Root maggots are serious pest of brassica crops (broccoli and cauliflower, Brassica oleracea var. botrytis) in the Salinas Valley causing widespread economic damage. Maggots are the larval stages of true flies (Order Diptera). In the Salinas Valley, broccoli and cauliflower are grown in 28,328 Ha mostly in rotation with lettuce. Root maggots mostly infest roots (Fig. 1a), but if the population pressure is severe, they could even attack the floret/flower head (Fig. 1b). Cauliflower is a transplanted crop, thus, seedlings are raised in nurseries whereas, broccoli is direct seeded. One of the anecdotal hypotheses among growers and pest control advisors is that the transplants are infested with eggs or maggots prior to planting, thus causing widespread losses.

Method: Plants infested with root maggots were collected from the field during Dec. 2012 to Mar. 2013 and were identified at the species level using dipteran keys. Also, representative samples were identified by an insect taxonomist at California Department of Food and Agriculture. Root samples were collected from seven cole fields (5 cauliflower and 2 broccoli) in the Salinas Valley during Dec. 2012 to Mar. 2013. Each field was broken up into two zones, border and central. Border zone was adjacent to surrounding field/road. A zone consisted of two beds. Number of healthy plants was qualified per zone and the percent plant mortality was determined. Within each zone, 100 root samples were randomly collected and were examined for root maggot infestation.

Results and Discussion: Root maggots sampled from infested-broccoli, cauliflower, and turnip fields in the Salinas Valley of California were cabbage maggot, Delia radicum (L.). Location of the fields positively identified as infested with cabbage maggot is shown in the Figure 2. The plant mortality tended to be more common in the border than in the central zone of the cole fields (Fig. 3). This result suggests that cabbage maggot infestations have been most likely related to invading flies from the surrounding fields than pre-infested transplants. I will continue monitoring the root maggot species on brassica and pattern of infestation in the Salinas Valley.