AGRICULTURAL CONTROL CHEMICALS

DDT and Parathion Spray Residues on Apples W. E. WESTLAKE and JACK E. FAHEY

Downloaded by AUBURN UNIV on December 26, 2017 | http://pubs.acs.org Publication Date: January 1, 1950 | doi: 10.1021/ba-1950-0001.ch024

Bureau of Entomology and Plant Quarantine, U. S. Department of Agriculture, Beltsville, Md.

The tests reported were conducted in 1948 on apples growing in the Yakima Valley in the Pacific Northwest and in the Mississippi Valley, to determine the magnitude of parathion and DDT spray residues at harvest. The climates and spray schedules differ markedly in the two areas; consequently, spray residues also differ, and are larger in the Mississippi Valley than in the Yakima Valley.

T h e use of insecticides on the edible parts of plants presents the problem of removal or avoidance of excessive toxic residues on the harvested crops. This paper shows the magnitude of residues that may result from the application of sprays containing parathion and D D T insecticides. I n 1948 tests were made on apples growing i n the Y a k i m a Valley i n the Pacific N o r t h west and i n the Mississippi Valley. The climates of these two areas differ strikingly. The Mississippi Valley is characterized b y moderately heavy precipitation during the growing season, the average rainfall being 3.5 to 4.3 inches per month. The Y a k i m a Valley, on the other hand, is very arid, the average precipitation being less than 1 inch per month during the summer, and is completely dependent upon irrigation for orchard growth. Spray schedules also differ i n the two areas. I n the Mississippi Valley the orchards are sprayed more often, and the interval between the last spray and harvest is shorter, than i n the Y a k i m a Valley. Spray residues at harvest may be expected to differ also.

Methods Spray schedules applied on experimental plots at the Y a k i m a . Wash., and Vincennes, Ind., laboratories of the United States Bureau of Entomology and Plant Quarantine were studied to determine the magnitude of parathion and D D T spray residues at harvest. The parathion sprays were prepared from 2 5 % wettable powder and the D D T sprays from 5 0 % wettable powder, except i n one series of tests, when a 2 5 % D D T wettable powder was used. A l l spray treatments were planned and made by members of the Division of F r u i t Insect Investigations. Conventional hydraulic sprayers were used in this work. The studies in the Y a k i m a Valley were made on two varieties of apples and those i n the Mississippi Valley on five varieties. Duplicate samples of 1500 and 2000 grams of fruit were employed for each analysis at Vincennes and samples of 1000 to 1500 grams at Yakima. Parathion analyses were made by the method of Averell and Norris (1). D D T residues were determined at Vincennes b y the total-chlorine method of Wichman et al. (4), and at Y a k i m a by the colorimetric method of Stiff and Castillo (5), as modified by the Food and D r u g Administration (#). 117

AGRICULTURAL CONTROL CHEMICALS Advances in Chemistry; American Chemical Society: Washington, DC, 1950.

118

ADVANCES IN CHEMISTRY SERIES

Parathion Residues Table I shows the parathion residues on Delicious and Winesap apples i n the Y a k i m a \ alley immediately after the last spray application and at intervals until harvest. P a r a thion was used at two concentrations, both as close as possible to the minimum necessary to give the desired control. Consequently, the residues found were comparatively low and dropped to 0.1 p.p.m. or less i n approximately 2 weeks. r

Table I.

Plot No.


7

Parathion Residues on Delicious and Winesap Apples, Yakima Valley

Treatment (Active Ingredient in 100 Gal.) DDT, Parathion, ounces lb. 1 1 25 1 25 1 25

