What spray to kill fireblight on a loquat tree?
Leaves of loquat have drooped and turned brown
It's not as simple as that, there is no spray to kill advanced fireblight, there are only preventive measures.
First of all identify the disease. There are other reasons possible for "leaves druped and turned brown". Fireblight is characterized by those signs, plus blackening of the woody stems and a "shepherds crooked" disfiguration of the dying tips.
You can reduce the spread within the plant and to nearby plants (pome tribe of the rose family are susceptible, pears, apples, quince) by pruning out the infected branches well below the discolored area on the stems. Disinfect pruning tools between cuts if you think you cut into infected tissues.
There is chemical control available but the best and most effective method and material needs a professional applicator with stem injection equipment for anti-biotic treatment with ArborJet ArborOTC (oxytetracycline).
I have found that the best prevention and suppression of an active infection is achieved with multiple approach. Soil fertility and water management is primary. A healthy tree with good growing conditions and fertilization and avoidance of drought stress will reist the disease.
Repeat spraying of a biological fungicide-bactericide before and during and after the flower bud break will prevent the rain and windblown and honeybee transmitted spores from infecting the flowers (from where the disease spreads downward into the branches).
For a larger tree or multiple trees you will need a tree sprayer and more product:
Pruning out infected tips weekly during the spring is also required.