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PubMed2002

Biological substitutes for pesticides.

In the 20th century an increasing number of pesticides, based on biocidal molecules, were the means for a substantial increase in food and fibre production and quality. Because of health and environmental concerns continued extensive use of such molecules is intensively debated and substitutes are often urgently required. Beside crop plant resistance, various biological control methods based on natural pest suppressing organisms are regarded as main alternatives. Several approaches and concepts also have been tested and commercial organism-based preparations are steadily increasing. However, further biotechnological efforts are required to give them status of being practical substitutes to pesticides. At present they are not comparable to pesticides in meeting efficacy, market and other expectations, but they still have a promising future, especially where genetically modified organisms can be used.

Agriculture↗
PubMed1999

Toxicity of Bacillus thuringiensis beta-exotoxin to three species of fruit flies (Diptera: Tephritidae).

The current study describes toxic effects of the Bacillus thuringiensis beta-exotoxin toward 3rd instars of 3 fruit fly species: Anastrepha ludens (Loew), A. obliqua (Macquart), and A. serpentina (Wiedemann). The beta-exotoxin was highly toxic to all 3 species tested, with LC50 values calculated as 0.641, 0.512, and 0.408 microgram/cm2 of filter paper used to expose the larvae, for A. ludens, A. obliqua, and A. serpentina, respectively. Exposure to beta-exotoxin was associated with an increase in the incidence of deformed pupae. The adult survivors from beta-exotoxin treatments showed no negative effects in terms of their longevity, fecundity, or egg eclosion (fertility). We conclude that the beta-exotoxin may have potential as a control agent for fruit fly pests.

Adenosine↗
PubMed2006

Additive effects of vertebrate predators on insects in a Puerto Rican coffee plantation.

A variety of studies have established the value of shaded coffee plantations as habitat for birds. While the value of birds as biological controls in coffee has received some attention, the interactions between birds and other predators of insects have not been tested. We used exclosures to examine the effects of vertebrate predators on the arthropods associated with coffee, in particular the coffee leafminer (Leucoptera coffeella) and the flatid planthopper Petrusa epilepsis, in a shaded coffee plantation in Puerto Rico. We used a 2 x 2 factorial design with four treatments: exclusion of birds, lizards, birds and lizards, and control (no exclusion). Abundance of insects > 5 mm increased when birds or both birds and lizards were removed. Birds and lizards had an additive effect for insects < 5 mm and for all insects combined. Coffee leafminers showed a weak response to removal of predators while planthopper abundance increased significantly in the absence of avian predators. Arthropod predators and parasitoids did not differ significantly between treatments. Our findings suggest that vertebrate insectivores have an additive effect on insects in coffee and may help control abundances of some coffee pests. Equally important, we present evidence suggesting that they do not interfere with other known natural enemies of coffee pests.

Animals↗
PubMed2001

Control of Musca domestica third instar larvae by the latex of Calotropis procera (Family: Asclepiadaceae).

Calotropis procera (Family: Asclepiadaceae) is known to contain alkaloids, steroids and resinous substance. Different concentrations of its latex were topically applied to the 3rd stage larvae of Musca domestica. A dose of 3 ul (5% of the latex) killed and partially digested the larvae in three hours. The effect of this latex is most probably enzymatic in nature. No doubt, the shift to plant extracts in controlling insect-vectors or pests in general, pave the way to a health environment.

Animals↗
PubMed2006

[Standard operating procedure for Astragalus membranaceus].

In order to ensure the superior quality and safety of the raw materials of the Chinese herbal medicine, a standard operating procedure for astragalus was established on the base of the GAP of the Chinese herbal medicine as well as practice investigation and experiments. This standard operating procedure provides the technical requirements for astragalus's growing, field management, controlling of the diseases and pests, harvesting, processing, packing, storing, transporting and quality monitoring.

Astragalus propinquus↗
PubMed1990

Abamectin as a pesticide for agricultural use.

The avermectins are a family of macrocyclic lactones, produced by the soil organism Streptomyces avermitilis, which were discovered in the mid-1970's as a direct result of a screening effort for natural products with anthelmintic properties. Avermectin B1 (abamectin), the major component of the fermentation, also showed potent activity against arthropods in preliminary laboratory evaluations and was subsequently selected for development to control phytophagous mites and insect pests on a variety of agricultural and horticultural crops worldwide. Major applications for which abamectin is currently registered include uses on ornamental plants, citrus, cotton, pears and vegetable crops at rates in the range of 5 to 27 grams abamectin per hectare as a foliar spray. Abamectin has shown low toxicity to non-target beneficial arthropods which has accelerated its acceptance into Integrated Pest Management (IPM) programs. Extensive studies have been conducted to support the safety of agricultural uses of abamectin to man and the environment. Abamectin is highly unstable to light and has been shown to photodegrade rapidly on plant and soil surfaces and in water following agricultural applications. Abamectin was also found to be degraded readily by soil microorganisms. Abamectin residues in or on crops are very low, typically less than 0.025 ppm, resulting in minimal exposure to man from harvesting or consumption of treated crops. In addition, abamectin does not persist or accumulate in the environment. Its instability as well as its low water solubility and tight binding to soil, limit abamectin's bioavailability in non-target organisms and, furthermore, prevent it from leaching into groundwater or entering the aquatic environment.

