The rabbinate in Israel strictly impose the taking of maaser from growers (1% of everything grown). The rabbinate are scrupulous in ensuring that ONLY the best produce will be taken. The quantity separated is then destroyed or ruined with having soda poured onto it, thus preventing ANY person from having benefit.
Is there no halacha for passing this separated maaser to the poor and needy?
The rabbinate is actually doing its best to not impose at all. There are many tithes separated from produce in Israel and the rabbinate, in certifying that given produce is kosher (if requested to do so by the grower), only removes those tithes which cannot be eaten nowadays, namely, Terumah Gedolah and Terumat Maaser (totaling about 1% of the crop), plus in years 1,2,4,5 of the Shemitta cycle, there is 10% of the crop (called Maaser Sheni) whose value is redeemed onto a small coin before becoming edible.
There remains 10% of the crop (called Maaser Rishon) which should ideally be given to a Levi, and, in years 3 and 6 of the Shemitta cycle, there is 10% of the crop (called Maaser Ani) which must be given to the poor. The rabbinate does not enforce this and many growers regularly, unfortunately, steal this from the poor. There is no holiness attached to that produce, so the food in the market is still Kosher to eat.
So to answer your question: yes there are tithes that need to be given to the poor, but the rabbinate generally does not impose this and it usually ends up getting stolen back by the grower :(
You are talking about terumah or trumas ma'aser which cannot be eaten nowadays because it must be kept in a state of tahara (ritual purity). Thanks to @DannySchoemann for the correction. Since everyone is tamei meis (ritual impurity because of contact with the dead), it cannot be eaten and must be destroyed. It cannot be redeemed.
From the Torah there is no specified amount for trumah. However, we are supposed to set aside 1% nowadays for it (miderabbanan).
A similar rule applies to ma'aser sheni (the second tithe) but it can be redeemed and the coin used for the redemption destroyed.
What is done with terumah and maaser nowadays?
Nowadays the Levites' tithe is separated and kept (since anyone can eat it); the kohanim's 1% (plus a token amount for terumah) is separated and destroyed (because it can only be eaten in a state of ritual purity, which is no longer possible); the second tithe is redeemed for a token amount, which is destroyed, or in the third and sixth years its value is given to charity.
