Pesticides phytotoxicity

Agricultural Products. Pesticides are frequendy appHed as emulsiftable concentrates. The active insecticide or herbicide is dissolved in a hydrocarbon solvent which also contains an emulsifier. Hydrocarbon solvent selection is critical for this appHcation. It can seriously impact the efficacy of the formulation. The solvent should have adequate solvency for the pesticide, promote good dispersion when diluted with water, and have a dash point high enough to minimise dammabiUty ha2ards. When used in herbicide formulas, low solvent phytotoxicity is important to avoid crop damage. Hydrocarbon solvents used in post-harvest appHcation require special testing to ensure that polycycHc aromatics are absent. 

Mechanism of action can be an important factor determining selectivity. In the extreme case, one group of organisms has a site of action that is not present in another group. Thus, most of the insecticides that are neurotoxic have very little phytotoxicity indeed, some of them (e.g., the OPs dimethoate, disyston, and demeton-5 -methyl) are good systemic insecticides. Most herbicides that act upon photosynthesis (e.g., triaz-ines and substituted ureas) have very low toxicity to animals (Table 2.7). The resistance of certain strains of insects to insecticides is due to their possessing a mutant form of the site of action, which is insensitive to the pesticide. Examples include certain strains of housefly with knockdown resistance (mutant form of Na+ channel that is insensitive to DDT and pyrethroids) and strains of several species of insects that are resistant to OPs because they have mutant forms of acetylcholinesterase. These... 

As a result, organic fruit growers have to make maximum use of preventative or indirect plant protection measures, some of which were already described in terms of their effect on fruit quality (e.g. lower planting densities, see sections above). However, there remains an increased risk for pests and diseases causing stress, decreased photosynthetic activity and capacity. Also in certain sensitive cultivars, the application of permitted plant protection products (such as lime sulphur) can result in phytotoxic effects or latent stress in trees (Palmer et al, 2002). The decrease in photosynthetic activity by both pest/disease attack and pesticides may, in turn, result in reduced fruit quality. Both long-term latent and short-term acute side effects of organic plant protection products have not yet been sufficiently investigated. 

Harms, H. H., 1992, In-vitro systems for studying phytotoxicity and metabolic fate of pesticides and xenobiotics in plants. Pestic. Sci. 35 277-281. 

The tnicroencapsululion of pesticides (qv) and herbicides active area of development that has produced several commercial products. The function of the microcapsules is to prolong activity while reducing mammalian toxicity, volatilization losses, phytotoxicity. environmental degradation, and movement in the soil. Ideally, encapsulation would also reduce the amount of agrochemical needed. 

As illustrated (Fig. 1), synthesis of related compounds to maximize activity (and incidental balancing of phytotoxicity and potential costs) can involve the preparation of several hundred materials - an expensive proposition. For pesticides generally, only 1/200 compounds survives the initial synthesis and screening stage (10, 11, 12, 13). (There was no exception in the case of RELEASE -related materials). In expanded confirmatory tests, questionable chemicals are constantly discarded because of narrow toxicity/efficacy ratios or performance is too erratic. Synthesis or formulation difficulties often compound this picture. 

Arsenic is a constituent of most plants. As can be phytotoxic and the toxicity of arsenite is greater than that of arsenate (Peterson et al., 1981). It is suggested that As uptake is passive (Streit and Stumm, 1993), and that it is translocated to most parts of the plant, most being found in roots and old leaves. Natural As levels in plants seldom exceed 1 mg kg 1, but the leaf content may be higher if arsenic pesticides have been used. As accumulates in Pseudotsuga mensiesii, up to 2000 — 5000 mg kg-1 have been reported in the plant ash (Hewitt and Smith, 1975). 

In addition to getting sufficient pesticide loading on the seeds or fertilizer granules, there are two other potential problem areas which require extensive investigation phytotoxicity of pesticide on seeds and chemical degradation of pesticide on fertilizer granules. 

Evaluation of natural compounds has been a relatively small part of the herbicide discovery effort of most companies involved in pesticide discovery. In some cases, the company has put significant effort into isolation of phytotoxic compounds from various organisms as part of a bioprospecting effort. This activity has led to several commercial herbicides, including glufosinate, bialaphos, the triketones, and pelargonic acid. 

End-use properties of release on demand, stabilization of compounds, enhanced efficacy, reduced environmental loss, successful combination of incompatible compounds, reduced handling toxicity, reduced phytotoxicity to crops, and universal formulation compositions will continue to improve pesticide use. Controlled release technologies, just... 

SAFETY PROFILE A deadly human poison by ingestion. An experimental poison by ingestion, inhalation, intravenous, intraperitoneal, subcutaneous, and intramuscular routes. Moderately toxic by skin contact. Experimental teratogenic and reproductive effects. Human systemic effects body temperature increase, change in heart rate, coma. A skin irritant. Mutation data reported. Phytotoxic. A pesticide. An explosive. Forms explosive salts with alkalies and ammonia. When heated to decomposition it emits toxic fumes of NOx. See also NITRO COMPOUNDS of AROMATIC HYDROCARBONS. 

Sometimes the use of one pesticide soon after the use of another can cause phytotoxicity. The label of at least one of the products will warn of the potential problem. Likewise, in addition to providing instructions on mixing pesticides, the label will teU which mixtures to avoid (usually because of physical or chemical incompatibility). 

An adjuvant or additive is a chemical added to a pesticide to increase its effectiveness or to reduce its phytotoxicity or drift. Adjuvants are used most extensively in products designed for foliar applications. Most pesticide formulations already contain adjuvants. Several different types of adjuvants are ... 

Adjuvants are added only if recommended on the product label otherwise, you will do so at your own risk. Some labels expressly prohibit the use of adjuvants. Always bear in mind that while increasing the effectiveness of a particular pesticide, you also may be increasing the potential for phytotoxicity and perhaps harm to non-target organisms and the environment. 

Dragicevic V., Simic M., Brankov M. Spasojevic I., Secanski M., Kresovic B. Thermodynamic characterization of early phytotoxic effects of sulfonylurea herbicides to maize lines. Pesticides Phytomedicine 2012 27(3) 231-237. 

Genetically conditioned pest resistance Is Important In efficient and economical production of florlcultural plants. Resistance to Insect and arthropod pests Is usually genetically stable, and can be used to avoid plant problems associated with phytotoxic pesticides and residues. This allows for safe and economical production of plants without additional expense for chemicals and their application. 

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