Collard plant is commercially cultivated for its thick, slightly bitter, edible leaves. They are available year-round, but are tastier and more nutritious in the cold months, after the first frost. For best texture, the leaves are picked before they reach their maximum size, at which stage they are thicker and are cooked differently from the new leaves. Age does not affect flavor. Flavor and texture also depend on the cultivar; the couve manteiga and couve tronchuda are especially appreciated in Brazil and Portugal.
The sting nematode Belonolaimus gracilis and the awl nematode, Dolichodorus spp. are both ectoparasites that can injure collard. Root symptoms include, stubby or coarse roots that are dark at the tips. Shoot symptoms include, stunted growth, premature wilting and chlorosis (Nguyen and Smart, 1975). Another species of the sting worm, Belonolaimus longicaudatus is a pest of collards in Georgia and North Carolina (Robbins and Barker, 1973). B. longicaudatus is devastating to seedlings and transplants. As few as three nematodes per 100g of soil when transplanting can cause significant yield losses on susceptible plants. They are most common in sandy soils (Noling, 2012).
The stubby root nematodes Trichodorus and Paratrichodorus attach and feed near the tip of collard’s taproots. The damage caused prevents proper root elongation leading to tight mats that could appear swollen, therefore resulting in a “stubby root” (Noling, 2012).
Several species of the root knot nematode Meloidogyne spp. infest collards. These include: M. javanica, M. incognita and M. arenaria. Second-stage juveniles attack the plant and settle in the roots. However, infestation seems to occur at lower populations compared to other cruciferous plants. Root symptoms include deformation (galls) and injury that prevent proper water and nutrient uptake. This could eventually lead to stunting, wilting and chlorosis of the shoots (Crow and Dunn, 2012).