From a gardening forum.
"Shrimp shell meal or crab shell meals, when composted are incredibly rich in so many trace minerals it can boggle the mind. They have to be used sparingly on occasion in order to maintain a balance of certain mineral nutrients like phosphorus and calcium. One of the truly amazing things about these meals from crustacean shells is the wealth of enzymes and plant growth stimulating compounds including chitinase. Chitinase will literally keep bugs, both chewing and sucking from ever infesting your plants. The primary function of chitinase is the breakdown of chitin, which is what all insect pests are made of. They take in the enzymes from walking on plants and the chitinase goes to work basically digesting the insects.
This was proven in studies done by Los Angeles area gardeners in conjunction with the University of California at Riverside on a whitefly species that was out of control here in southern California a few years back. The whitefly was the Giant Mexican Whitefly (Aleurodicus dugesii). Infestations were reduced with mild chitinase containing organics like worm castings and were wiped out with materials containing higher levels of this enzyme like crab shell and shrimp shell meal."
Pretty sweet s#it.
