Even if enough Fe is in the soil, deficiency can occur under the following conditions: poorly drained soil, high Ca, high Mn, high pH, high P, high heavy metals, oxygen deficiency. Deficiency symptoms General: Yellow or white areas on youngest leaves. Older leaves remain green.
Bt corn is a variant of maize that has been genetically altered to express one or more proteins from the bacteria Bacillus thuringiensis. The protein is poisonous to certain insect pests and is widely used in organic gardening. The European corn borer causes about a billion dollars in damage to corn crops each year.
In particular, bee larvae are exposed since they consume large quantities of pollen which they sometimes source from maize plants (Sabugosa-Madeira et al. 2007). Up to now however there has been no specific evidence that any Bt toxin has negative effects on bees, but equally such studies have been rare.