206 Extended Summaries-Pesticides Group Symposium

Cq6 GROUP OF ACIDS

H OC H,-(CH 2)q d-COOH 16 - Hydroxyhexadecanoic

OH HOC H 2-( C H2)S-C H-(C H 2)B-COOH 10,16 - Dihydroxyhexadecanoic (and other positional isomers)

Cq8 GROUP OF ACIDS

H OC H 2-( C H 2)7-C H=C H- (C H 2 )7-C OOH

18 - Hydroxyoctadec - 9 - enoic

OH OH H OC H 2-( C H 2h-C H-C H- (C H 2h-C OOH

9,10,18 - Trihydroxyoctadecanoic

0 H OC H2- (C H 2h-Hd(-\CH-(CH&-COOH

9,lO - Epoxy - 18 - hydroxyoctadecanoic

Fig. 2. Most common monomeric constituents of plant cutins.

invariably ‘contaminated’ with polysaccharides and other constituents of the underlying cell wall of which the cuticle is an integral part.

Fundamental anatomical and chemical studies on plant cuticles serve to highlight their highly hetero- geneous nature; this fact should always be borne in mind when devising formulation and adjuvant strategies for foliage-applied agrochemicals.

References 1.

2. 3.

4.

5 .

6.

7.

8.

9.

10.

11.

12.

Martin, J. T. & Juniper, B. E., The Cuticles of Plants. Edward Arnold, London, 1970, 347 pp. Holloway, P. J., Pestic. Sci., 1 (1970) 15663. Harr, J., Guggenheim, R., Schulke, G. & Falk, R. H., The Leaf Surface of Major Weeds. Sandoz Agro Ltd, Witter- swil, 1991, unpaginated. Holloway, P. J., In The Plant Cuticle, Linnean Society Symposium Series No. 10, ed. D. F. Cutler, K. L. Alvin & C. E. Price. Academic Press, London, 1982, pp. 1-32. Holloway, P. J. & Wattendorff, J., In CRC Handbook of Plant Cytochemistry, Vol. 11, ed. K. C. Vaughn. CRC Press, Inc., Boca Raton, 1987, pp. 1-35. Nip, M., Tegelaar, E. W., de Leeuw, J. W., Schenck, P. A. & Holloway, P. J., Naturwissenschuften, 73 (1986) 579-85. Holloway, P. J., In CRC Handbook of Chromatography, Lipids, Vol. I, ed. H. K. Mangold. CRC Press, Inc., Boca Raton, 1984, pp. 347-80. Walton, T. J., In Lipids, Membranes and Aspects of Photobiology, Methods in Plant Biochemistry, Vol. 4, ed. J. L. Harwood & J. R. Bowyer. Academic Press, London,

Baker, E. A., In The Plant Cuticle, Linnean Society Symposium Series No. 10, ed. D. F. Cutler, K. L. Alvin & C. E. Price. Academic Press, London, 1982, pp. 139-66. Holloway, P. J., In CRC Handbook of Chromatography, Lipids, Vol. I, ed. H. K. Mangold. CRC Press, Inc., Boca Raton, 1984, pp. 32145. Holloway, P. J., In The Plant Cuticle, Linnean Society Symposium Series No. 10, ed. D. F. Cutler, K. L. Alvin & C. E. Price. Academic Press, London, 1982, pp. 45-85. Kolattukudy, P. E., Science (Washington), 208 (1980) 99Ck1000.

1990, pp. 105-58.

The Use of a ‘Sticker’ Type of Adjuvant with Insecticides

Bob Reeves

Loveland Industries Inc, Greeley, Colorado 80632-1289, USA

Stickers have long been used as adjuvants to impart specific properties to spray solutions, these properties being determined by the composition of the sticker, the dose rate and the nature of the surface to which they are applied. Stickers that impart adhesion and viscoelasticity to spray solutions can be expected to enhance the initial deposition of active ingredient and its subsequent retention. There may also be some secondary effects due to the formation of a film over the pesticide deposit upon drying, since such a film may protect the active material against degradation and removal.

