Why the mode of pollination in maize is cross-pollination? Why it is important to cover the ear shoot with a butter paper bag before the emergence of silks? What could be the consequences if a few silks emerge before bagging?

The correct answer is -

1. due to the fact that maize is a monoecious crop that has male and female flowers in separate parts of the same plant that distributed pollen by the wind to other female parts of another maize plant.

2. Once silks are visible, they may already  be contaminated with foreign pollen, so it is vital that ears shots are  bagged before the emergence of silks.

3. If silks have emerged before bagging which means they are already been contaminated with other pollen and which will affect the process of hand pollination and have other varieties than desired.