No, he is not allowed to spray poison on your plants or throw debris into your yard; he may trim overhanging limbs and vines, however. The problem is, there is no way to enforce your rights other than by suing him; and in a lawsuit, you can only get the actual costs you incurred (e.g. if you hired someone to clean up the debris thrown into your yard) or damage suffered (e.g. he killed one or more of your bushes, the economic value of that bush). It may well be that a lawsuit is not cost-effective for what he did--you may get back much less than the cost of the suit and/or value of the time you put into it.