Weed-EX is a special spray that is specially designed for IC2 crops, that prevents weeds from appearing. To use Weed-Ex simply right click on an empty crop; however it is more beneficial to use it in a Crop-Matron as doing so will prevent accidental overdosing of crops, which reduces their stats. Weed-Ex should also be used in a Crop-Matron if users are cross-breeding or leaving their crops unattended for any period of time. While not intended, and possibly considered an exploit, Weed-Ex can be repaired by some tool repair devices in various modpacks.
Beware, empty Crops can grow weeds, which can spread. Plants with stronger growth stats are more resilient to weeds.