The cochineal insect has been used in checking the wild growth of:

Which group consists of biocontrol microorganisms?

In modern biology,the bacterium $Bacillus$ $thuringiensis$ is widely used as a/an:

Ratio of $CuSO_4$, $Ca(OH)_2$ and water in 'Bordeaux mixture' is

Consider the following statements:
$I.$ Ladybirds and dragonflies are used to get rid of aphids and mosquitoes.
$II.$ The bacteria $Bacillus$ $thuringiensis$ $(Bt)$ are used to control butterfly caterpillars.
$III.$ $Trichoderma$ $sp.$,free-living fungi,are present in root ecosystems where they act against several plant pathogens.
$IV.$ $Rhizobium$ is a symbiotic bacterium that lives in the stem of legumes.
Which of the statements given above are correct?

Which one of the following proved effective for biological control of nematodal diseases in plants?