Monthly counts, in plantations ofPinus patula at Kodaikanal in southern India, during 1977 and 1978, indicate that fruitbody production byAmanita muscaria, a fungus forming sheathing (ecto-) mycorrhizas, was influenced by (i) the current month’s rainfall and (ii) the age of the plantation.
Fruitbodies rarely appeared in the absence of rain. Average monthly numbers increased in rain-months from 11 to 320 per thousand trees when monthly rainfall increased from 40 to 640 mm.
During a period of 11 months (February/December 1978) numbers of fruitbodies per 1000 trees ranged fromc. 150 to 10800 in plantations 5 and 16 years old respectively.
After rainfall-thresholds for fruitbody production had been exceeded—they were less in old, than in young, plantations—young plantations, judged by the production ofA. muscaria fruitbodies, were more responsive to additional rainfall than older plantations.