Endophytes are microorganisms that live within plant tissues without causing symptoms of disease. They are important components of plant microbiomes. Endophytes interact with, and overlap in function with, other core microbial groups that colonize plant tissues, e.g., mycorrhizal fungi, pathogens, epiphytes, and saprotrophs. Some fungal endophytes affect plant growth and plant responses to pathogens, herbivores, and environmental change; others produce useful or interesting secondary metabolites. Here, we focus on new techniques and approaches that can provide an integrative understanding of the role of fungal endophytes in the plant microbiome. Clavicipitaceous endophytes of grasses are not considered because they have unique properties distinct from other endophytes. Hidden from view and often overlooked, endophytes are emerging as their diversity, importance for plant growth and survival, and interactions with other organisms are revealed.

Hidden Fungi, Emergent Properties: Endophytes and Microbiomes

Pesticides are used to kill the pests and insects which attack on crops and harm them. Different kinds of pesticides have been used for crop protection for centuries. Pesticides benefit the crops; however, they also impose a serious negative impact on the environment. Excessive use of pesticides may lead to the destruction of biodiversity. Many birds, aquatic organisms and animals are under the threat of harmful pesticides for their survival. Pesticides are a concern for sustainability of environment and global stability. This chapter intends to discuss about pesticides, their types, usefulness and the environmental concerns related to them. Pollution as a result to overuse of pesticides and the long term impact of pesticides on the environment are also discussed in the chapter. Moving towards the end, the chapter discusses the methods to eradicate the use of pesticides and finally it looks forward towards the future impacts of the pesticide use the future of the world after eradicating pesticides.

Effects of Pesticides on Environment

Plant-microbe interactions are ubiquitous. Plants are often colonized by pathogens but even more commonly engaged in neutral or mutualistic interactions with microbes: below-ground microbial plant associates are mycorrhizal fungi, Rhizobia and rhizosphere bacteria, above-ground plant parts are colonized by bacterial and fungal endophytes and by microbes in the phyllosphere. We emphasize here that a completely microbe-free plant is an exotic exception rather than the biologically relevant rule. The complex interplay of such microbial communities with the host plant affects plant nutrition, growth rate, resistance to biotic and abiotic stress, and plant survival and distribution. The mechanisms involved reach from nutrient acquisition, the production of plant hormones or direct antibiosis to effects on host resistance genes or interactions at higher trophic levels. Plant-associated microbes are heterotrophic and cause costs to their host plant, whereas the benefits depend on the environment. Thus, the outcome of the interaction is highly context-dependent. Considering the microbe-free plant as the ‘normal’ or control stage significantly impairs research into important phenomena such as (1) phenotypic and epigenetic plasticity, (2) the ‘normal’ ecological outcome of a given interaction and (3) the evolution of plants. For the future, we suggest cultivation-independent screening methods using direct PCR from plant tissue of more than one fungal and bacterial gene to collect data on the true microbial diversity in wild plants. The patterns found could be correlated to host species and environmental conditions, in order to formulate testable hypotheses on the biological roles of plant endophytes in nature. Experimental approaches should compare different host-endophyte combinations under various environmental conditions and study at the genetic, transcriptional and physiological level the parameters that shift the interaction along the mutualism-parasitism continuum.

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The Microbe-Free Plant: Fact or Artifact?

The avermectins, milbemycins and spinosyns are collectively referred to as macrocyclic lactones (MLs) which comprise several classes of chemicals derived from cultures of soil micro-organisms. These compounds are extensively and increasingly used in veterinary medicine and agriculture. Due to their potential effects on non-target organisms, large amounts of information on their impact in the environment has been compiled in recent years, mainly caused by legal requirements related to their marketing authorization or registration. The main objective of this paper is to critically review the present knowledge about the acute and chronic ecotoxicological effects of MLs on organisms, mainly invertebrates, in the terrestrial and aquatic environment. Detailed information is presented on the mode-of-action as well as the ecotoxicity of the most important compounds representing the three groups of MLs. This information, based on more than 360 references, is mainly provided in nine tables, presenting the effects of abamectin, ivermectin, eprinomectin, doramectin, emamectin, moxidectin, and spinosad on individual species of terrestrial and aquatic invertebrates as well as plants and algae. Since dung dwelling organisms are particularly important non-targets, as they are exposed via dung from treated animals over their whole life-cycle, the information on the effects of MLs on dung communities is compiled in an additional table. The results of this review clearly demonstrate that regarding environmental impacts many macrocyclic lactones are substances of high concern particularly with larval instars of invertebrates. Recent studies have also shown that susceptibility varies with life cycle stage and impacts can be mitigated by using MLs when these stages are not present. However information on the environmental impact of the MLs is scattered across a wide range of specialised scientific journals with research focusing mainly on ivermectin and to a lesser extent on abamectin doramectin and moxidectin. By comparison, information on compounds such as eprinomectin, emamectin and selamectin is still relatively scarce.

