It's leaves are drying why ???

This plant is just 10 cm of the another mango plant which is having also the same problem that I asked earlier this plant is also suffering from ants and white citrus type insects in its roots . I am able to see the insects attached to plants roots . By seeing from Google I provided the plant with surf water 25 days ago but still no improvement . I also gave urea in the roots but it was also unsuccessful .what to do please Suggest some home treatment. Thanku