10

12

G

Parathion Found, P . P . M . Delicious Apples July 29 Aug. 16 Oct. 11 0.90

0.09

ι

0.40

0.05

Aug. 5

Winesap Apples Aug. 11 Aug. 17

Oct. 18

0.07

0.5

1 25

11

No f' Sprays

1.10

0.36

10

0.90

0.24

03

0.05

ι

0 6 0 6 0 6

0.5

0 è

0.5

1 25 1 25

0.5

0.03

0.30

0.04

On Delicious apples the initial residues were 0.9 and 0.4 p.p.m. i n plots 7 and 10, respectively, both of which were sprayed with 1.25 ounces of parathion. T h e difference between the two plots was consistent throughout the individual trees sampled. T h e spray mixture used on plot 7 also contained D D T , while that used on plot 10 contained only parathion. These plots showed the same relative magnitude of residues 18 days after spraying, and at harvest, 74 days after the spraying. Plot 11, sprayed with 0.6 ounce of parathion, showed an initial residue of 0.3 p.p.m. Initial residues on the Winesap apples were somewhat higher than those on Delicious. Six days later approximately one third of the residue had been lost, and 12 days after the spraying the deposits were down to 0.10 and 0.03 p.p.m. for the respective strengths. A t harvest little more than a trace of parathion was found on the fruit. Table I I shows the parathion residues on Golden Delicious apples i n the Mississippi Valley immediately after the final spray application and after 25 and 38 days of weathering. Five plots received six parathion sprays and a sixth plot received parathion i n only the last two sprays. Table II.

Parathion Residues on Golden Delicious Apples, Mississippi Valley (Six sprays on all plots; final spray Aug. 5)

No. 27 30 25 28 24 21

Treatment (Active Ingredient in 100 Gal.) D D T , ounces Parathion, ounces 1 2 4 4 8

8 4 8

(2 sprays) (4 sprays)

12

Aug. 5 1.09 3.49 3.04 3.40 6.14 3.20

Parathion Found, P . P . M . Sept. 13 Aug. 30 0.19 0.24 0.37 0.36 0.88 0.42

0.10 0.15 0.20 0.15 0.42 0.25

12

W i t h the exception of plot 30, the residues after the final spraying show a good correlation with the amount of parathion applied. T h e loss of residue was very rapid, however. The results i n plot 21, which received parathion only i n the last two sprays, as AGRICULTURAL CONTROL CHEMICALS Advances in Chemistry; American Chemical Society: Washington, DC, 1950.

119

WESTLAKE AND FAHEY—DDT AND PARATHION SPRAY RESIDUES ON APPLES


compared with those i n plots 25 and 28, which received the same amount of parathion i n all six sprays, show that the first four parathion sprays had little effect on the residue at harvest. Table I I I shows the parathion residues on Jonathan and Starking Delicious apples from seven spray plots i n the Mississippi Valley. Identical treatments were used on both varieties. The Starking variety showed a slightly lower parathion residue than the Jonathan. The difference was not great, however. I n general, the residue after the final spraying was proportional to the concentration of parathion i n the spray mixture. The exception is plot 4, sprayed with 2 ounces of parathion with nicotine-bentonite-oil, which shows a residue approximately equal to that obtained on plots sprayed with 4 ounces of parathion, alone or i n combination with D D T (plots 11 and 12). The residue 2 weeks after spraying was only one quarter to one third of that found immediately after spraying, and 46 days after spraying only one plot (No. 14 sprayed with 8 ounces of parathion) showed a residue significantly i n excess of 0.1 p.p.m. Table III.

Parathion Residues on Jonathan and Starking Delicious Apples, Mississippi Valley (Six sprays, except where otherwise indicated)

(Active iigredient in 100 Gal.) Parathion, ounces D D T , lb. e

No. 9 11 12

15

14 4 13

1 1 4 0.5 4 0.5 (Sprays 3 and 6) (In sprays 1, 2, 4, 5) ι 1.5 (In sprays 1, 2, 4) 1 (In spray 6) 4 (In sprays 4 and 6) (Sprays 3 and 5 ο nitted) 8 2 (With nicotine-bentonite-oil) 2 12 (In sprays 1 to 4)

Parathion Found, P . P . M . Jonathan Apples Starking Delicious Apples Sept. 14 July 30 Aug. 13 Aug. 13 Sept. 14 July 30 0.53 1.41 1.23

0.12 0.41 0.33

0.03 0.11 0.09

0.32 1.22 0.99

0.07 0.24 0.23

0.03 0.07 0.04

1.65

0.39

0.11

1.22

0.20

0.07

3.80 0.99

1.06 0.23

0.28 0.02

3.39 1.08

0.73 0.20

0.20 0.03

0.10

0.00

0.00

0.12

0.01

0.00

(In sprays 5 and 6)ι α

Final parathion spray on July 28 except plot 13, which received final spray on June 16.

