DISSIPATION DYNAMICS OF CERTAIN INSECTICIDES IN POLYHOUSE AND OPEN FIELD SITUATIONS IN CHILLI (Capsicum annum L.)
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Date
2014
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
Abstract
The survey on pesticide use pattern was carried out by interviewing farmers
growing chill in open fields and poly houses based on the questionnaire prepared to
assess their knowledge and practices on crop cultivation, general awareness on pesticide
recommendations and use. Studies were undertaken to establish dissipation dynamics of
commonly used insecticides at recommended dose both in open field and poly house
situations to assess the differences in rate of dissipation, and also to recommend Pre-
Harvest Intervals based on MRLs established by CAC and FSSAI. Insecticides viz.,
dimethoate 30% EC @ 300 g a.i. ha-1, λ-cyhalothrin 5% EC @ 15 g a.i. ha-1, phosalone
35% EC @ 450 g a.i. ha-1, flubendiamide 20% WG, profenophos 50%EC @ 500 g a.i.
ha-1 were sprayed and chilli samples collected at regular intervals were analyzed for
residues. Various decontamination methods were evaluated to assess the efficiency of
method for removal of pesticide residues from chilli for food safety.
Education levels of poly house farmers are high compared to open field
farmers, where 57.14% poly house farmers are high school educated, whereas 35%
open field farmers are illiterates. Majority farmers use nursery of 35 days and grow in
<0.5 acre poly house in summer and rabi and <1 acre in open field during kharif.
Awareness on pesticide related issues is varying among poly house and open field
farmers with some commonality, where 28.57% poly house farmers know about
recommended pesticides while only 10% open field farmers are aware of this issue.
However, in general, all farmers contact pesticide dealer for recommendations, poly
house farmers prefer to contact scientists (35.71%) and open field farmers prefer to
contact agricultural officers (33.33). Most farmers are unaware about pesticide
classification and toxicity symbols on packing. Farmers are aware about endosulfan
ban, but only 21.42% poly house and 11.66% open field farmers know about ban of
monocrotofos on vegetables. Very few farmers know about pesticide residues and
related issues, but know washing helps to reduce contamination.
The dissipation pattern of insecticides varied in poly houses and open fields,
where initial deposits were comparatively higher and dissipated slowly in poly houses,
Dimethoate initial deposits (0.19 mg kg-1) are less than FSSAI MRL of 2 mg kg-1, hence
a PHI of 1 day can be recommended. In case of poly house, initial deposit of 2.42 mg
kg-1 was observed and hence a safe waiting period of 7 days can be recommended since
FSSAI MRL is 2 mg kg-1. As no MRLs are available for lambda-cyhalothrin, PHI of 5
can be recommended as residues dissipated to BDL, though the initial residues are 0.16
mg kg-1 and 0.37 mg kg-1 in open fields and poly house, respectively, due to very less
field dose. In case of phosalone, initial deposits of 5.35 mg kg-1 were recorded in poly
house and hence a safe waiting period of 10 days should be recommended since FSSAI
MRL is 1 mg kg-1. Spray of flubendiamide at recommended dose resulted in 1.19 mg
kg-1 initial deposit which dissipated to BDL by 15th day in poly house. However, as the
Codex MRL is 2 mg kg-1, a PHI of 1 day is ideal for food safety. As per the Insecticide
Act, 1969, profenofos is not recommended for use, but when sprayed at farmer’s dose
on chilli, 3.71 mg kg-1 and 2.24 mg kg-1 initial deposits were recorded in poly house and
open field, respectively. Codex suggests MRL as 10 mg kg-1, hence it can be concluded
that profenofos application does not leave residues above MRL. Out of five insecticides
tested in poly house phosalone, flubendiamide and profenophos residues are found in
chillies up to 10 days, while dimethoate and lambda-cyhalothrin are detected up to 7
days. Whereas in open field phosalone and profenophos residues are found up to week
while dimethoate, lambda-cyhalothrin and flubendiamide are detected up to five days.
Among various decontamination methods tested, veggy wash was found to be
very effective in removing pesticide residues to an extent of 60-78% varying with type
of pesticides, and common method i.e. 2% salt solution wash is also effective method
removing residues in the range of 40-65%.
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Keywords
DISSIPATION, DYNAMICS, CERTAIN, INSECTICIDES, POLYHOUSE, OPEN FIELD, SITUATIONS, CHILLI