John T. Trumble
Other affiliations: University of California
Bio: John T. Trumble is an academic researcher from University of California, Riverside. The author has contributed to research in topics: Population & Bactericera cockerelli. The author has an hindex of 48, co-authored 222 publications receiving 7622 citations. Previous affiliations of John T. Trumble include University of California.
Papers published on a yearly basis
TL;DR: A primary purpose for this review is to integrate the forms of compensation reported in the literature in the context of natural and agricultural habitats.
Abstract: Plant compensation for arthropod damage is a general occurrence of considerable importance in both natural and agricultural systems. In natural systems, plant species that can tolerate or compensate (e.g. recover equivalent yield or fitness) for herbivore feeding have obvious selective advantages that lead to genotype maintenance. Scientists publishing in this area often cite an optimal strategy for enhancing fitness (90, 108). In agricultural crops, reports of plant compensation mostly are concerned with yields rather than fitness (164). However, variation in compensatory response also affects sampling strategies and economic threshold levels [sensu Stern (166)] and provides viable tactic for breeding insect resistance to key arthropod pests into plants. Not surprisingly, the relative importance of the various forms of compensation in agricultural and natural systems is still relatively unknown. Therefore, a primary purpose for this review is to integrate the forms of compensation reported in the literature in the context of natural and agricultural habitats. Several previous reviews and articles have had a significant impact on the development of an understanding of plant compensatory responses. Some provide extensive lists of examples of plant compensation and the pest-yield relationship (4, 164), while others stress the complexity and interrelatedness
TL;DR: It is suggested that competitive displacement has the potential to be a widespread phenomenon, and the frequency of these displacement events may increase, given the ever-increasing degree of anthropogenic changes to the environment.
Abstract: Competitive displacement is the most severe outcome of interspecific competition. For the purposes of this review, we define this type of displacement as the removal of a formerly established species from a habitat as a result of direct or indirect competitive interactions with another species. We reviewed the literature for recent putative cases of competitive displacement among insects and arachnids and assessed the evidence for the role of interspecific competition in these displacements. We found evidence for mechanisms of both exploitation and interference competition operating in these cases of competitive displacement. Many of the cases that we identified involve the operation of more than one competitive mechanism, and many cases were mediated by other noncompetitive factors. Most, but not all, of these displacements occurred between closely related species. In the majority of cases, exotic species displaced native species or previously established exotic species, often in anthropogenically-altered habitats. The cases that we identified have occurred across a broad range of taxa and environments. Therefore we suggest that competitive displacement has the potential to be a widespread phenomenon, and the frequency of these displacement events may increase, given the ever-increasing degree of anthropogenic changes to the environment. A greater awareness of competitive displacement events should lead to more studies documenting the relative importance of key factors and developing hypotheses that explain observed patterns.
TL;DR: For insect conservation purposes, it is critical to begin long-term studies on the effects of enhanced CO 2 levels on insect populations, and many orders containing insect species important for ecosystem conservation, and even those important as agricultural or medical pests have not been examined.
Abstract: In the enriched carbon dioxide atmosphere expected in the next century, many species of herbivo- rous insects will confront less nutritious host plants that will induce both lengthened larval developmental times and greater mortality. The limited data currently available suggest that the effect of increased atmo- spheric CO 2 on herbivory will be not only highly species-specific but also specific to each insect-plant system. Several scenarios can be predicted, however: (1) local extinctions will occur; (2) the endangered species status as well as the pest status of some insect species will change; (3) geographic distributions for some insect spe- cies will shift with host-plant ranges; and (4) changes in the population dynamics of affected insect species will influence their interactions with other insects and plants. For insect conservation purposes, it is critical to begin long-term studies on the effects of enhanced CO 2 levels on insect populations. An analysis of the avail- able literature indicates that many orders containing insect species important for ecosystem conservation, and even those important as agricultural or medical pests, have not been examined. Without a major in- crease in research on this topic, we will be unprepared for the species changes that will occur, we will lose the opportunity to document just how some insects adapt to elevated CO 2 levels, and we will lack the informa- tion necessary for effective conservation efforts.
TL;DR: A new huanglongbing (HLB) species is genetically characterized, and the bacterium is designated “Candidatus Liberibacter psyllaurous,” potentially resulting in “psyllid yellowing.”
Abstract: A new huanglongbing (HLB) "Candidatus Liberibacter" species is genetically characterized, and the bacterium is designated "Candidatus Liberibacter psyllaurous." This bacterium infects the psyllid Bactericera cockerelli and its solanaceous host plants potato and tomato, potentially resulting in "psyllid yellowing." Host plant-dependent HLB transmission and variation in psyllid infection frequencies are found.
TL;DR: Data indicate that for the future expected elevated CO(2) concentrations, plant allocation to defensive compounds will be affected enough to impact plant-herbivore interactions.
