#### § 520.596 Dichlorvos powder.

(a) *Specifications* —

(1) Each 2-ounce packet contains 2.27 grams (4 percent) dichlorvos.

(2) Each milligram of powder contains 2.27 milligrams (mg) dichlorvos.

(b) *Sponsor.* See No. 069043 in [§ 510.600(c) of this chapter](/on/2024-09-23/title-21/section-510.600#p-510.600(c)) for use of the product described in [paragraph (a)(1)](/on/2024-09-23/title-21/section-520.596#p-520.596(a)(1)) of this section as in [paragraph (d)(1)](/on/2024-09-23/title-21/section-520.596#p-520.596(d)(1)) of this section and the product described in [paragraph (a)(2)](/on/2024-09-23/title-21/section-520.596#p-520.596(a)(2)) of this section as in [paragraph (d)(2)](/on/2024-09-23/title-21/section-520.596#p-520.596(d)(2)) of this section.

(c) *Related tolerances.* See [§ 556.180 of this chapter](/on/2024-09-23/title-21/section-556.180).

(d) *Conditions of use* —

(1) *Swine (adult gilts, sows, and boars)* —

(i) *Amount.* Add powder to the indicated amount of feed and administered shortly after mixing, as follows:

| Weight of animal in pounds | Pounds of feed to be mixed with each 0.08 ounce of dichlorvos | Pounds of mixed feed to be administered to each pig as a single treatment | Number of pigs to be treated per 0.08 ounce of dichlorvos |
| --- | --- | --- | --- |
| 20-30 | 4 | 0.33 | 12 |
| 31-40 | 5 | 0.56 | 9 |
| 41-60 | 6 | 1.00 | 6 |
| 61-80 | 5 | 1.00 | 5 |
| 81-100 | 4 | 1.00 | 4 |
| | 16 | 4.00 | 4 |

(ii) *Indications for use.* For the removal and control of sexually mature (adult), sexually immature and/or 4th stage larvae of the whipworm (*Trichuris suis*), nodular worms (*Oesophagostomum* spp.), large round-worm (*Ascaris suum*), and the mature thick stomach worm (*Ascarops strongylina*) occurring in the lumen of the gastrointestinal tract of pigs, boars, and open or bred gilts and sows.

(iii) *Limitations.* Do not use this product on animals either simultaneously or within a few days before or after treatment with or exposure to cholinesterase inhibiting drugs, pesticides, or chemicals. The preparation should be mixed thoroughly with the feed on a clean, impervious surface. Do not allow swine access to feed other than that containing the preparation until treatment is complete. Do not treat pigs with signs of scours until these signs subside or are alleviated by proper medication. Resume normal feeding schedule afterwards. Swine may be retreated in 4 to 5 weeks.

(2) *Horses* —

(i) *Amount.* Administer in the grain portion of the ration at a dosage of 14.2 to 18.5 mg per pound of body weight as a single dose. Administered at one-half of the single recommended dosage and repeated 8 to 12 hours later in the treatment of very aged, emaciated, or debilitated subjects or those reluctant to consume medicated feed. In suspected cases of severe ascarid infection sufficient to cause concern over mechanical blockage of the intestinal tract, the split dosage should be used.

(ii) *Indications for use.* For the removal and control of bots (*Gastrophilus intestinalis, G. nasalis*), large strongyles (*Strongylus vulgaris, S. equinus, S. edentatus*), small strongyles (of the genera *Cyathostomum, Cylicocercus, Cylicocyclus, Cylicodontophorus, Triodontophorus, Poteriostomum, Gyalocephalus*), pinworms (*Oxyuris equi*), and large roundworm (*Parascaris equorum*) in horses including ponies and mules. Not for use in foals (sucklings and young weanlings).

(iii) *Limitations.* Do not use in horses which are severely debilitated, suffering from diarrhea or severe constipation, infectious disease, toxemia, or colic. Do not administer in conjunction with or within 1 week of administration of muscle relaxant drugs, phenothiazine derived tranquilizers or central nervous system depressant drugs. Horses should not be subjected to insecticide treatment for 5 days prior to or after treating with the drug. Do not administer to horses afflicted with chronic alveolar emphysema (heaves) or related respiratory conditions. The product is a cholinesterase inhibitor and should not be used simultaneously or within a few days before or after treatment with or exposure to cholinesterase inhibiting drugs, pesticides or chemicals. Do not use in animals other than horses, ponies, and mules. Do not use in horses, ponies, and mules intended for food purposes. Do not allow fowl access to feed containing this preparation or to fecal excrement from treated animals.

[[83 FR 48944](https://www.federalregister.gov/citation/83-FR-48944), Sept. 28, 2018]