Potato Dextrose Agar (PDA) is a general purpose medium for  non comercial entomopathogenic fungi that can be supplemented with acid or antibiotics to inhibit bacterial growth.  The nutritionally rich base (potato infusion) encourages mold sporulation and pigment production. Potato Dextrose Agar is composed of dehydrated Potato Infusion and Dextrose that encourage fungal growth. Agar is added as the solidifying agent. Many standard procedures use a specified amount of

sterile tartaric acid (10%) to lower the pH of this medium to 3.5, inhibiting bacterial growth. 

Agree with Luis, PDA is probably the best medium, you can add to it max. 5 drops of lactic acid per liter of PDA, also it is worth try 1/2 PDA to stress the fungus and make it sporulate (if it is the case). 

Thank you very much Claudia and Luis! 

Hello Dear

I conducted some experiment to find mass rearing of Beauveria and Metarhizium with agriculture waste production by Liquid-Solid diphasic methods. Please flow my publications. Thanks