Chili (Capsicum sp.) is widely grown in our country and around the world. This spice plant brings high economic
value to many farmers. Currently, chili cultivation is facing difficulties due to the harmful effects of yellow wilt
caused by Fusarium oxysporum and leaf spot disease caused by Cercospora sp. In addition, the abuse of fertilizers,
chemical drugs and growth regulators during the production process to increase the yield of chili has left chemical
residues in the product beyond the allowable threshold. In addition, the cultivation of crops under a number of clean
agricultural programs and limited use of chemical drugs such as VietGap and Global Gap are becoming popular in
our country. The use of beneficial microorganisms to replace chemical drugs is essential. Therefore, a study was
performed to evaluate the effect of the beneficial fungus Penicillium on chili peppers. In which, the experiment to
evaluate the effectiveness of Penicillium sp. For chili plants, it was shown that Penicillium fungus was able to
promote IAA content at the germination stage of chili seeds when seeds were soaked in a suspension of Penicillium
sp. The density of 106 cfu/ml showed high efficiency in terms of root length (19.66mm), stem length (19.87mm),
root weight (0.31g) and stem weight (0.42g). Continuing the experiment under net house conditions, the fungus
Penicillium sp. demonstrated the ability to help chili plants to resist pathogens when treated with a spore density of
106 cfu/ml and the experiment showed that Penicillium sp. Highly effective in helping pepper plants to resist yellow
wilt caused by Fusarium oxysporum and leaf spot caused by Cercospora sp. The results showed that the infection
rate and disease index were low in the treatment treatments compared with the control distilled water with high
disease rate and disease index, respectively (68%), (46.67%) for yellow wilt disease and (91.43%) (26.67%) for leaf
spot disease.