2019 ASHS Annual Conference

An important challenge in broccoli production is the intensive use of pesticides (conventional and organic), to manage pests such as cabbage loopers, imported cabbage worm, flea beetles, and cabbage aphids that cause immense damage by direct feeding and defoliating the plant. Many conventional/sustainable growers use spun-bond polypropylene row covers (Agribon, Reemay) to insure early harvest and exclude pests. Although they help with pest exclusion, they can overheat plants and must be pulled off by early summer, leaving the crop exposed to pests. This study conducted at the Horticulture Research Station, Ames, IA evaluated a new nylon-mesh row cover material (Protek net) that could be used to extend the growing season and protect plants from insect pests. The study investigated the effect of three row cover treatments (Agribon, Protek net, or no-cover) and six broccoli cultivars (Asteroid, Emerald Star, Green Gold, Green Magic, Gypsy, and Luna) on crop growth, yield, and head quality. The experimental design was a split plot randomized complete block design with row cover treatments as the whole and cultivars as the subplot factor with four replications. There were no significant differences in broccoli yield between row cover treatments, however, cultivars had a significant effect on yield with ‘Green Gold’ and ‘Emerald Star’ producing higher marketable yields than ‘Green Magic’, ‘Gypsy’, and ‘Luna’. Row cover treatments did not affect average head diameter. Differences existed between cultivars with head diameters ranging from 10.4 to 14.5 cm. ‘Green Magic’ had the lowest head diameter when compared to Asteroid, Emerald Star, Green Gold, and Luna. Row cover treatment was significant for hollow stem. No-cover treatment had heads with lower hollow stems than Agribon treatment. Between cultivars, ‘Gypsy’ and ‘Asteroid’ had the highest and ‘Emerald Star’ had the least number of heads with hollow stem.

The study shows that Protek net and Agribon could be successfully utilized to mitigate insect pest damage in broccoli production. Specially, with Protek net, there is an added advantage of zero insecticide applications as the netting can remain on the crop until harvest. Cultivars play a critical role in broccoli production and growers should utilize appropriate cultivars that are better adapted to their growing region. ‘Emerald Star’ and ‘Green Gold’ produced higher number of marketable heads and lower number of non-marketable heads. Soil Boron concentration should also be taken in to consideration as it has direct implications on hollow stem.