Pesticide residue studies
Pesticide residue
analysis conducted on mango
Mango is the national fruit of India. Many pests
affect the mango crop. To control these pests, a
number of pesticides are used. Use of pesticides may
lead to their deposit in or on the crop after
harvest or during storage. Pesticide residues also
include any breakdown products of the pesticide.
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For
every pesticide on mango, Maximum Residue Limits (MRLs)
are fixed. MRLs are the levels of pesticides that can be
ingested daily by man without appreciable risk. MRLs are
expressed in terms of mg/kg or ppm. To achieve these
levels, a time gap needs to be maintained between the
last spray and the first harvest. This time gap is known
as the Pre Harvest Interval (PHI) or waiting period.
Post Harvest Interval of pesticides is also calculated
on a crop where treatment is imposed after harvesting
the crop.
In the Pesticide Residue Laboratory at IIHR, supervised
field trials of various pesticides used on mango for
control of pests and diseases have been undertaken.
Results of the persistence study and prescribed MRL
values are taken into account to work out the Pre
Harvest Interval (PHI) for every individual pesticide on
mango. It is necessary to follow this recommendation to
limit the residues within the permissible level
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Pesticide
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Dosage
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MRL (ppm)
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Pre Harvest
Interval (days)
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Acephate
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1.0 g/L
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0.01
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30
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Benomyl
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1.0 g/L
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2.00
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30
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Bifenthrin
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0.5 ml/L
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0.50
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I6
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Carbaryl
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2.0 ml/L
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3.00
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10
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Carbendazim
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1.0 g/L
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2.00
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30
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Cypermethrin
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1.0 ml/L
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0.03
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21
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Difenoconazole
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0.5 ml/L
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0.07
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28
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Deltamethrin
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1.0 ml/L
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0.50
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21
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Dimethoate
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2.0 ml/L
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1.00
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15
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Fenthion
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2.0 ml/L
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2.00
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21
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Fenvalerate
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1.0 ml/L
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1.00
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30
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Imidacloprid
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0.4 ml/L
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1.00
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60
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Iprodione
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2.0 g/L
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10.0
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3
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Lambda
cyhalothrin
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0.5 ml/L
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0.50
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15
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Prochloraz
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1.0 g/L
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2.00
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6
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Quinalphos
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0.5 ml/L
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0.02
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20
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Thiophanate
methyl
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1.0 g/L
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2.00
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30
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Post
harvest treatment of mango fruit with
insecticides/fungicides should be avoided as far as
possible. In case the treatments is carried out, an
insecticide/fungicide should be selected that has a post
harvest waiting period of 1 week or less. |
Post Harvest Interval of pesticides on Mango |
Pesticide
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Dosage
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MRL (ppm)
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Post Harvest
Interval (days)
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Carbendazim
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1.0 g/L
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2.0
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35
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Deltamethrin
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1.0 ml/L
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0.5
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25
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Dimethoate
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1.0 ml/L
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1.0
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10
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Iprodione
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2.0 g/L
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10.0
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5
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Prochloraz
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1.0 g/L
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2.0
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7
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Thiophanate
methyl
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1.0 g/L
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2.0
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35
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Simple process to reduce pesticide residue
deposit on mango |
Major portion of the
non-systemic pesticide sprayed on mango remains on the
fruit skin. Even systemic pesticide residues that are
absorbed by the plant can result in more residue deposit
on the fruit surface. Therefore, some simple processes
can be followed to reduce deposit on mango fruits:
·
Washing with water
·
Washing with dilute solution of common salt
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Washing with dilute soap solution
·
Peeling off the fruit skin.
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Reducing Pesticide Residues on Mango by Washing
Pesticide
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Percent loss of
residues
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Carbendazim
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25-30
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Difenoconazole
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30-50
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Iprodione
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75-80
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Prochloraz
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75-80
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Guideliness to minimize
pesticide residues on mango
·
Always use approved pesticide at recommended doses
·
Apply chemical pesticides at the vegetative growth stage
and botanicals in fruit bearing stages
·
Do not spray the crop when it is ready for harvest
·
Use eco-friendly pesticide effective at lower doses
·
Adopt IPM package of practices
·
Use protective gear while spraying pesticides
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Residue of
azoxystrobin and trifloxystrobin in/on mango from pre-
and post-harvest treatments
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Azoxystrobin (250 SC) pre and post harvest treatments
were given to mango crop at 1.0 and 2.0 mL/L,
respectively. Residues on the mango whole fruits from
pre-harvest treatments were 0.268 and 0.641 mg/kg which
degraded with the half-life of 6.5 and 7.3 days, and
remained up to 30 and 35 days, respectively. The
pre-harvest interval (PHI) was one day for both
treatments (MRL 0.7 mg/kg). Azoxystrobin residues on the
mango whole fruits from post-harvest treatments were
0.423 and 0.926 mg/kg. The residues remained beyond 20
days and the PHI was 1 and day 7 days, for treatments at
1.0 & 2.0 mL/L, respectively. Residue levels in the
fruit pulp were very low from both treatments.
Trifloxystrobin (50 WG) pre and post harvest treatment
was given to mango at the recommended and double doses
of 0.5 and 1.0 mL/L. The residues on the mango whole
fruit from pre-harvest treatments were 0.422 and 0.753
mg/kg from standard and double dose treatments. The
residues remained on the fruits up to 25 and 30 days and
degraded with the halflife of 9.2 and 10.5 days,
respectively. The pre-harvest interval calculated based
on the persistence study and maximum residue limit (MRL)
of 0.5 mg/kg was 1 and 7 days, respectively.
Trifloxystrobin residues from post-harvest treatments
were 0.651 and 0.943 mg/kg, from treatment at 0.5 and
1.0 mL/L. The required post-harvest interval was 6 and
16 days. Traces of residues were detected in the fruit
pulp from post-harvest treatment only.
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Efficacy of paclobutrazol
in mango and its residue analysis
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Paclobutrazol (PBZ) was applied @ 0.25, 0 . 5 0 and
0.75g a.i/m canopy in the collar region of plant during
September in 17- years-old trees of mango var. Arka
Neelachal Kesari. Application of PBZ @ 0.75g a.i was
found effective in advancing flowering by 10- 12 days,
increasing flowering intensity (77.5%), perfect flower
(26.5%) and yield (74.5kg/tree). However TSS was
unaffected with the treatment.
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Under high density plantation (Y shaped trellis; spacing
3 x 4 m) PBZ was applied through three different
methods; collar drench, ring method and dibble method
and among the application method of PBZ @ 0.75 a. i.
through collar drench significantly increased the
flowering intensity (87.6%)
and
yield (14.2 t/ha).
Whereas, KNO3 was found ineffective in manipulating flowering
in mango.
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Residue of PBZ was analyzed in soil, leaf and in panicle
after three months of application. It was observed that
soil application of PBZ @ 1.0 g and 0.50 g had the
residue level 4.976 ppm and 1.403 ppm, respectively,
whereas, leaves and panicles had no residue under
different applications.
·
PBZ residue was analyzed under different application
methods and the highest residue (7.504 ppm) was recorded
when PBZ was applied @ 1.0 g a.i through dibbling method
whereas minimum (1.656 ppm) was recorded in ring
application.
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