Methyl parathion microencapsulated

Slow release formulations incorporate nonpersistent compounds, eg, methyl parathion, insect growth regulators, and sex pheromones, in a variety of granular, laminated, microencapsulated, and hoUow-ftber preparations. 

Atmospheric concentrations of methyl parathion following application of the pesticide to tobacco fields were studied by Jackson and Lewis (1978). They found that levels of methyl parathion decreased rapidly following application of either the emulsifiable concentrate or the microencapsulated form. Air concentrations for the emulsifiable concentrate ranged from 7,408 ng/m immediately following application to 13 ng/m 9 days later. The corresponding measurements for the microencapsulated form were 3,783 and 16 ng/m. ... 

Palmer JS. 1978. Toxicologic evaluation of a microencapsulated formulation of methyl parathion applied dermally to cattle. Am J Vet Res 39 429-431. 

Uses Methyl parathion is a contact insecticide and acaricide used for the control of boll weevils and many biting or sucking insect pests of agricultural crops. It kills insects by contact, stomach, and respiratory action. The formulations include dusts, emulsifiable concentrate, ULV liquid, microencapsules, and wet-table powders. 

By virtue of their unique formulation, microencapsulated pesticides have significantly lower dermal and oral toxiclties than the corresponding emulslflable concentrate formulations. Microencapsulated methyl parathion (MMP) was Introduced commercially in 1974 In 1976 and thereafter reports of bee kills allegedly caused by this product were published, primarily In the news media and non-refereed journals. Claims were subsequently made that MMP Is carried back to the hive and Is uniquely hazardous because the size of the microcapsules Is In the range of many pollens. 

Our first objective was to determine whether microencapsulated methyl parathion Is unique In Its property to be carried back to the hive by bees. To that end a mixture of three commonly used insecticides along with MMP was applied to a plot of blooming rape. The agents were azlnphos-methyl (Guthlon), parathion, and carbaryl (Sevin). By using a mixture on a single plot the effects of variation In bee visitation were eliminated and the tendencies to be carried to the hive could be measured by the relative residue levels in the pollen samples. Five applications were made over a period of seventeen days. Pollen samples were collected from hives placed near the field after two, three, four, and five successive applications approximately two days after each application was made. The application rates were doubled for the last two applications. The data are shown In Table I. 

Another area of concern is the residual life of a pesticide once it is brought back to the hive. Microencapsulated methyl parathion was at one time believed to represent a special hazard because of its controlled release feature. Thus methyl parathion from MMP was reported to persist in stored pollen for up to 17 months.( ) Unfortunately, little is known about the persistence of insecticides in honey bee combs etnd the subsequent effects of their residues on the honey bees. Carbaryl has been shown to persist for at least eight months in colonies ( ) euid permethrln for at least seven months.O) Recently, USDA researchers at the University of Wisconsin studied samples from two bee kills that apparently Involved methomyl and MMP applied to sweet com. Samples were collected to determine, among others, whether methomyl persisted in combs. Analysis demonstrated that eight months after the insecticide application, residues of 0.03 ppm of methyl parathion and 0.03 ppm of methomyl ( 5) remained, even though the latter is considered to be a short-residual pesticide. 

In summary, studies conducted by Pennwalt Gorporation, USDA, and university researchers have demonstrated that microencapsulated methyl parathlon does not represent an Increased hazard to bees when compared to conventional formulations of methyl parathion on the contrary, it is found to be less hazardous in controlled... 

See methyl parathion. Virtually all pesticides are toxic to humans to some degree. They vary in biode-gradability. The use of more- toxic types, especially DDT, has been restricted. Microencapsulated con-trolled-release forms are available. 

Microencapsulation. Microencapsulation (qv) has now been commercially practiced for more than 30 years, following the first application of the technology to carbonless copying paper. Pesticide formulations based on microcapsules appeared in 1974 with the product Penncap-M containing the insecticide methyl parathion (4). Since then many microcapsule suspension formulations have been introduced and form the major group of CRF. 

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