Methomyl
PESTICIDE NAME: Methomyl
______________
Trade name(s): Lannate, Nudrin
_____________
Manufacturer(s): E.I.duPont de Nemours & Co., Inc.
_______________
DuPont Building
Wilmington, DE. 19898
Shell Chemical Co.
A Division of Shell Oil
P.O. Box 3871
Houston, TX. 77001
I. Basic information
_________________
A. Molecular structure: C5H10N2O2S
___________________
B. Chemical name: S-methyl-N((methylcarbamoyl)oxy)thioacetimidate
_____________
C. Derivatives: S-methyl N-hydroxythioacetimidate (product of
___________
hydrolysis)
D. Molecular weight: 162.2 g/mole
________________
E. Solubility in water: 58 g/l (58,000 mg/l)
__________________
F. Common physical appearance: white crystalline solid
_________________________
G. Oral LD50(rat): 17-24 mg/kg
______________
H. Pesticide classification: carbamate insecticide
_______________________
I. Restricted use list (N.Y.): yes
__________________________
EPA priority pesticide list: no
___________________________
J. Crop use: alfalfa, corn, apple, pear, peach, grape, beans,
________
celery, cabbage, cauliflower, broccoli, Brussels sprouts, cucurbits,
lettuce, endive, escarole, onion, peppers, potato, spinach, sweet corn,
tomato
II. Text
____
Methomyl is a water soluble carbamate insecticide which is rapidly
degraded by microbes. It is used on a variety of fruit and vegetable
crops in New York, is not subject to leaching and has a half-life in
soil of approximately 6 weeks. Methomyl is not widely treated in the
literature; however, there is information available concerning
degradation and transport.
III. Soils information
_________________
A. Degradation and transformation
______________________________
Methomyl is rapidly degraded by microbes with the by-product CO2
and S-methyl N-hydroxythioacetimidate as a hydrolysis by-product(4).
The degradation of methomyl has been reported under a variety of
conditions. The percent reduction of methomyl on diatomaceous earth
3wks after initial application was 18.4%(1). On fine sandy loam with
an initial application rate of 6ppm methomyl, there was a 5% loss in
the first 3d and 58% and 38% loss on replicate treatments in 42d. In
this same study an azide-treated soil showed 3-5% loss at 21d (less
than the non-treated soil above), and for both of these soils a 7-14d
lag time appeared. The half-life of methomyl was calculated to be
_5-6wks. A third experiment by these researchers showed no lag time;
at 3d the loss rate was constant and at 21d that rate was similar to
those found previously. The authors concluded that the half-life in
soil seems to be shortened in soils recently treated with methomyl(2).
The tables below present data concerning methomyl degradation in
soils. The reference is given in parentheses at the end of each title.
Percent methomyl residue in three soils, silt loam (pH4.7), silt loam
(pH7.9), and San Joaquin Valley, Calif. (pH7.9) at three different
treatment levels(4)
% methomyl remaining
__________________________________
LAB STUDY SiL(4.7) SiL(7.9) Calif(7.9)
____________________________________________________________
(4 lb/a) (4.3 lb/a) (5.5 lb/a)
________ __________ __________
methomyl 48% 44% 31%
by-product 1 2 1
polar fraction 1 1 1
CO2 39 31 45
unextracted resid. 14 18 12
**********************************************************************
Percent residue in field study on 3 soils in Delaware, Florida and
North Carolina(4)
FIELD STUDY
_________________________________________________________
DELAWARE FLA. N.C.
_________________________________________________________
Top Layer 1 mo.(%) 3mo.(%) 12mo.(%) 3mo.(%) 5mo(%)
_________ _________________________________________________________
volatility 70.7 80.7 85.0 90.3 84.8
methomyl 1.8 0.3 0 <0.005 <0.005
by-product 0.2 0.1 0 <0.005 <0.005
polar frac. 0.9 0.7 0.3 0.2 0.04
unextr.resid. 26.4 18.2 14.7 9.5 15.2
***********************************************************************
B. Adsorption and transport
________________________
Methomyl is generally considered to be non-leaching and available
for uptake and transformation. The approximate Kd is estimated to
equal 2 with the assumption that adsorption is described by a linear
isotherm and, therefore, equal to 1. Equilibrium between 10g of soil
and 190ml perfusing solution is reached in 28d(2). One study reported
methomyl to not be carried in the run-off water and none was found
below 8in(2). In fine sandy loam (replicate treatments) researchers
reported constant leaching of methomyl from columns at the end of the
experiment, but methomyl was continually leached to some degree
throughout the experiment. The percent methomyl leached was 7 and 8%,
methomyl retained by the columns in 3wks was 58 and 50% and the
methomyl lost from the columns through transformation and
volatilization was 34 and 43%. From this it was shown that half the
applied methomyl was retained in the column(3).
The table below presents data concerning leaching of methomyl with
time. The reference is given at the end of the title.
Percent methomyl remaining in field experiments in Delaware, Florida
and North Carolina(4)
FIELD STUDY
___________
% methomyl remaining
_________________________________________________________
DELAWARE FLA. N.C.
_________________________ _______ ______
Depth 1 mo.(%) 3mo.(%) 12mo.(%) 3mo.(%) 5mo(%)
_______________________________________________________________________
0-3 28.1 18.9 14.4 8.9 11.1
3-4.5 0.9 0.3 0.4
3-7 0.7 3.8
4.5-6 0.2 0.1 0.1
6-8 0.1 0 0.1
7-11 0.1 0.1
8-10 0 0 0
10-12.5 0 0 0
11-15 0 0.2
12.5-15 0 0 0
**********************************************************************
IV. References (*denotes key reference)
__________
1.El-Attal, Z.M., O.K. Moustafa, N.M. Ahmed. Bull. Ent. Soc.,
________________
Egypt. 1975. No. 9. 105-110.
_______
*2.Fung, K.K.H. and Uren, N.C. 1977. J. Agric. Food Chem. 25(4).
____________________
966-69.
3.Fung, K.H. and G.P. Briner. 1977. Tobacco Science. 21. 120-1.
_______________
*4.Harvey, J., H.L. Pease. 1973. J. Agr. Food Chem.21 (5).784-6.
_________________
Disclaimer: Please read
the pesticide label prior to use. The information contained at this web
site is not a substitute for a pesticide label. Trade names used herein
are for convenience only; no endorsement of products is intended, nor is
criticism of unnamed products implied. Most of this information is historical
in nature and may no longer be applicable.
To Top
For more information relative to pesticides and their use in New York State, please contact the PMEP staff at:
| |
5123 Comstock Hall
Cornell University
Ithaca, NY 14853-0901
(607) 255-1866
|
|
 |
This site is supported, in part, by funding from the
 |
Questions regarding the development of this web site should be directed to the
PMEP Webmaster
