EFFECT OF CHLORPYRIFOS 50W ON FRUIT FINISH AND PACKOUT OF 'GOLDEN DELICIOUS"

H. W. Hogmire, V. L. Cnm, and R. O. Annan Division of Plant and Soil Sciences

West Virginia University Experiment Farm Kearneysville, WV 25430

Abstract: A full season spray program of chlorpyrifos compared to 8zinphosmethyl applied to 'Starkspur Golden Delicious' reduced extra fancy/fancy p8ckout by 54% and reduced crop value because of fruit russeting by $967/ha. Substituting 8zinphosmethyl for chlorpyrifos during the petal fall, first cover and second cover applications reduced russeting and increased crop value to levels similar to the season long program of 8zinphosmethyJ. Of the three applications. the substitution at ftrst cover accounted for most of the reduction in russeting. Four applications of GAH7• 7 days apart, significantly improved the extra fancy/ fancy packout of chlorpyrifos treated 'Smoothee' fruit.

Key Words: Chlorpyrifos, GAH7, russeting, economic losses, apples.

J. Agric. Entomo!. 5(3): 209-214 (July 1988)

Chlorpyrifos 50W was introduced 8S a broad spectrum insecticide for use on apple in 1983. Numerous studies have been conducted to evaluate the performance of this organophosphate against both fruit and foliage feeding pests of apple (Forsythe 1987; Hamilton et al. 1986; Hogmire and Crim 1986, 1987; Horsburgh and Cobb 1986; Hull 1987; Reissig et al. 1986). Chlorpyrifos has fit well into apple IPM programs because of its safety to mite predators (Anon. 1985; Howitt and Hays 1986; Hull and Baldwin 1982).

Season-long spray programs of chlorpyrifos have resulted in increased fruit russeting of 'Golden Delicious' (Hamilton et al. 1986; Horsburgh and Cobb 1986; Hull 1987; Weires 1987). Although not statistically significant, daytime applications of chlorpyrifos appeared to cause more russeting of 'Golden Delicious' than applications at night (Hogmire and Crim 1987).

This study was conducted in 1987 to determine: 1) the time during the season when chlorpyrifos was causing fruit russeting of 'Golden Delicious', 2) the economic impact of the russeting, and 3) if the russeting could be reduced.

MATERIALS AND METHODS

Two experiments were conducted at the \Vest Virginia University Plant Science Experiment Farm in Kearneysville, WV. The ftrst experiment was conducted in 8

block of 23 yr·old 'Starkspul' Golden Delicious' on MM 106 rootstock with a tree spacing of 3.0 X 6.1 m. The average tree canopy measured 4.3 m in height and 4 m in width. The block was divided into six unreplicated plots of 0.16 - 0.22 ha in size. The block was relatively uniform in elevation, except for a lower region in the extreme western end which was not used in the study. Chlorpyrifos and azinphosmethyl (standard) were each applied in a full season program beginning at

Published with the approval of the Director of the West Virginia Agricultural and FOfCstl'}' Experiment Station as Scientific Article No. 2117. This research was supported with funds appropriated from the Hatch Act and in part by 8 gmnt from Dow Chemiclil Company. Accepted for pul.llication 29 August 1988.

209

I

210 J. Agric. Entomol. Vol. 5. No.3 (1988)

petal fall. The remaining fOUf plots consisted of various chlorpyrifos treatment schedules with 8zinphosrnethyl substituted at specific times during the early season (Table 1). Rates of application (glAIllhal were 1120 and 840 for chlorpyrifos and 8zinphosmethyl, respectively. Treatments were applied as complete sprays (both sides of trees) with a Swanson DA500A airblast sprayer which traveled at 3.86 kmlh and delivered 935 liters/ha of finished spray. Dates of application were 6 May Ipetal fall (PF)J, 21 May lfirst cover (ICl!, 5 Jun Isecond cover (2C)J, 19 Jun Ithird cover (3C)I, 3 JuJ Ifourth cover (4ClI, 17 Jul lfifth cover (5ClI, 31 Jul IsL<th cover (GCll, 13 Aug Iseventh cover (7ClI, and 27 Aug leighth cover (BClj. Methomyl was applied across all plots at petal fall and seventh cover for the control of white apple leafhopper and spotted tentifonn leafminer. Fungicides applied as tank mixes to all treatments were metiram (PF-4C), Dikar (5C-7C), benomyl (BC) and captan (8C).