Plots 12 and 13 afford a comparison of the harvest residues from first- and secondbrood sprays. O n plot 13, which was sprayed on M a y 11 and 20 and June 3 and 16, the parathion residue was only 0.1 p.p.m. on July 30 and none i n subsequent samplings. On plot 12, which received two sprays on J u l y 7 and 28, the residue on Jonathan apples was 1.23 p.p.m. on July 30 and 0.09 on September 14. Table I V gives the data from seven plots of Winesap and Rome Beauty apples i n the Mississippi Valley. The spray schedules are similar to those used for the plots included in Table I I I , except that an additional parathion spray was applied on plots 9, 11, 14, and 4 on August 19, and the final harvest sample was taken on October 5. Only on the plot that was sprayed seven times with the 8-ounce strength of parathion (plot 14) d i d the spray residue at harvest approximate 0.1 p.p.m. The data presented indicate that parathion spray residues weather very rapidly on apples. Sprays applied to the fruit prior to J u l y 1 would not be expected to leave more than a trace of parathion on the fruit at harvest. The harvest residues vary i n magni tude according to the concentration of parathion i n the spray mixture. Adhesives such as nicotine-bentonite-oil, although increasing the initial residue of a given spray mixture, do not show an appreciable effect on the final harvest residue. When the concentration of parathion is not greater than 4 ounces in 100 gallons of spray, and the final spraying is done not less than 40 days before harvest, the parathion residue at harvest, under the conditions of the experiments, does not exceed 0.1 p.p.m. AGRICULTURAL CONTROL CHEMICALS Advances in Chemistry; American Chemical Society: Washington, DC, 1950.

120


Table IV.

Parathion Residues on Rome Beauty and Winesap Apples, Mississippi Valley (Seven sprays, except where otherwise indicated)

Treatment (Active Ingredient in 100 Gal.) Parathion, ounces D D T , lb.

Plot No.


9 1 12

Date of Final Parathion Spray

1. 1 8 4 0.5 (In sprays 3 and 6) 1 (In sprays 1, 2, 4, 5, 7) 15 .. 1.5 (In sprays 1, 2, 4) 1 (In spray 6) 4 (In sprays 4 and 6, sprays 3, 5, 7 omitted) 14 8 4 2 (With nicotine-bentonite-oil) 13 2 0.75 (In sprays 1 to 4) 1 (In sprays 5, 6, 7) 1

4

Parathion Found, P . P . M . Winesap Apples Rome Beauty Apples July 30 Aug. 20 Oct. 5 July 30 Aug. 20 Oct. 5

Aug. 19 Aug. 19 July 28

1.16

0.45 0.28 0.14

0.01 0.01 0.01

1.28

0.72 0.46 0.16

0.02 0.04 0.03

July 29

1.55

0.14

0.04

1.83

0.27

0.06

0.49 1.13

0.09 0.05

1.03 1.39

0.12 0.05

0.00

0.00

0.01

0.00

Aug. 19 Aug. 19 June 16

0.10

0.12

DDT Residues Table V shows the D D T spray residues at harvest on Delicious and Winesap apples in the Y a k i m a Valley. M o s t of the Delicious plots received two sprays containing D D T , the last one 97 days before harvest. The Winesap plots received four sprays containing D D T , the last spray 74 days before harvest. The harvest residues i n the Winesap plots were significantly higher than those i n the Delicious plots, but were less than one half the proposed tolerance of 7 p.p.m. of D D T . Table V.

