Cardamom growers in South India are already using neem cake to control nematodes. Of 19 growers interviewed recently, 17 said that nothing works as well. These were sophisticated farmers who monitor world cardamom prices regularly and use synthetic chemicals for controlling other pests in their fields. In other words, they weren't using neem out of ignorance or poverty. They incorporate 100-259 kg per hectare of neem cake in their cardamom fields every year. About 3,000 tons of neem cake are now used annually in India's Cardamom Hills. It is sold by pesticide dealers, who transport it from 250-300 km away. 3
Various neem extracts kill snails. This appears to be beneficial in some cases.
In laboratory tests, for example, ethanol extracts proved toxic to the aquatic snail (Biomphalaria glabrata), a species that is necessary to the life cycle of the parasite causing schistosomiasis (bilharzia). The extracts killed both the adult snail and its eggs.4 This raises the possibility that neem products may find a role in controlling schistosomiasis, a horrible scourge that infects some 200 million people in the tropics.
In another test, an aqueous solution of neem fruit resulted in a 100-percent kill of Melania scabra.5 This snail, common throughout the Orient, is a vector of lung flukes, a parasitic flatworm that encysts in the lungs of livestock, wildlife, and people, causing debilitation and sometimes death.
Little is known about neem's effects—beneficial or detrimental—on crustaceans. However, in one intriguing set of experiments in the Philippines, it proved beneficial.
In rice paddies, the ostracod Heterocypris luzonensis feeds on the blue-green algae that fix nitrogen from the air. This minute aquatic crustacean thereby reduces a source of fertilizer for the crop. Killing this tiny creature thus would indirectly boost the nitrogen available and probably increase rice yields.6 Aqueous neem-kernel extracts have killed it very effectively under laboratory conditions.7