Agriculture↗
PubMed1998

Myths, models and mitigation of resistance to pesticides.

Resistance to pesticides in arthropod pests is a significant economic, ecological and public health problem. Although extensive research has been conducted on diverse aspects of pesticide resistance and we have learned a great deal during the past 50 years, to some degree the discussion about 'resistance management' has been based on 'myths'. One myth involves the belief that we can manage resistance. I will maintain that we can only attempt to mitigate resistance because resistance is a natural evolutionary response to environmental stresses. As such, resistance will remain an ongoing dilemma in pest management and we can only delay the onset of resistance to pesticides. 'Resistance management' models and tactics have been much discussed but have been tested and deployed in practical pest management programmes with only limited success. Yet the myth persists that better models will provide a 'solution' to the problem. The reality is that success in using mitigation models is limited because these models are applied to inappropriate situations in which the critical genetic, ecological, biological or logistic assumptions cannot be met. It is difficult to predict in advance which model is appropriate to a particular situation; if the model assumptions cannot be met, applying the model sometimes can increase the rate of resistance development rather than slow it down. Are there any solutions? I believe we already have one. Unfortunately, it is not a simple or easy one to deploy. It involves employing effective agronomic practices to develop and maintain a healthy crop, monitoring pest densities, evaluating economic injury levels so that pesticides are applied only when necessary, deploying and conserving biological control agents, using host-plant resistance, cultural controls of the pest, biorational pest controls, and genetic control methods. As a part of a truly multi-tactic strategy, it is crucial to evaluate the effect of pesticides on natural enemies in order to preserve them in the cropping system. Sometimes, pesticide-resistant natural enemies are effective components of this resistance mitigation programme. Another name for this resistance mitigation model is integrated pest management (IPM). This complex model was outlined in some detail nearly 40 years ago by V. M. Stern and colleagues. To deploy the IPM resistance mitigation model, we must admit that pest management and resistance mitigation programmes are not sustainable if based on a single-tactic strategy. Delaying resistance, whether to traditional pesticides or to transgenic plants containing toxin genes from Bacillus thuringiensis, will require that we develop multi-tactic pest management programmes that incorporate all appropriate pest management approaches. Because pesticides are limited resources, and their loss can result in significant social and economic costs, they should be reserved for situations where they are truly needed--as tools to subdue an unexpected pest population outbreak. Effective multi-tactic IPM programmes delay resistance (= mitigation) because the number and rates of pesticide applications will be reduced.

Animals↗
PubMed2002

Novaluron (Rimon), a novel IGR--mechanism, selectivity and importance in IPM programs.

Novaluron (Rimon), a new IGR, acts by both ingestion and contact. It is a powerful toxicant for controlling lepidopteran larvae resulting in LC-90 values of 0.42 and 0.30 mg a.i./liter for Spodoptera littoralis and S. exigua, respectively. Its residual activity under field conditions ranges between 10 and 30 days depending on environmental conditions. The compound is a powerful toxicant against developing stages of whiteflies, resulting in LC-90 values of 0.68 and 8.56 mg a.i./liter for Bemisia tabaci and Trialeurodes vaporariorum, respectively. It has translaminar activity, enabling the control of the leaf miner Liriomyza huidobrensis at concentrations ranging between 5 and 45 mg a.i./liter. Novaluron has no cross-resistance with other leading compounds for controlling whiteflies such as buprofezin and pyriproxyfen. It is a rain fast compound suitable in the tropics and in rainy seasons. It has no appreciable effect on parasitoids and phytoseiids and a mild effect on other natural enemies and may be considered a potential component in IPM programs. The compound is in the process of commercialization worldwide by Makhteshim Chemical Works for controlling agricultural pests.

Animals↗
PubMed2003

A ratio-dependent food chain model and its applications to biological control.

