Chlorpyrifos (Chlorpyrifos, Lorsban)

Chlorpyrifos is an organophosphate insecticide with nonsystemic contact, stomach, and vapor action highly effective on a wide range of insects on apples, peaches, and nectarines. This material is formulated as an emulsifiable concentrate and as a wettable powder. Chlorpyrifos 4E and Lorsban 4E are equivalent products labeled for dormant to delayed dormant applications on apples, peaches, nectarines, and plums to control scale and other pests. Trunk sprays of these products thoroughly wetting all bark areas from ground level to scaffold limbs will control peachtree borer. Apply only one borer application per season, and do not apply within 14 days of harvest. As a postharvest spray, these products at 1 to 2 quarts per 100 gallons are effective on second-generation lesser peachtree borer.

Lorsban 50WP is no longer manufactured and is being replaced on the market by a new formulation--Lorsban 75WG. This new formulation is labeled for use on apples at the rate of 0.33 pound to 0.67 pound per 100 gallons of water in dilute sprays and no less than 1 lb per acre in concentrate sprays. Lorsban can not be applied for foliar applications post bloom. A supplemental label allows Lorsban 4E to be used to directly treat burr knots for control of dogwood borer and other borers on apples. Apply 1.5 quarts per 100 gallons of Lorsban 4E and do not exceed 100 gallons per acre. On young trees, as little as 6 fluid ounces per tree can provide successful control. Optimum timing is during the summer at peak flight. Do not apply the last treatment within 28 days before harvest. Do not make more than 2 applications per year for borer control.