DDT Residues on Delicious and Winesap Apples, Yakima Valley (One to three sprays)

Plot No. 4 7

10 11

12

Treatment (Active Ingredient m 100 Ual.) Parathion, ounces D D T , lb. Γ.25 1.25 1.25

1 1 0.5

i

0.5 1.25 1 (1 lb. benzene hexachloride technical + 2 quarts oil) 0.6 1 0.6 0.5 0.6 1.25

o'.è

i' '

0.5 1 (1 lb. benzene hexachloride + 2 quarts oil) 1.25 0.5 1.25

No. of Sprays 2 1 1 1 1 3 1 2 1 1 1 1 3 1 1 1

Date of Last D D T Spray

D D T Found, P . P . M . Winesap apples, Delicious apples, Oct. 11 Oct. 18

July 7

1.0

July 7

1.0 2.7

Aug. 5 June 16

1.4

July 7

1.5 3.3

Aug. 5

July 7

1.7

Table V I shows the D D T residues at harvest on plots i n a Golden Delicious orchard i n the Mississippi Valley. A l l plots received six sprays containing D D T . The harvest residue i n plot 1, i n which a 5 0 % D D T wettable powder was used, was only slightly less than where the same amount of D D T i n a 2 5 % wettable powder was applied i n plot 2. Reduction of the concentration of actual D D T i n the spray mixture (plots 3 and 4) resulted i n lower residues at harvest. Table V I I shows the residues of D D T at harvest i n the Mississippi Valley on Jonathan and Starking Delicious apples on which a six-spray schedule was used. A l l plots except plot 8 were sprayed six times with D D T at 8 ounces to 1 pound per 100 gallons. Plot 8 received only four sprays, three containing 1.5 pounds and one containing 1 pound AGRICULTURAL CONTROL CHEMICALS Advances in Chemistry; American Chemical Society: Washington, DC, 1950.

121

WESTLAKE AND FAHEY—DDT AND PARATHION SPRAY RESIDUES ON APPLES

Table VI.

DDT Residues on Golden Delicious Apples, Mississippi Valley (Six sprays on all plots; final spray Aug. 5; analyses Sept. 13) Treatment (Active Ingredient in 100 Gal.) & Parathion, ounces D D T , ounces

Plot No. a

1

D D T Found, P.P.M.

.. 12 (No adhesive or spreader used on 1 plot) .. 12 8 (No adhesive or spreader) 2 4

2 3 4

7.9 8.8 7.1 3.7

Plots 1 and 3 represent averages of 3 plots each. 6 50% wettable powder used in plot 1 and 25% wettable powder in other plots.


β

of D D T . I n plots 2 and 3, adhesives were included i n all sprays, and harvest residues approximated 10 p.p.m. of D D T even though only 8 ounces of D D T were used. I n a l l other plots the harvest residues were less than 7 p.p.m. of D D T except i n plots 7 and 8, i n which they were 7.8 and 7.3 p.p.m., respectively, on the Starking apples. I n general, the harvest residues were proportional to the amount of D D T applied i n the last cover spray.

Table VII.

DDT Residues on Jonathan and Starking Delicious Apples, Mississippi Valley (Six sprays on all plots; final spray on July 28)

Plot No.

Treatment (Active Ingredient in 100 Gal.) Parathion, ounces D D T , ounces 8 (With lead arsenate-Bordeaux-oil or nicotinebentonite-oil) 8 (With nicotine-bentonite-oil) 1 (Av. of 5 plots, no adhesive or spreader) 4 8 1 (In sprays 1, 2, 4, 5) 4 8 (In s prays 3 and 6) 2 12 (In sprays 1 to 4) 1 (In sprays 5 and 6) 1.5 (In sprays 1, 2, 4) 4 (In spray 6, sprays 3 and 5 omitted)

D D T Found, P . P . M . Starking Delicious Jonathan apples, apples, Aug. 31 Sept. 2 10.2 7.8 10.0