While biological controls have been successfully and frequently implemented by nature and human, plausible mathematical models are yet to be found to explain the often observed deterministic extinctions of both pest and control agent in such processes. In this paper we study a three trophic level food chain model with ratio-dependent Michaelis-Menten type functional responses. We shall show that this model is rich in boundary dynamics and is capable of generating such extinction dynamics. Two trophic level Michaelis-Menten type ratio-dependent predator-prey system was globally and systematically analyzed in details recently. A distinct and realistic feature of ratio-dependence is its capability of producing the extinction of prey species, and hence the collapse of the system. Another distinctive feature of this model is that its dynamical outcomes may depend on initial populations levels. Theses features, if preserved in a three trophic food chain model, make it appealing for modelling certain biological control processes (where prey is a plant species, middle predator as a pest, and top predator as a biological control agent) where the simultaneous extinctions of pest and control agent is the hallmark of their successes and are usually dependent on the amount of control agent. Our results indicate that this extinction dynamics and sensitivity to initial population levels are not only preserved, but also enriched in the three trophic level food chain model. Specifically, we provide partial answers to questions such as: under what scenarios a potential biological control may be successful, and when it may fail. We also study the questions such as what conditions ensure the coexistence of all the three species in the forms of a stable steady state and limit cycle, respectively. A multiple attractor scenario is found.

Animals↗
PubMed2004

Microbial control of diamondback moth, Plutella xylostella L. (Lepidoptera: Yponomeutidae) using bacteria (Xenorhabdus nematophila) and its metabolites from the entomopathogenic nematode Steinernema carpocapsae.

Cells and cell-free solutions of the culture filtrate of the bacterial symbiont, Xenorhabdus nematophila taken from the entomopathogenic nematode Steinernema carpocapsae in aqueous broth suspensions were lethal to larvae of the diamondback moth Plutella xylostella. Their application on leaves of Chinese cabbage indicated that the cells can penetrate into the insects in the absence of the nematode vector. Cell-free solutions containing metabolites were also proved as effective as bacterial cells suspension. The application of aqueous suspensions of cells of X. nematophila or solutions containing its toxic metabolites to the leaves represents a possible new strategy for controlling insect pests on foliage.

Animals↗
PubMed1983

The Florey lecture, 1983. Biological control, as exemplified by smallpox eradication and myxomatosis.

Biological control is an important method of dealing with plant and insect pests. The control of rabbits by myxomatosis and the eradication of smallpox by vaccination are unusual examples of biological control, in that they involve a vertebrate and a viral pest respectively. Myxomatosis is a benign disease in Sylvilagus rabbits in South America which is transmitted mechanically by mosquitoes. In the European rabbit, Oryctolagus, which is a pest in Australia and England, the virus from Sylvilagus produces a generalized disease that is almost always lethal. Myxomatosis was deliberately introduced into Australia in 1950 and into Europe in 1952. It was at first spectacularly successful in controlling the rabbit pest, but biological adjustments occurred in the virulence of the virus and the genetic resistances of rabbits. After 30 years of interaction, natural selection has resulted in a balance at a fairly high level of viral virulence. Smallpox has been a major scourge of mankind for over 1500 years. It spread from Asia to Europe in the Middle ages and from Europe to Africa and the Americas in the 15th and 16th centuries. Jenner's cowpox vaccine provided a method of control that reduced the severity of the disease during the 19th century but failed to eliminate the disease from many countries before the 1930s. Thereafter it was eradicated from Europe and North America, but remained endemic in South America, Africa and Asia. In 1967 it was still endemic in 33 countries and W.H.O. established a programme for global eradication within 10 years. The goal was achieved in 1977. Problems of the eradication programme and reasons for its success will be described.

Animals↗
PubMed2005

Role of host plant alternation in the precocity and intensity of parasitoid activity on of cereal aphids.

Integrated pest management programs tend to reduce the chemical input by enhancing the development of biological control. Cereal aphids cause important damages to winter wheat in Europe but are currently under the pressure of several parasitoid species (Braconidae: Aphidiinae). Previous ecological studies have reported the existence of an asynchrony between aphid and parasitoid populations in early spring in cereal cultures. Here, we tested the presence of rose bushes (Rosa rugosa) as a host plant for alternative aphid-host. Aphid and parasitoid densities were recorded for two years using the plant cutting sampling method. The main results were: (i) rose bushes constitute a potential reservoir of alternative aphid hosts species for a number of parasitoid and predator species, (ii) rose aphids appear earlier in spring and were more abundant than the aphids on wheat, (iii) parasitism activity in rose bushes is synchronized with cereal fields, however (iv) rose bushes management did not induce a decrease of cereal aphid population.

Animals↗
PubMed1976

Entomopathogens: ecological manipulation of natural associations.