Abstract: Plant allocation to defensive compounds in response to growth in elevated atmospheric CO(2) in combination with two levels of nitrogen was examined. The aim was to discover if allocation patterns of transgenic plants containing genes for defensive chemicals which had not evolved in the species would respond as predicted by the Carbon Nutrient Balance (CNB) hypothesis. Cotton plants (Gossypium hirsutum L.) were sown inside 12 environmental chambers. Six of them were maintained at an elevated CO(2) level of 900 micromol mol(-1) and the other six at the current level of approximately 370 micromol mol(-1). Half the plants in each chamber were from a transgenic line producing Bacillus thuringiensis (Bt) toxin and the others were from a near isogenic line without the Bt gene. The allocation to total phenolics, condensed tannins, and gossypol and related terpenoid aldehydes was measured. All the treatments were bioassayed against a non-target insect herbivore found on cotton, Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae). Plants had lower N concentrations and higher C:N ratios when grown in elevated CO(2). Carbon defensive compounds increased in elevated CO(2), low N availability or both. The increase in these compounds in elevated CO(2) and low N, adversely affected growth and survival of S. exigua. The production of the nitrogen-based toxin was affected by an interaction between CO(2) and N; elevated CO(2) decreased N allocation to Bt, but the reduction was largely alleviated by the addition of nitrogen. The CNB hypothesis accurately predicted only some of the results, and may require revision. These data indicate that for the future expected elevated CO(2) concentrations, plant allocation to defensive compounds will be affected enough to impact plant-herbivore interactions.
TL;DR: Researchers are reporting promising results in engineering more-useful toxins and formulations, in creating transgenic plants that express pesticidal activity, and in constructing integrated management strategies to insure that these products are utilized with maximum efficiency and benefit.
Abstract: During the past decade the pesticidal bacterium Bacillus thuringiensis has been the subject of intensive research. These efforts have yielded considerable data about the complex relationships between the structure, mechanism of action, and genetics of the organism’s pesticidal crystal proteins, and a coherent picture of these relationships is beginning to emerge. Other studies have focused on the ecological role of the B. thuringiensis crystal proteins, their performance in agricultural and other natural settings, and the evolution of resistance mechanisms in target pests. Armed with this knowledge base and with the tools of modern biotechnology, researchers are now reporting promising results in engineering more-useful toxins and formulations, in creating transgenic plants that express pesticidal activity, and in constructing integrated management strategies to insure that these products are utilized with maximum efficiency and benefit.
TL;DR: In the context of agricultural pest management, botanical insecticides are best suited for use in organic food production in industrialized countries but can play a much greater role in the production and postharvest protection of food in developing countries.
Abstract: Botanical insecticides have long been touted as attractive alternatives to synthetic chemical insecticides for pest management because botanicals reputedly pose little threat to the environment or to human health. The body of scientific literature documenting bioactivity of plant derivatives to arthropod pests continues to expand, yet only a handful of botanicals are currently used in agriculture in the industrialized world, and there are few prospects for commercial development of new botanical products. Pyrethrum and neem are well established commercially, pesticides based on plant essential oils have recently entered the marketplace, and the use of rotenone appears to be waning. A number of plant substances have been considered for use as insect antifeedants or repellents, but apart from some natural mosquito repellents, little commercial success has ensued for plant substances that modify arthropod behavior. Several factors appear to limit the success of botanicals, most notably regulatory barriers and the availability of competing products (newer synthetics, fermentation products, microbials) that are cost-effective and relatively safe compared with their predecessors. In the context of agricultural pest management, botanical insecticides are best suited for use in organic food production in industrialized countries but can play a much greater role in the production and postharvest protection of food in developing countries.
TL;DR: It is concluded that host plant quality affects the fecundity of herbivorous insects at both the individual and the population scale.
Abstract: Host plant quality is a key determinant of the fecundity of herbivorous insects. Components of host plant quality (such as carbon, nitrogen, and defensive metabolites) directly affect potential and achieved herbivore fecundity. The responses of insect herbivores to changes in host plant quality vary within and between feeding guilds. Host plant quality also affects insect reproductive strategies: Egg size and quality, the allocation of resources to eggs, and the choice of oviposition sites may all be influenced by plant quality, as may egg or embryo resorption on poor-quality hosts. Many insect herbivores change the quality of their host plants, affecting both inter- and intraspecific interactions. Higher-trophic level interactions, such as the performance of predators and parasitoids, may also be affected by host plant quality. We conclude that host plant quality affects the fecundity of herbivorous insects at both the individual and the population scale.
01 Jan 1998
TL;DR: The mechanisms underlying plant resistance to invading herbivores on the one side, and insect food specialization on the other, are the main subjects of this book.
Abstract: Half of all insect species are dependent on living plant tissues, consuming about 10% of plant annual production in natural habitats and an even greater percentage in agricultural systems, despite sophisticated control measures. Plants are generally remarkably well-protected against insect attack, with the result that most insects are highly specialized feeders. The mechanisms underlying plant resistance to invading herbivores on the one side, and insect food specialization on the other, are the main subjects of this book. For insects these include food-plant selection and the complex sensory processes involved, with their implications for learning and nutritional physiology, as well as the endocrinological spects of life cycle synchronization with host plant phenology. In the case of plants exposed to insect herbivores, they include the activation of defence systems in order to minimize damage, as well as the emission of chemical signals that may attract natural enemies of the invading herbivores and maybe exploited by neighbouring plants that mount defences as well.
TL;DR: In this paper, the most important potential impacts of climate change on forest goods and services are summarized for the Boreal, Temperate Oceanic, TOC, Mediterranean, and mountainous regions.