It says in SA OC Siman 629 Sif 3 that one may use for scach “chitzim” that don’e have a beis kibbol. However if they do have a beis kibbul then it’s pasul for scach. The M”A writes in Sif-Katan Beis there that kanim that have a beis kibbol they are kosher since they weren’t made to be “m’kabel”. Seemingly this is similar to our bamboo sticks or the like that people use for scach. However what would be the din of one would put some sort of “chomer” (a poision or the like) used to kill bugs inside of the sticks. I’m not talking about a spray or something of the like – rather something that has to it mamoshos (substance) that sits in the sticks and helps to kill the bugs. Even though these kanim like the M”A says weren’t made to be a beis kibbol however now l’maseh being used it such a way does this pasul it for being scach?
This will not pasel the sechach, because the kanim are not being ‘used,’ and the introduction of the substance is only for the sake of preserving them. This does not make them into a keli, and there is no reason why this should invalidate them for use as sechach.