Pansies are cool-season ornamental flowers often used as annual bedding plants, though they are perennial in mild climates. The plants grow best in full sun or partial shade and are available in blossom colours ranging from white to deep red, blue or even black and multicolour, and vary in flower size depending on the cultivar. A number of pests, diseases and problems affect pansies.
Aphids, spider mites and mealybugs suck sap from pansy foliage. Aphids are small, soft-bodied, pear-shaped insects that vary in colour depending on what they have been eating as well as their species. Spider mites are less than 0.05 inches long, which is too small to see clearly without magnification. These eight-legged arthropods have oval-shaped bodies and red spots near their heads. Mealybugs are usually less than 0.2 inches long, with soft, oval-shaped, waxy grey bodies. Heavy infestations stunt plant growth and discolour leaves. Spider mites also spin unsightly webs on the foliage, while aphids and mealybugs exude copious amounts of a sticky liquid called honeydew. A thick, unsightly black fungus called sooty mould grows on the honeydew.
Slugs, snails, caterpillars, cutworms and flea beetles feed on pansy foliage. Slugs and snails are nocturnal feeders that leave mucus trails on foliage and chew large, unattractive holes in the leaves. Caterpillars, which are larval butterflies and moths, seriously damage pansies by eating the leaves, blossoms, flower buds and emerging leaf shoots. Cutworms sever pansy stems before feeding on the leaves, while flea beetles, which are 0.25-inch-long black beetles, eat the blossoms, shoots and leaves.
Several common pansy diseases include root and crown rot, leaf spot diseases and botrytis blight. Several fungal pathogens such as Fusarium and Phytophthora fungi infect the roots; diseased plants have yellow leaves and discoloured or rotted roots. Root and crown rot infections often cause plant death. Pansies with leaf spot infections have unattractive black, purple, or brown spots or blotches on their foliage. The Botrytis fungus causes botrytis blight. A grey fungus grows on the stems and blossoms, and infected plants may have slimy, rotten tissue.
Nutrition and Environmental Issues
Pansies that receive too much or too little water suffer from plant damage. Pansy roots die if they get too much water, and the foliage decays and dies. Plants that get too little water become water-stressed, which invites attacks from insect pests. Too little water also results in leaf loss or wilting. Plants that do not receive enough nitrogen may fail to grow, and the foliage turns yellow. A lack of boron results in distorted growth and plant death.