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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.

 
       

 

 

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

Pesticide

Dosage

MRL (ppm)

Pre Harvest Interval (days)

Acephate

1.0 g/L

0.01

30

Benomyl

1.0 g/L

2.00

30

Bifenthrin

0.5 ml/L

0.50

I6

Carbaryl

2.0 ml/L

3.00

10

Carbendazim

1.0 g/L

2.00

30

Cypermethrin

1.0 ml/L

0.03

21

Difenoconazole

0.5 ml/L

0.07

28

Deltamethrin

1.0 ml/L

0.50

21

Dimethoate

2.0 ml/L

1.00

15

Fenthion

2.0 ml/L

2.00

21

Fenvalerate

1.0 ml/L

1.00

30

Imidacloprid

0.4 ml/L

1.00

60

Iprodione

2.0 g/L

10.0

3

Lambda cyhalothrin

0.5 ml/L

0.50

15

Prochloraz

1.0 g/L

2.00

6

Quinalphos

0.5 ml/L

0.02

20

Thiophanate methyl

1.0 g/L

2.00

30

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

Dosage

MRL (ppm)

Post Harvest Interval (days)

Carbendazim

1.0 g/L

2.0

35

Deltamethrin

1.0 ml/L

0.5

25

Dimethoate

1.0 ml/L

1.0

10

Iprodione

2.0 g/L

10.0

5

Prochloraz

1.0 g/L

2.0

7

Thiophanate methyl

1.0 g/L

2.0

35

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

         Washing with dilute soap solution

         Peeling off the fruit skin.

Reducing Pesticide Residues on Mango by Washing

 

Pesticide

Percent loss of residues

Carbendazim

25-30

Difenoconazole

30-50

Iprodione

75-80

Prochloraz

75-80

 

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

 

Residue of azoxystrobin and trifloxystrobin in/on mango from pre- and post-harvest treatments

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.

 

Efficacy of paclobutrazol in mango and its residue analysis

      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.

       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.

        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.