<P> In California, almost all female pistachio trees are the cultivar' Kerman' . A scion from a mature female' Kerman' is grafted onto a one - year - old rootstock . </P> <P> Pistachio trees are vulnerable to numerous diseases and infection by insects such as Leptoglossus clypealis . Among these is infection by the fungus Botryosphaeria, which causes panicle and shoot blight (symptoms include death of the flowers and young shoots), and can damage entire pistachio orchards . In 2004, the rapidly growing pistachio industry in California was threatened by panicle and shoot blight first discovered in 1984 . In 2011, anthracnose fungus caused a sudden 50% loss in the Australian pistachio harvest . Several years of severe drought in Iran around 2008 to 2015 caused significant declines in production . </P> <Table> <Tr> <Th_colspan="4"> Top Pistachio Producers in 2014 </Th> </Tr> <Tr> <Td> Region </Td> <Td> Production (metric tonnes) </Td> </Tr> <Tr> <Td> Iran </Td> <Td> 415,531 </Td> </Tr> <Tr> <Td> United States </Td> <Td> 233,146 </Td> </Tr> <Tr> <Td> Turkey </Td> <Td> 80,000 </Td> </Tr> <Tr> <Td> China </Td> <Td> 76,943 </Td> </Tr> <Tr> <Th> World </Th> <Th> 857,878 </Th> </Tr> </Table> <Tr> <Th_colspan="4"> Top Pistachio Producers in 2014 </Th> </Tr>

Who produces the most pistachios in the world