What is the best way to analyze this problem? I took the difference of after and before. then used insecticides vs fertilizer and lablled all as randome, but it doesn't look right.

3. (25) An experiment was conducted in a completely randomized design to study the effect of insecticides and fertilizer, on the control of homworm infestations on a crop plant. The insecticide types were four sources of bacillus, and two types of chemicals. There are 4 types of fertilizer. The number of wonns present was counted before and after treatment. The results of the experiment are as follows. The response variable should be the difference \"After\" W \"Before\". Fertilizer 3 Insecticide After Before Bacillus 1 26 18 Bacillus 2 22 20 Bacillus 3 21 21 Bacillus 4 26 17 Chemical 1 6 26 Chemical 2 19 22