What is the definition/explanation of the term 'Nematophagous'?

Identify the incorrect statement.
$(i)$ Bacillus thuringiensis are available in sachets as dried spores which are mixed with kerosene and sprayed on to vulnerable plants.
$(ii)$ $B. thuringiensis$ are used to control butterfly caterpillars,but leave other insects unharmed.
$(iii)$ The toxin of $B. thuringiensis$ is released in the blood of larvae and the larvae get killed.
$(iv)$ By the development of methods of genetic engineering,$B. thuringiensis$ toxin genes have been introduced into plants.

The common biological control agent for plant diseases is ......

Which bacteria was the first to be used as a biopesticide on a commercial scale in the world?

Which was the first commercially developed insecticide?

Which weed has been eradicated by biological control?