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A Review on the Toxicity and Non-Target Effects of Macrocyclic Lactones in Terrestrial and Aquatic Environments

Can we use entomopathogenic fungi as endophytes for dual biological control of insect pests and plant pathogens

Colonization of crop plants by fungal entomopathogens and their effects on two insect pests when in planta

Tandem use of selective insecticides and natural enemies for effective, reduced-risk pest management

A new invert emulsion formulation of entomopathogenic fungi was developed using non-toxic ingredients readily available in Australia and tested for compatibility with two Australian strains of Beauveria bassiana (Bals.). Laboratory bioassays were conducted to determine the efficacy of these fungi when applied in an invert emulsion formulation against yellow mealworm larvae, Tenebrio molitor L. The entomopathogenic fungi consistently caused higher mortality of T. molitor larvae when the invert emulsion was used compared with aqueous conidia suspensions. When B. bassiana strain BG1 was applied as an invert emulsion using different concentrations, the LC50 (measured as conidia mL) was > 600x lower than the LC50 of aqueous suspension of the conidia. The invert emulsion formulation tested improved the consistency and efficacy of the fungal strains tested against T. molitor under controlled conditions and has the potential to increase their efficacy when used on a commercial scale.

Investigations into the formulation and efficacy of entomopathogenic fungi against larvae of yellow mealworm (Tenebrio molitor L., Coleoptera: Tenebrionidae).

The elephant weevil Orthorhinus cylindrirostris (F.) (Coleoptera: Curculionidae) is endemic to Australia and has colonized several exotic crops including citrus, blueberries, and grapevines. We compared the life history of this pest on two native and two exotic host plants: hickory wattle Acacia falcata Willdenow, rough-barked apple Angophora floribunda (Smith) Sweet, lemon Citrus limon (L.) Burman, and blueberry Vaccinium corymbosum (L.). Blueberry was attacked more often (22 of the 24 plants) than lemon, rough-barked apple, and hickory wattle (6-8 plants of each species attacked of the 24). Adult emergence followed a similar pattern across hosts but emergence was low overall (58 adults from 176 eggs). Only blueberry had more than one weevil emerge from a single plant. Development from oviposition to adult emergence can take up to 2 yr, particularly on blueberry. Adult life span and weight varied between individuals although no effect of host plant was detected. Similar plant chemistry is unlikely to have triggered host range expansion by this species because the exotic host plants are from different families (Rutaceae, Vitaceae, and Ericaceae) to the native host plants (Myrtaceae, Mimosaceae, and Fabaceae). O. cylindrirostris colonized citrus trees over a century ago, yet it appears to have no preference for lemon over native host plants. In contrast, O. cylindrirostris has developed a preference for blueberry, the higher quality host plant, only a few decades after colonization.

Adoption of exotic plants by an endemic Australian weevil, Orthorhinus cylindrirostris (Coleoptera: Curculionidae).

The accumulated damage from elephant weevil larvae, Orthorhinus cylindrirostris (F.) (Coleoptera: Curculionidae), reduces blueberry yield and shortens the productive lifespan of blueberry plants by several years. Selective breeding to develop pest-resistant blueberry cultivars is a possible control option, but the relationship between O. cylindrirostris populations, plant damage, and blueberry yield has not been described. A field survey of 17 blueberry cultivars was conducted on a commercial farm to measure O. cylindrirostris populations (emergence holes and adult numbers) and yield from plants of different ages (2-12 yr). Blueberry plants accumulated damage over time, that is, older plants tended to have more O. cylindrirostris emergence holes than younger plants. All cultivars received some level of O. cylindrirostris attack but this did not always lead to yield losses. Newer cultivars that have been in production since 2000 were less susceptible to O. cylindrirostris than older cultivars. Removal of highly susceptible cultivars from commercial blueberry farms may reduce O. cylindrirostris populations. There is potential for selective breeding to increase plant resistance to O. cylindrirostris if the specific resistance mechanisms can be identified in blueberry.

Gregory Murdoch

Papers

Colonization of crop plants by fungal entomopathogens and their effects on two insect pests when in planta

Tandem use of selective insecticides and natural enemies for effective, reduced-risk pest management

Investigations into the formulation and efficacy of entomopathogenic fungi against larvae of yellow mealworm (Tenebrio molitor L., Coleoptera: Tenebrionidae).

Adoption of exotic plants by an endemic Australian weevil, Orthorhinus cylindrirostris (Coleoptera: Curculionidae).

Blueberry Cultivars Differ in Susceptibility to the Elephant Weevil, Orthorhinus cylindrirostris (Coleoptera: Curculionidae).