How often do I spray Sevin on a tree?
Sevin is an insecticide from Bayer that contains carbaryl; a broad-spectrum insecticide that works on contact and through ingestion. The application dose rages from 0.25 kilograms per hectare in agriculture to 10 kilograms per hectare for tree fruit.
The International Program on Chemical Safety considers it to have a low risk for humans.
Timing general application
Bayer gives specific schedules which detail when to apply Sevin to various trees and pests. However their general protocol advises that gardeners apply Sevin when insects or insect damage are first noticed. Following the initial application, gardeners should apply Sevin at seven- to ten-day intervals until the gardener sees that the insects have gone or the damage has ceased. Gardeners should ensure that they are using the dosage that is indicated on the label as appropriate for the pests they wish to control.
The constant use of insecticides within the same family can cause insect populations to develop resistance to these families of insecticide. Sevin contains an insecticide from the group 1A. Gardeners should rotate their use of insecticides from different groups in different treatment cycles so as to avoid the development of resistance. Gardeners should ensure that they are using the correct dosage and timing of Sevin applications. If Sevin does not appear to be controlling the pest problem despite that particular pest being susceptible to Sevin there may be a problem with resistance.
Use on specific trees
Bayer gives specific protocols for the use of Sevin on fruit trees including Apples, Pears, Apricots, Peaches, Cherries and Plums. The time that should be left between spraying and harvest varies from eleven days for apples to one day for peaches. When used on apple trees, gardeners should apply Sevin at least 30 days after full bloom to prevent apple thinning. Sevin can injure Virginia and sand pines during the early season. Sevin should not be applied to wet foliage or when humidity is high as this can cause leaf damage.
Effect on honeybees
Sevin is toxic for honeybees and the The International Program on Chemical Safety advises that it should not be applied during flowering so as to minimize honeybee exposure. To further minimize injury to honeybees apply Sevin during periods when bees are not foraging -- late evening to early morning. If this is not possible, gardeners can inform local beekeepers so that they can confine bees to the hive.