Bath white

The Bath white is a member of the Pieridae family within the order Lepidoptera. The adult is a butterfly with a wingspan of approximately 45–50 mm.

The upper side of the wings is white with distinctive black markings on the tips of the forewings and a dark pattern near the base.

The underside of the wings features a mottled greenish-yellow pattern, which provides excellent camouflage when the insect is at rest.

The larva reaches a length of up to 30 mm and is greyish-green in color, adorned with yellow side stripes and fine black spots and hairs.

The pupa is pointed in shape, ranging from grey to greenish, and typically overwinters in the soil or among plant debris.

The larvae are responsible for the damage, feeding voraciously on the foliage and reproductive structures of host plants.

Primary targets include members of the Brassicaceae family, such as oilseed rape, mustard, turnip, and various types of cabbage.

During outbreaks, the larvae can cause severe defoliation, leaving only the main veins of the leaves intact.

Beyond foliage, the caterpillars often feed on buds and blossoms, which significantly reduces the seed yield of the crops.

Damaged tissue is highly susceptible to secondary infections, which can further impact plant health and the quality of the harvested product.

Depending on the climatic zone, the Bath white can complete two to four generations within a single growing season.

The first emergence of adults usually occurs in the spring, typically from late April or May, when temperatures become conducive for activity.

Females lay their eggs singly on the undersides of host plant leaves, making them difficult to detect during initial field scouting.

The adult flight period is prolonged, meaning that larvae of different developmental stages may be found simultaneously in the field.

The peak of damage often occurs during the summer months of June and July, coinciding with the mass development of successive larval generations.

A primary indication of infestation is the presence of adult butterflies fluttering actively over cruciferous crop fields.

Small holes or «window» patterns on the leaves indicate early feeding by young larvae that skeletonize the underside of the leaf surface.

As the larvae mature, they consume the edges of the leaves, eventually causing significant damage to the entire plant canopy.

Visible frass on the leaves serves as a clear indicator of larval feeding activity and current infestation within the crop.

During field inspection, larvae can be found resting on the underside of leaves or within the dense areas of the inflorescences.

Cultural practices include deep plowing after harvest, which disrupts the overwintering pupae and reduces the next season's population.

Effective weed management, particularly removing cruciferous weeds, is essential to eliminate alternative host sites for the pest.

Biological control methods, such as the use of Trichogramma wasps, can successfully suppress population levels without chemical input.

Chemical control is advised when population densities exceed economic thresholds, utilizing appropriate contact or systemic insecticides.

When applying pesticides, it is crucial to follow regulatory guidelines regarding application timing and harvest intervals to ensure food safety.