Alkylphosphines as pesticidal agents

Details Alkylphosphines as pesticidal agents Alkylphosphines as pesticidal agents

1998-05-19

2000-08-01

Levy, Neil S.

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Biocides; animal or insect repellents or attractants

424 45, 424406, 514134, 514135, A01N 2500, A01N 5718

Patent

active

060963301

DESCRIPTION:

BRIEF SUMMARY
This application was filed under 35 U.S.C. .sctn.371 and is based on international application number PCT/GB96/02876, citing priority of Great Britain applications numbers 9523832.5 and 9614164.3.
The present invention relates to methods and compositions having a pesticidal effect. The invention further relates to methods of preparation and use of pesticidal agents and compositions.
There is an ongoing requirement for materials having pesticidal activity e.g. for use in post-harvest protection of foodstuffs, the sterilisation of soil, or in insect-mediated disease control. In particular, novel materials are required to overcome the problem of resistance to existing agents.
Phosphine gas (PH.sub.3) has been extensively used for the past four decades to control insect pests of food-grains and other stored commodities. PH.sub.3 fumigation does not leave toxic residues in the food, and the availability of solid phosphide formulations that generate the gas in situ have made PH3 a Fumigant of choice throughout the world. In fact, with the recent restrictions on production of the other alternative, methyl bromide (CH.sub.6 Br), due to possible deleterious effects on the environment, PH.sub.3 is becoming the only fumigant available for disinfecting stored food commodities. The future availability of PH.sub.3 as a fumigant is especially important for developing countries where grain storage is mainly in bags and the technology for the application of non-gaseous grain protectants is not available.
The emergence of PH.sub.3 resistance in several species of stored-product insects in the past two decades has however threatened the use of this fumigant. PH.sub.3 resistance has now been reported from many countries and is linked to poor fumigation practices leading to selection of resistant insect strains. It is particularly alarming that in some instances resistance has reached a level where it can lead to control failures even when the best current fumigation practices are applied.
In view of the importance of PH.sub.3 in post-harvest management of grains and other commodities, its mode of action, and the mechanism of resistance to PH.sub.3 in insects, have been the subject or a number of studies.
Regarding mode of action, the metabolism of PH.sub.3 in insects has been suggested to be oxidative, ultimately resulting in essentially non-toxic oxyacids of phosphorus mainly hypophosphite, phosphite and orthophosphate. The process possibly involves formation of unstable intermediate phosphine oxide [H.sub.3 P(O)] and leads to the disruption of normal O.sub.2 -metabolism. and generation of highly deleterious oxyradicals in insects (see e.g. Chaudhry & Price (1992) Pestic Biochem Physiol 42: 167-179).
Regarding resistant insects, the use of 32P-radiolabelled PH.sub.3 revealed that resistant insects absorb very small amounts of the gas compared to their susceptible counterparts. The resistant strains of several species of stored-product insects, some collected from different countries, were found to exhibit the same phenomenon (see e.g. Chaudhry & Price (1989) Comp Biochem Physiol 94C(2): 425-429; Chaudhry & Price (1990) J stored Prod Res 26(2): 101-107) indicating a common mechanism of PH.sub.3 -resistance in insects. The amount of PH.sub.3 absorbed by some live resistant insects was even lower than that passively absorbed by dead insects and an active exclusion of PH.sub.3 in resistant insects was proposed (Price (1984) J stored Prod Res 20(3): 163-168). This phenomenon was also confirmed by pulse-chase studies where a higher respiratory exclusion of the gas was found in the resistant insects than in the susceptible ones (Chaudhry & Price, 1992, supra). Other studies have indicated that the reduced uptake of PH.sub.3 was not the only underlying mechanism of resistance and the involvement of an additional detoxification process was established (Chaudhry & Price, 1990, supra). This was supported by conventional genetic studies that at least two genes were linked to PH.sub.3 -resistance in insects (Ansell et al, Proc 5th Workin

REFERENCES:
patent: 3054718 (1962-09-01), Gordon et al.
Chaudry et al, 1996, Phytoparasitica, 24:216.
Crosbie et al, 1969, J. Inorg Nucl Chem, 31:3684-5.
Rajendran, 1990, Pesticide Science, 29:75-83.
Roland et al, 1986, Chem Ber, 119:2566-81.

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