Root-knot nematodes begin their lives as eggs that rapidly develop into J1 (first-stage juvenile) nematodes (Figure 16). The J1 stage resides entirely inside the translucent egg case, where it molts into a J2 nematode. The motile J2 stage is the only stage that can initiate infections (Figure 20). J2s attack growing root tips and enter roots intercellularly, behind the root cap (Figure 21). They move to the area of cell elongation where they initiate a feeding site by injecting esophageal gland secretions into root cells. These nematode secretions cause dramatic physiological changes in the parasitized cells, transforming them into giant-cells (Figure 11). If the nematode dies, so will the giant-cells upon which it feeds.
For more detail, please see the source: https://www.apsnet.org/edcenter/disandpath/nematode/pdlessons/Pages/RootknotNematode.aspx