Question: asking about canker, fruit drop-in citrus . spray streptomycin or planto mycin 2 1g/4.5 lit of water at 7 days interval 
for fruit drop- spray planofix @ 1ml/4.5 lit of water before flowering
Answer:  spray streptomycin or plantomycin 2 1g/4.5 lit of water at 7 days interval 
for fruit drop- spray planofix @ 1ml/4.5 lit of water before flowering