Although primula flowers, commonly referred to as primroses, are favoured in the home garden for their variety of colours during spring bloom, hungry pests can leave behind a path of destruction. The act of eating typically brings biting and chewing to mind, but sucking pests also target primula flowers and sustain themselves on plant tissue fluid. Since vigorous plants have a greater capacity for recovery from pest infestations than weakened plants, home gardeners should maintain consistent care. Act quickly when symptoms are apparent.
Beet armyworms are foliage-eating caterpillars that attack primula leaves and flowers. These caterpillars are typically hairless, displaying bodies in green to near black with yellow side stripes. Full body lengths measure approximately 1 inch. These pests skeletonise primula leaves by eating all plant tissue except for the veins, creating the appearance of a skeleton and then move onto blooms. Gardeners should control these caterpillar pests by first releasing natural enemies available at garden supply stores. The best options are parasitic wasps and tachinid flies that kill caterpillars. For minor infestations, home gardeners can simply hand pick caterpillars from plants. For severe problems, effective chemical insecticides include chlorpyrifos and malathion.
Black Vine Weevil
Black vine weevils are chewing bugs that target a number of host plants including primrose, along with roses, clematis and phlox. With dark brown-to-black bodies measuring approximately 1/3 to 1/2 inches in length, these weevils are beetle pests that chew notched shapes into primrose plants during nighttime hours, making them hard to handpick during the day. Home gardeners can control these pests by releasing the fungus Beauveria bassiana, which kills weevils, onto primrose plants. Effective insecticides include soil-derived spinosad or a chemical-based insecticide with the active ingredient azadirachtin.
Whiteflies are sucking bugs that, as their name implies, are white in colour and winged, measuring 1/16 inch in length. Fond of primroses, these pests result in distortion and yellowing of plant parts, particularly leaves. Additionally, as whiteflies feed, they release a sticky-sweet substance called honeydew that drips onto plant parts. Honeydew encourages the growth of sooty mould, a black-hued fungus that covers plant parts, blocking out essential sunlight. Home growers can manage these primula pests with the application of a chemical insecticide with the active ingredient malathion, according to the University of Kentucky College of Agriculture.
Selecting plants that deer do not eat is a challenge, as deer are known for their tendency to eat just about anything. Primula flowers fare better than many in avoiding deer damage. The Rutgers New Jersey Agricultural Experiment Station gives primula flowers a grade of B on their A through D scale, indicating primula plants are seldom damaged by deer.