A fungicide will kill fungi, so, on the positive side it will kill fungi which are pathogenic towards peas and which would kill or harm your plants. On the negative side, it would kill helpful fungi such as ones which would form endomycorrhizae.
Work Step by Step
The key is to see the nature of the chemical: it eliminates fungi. Then, scan the chapter for examples of how fungi help (fungicide is a negative) or hinder (fungicide is a positive) plants.