Common Basil Plant Problems and Diseases

Basil is a relatively easy plant to grow. There are many benefits as well as few harmful challenges relating to its growth and transplanting. The most common disease is Fusarium wilt. The major factor in the presence and accumulation of Fusarium wilt is poor water drainage. As the basil plant needs the soil to remain moist, when not properly drained, the accumulated water promotes the fungus which creates the environment for the Fusarium wilt fungus. Symptoms of this disease make the plant look under-watered as it attacks roots and blocking its water uptake. Symptoms include browning or discolored stems and leaves, visible wilting, dropping leaves and damaged twisted stems. This fungus can remain in the soil and contaminate new crops. Even with wilt resistant strains, the soil can still harbor the fungus and should be removed.
Downy mildew (Peronospora belbahrii) is another disease that is damaging to the basil plant due to excessive water and mold in the soil. This mildew will begin to appear at the underside of the leaves, hence the name "downy", which will create a grey, white or brown fuzz. Spotting will appear brown, lighter green, purple, black or yellow.
The basil plant can also be damaged by discoloration and decay due to root rot, insects such as Aphids (also known as plant lice), Thrips (Thysanoptera) and nitrogen deficiency