Pontia protodice Boisduval and LeConte Lepidoptera Pieridae

Natural History

Distribution. Southern cabbageworm, also known as the checkered white, is found throughout the United States and south into Mexico. It is native to North America. As its common name suggests, it is principally a southern insect, and occurs in the North only sporadically. It is rare in the New England states and southern Canada.

Host Plants. Southern cabbageworm attacks a variety of cultivated crucifers, but is much less abundant than imported cabbageworm, Pieris rapae (Linnaeus). Apparently southern cabbageworm, which formerly was quite abundant in some localities, has been largely displaced by Pieris rapae. Vegetable crops known to be attacked are cabbage, cauliflower, Chinese cabbage, radish, and turnip. The host range is probably equivalent to imported cabbageworm, but because southern cabbageworm is not a serious pest it has not been well studied. Wild crucifers that support the growth of southern cabbageworm include pepperweed, Lepidium spp.; yellow rocket, Barbarea vulgaris; shepherdspurse, Capsella bursa-pastoris; tansy-mustard, Descurainia pinnata; field pennycress, Thlaspi arvense; hoary cress, Cardaria draba; black mustard, Brassica nigra; and others.

Life Cycle and Description. Three or four generations occur annually. Southern cabbageworm overwinters in the pupal stage.

  1. The eggs are pale yellow initially, but turn orange as they mature. The are deposited singly on flowers or leaves of the larval host plants.
  2. Larvae are pale blue-green or bluish-gray, with numerous small black spots. They bear a pair of yellow stripes running the length of the back, and a stripe on each side. The head is yellow with reddish spots. A key to distinguish this caterpillar from similar pierid larvae feeding on crucifers is provided in Appendix A. (See color figure 94.)
  3. The chrysalis is light blue-grey and speckled with black. In general shape, the chrysalis resembles that of imported cabbageworm, bearing sharp keellike structures on the back. This is the overwintering form.
  4. The adults have a wingspan of about 3.55 cm. They are similar in appearance to imported cab-bageworm, but the southern cabbageworm butterflies are more heavily marked with scattered grayish-brown or black spots, both dorsally and ventrally, on their white background. The female, in particular, may be dark, with up to 50% of the wings darkened. The males, in contrast, bear only a few dark spots, but are still more heavily marked than Pieris rapae. The first generation butterflies, which emerge in the spring following diapause, may be smaller and very light in color. Adults can be seen feeding on nectar from a wide variety of flowering plants, and are highly dispersive. A key for differentiating this species from other cabbage white butterflies is included in Appendix A.

The biology of southern cabbageworm was given by Opler and Krizek (1984), and Scott (1986).

Damage

Larvae prefer to feed on flowers and flower buds, but they also eat leaves. On cabbage, they restrict their

Pontia Protodice
Adult male southern cabbageworm.
Adult female southern cabbageworm.

feeding to the outer leaves. This makes them much less damaging than imported cabbageworm, which bore into the head.

Management

Southern cabbageworm butterflies were observed to be highly attracted to fluorescent orange, and to be captured with sticky traps, especially when the traps were positioned close to the soil surface (Capi-nera, 1980). The methods discussed for management of imported cabbageworm are also appropriate for southern cabbageworm.

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