All fruit were harvested on 21 Sep from each of 5 single-tree replications which were selected at random from the center row(s) of each plot. Treatments were evaluated by examining a 100 fruit sample which was selected blindly from the entire fruit harvest per tree. Fruit were rated for russeting using the following scale modified after Byers et a!. (1983): 0 = no I"usseting or enlarged lenticels; 1 = no russeting but lenticels enlarged, rough and raised to touch; 2 = 1-10% surface russeted; 3 = 11-25% surface russeted; 4 = 26-50% surface russeted; and 5 = >50% surface russeted. Fruit were categorized into U.S. grade classifications (USDA 1972) based on the russet rating as follows; 0-2 = extra fancy/fancy; 3 = U.S. no. 1; nnd 4-5 = utility. The crop value was calculated for each treatment using an average West Virginia yield of 1236 bu/ha and an average price of $8.00, $5.00 and $4.00/bu for extra fancy/faney combination, U.S. no. 1 and utility grade, respectively. Data are presented as means with standard error to show variability.

A second experiment was conducted in a 0.37 ha block of 5 yr-old 'Smoothee' (a russet resistant mutation of 'Colden Delicious') on MM 106 rootstock with a tree spacing of 6.1 X 6.1 m. The average tree canopy measured 4.5 m in height and 3.2 m in width. Three treatments, consisting of chlorpyrifos applied alone and in combination with two spray schedules of GA4+7 (gibberellic acid), were each applied to 4 single-tree replications in a complete randomized block design. GA4+7 has been shown to reduce russeting in 'Golden Delicious' (Weltheim 1982; Steenkarnp et al. 1984) and is labeled for this use. It was used in this test to detennine its effectiveness in suppressing russeting of fruit treated with chlorpyrifos. Treated trees were separated by two unsprayed rows and at least one unsprayed tree within treatment rows. Chlorpyrifos was used in four applications (PF-3C) in all treatments at the same rate as in the first experiment. In a second treatment, GA4+7 (15.3 g IAlllha) was applied in four sprays on a 7-day interval as specified in product literature. In the first (PF) and third (1C) application, GAH7 was applied in combination with chlorpyrifos, whereas it was used alone in the second and fourth application. Since the chlorpyrifos applications were scheduled on a 14-day intelVal, which is standard for insecticides, the 7-day intelVal for GA4+7 necessitated two extra trips through the orchard. As this would present some inconvenience and additional expense for growers, a third treatment was included whereby GA-l+7 was applied on 8 14-day schedule in combination with chlorpyrifos in each of the 4 applications. Azinphosmethyl was applied to all treatments for the second half of the season beginning at fowth cover. Fungicides, as specified in the first experiment, were applied separately to all treatments. Application method and dates were the same as in the first experiment, with the addition of 13 and 28 May for the second and fourth application of GA-l+7 in the 7-day schedule. All fruit were harvested from each replication on 23 Sep, with treabnents evaluated in the same manner as in experiment one. Data were subjected to Duncan's (1951) multiple range test to determine differences between treatment means.

211 HOGMJRE et at.: Chlorpyrifos Effect on 'Golden Delicious'

RESULTS AND DISCUSSION

A full season spray program of chlorpyrifos caused more fruit russeting than a comparable azinphosmethyl program~ resulting in a 54% reduction of extra fancy/ fancy fruit and an estimated decrease in crop value of $967/ha (Table 1). This was accompanied by a three-fold increase of utility grade apples under the chlorpyrifos program. Chlorpyrifos treated fruit had a higher incidence of solid versus net russeting compared to azinphosmethyl. The high susceptibility of lStarkspur Golden Delicious' to russeting (Cummins 1977) undoubtedly contributed to the poor overall packout in this study.

Substituting azinphosmethyl for chlorpyrifos during the first three applications (PF~2C) reduced russeting and increased crop value to levels similar to the season long program of azinphosmethyl. Of the three applications, the substitution at first cover accounted for most of the reduction in russeting.