10.3 6.4

6.8

3.7 4.3

4.7 5.6

5.6

7.8

6.5

7.3

Table VIII. DDT Residues on Rome Beauty and Winesap Apples, Mississippi Valley (Seven sprays on all plots; final spray on Aug. 19; analyzed on Oct. 5) Plot No. 2 3 4 5 6

7

8

Treatment (Active Ingredient in 100 Gal.) Parathion, ounces D D T , ounces 8 lead arsenate-Bordeaux-oil or nicotine-bentonite-oil) 8 (With nicotine-bentonite-oil) 16 (Av. of 5 plots, no adhesive or spreader) 4 8 16 (In sprays 1 2, 4, 5, 7) 4 8 (In sprays 3 and 6) 2 12 (In sprays 1 to 4) 16 (In sprays 5, 6, 7) 24 (In sprays 1, 2, 4) 4 16 (In spray 6, sprays 3. 5. 7 omitted)

(With

D D T Found, P . P . M . Winesap Rome Beauty apples apples 9.1

11.8

12.1

11.1

9.5

10.4

6.7 8.6

6.9 9.8

11.3

11.2

5.1

6.8


122


Table V I I I shows the residues of D D T at harvest on Rome Beauty and Winesap apples i n the Mississippi Valley. The plot treatments are the same as for Jonathan and Starking Delicious apples (Table V I I ) except that a seven-spray schedule was used. T h e residues at harvest shown i n Table V I I I are greater than those i n Table V I I . A com parison shows that when six cover sprays of D D T are applied without adhesives the harvest residues are approximately 7 p.p.m. or slightly more. If, however, seven cover sprays are applied, the residues may exceed 9 p.p.m. of D D T , unless the concentration is reduced to less than 1 pound of D D T i n 100 gallons.


Summary I n 1948 spray schedules used experimentally i n the Y a k i m a Valley i n the Pacific Northwest and i n the Mississippi Valley were studied to determine the magnitude of the parathion spray residues during the interval between the last spray and harvest. D D T residues were also studied and results of analyses made at harvest are reported. The spray schedules studied i n the Y a k i m a Valley included at least three sprays containing not more than 1.25 ounces of parathion in 100 gallons. Harvest residues were less than 0.1 p.p.m. of parathion. I n the Mississippi Valley the studies included sprays containing as much as 8 ounces of parathion i n 100 gallons. When 4 ounces or less of parathion were used, and no spray was applied less than 40 days before harvest, parathion residues were generally less than 0.2 p.p.m. Increasing the concentration of parathion i n the spray mixture or decreasing the time interval between the last spray and harvest sometimes resulted i n heavier residues. Spray schedules using 1 pound or less of D D T i n 100 gallons i n one to four sprays were studied i n the Y a k i m a Valley. D D T residues were well below the proposed toler ance of 7 p.p.m. i n all treatments studied. A four-spray schedule with 74 days between the last spray and harvest resulted i n a residue of only 3.3 p.p.m. of D D T at harvest. Spray schedules with as much as 1.5 pounds of D D T i n 100 gallons were studied i n the Mississippi Valley. The number of sprays containing D D T was as high as seven, six being applied i n most of the treatments. A six-spray schedule i n which 1 pound of D D T was used, without any adhesive, resulted i n harvest residues approximating or slightly i n excess of 7 p.p.m. of D D T . When seven sprays were u s e d * D D T residues i n some treatments were considerably i n excess of 7 p.p.m. The use of adhesives, such as nicotine-bentonite-oil or lead arsenate-Bordeaux-oil, increased the D D T residues at harvest.

Literature Cited (1) (2) (3) (4)

Averell, P. R., and Norris, M . V., Anal. Chem., 20, 753 (1948). Food and Drug Administration, unpublished. Stiff, Η. Α., and Castillo, J . C., Science, 101, 440 (1945). Wichman, H . J . , Patterson, W. I., Clifford, P. Α., Klein, A. K., and Claborn, Η. V.,J.Assoc. Offic. Agr. Chemists, 29, 188-218 (1946).


AGRICULTURAL CONTROL CHEMICALS

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