Well, its almost May in South Georgia, which means row crop fields are being prepared for planting. As farmers burn down weeds in these fields, pecans often take a hit from herbicide drift. Many farmers are in a hurry to get fields planted and this often leads to herbicide spraying under less than desirable conditions. Unfortunately pecan trees are often planted directly adjacent to many of these fields and we sometimes see damaging results. The following photos show Reflex damage to pecan trees from an adjacent burndown application on a newly planted cotton field. Since Reflex is a contact herbicide, the injury will only be observed on the leaves that were present at application and the trees should grow out of the damage eventually, although the trees’ growth will be set back considerably. On bearing trees, this can result in some yield loss if female flowers or entire shoots are damaged. This consumes excess carbohydrates but the trees will recover. Yield loss is usually minimal unless a large amount of foliage is lost. Paraquat and Ignite bring similar results. More long term damage may be observed with a systemic herbicide like glyphosate, 2,4-d, or dicamba.
We also occasionally see herbicide injury of our own making. The photo below shows Diuron injury to pecan. Diuron is a pre-emergence herbicide often used in herbicide strip applications. It is a very effective material but extreme caution is suggested when using on sandy soils, in which case the low rate should be used. Trees will normally grow out of this as rains or irrigation flush the material out of the soil.