The control of insect pests with entomopathogens is unique, in that naturally occurring host-pathogen relations are manipulated to the benefit of man: protecting agricultural crops and forests or controlling insect vectors of disease. The isolation and identification of a virulent pathogen is the initial step in the development of a potential control agent. Production of the pathogen in adequate quantities must be possible either in vivo (insects) or in vitro (artificial medium). To insure usefulness, the pathogen must remain viable in the formulated form and after application in the field. Since inactivation rather than persistence is a problem, the pathogens must be formulated, protected, and applied to insure satisfactory pest control action. Studying the natural host--pathogen interactions will be necessary in order to manipulate the pathogen effectively, by introducing it at the most opportune time in the life cycle of the target pest. Generally, insect pathogens are more selective than conventional pesticides; this will limit their use and industrial development. Development, at least in part, by the public sector may be necessary and desirable. The most promising areas for the use of pathogens are in integrated pest management and in situations where pests have developed resistance to chemical control.

Animals↗
PubMed2004

Rearing of the cucurbit fly Dacus cilratus Loew (Dip: Tephritidae) on artificial diet under laboratory conditions.

Cucurbit fly is an important pest of cucurbit plants (Cucumber, melon and watermelon) in most mid-east countries including, Iran. This insect causes a high damage so that several sprayings are required to control the pest. Using male strile is another physical method for controlling this pest. For this purpose it is necessary to rear many male insects. Therefore an investigation was carried out to compare different artificial diets for rearing the melon fly. First, pupae were collected from cucurbit field and transferred to laboratory. In this experiment five diet formulations were compared and the following was used for rearing: Wheat bran (14 g), soybean lees (3 g) sugar (50 g), yeast extract (2.7 g) nipagin (0.1 g). sodiumbenzoate (0.1 g) Hydrochloric acid 3.5% (4.0 ml) and distilled water 70.5 mil. For rearing the adult, the best diets contained: Brower yeast (1 part), Honey (5 parts), water (94 parts) and a slice of cucumber. These diet caused abundance of oviposition and egg fertility.

Animal Feed↗
PubMed2003

Effect of the combined treatment of insecticides and an attractant for the control of Phloeotribus scarabaeoides, a pest of Olea europea.

Different insecticides have been tested for the control of the olive bark beetle, Phloeotribus scarabaeoides Bern. This scolytid can be managed at two points in its biological cycle: in pruned logs, where it excavates reproduction galleries, or in living trees, after emergence from the logs, where it digs feeding galleries. In mortality laboratory bioassays, the efficiency of organophosphorus insecticides has been ranked as follows: chlorpyrifos + dimethoate < formothion < methidathion. Formothion and methidathion, the two most efficient, were sprayed on olive logs together with a pyrethroid insecticide, deltamethrin, and a formulation which combined an organophosphorus (fenitrothion) and a pyrethroid (cypermethrin) insecticide. Deltamethrin inhibited the excavation of new reproduction galleries and induced a repellent effect on the olive pest. In contrast, none of the organophosphorus insecticides or the combination, fenitrothion + cypermethrin, were able to control the olive bark beetle. In olive trees, deltamethrin controlled this olive pest without showing the repellent effect observed for logs. Ethylene, a plant hormone, has been reported as an attractant for the olive bark beetle. The use of dispensers which released ethylene increased the number of P. scarabaeoides approaching the treated olive trees, thus favouring its use in a lure-and-trap control system.

Animals↗
PubMed1999

[Bacillus thuringiensis: a biotechnology model].

This paper is on the different biotechnological approaches that have been used to improve Bacillus thuringiensis (Bt) for the control of agricultural insect pests and have contributed to the successful use of this biological control agent; it describes how a better knowledge of the high diversity of Bt strains and toxins genes together with the development of efficient host-vector systems has made it possible to overcome a number of the problems associated with Bt based insect control measures. First we present an overview of the biology of Bt and of the mode of action of its insecticidal toxins. We then describe some of the progress that has been made in furthering our knowledge of the genetics of Bt and of its insecticidal toxin genes and in the understanding of their regulation. The paper then deals with the use of recombinant DNA technology to develop new Bt strains for more effective pest control or to introduce the genes encoding partial-endotoxins directly into plants to produce insect-resistant trangenic plants. Several examples describing how biotechnology has been used to increase the production of insecticidal proteins in Bt or their persistence in the field by protecting them against UV degradation are presented and discussed. Finally, based on our knowledge of the mechanism of transposition of the Bt transposon Tn4430, we describe the construction of a new generation of recombinant strains of Bt, from which antibiotic resistance genes and other non-Bt DNA sequences were selectively eliminated, using a new generation of site-specific recombination vectors. In the future, continuing improvement of first generation products and research into new sources of resistance is essential to ensure the long-term control of insect pests. Chimeric toxins could also be produced so as to increase toxin activity or direct resistance towards a particular type of insect. The search for new insecticidal toxins, in Bt or other microorganisms, may also provide new weapons for the fight against insect damage.

Agriculture↗