Ladybird is useful for getting rid of which of the following?

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?

Identify the organism based on the following characteristics:
- They are pathogens.
- They attack insects and other arthropods.

Among pesticides,$Zinc \ phosphide$ is used for:

The first bioinsecticide to be developed on a commercial scale was:

Given below are two statements.
Statement $I$: Baculoviruses are pathogens that attack nematodes.
Statement $II$: Baculoviruses are used as biological control agents in ecologically sensitive areas as they are species-specific in their action.
In the light of the above statements, choose the correct answer from the options given below.