the drying is known as "dieback disease" caused by fungus called phomopsis, these fungi enters the plant through wound caused by helopeltis ssp bites (tea bugs/mosquito bugs), helopeltis bites the tender parts of the plant seeking for (juice) as food for them, by so doing it leaves wounds whereby fungus penetrates and causing drying of the tender parts of cashew So it is better to control helopeltis as the main source of the disease to occur by applying insecticides. thanks