Many different pests could be eating your pea plants. Most are insects that feed on either the seeds, leaves, stems or pods of the plant.
According to the Integrated Pest Management Program at North Carolina State University, there are three pests that can eat and destroy the foliage of your pea plant: the bean leaf beetle, Mexican bean beetle and the vegetable leafminer. Both beetles are small insects about 6mm long with black spots on their body, while the leafminer is a maggot-shaped insect. Randall P. Griffin, Entomologist at the Clemson Cooperative Extension, also identifies spider mites, which are so small they are barely visible, and two caterpillars, the Lima bean vine borer and the cabbage looper, as potential pea foliage pests.
Many different insects can feed on the actual pods of the pea plant. NCSU's IPM lists the corn earworm, European corn borer, cowpea curcculio, stinkbugs, bean leaf beetle larva and the seedcorn maggot as bugs that can devour pea pods. Griffin from the Clemson Cooperative Extension also includes the small tarnished plant bug as another insect that can tear apart pea pods.
Sapsuckers and Seedling Eaters
The IPM at NSCU also states that various species of aphid, pear-shaped insects that are about 3mm long can suck the sap out of pea plants, causing discolouration and deformation of the plant. According to Griffin, aphids will also infest and eat seedlings of the pea plant.