for 251;
some officer told me, it produces more latex than the other rubber, but we only harvest one day and stop in the second day[so 1 month can only harvest for 15 days]
for 600;
we can harvest 2 days and stop in the third day before harvest it again ,so 1 month we harvest for 20 days]
my plantation, we plant both 600 and 251. 600s grow well but some of them have been infected, some can live and some 's gone. 251s are in the little amout compare to 600 ,but they also grow well .
i just apologize for any mistake in my comment...
i can't type thai language because my father pour a cup of beer on a keyboard so i use on-screen keyboard instead. 
i will change this comment into thai tonight.
