well Bugkiller.
1. do your area farms use allot of Liquid Fertilizers ?
2. do You apply Lime according to the soil PH ? for the Most Part.
3. what is the Base Saturation % of K on most of your soils.
4. what is the ppm of Zinc
of Boron ? Bugkiller.
If Yes to the top Two questions. You may be dealing with some Cultural Farming Practicies that may lead to some severe pressure issues.
in my opinion.