During an 8~year study under natural orchard conditions, Creasy (1980) discovered an excellent correlation between russet severity on 'Golden Delicious' and humidity during 16~20 days after full bloom. The first cover application occurred 24 days after full bloom, compared to 9 and 39 days for the pewl fall and second cover applications, respectively. It would appear that chlorpyrifos was enhancing the expression of weather-induced russeting, which was reduced by substituting azinphosmethyl during the most susceptible period at first cover. It would also appear that chlorpyrifos may be causing some russeting after second cover, as substitution of azinphosmethyl in the first 3 applications still resulted in a higher percentage of utility grade apples compared to the full season azinphosmethyl program.

Chlorpyrifos is not the only pesticide currently used on apples which may have a detrimental effect on the fruit finish of 'Golden Delicious'. Russeting has also been demonstrated with dodine (Hatch 1975), a fungicide which is used for early season control of apple scab. Creasy and Swartz (1981) found that both oil and diazinon resulted in increased russeting of 'Golden Delicious' following a single application 18 days after full bloom.

Four applications of GA'l+7' scheduled 7 days apart, significantly reduced the russeting by chlorpyrifos and increased the pockout of extra fancy/fancy fruit by 68% as compared to chlorpyriJos applied alone (Table 2). Although the 14·day schedule of GAH7 also improved fruit finish and packout, it was not significantly better than chlorpyrifos applied alone. The 7·day application schedule of GAH7 increased the crop value of chlorpyrifos treated fruit by S924/ha. Subtracting the cost of the GAHi and the two extra trips through the orchard necessitated by the 7-day spray interval would result in a benefit of approximately $625/ha.

The decision to use GAH7 will have to be made on an orchard block by block basis with consideration given to the packout percentage needed to justify packing the fruit versus sending the fruit to the processor. For example. an increase in extra fancy/fancy packout from 34 to 58%. as occurred in this study with the use of GA4+7' would not be sufficient to justify packing the fruit if the grower needed 75% packout to break even. In less severely russeted blocks, GA4+7 could provide enough benefit to make packing profitable.

Without the aid of 8 russet suppressant, growers should probably refrain from using chlorpyrifos (1120 gIAII/ha) at least during the first 25 days, and preferably the first 40 days, after full bloom on lGolden Delicious' if the crop is to be marketed as fresh fruit. Chlorpyrifos could be used without restriction in orchard blocks of 'Golden Delicious' grown for processing since russeting does not reduce fruit value for this market.

Table 1. Effect of chlorpyriIos 50W application timing on fruit finish and packout of HStarkspur Golden Delicious" in 1987.

Distribution of fruit in US grades (%)'

Time of Russet Crop value Treatment application rating* extra fancy/fancy no. 1 utility ($ per hectare') ,..

Azinphosmethyl 50W PF·8C 2.73 ± 0.13 34.6' ± 7.4 54.4 ± 3.5 11.0 ± 4.2 7327 ± 325 Chlorpyrifos 50W PF·8C 3.31 ± 0.06 16.0 ± 3.5 50.6 ± 4.7 33.4 ± 3.3 6360 ± 74 ~,.>

Azinphosmethyl 50W PF 3.15 ± 0.05 15.8 ± 2.2 55.8 ± 2.7 28.4 ± 2.8 6415 ± 103 " Chlorpyrifos 50W IC·8C ,'"Azinphosmethyl 50W IC 3.02 ± 0.06 22.4 ± 3.8 54.8 ± 2.6 22.8 ± 1.5 6729 ± 159 S3

Chlorpyrifos 50W PF, 2C·8C ?-Azinphosmethyl 50W 2C 3.10 ± 0.09 17.4 ± 3.4 58.0 ± 7.6 24.6 ± 7.3 6521 ± 108

~ Chlorpyrifos 50W PF, IC, 3C-8C 9'Azinphosmethyl 50W PF-2C 2.91 ± 0.09 25.2 ± 6.2 54.6 ± 5.9 20.2 ± 3.3 6865 ± 246

Chlorpyrifos 50W 3C·8C ?z

* x ± SEM. '" :; ~

Table 2. Effect of GAH7 on fruit finish and p.ckout of "Smoothee" tre.ted with chlorpyrifos 50W in 1987'.

