Question: query about wilting of potato.
Answer: to diagnosis the disease for fungal or bacterial wilting, ooze test is necessary. 
to quickly diagnose of bacterial wilt: cut a young lesion across and place in a transparent glass container with clear water, after a few minutes, hold the container against light and observe for thick or turbid liquid or white substance coming from the cut end of the leaf. if the white substance comes out then it is bacterial wilt, then apply plantomycin or streptocycline @ 2g/10 litre of water.
and if the white substance does not comes out then it is a fungal wilt, then apply bavistin or indofil m-45 @ 2g/litre of water for 3 times at 5 days interval.