This summary reports trials to investigate the effects of a sticker adjuvant upon the initial deposition and bio- logical efficacy of two synthetic pyrethroids and their persistence in the presence and absence of simulated rainfall.

Trial 1, devised to examine the effect of adjuvants on persistence of permethrin residues, was carried out at Raleigh, N. Carolina in 1990. Permethrin (‘Ambush ’) was applied at 50 g acre-’ (123.5 g ha-’) by pressurized backpack sprayer at 8 US gal acre-l (74.8 litre ha-’), with or without a synthetic latex sticker (‘Bond’; 2.602 acre-’- 182 g ha-’), to four replicate plots of soybeans. The soybeans were sampled 1, 7 and 15 days after treatment and permethrin levels determined by HPLC.

Trial 2, in the same year and at the same location, involved cotton and soybeans and investigated the ability of seven commercial spray adjuvants to improve the efficacy of permethrin in controlling Corn Earworm (Helicoverpa zea (Boddie)). In this trial, formulations with and without the same sticker as used in Trial 1 were

Extended Summaries-Pesticides Group Symposium 207

TABLE 1 Residue Data for Permethrin Applied to Soybeans in the

Presence or Absence of a Synthetic Latex Sticker

Treatmenta Permethrin residue bg), days after treatment

1 7 14

Permethrin 0.75ab 0.30a 0.09b Permethrin + 1.15a 0.22a 0.06b

sticker

a For details see text (Trial 1). * Figures bearing the same letter do not differ significantly ( P = 0.05).

TABLE 2 Rainfastness and Residual Efficacy Data for Permethrin Applied to Cotton and Soybeans in the Presence or Absence of

a Synthetic Latex Sticker"

Mean of all Treatment with treatments sticker

without sticker

Rainfall cm 0 2.5 5.0

1 7

14

Days after treatment

Mortality (%) after rainfall 77 83b 53.5 82.5" 41.5 83.0'

Mortality (%) residual efJicacy 39.0 48.0b 133 18.5' 3.8 7.0"

a For details of treatments see text (Trial 2). Not significantly different P = 0.05. Significantly different P = 0.05.

compared. The insecticide was applied in the same way and at the same dose and rate as before. Biological efficacy was estimated by bioassay and residues estimated using HPLC.

Trial 3 was on sweet corn at Eaton, Colorado and was designed to determine the effect of the latex sticker at 1.36 oz acre-' (95.2 g ha-') on deposition, persistence and efficacy of esfenvalerate (' Asana' SC) applied by

TABLE 3 Effect of Applying Esfenvalerate With and Without Sticker"

Treatment Residue (mg g-I), days after Ears

(%) treatment infected

0 3 5 15

Untreated 46 Esfenvalerate 0.94 1.0 0.97 0.93 3 Esfenvalerate+ 1.53 0.65 0.84 0.63 0 sticker

a See text for details of treatments (Trial 3).

pressurized backpack sprayer (0.03 lb a.i. in 8.5 US gal acre-' = 13.6 g in 79.5 litre ha-') on a five-day spray schedule. Tissue was analyzed for residues of insecticide and the extent of infection by Corn Earworm was evaluated. All results were subjected to statistical analysis.

The data in Table 1 show that the sticker did not alter the extent of degradation of permethrin significantly. There was, however, significantly greater mortality of the target pest 14 days after treatment with the formulation containing sticker (data not shown). Since the sticker did not alter the droplet spectrum delivered by the nozzle, improved deposition cannot be attributed to droplet size. It is suggested that improved adhesion allowed droplets impinging on the plant surface to be retained so that bounce and run-off of droplets were reduced. Added viscoelasticity will aliow droplets to absorb the energy of impact and reduce, or minimize, the 'shattering' effect that contributes to loss of deposition.

The data for Trial 2, in Table 2, indicate a clear advantage for the sticker in improving rainfastness and in residual efficacy. The improved efficacy can be attributed to the deposition and retention of more pesticide when sticker is present.

Table 3 contains residue and efficacy data for esfenvalerate in the presence and absence of sticker. The sticker increased the initial deposit of a.i. and the treatment resulted in total elimination of the pest. However, it did not increase the persistence of the a.i. on sweet corn and this aspect will require more investigation.

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