Thrips and aphides succumb to tobacco smoke, but in order to make fumigating effectual for thrips repeated doses are necessary. It is not the amount of smoke that hurts the plants, but the hot smoke. Cold smoke does no injury. When plants are being fumigated their leaves and stems should be dry. Never fumigate in the daytime in sunny or windy weather; evenings and rainy days are the preferable times. Syringe your plants the morning after fumigating. Red spiders, scales, mealy bugs, cockroaches and weevils are smoke proof.