negatively regulates vulval development negative regulation of vulval development downregulation of vulval development inhibition of vulval development down-regulation of vulval development GO:0040027 down regulation of vulval development biological_process Any process that stops, prevents, or reduces the frequency, rate or extent of development of the vulva. Vulval development is the process whose specific outcome is the progression of the egg-laying organ of female and hermaphrodite nematodes over time, from its formation to the mature structure. In nematodes, the vulva is formed from ventral epidermal cells during larval stages to give rise to a fully formed vulva in the adult. regulation of vulval development negative regulation of nematode larval development biological regulation