Systemic herbicides, like 2,4-D, Amitrol 240 and glyphosates must be absorbed in great enough quantities to kill this huge reserve from which the weed will recover and regrow, even when affected by a herbicide. Amitrol 240 has been particularly effective when used as a fall treatment, especially when higher rates are used. This is a time of year when mature dandelion plants are using their resources to store energy in their roots to sustain them through the harsh winter and to begin regrowth in the spring. Even if they are not killed by a spray application, their metabolism can be set back enough with the herbicide that winter hardiness is reduced enough to cause death. The key with large plants and the granddaddies is to apply the herbicide when the plants are active, even in warm days after the first frosts.
Granddaddies are the toughest to control.
The fewer tillage operations, the easier it is for dandelions to remain established and competitive. Several herbicide programs can be planned to control dandelions in different crops. The control of seedling dandelion plants is much easier than attacking mature ones. Burndown with Amitrol 240 or glyphosate products does an excellent job on young plants, but higher rates are needed for the larger, more established dandelion. Several different products for in-crop treatments will control dandelions.