Distribution of fruit in US gr.des(%)

Russet Crop value Treatment rating extra fancy/fancy no. 1 utility ($ per hectare)

Chlorpyrifos 50W 2.72. 34.3b 59.3. 6.6. 7383b Chlorpyrifos 50W + GAH7 t 2.42b 57.8. 40.5. 1.8. 8307. Chlorpyrifos 50W + GAH7 i 2.53ab 47.6.b 49.0. 3.5. 7908.b

o • Means in 8 given column followed by the !lame letter are not significantly different by Duncan'~ (I951) multiple range test, P :: 0.05. cit Four Bpplications of GA';+7 at 7 day intervals. o '* Four Applications of GA4+7 at 14 day interl{als. 0:

o o

!>­'" o· o· o ~"

o

214 J. Agric. Entornol. Vol. 5, No.3 (1988)

REFERENCES CITED

Anonymous. 1985. Practice mite management. Amer. Fruit Grower 105: 30·33. Byers, R. E., K. S. Yoder, and G. E. Mattus. 1983. Reduction in russeting of 'Golden

Delicious' apples with 2,4,5·TP and other compoundR. HortScience 18: 63-65. Creasy, L. L. 1980. The correlation of weather parameters with russet of 'Golden Delicious'

apples under orchard conditions. J. Amer. Soc. Hart. Sci. 105: 735-738. Creasy, L. L. and H. J. Swartz. ]981. Agents influencing russet on 'Golden Delicious' apple t

fruits. J. Amer. Soc. Hart Sci. 106: 203·206. Cummins, J. N., P. L. Forsline. and R. D. Way. 1977. A comparison of russeting among

'Golden Delicious' subc1ones_ HortScience 12: 241-242. Duncan, D. B. 1951. A significance test for differences between ranked treatment means in

an analysis of variance. Virginia J. Sci. 2: 171·189. Forsythe. H. Y. 1987. Apple, insect and mite control. 1985. Insect. and Acar. Tests 12:

8-9_ Hamilton, G. C., E. Hennan, and F. C. Swift. 1986. Apple, all season insecticide test, 1985.

Insect. and AcRe. TesUi 11: 20-24. Hatch, A. H. 1975. The influence of mineral nutrition and fungicides on russeting of

'Goldspur' apple fruit.. J. Amer. Soc. Hort. Sci. 100: 52-55. Hogmire, H. W., and L. Crim. J986. Apple, insecticide evaluation, 1985. Insect.. and AcRe.

Tests. IJ: 27-29_ Hogmire, H. W., and L. Crim. 1987. Apple, insecticide evaluation, 1986. Insect. and Acar.

Tests 12: 13·16. Horsburgh, R. L., and L. J. Cobb. 1986. Apple, fun season insecticide evaluation, 1985.

Insect.. and Acae. Tests 11: 32-33. Howitt, A. J., and A. R. Hays. 1986. Apple, full season insecticide test, 1985. Insect. and

Acar. Tests 11: 42. Hull, L. A. 1987. Apple, concentrate airblast insecticide test., 1986. Insect. and Acnr. Tests 12:

28-30. Hull, L. A., and D. M. Baldwin. 1982. Evaluation of insecticides for use in an integrated pest

mnnagement program for apples. Down to Earth 38: 9-11. Reissig, H., D. H. Dunhnrn, and H. E. Hebding. 1986. Apple, preliminary insecticides test.,.

1985. [nsect.. and Acnr. Tests 11: 65-66. St.eenkamp, J., H. J. Van Zyl, and I. Westraad. 1984. A preliminary evaluation of various

chemical substances for the control of calyx-end russeting in Golden Delicious apples. J. Hart Sci. 59: 501-505.

USDA Agricultural Marketing Service. 1972. United States Standard for Grades of Apples. F. R. Doe. 67·7604, amended Oct. I, 1966 and July 1, 1972. Washington, D.C.

Weires, R. W. 1987. Apple, insect control, Hudson Valley, Highland, NY, 1986. Insect. and Acnr. Tests 12: 53-55.

Wertheim, S. J. 1982. Fruit russeting in apple liS affected by various gibberellins. J. Hort Sci. 57, 283-288.