous cultural conditions. This study was undertaken to determine how the efficacy of Dilophospora alopecuri inoculum was affected by various conditions, including length of fermentation, moisture content, and growth substrate. Dilophospora alopecuri (Fr.) Fr. provides biological control of the organisms (Rathayibacter toxicus and Anguina funesta) responsible for annual ryegrass toxicity. The effectiveness of D. alopecuri inoculum was evaluated under different conditions for establishment in ryegrass. Prolongation of incubation of the inoculum for 3–10 weeks had no significant effect on the inoculum as a biological control agent. The effect of inoculum moisture content was mixed. With wheat as the substrate, air-drying the inoculum had no apparent effect. However, with ryegrass as the substrate, air-drying the inoculum decreased the effectiveness of the inoculum in the field experiment but not in the pot experiment. The substrate itself also had a significant effect. In the pots, application of colonized ryegrass gave a mean of 56.9 infected inflorescences per pot compared to 30.4 for colonized wheat. In the field experiment, 87.5% of plots inoculated with colonized ryegrass had 25 or more infected inflorescences, twice that of plots treated with colonized wheat. [Copyright &y& Elsevier]

• Trichoderma stimulates resistance against to Pyricularia oryzae in Lolium multiflorum. • Coated seeds of L. multiflorum with T. atroviride reduces the severity of P. oryzae. • Silicon is accumulated in the leaves and improves the resistance to blast. • Biochemical and physical defenses are related to the protective action against blast. Ryegrass (Lolium multiflorum L.) is a forage species with a high content of protein and good palatability and digestibility. In winter, it is frequently used in southern Brazil as feed for livestock. The high humidity in this region is propitious for gray leaf spot, a disease caused by Pyricularia oryzae , considered to be the region's main biotic problem. In this study, we aimed to evaluate the effect of three types of management, namely seed coating with Trichoderma atroviride (T), application of silicon in the soil (Si), and combination of both treatments (TSi), to reduce the severity of gray leaf spot. In the first phase, the capacity of 10 native isolates of Trichoderma spp. were evaluated in vitro for direct inhibition of P. oryzae based on tests of dual cultures (DC), antibiosis for volatile (Vol), and non-volatile compounds (Nvol). In vivo trials involved the ability to induce resistance responses, such as quantifying severity (SEV) and number of lesions (NL) per cm2 of leaf area. In the second phase, the efficacy of T, Si, and TSi was tested under greenhouse conditions. The lesion expansion rate (LER), relative efficiency of infection (RIE), SEV and NL were measured (after inoculation with P. oryzae), and in parallel the activities of the enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POX) and phenylalanine ammonia-lyase (PAL) were quantified (at 24, 48, 72, and 96 h). The strain TR10 (identified by polyphasic taxonomy as T. atroviride) showed one of the highest inhibition values in Vol (23%) and DC (35%). Plants from seeds treated with the strain TR10 had the lowest levels of SEV (5.5%) and NL (3), in contrast with the other strains according to analysis of variance. Under greenhouse conditions, significant differences (P < 0.0001) were found for LER, RIE, NL and SEV in T, Si, and TSi concerning TE (control treatment). The defense response of T was related to the activities of CAT, POX, and PAL (mainly), while for Si, other mechanisms, which were not evaluated in this study, might have contributed to disease reduction, and TSi did not show an additive effect. The treatment of seeds with T. atroviride and the application of Si in the soil improved the resistance of L. multiforum against infection by P. oryzae. [ABSTRACT FROM AUTHOR]