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Pansy Diseases & Insect Pests

Pansies are among the most popular garden flowers grown today. They are most commonly grown as annuals, producing the best flowers and growth when temperatures are mild in the fall and spring. Although they are relatively trouble-free, there are several problems that can affect them.

Diseases

Anthracnose: Anthracnose is caused by the fungus Colletotrichum species and causes a browning and blotching of the leaves. Initially, the infected leaves have pale yellow spots with distinct black margins. As the disease progresses, the center of the spots becomes dry and tan and may have a concentric ring pattern. Flower petals of infected plants may be spotted and develop abnormally. Seriously infected plants may die.

Prevention & Treatment: Combat anthracnose by digging up and destroying severely infected plants. Pick off infected leaves as soon as they appear. Reduce disease development by avoiding overhead watering. Apply a thin layer of mulch around plants to help prevent fungal spores from splashing onto leaves from the soil. For serious infections of anthracnose, fungicide sprays containing either chlorothalonil or mancozeb are available for homeowner use. Apply at 7- to 14-day intervals until conditions no longer favor disease development. See Table 1 for examples of products containing these fungicides. As with all pesticides, read and follow all label instructions and precautions.

Other Leaf Spots: There are many fungi (Alternaria species, Cercospora species, Myrothecium species, and Ramularia species) that can cause unsightly spots on pansy foliage. Leaves may have transparent tan, brown, or black spots. Often these spots may grow together to form larger patches of dead tissue. Reduce leaf spot development by picking off and destroying infected leaves as soon as they appear. Avoid overhead irrigation. Moist leaf surfaces are ideal locations for these fungi to thrive. A layer of mulch will help to prevent the fungi from splashing from the soil onto plants.

Cercospora leaf spot commonly occurs in fall landscape beds. It appears as a dry, brown blotch or an irregular purple lesion, especially during cool weather. For serious infections of Cercospora leaf spot, fungicide sprays containing thiophanate-methyl can be used. Apply at 7- to 14-day intervals until conditions no longer favor disease development. See Table 1 for examples of products containing these fungicides. As with all pesticides, read and follow all label instructions and precautions.

Black Root Rot: This disease is caused by the fungal organism, Thielaviopsis basicola, which can affect a wide range of ornamental plants. Older plants affected by the disease turn yellow and have small crinkled leaves. Close observation reveals a black discoloration moving up from the tips of the roots. Diagnosis may be difficult without professional help.

Prevention & Treatment: Remove and discard any infected plants. Provide good drainage to plants and avoid overwatering. The disease can be suppressed but not cured, with regular applications of fungicides containing thiophanate-methyl. See Table 1 for examples of products containing these fungicides. As with all pesticides, read and follow all label instructions and precautions.

Root & Crown Rot: Many fungi (Phytophthora species, Pythium species, Rhizoctonia species, and Fusarium species) live in the soil, which can infect the roots or the base of the plant (crown) at the soil line. Plants may wilt and suddenly die, or the leaves may simply turn yellow. A dark sunken area may be seen on the stem at or near the soil line. Roots may appear rotted. Some plants may survive but remain weak and stunted.

Prevention & Treatment: The fungus thrives in areas with poor drainage and warm soils. Always choose locations that have good drainage for planting. The drainage of existing areas can be improved by using raised beds. Avoid applying too much water since many of these fungi thrive in moist conditions. Always allow the soil to dry between each watering. Promote drying of the soil by not setting plants too close or applying too much mulch around plants. Prevent future infection by always removing and destroying diseased plants.

Fungicides can be effective on a preventative basis only, and repeat applications are required. Fungicides containing potassium salts of phosphorous acid can be applied as a drench in the home landscape and will suppress but not cure infected plants. Apply all chemicals according to directions on the label. See Table 1 for examples of brands and products.

Gray Mold (Botrytis Blight): This disease is caused by a fungus, Botrytis species, which produces a fuzzy, gray coating on the flowers and stems of many plants. When infected flowers are picked, a puff of gray spores can usually be seen. Infected areas of the plant will eventually be soft, slimy, and decayed.

Prevention & Treatment: Reduce disease development by keeping plant surfaces dry, removing aging flower blossoms, and providing good air circulation. Do not overcrowd plants. Fungicide sprays containing chlorothalonil, mancozeb, or copper fungicides are available for serious infections. Repeat every 7- to 14-days when conditions favor disease development. See Table 1 for examples of products containing these fungicides. As with all pesticides, read and follow all label instructions and precautions. For more information about gray mold and control, please see HGIC 2100 Gray Mold (Botrytis Blight).

Insects & Other Pests

Aphids: Various aphid species are pests of pansies. Aphids are soft-bodied insects that range in color from tan to pink to green to almost black and in size from 1/16– to ⅜-inch. They feed by piercing plant tissue and sucking plant sap. On pansies, they feed mainly on new leaves and stems. As they feed, they excrete honeydew (a sugary waste material), which drips down onto nearby leaves. The sooty mold fungus grows on the honeydew, resulting in unsightly, dark fungal growth on the pansy foliage.

Control: Several natural enemies, such as ladybird beetles (ladybugs) and lacewings feed on aphids. As much as possible, these predators should be allowed to reduce aphid populations. Planting small-flowered nectar plants, such as Queen Anne’s lace (Daucus carota) will help attract these beneficial predators.

As a result of their phenomenal ability to reproduce, aphids are very difficult to control with insecticides. Leaving one aphid alive can result in the production of a new colony very quickly. In addition, the use of insecticides kills the beneficial insects that normally keep aphid populations under control. However, if natural predators do not reduce aphid populations sufficiently, the following insecticides are recommended: insecticidal soap, cyfluthrin, permethrin, bifenthrin, lambda cyhalothrin, zeta cypermethrin, malathion, or acephate. See Table 2 for examples of products containing these insecticides. As with all pesticides, read and follow all label instructions and precautions.

Spider Mites: Two-spotted spider mites (Tetranychus urticae) are also pests of pansies. Mites are not insects but are more closely related to spiders. They tend to be more of a problem during hot, dry periods. Mites are extremely small and can barely be seen without a magnifying lens. They have piercing mouthparts with which they puncture plant tissue and suck plant sap. Early symptoms on pansies are pinprick holes in leaves. These symptoms can be easily overlooked. Over time, tiny tan spots can be seen. Seriously infested leaves turn tan and die. A fine webbing is visible on some leaves.

Prevention & Control: Infestations are less likely to occur when pansies are grown during spring or fall when the weather is cool. When infestations do occur, begin spraying plants with insecticidal soap weekly as needed. Other pesticides labeled for homeowner use against spider mites include tau fluvalinate or bifenthrin. See Table 2 for examples of products containing these miticides. As with all pesticides, read and follow all label instructions and precautions.

Slugs & Snails: These pests feed on pansy leaves and blooms at night. In a single night, their feeding can result in large, irregular holes in leaves and flowers. A sign of their presence is the slimy trail of mucus that they leave behind as they move. During the day, they hide under leaf litter, mulch, and flower pots where it is moist. Snails and slugs are mollusks and, thus, are related to clams and oysters. Like all mollusks, they must stay moist all the time to survive.

Control: The first step in discouraging slugs and snails is to remove mulch and leaf litter near plants to reduce the moist conditions necessary for their survival. Slugs and snails can be removed by handpicking. The best time to look for them is a few hours after dark using a flashlight. Slug and snail traps can be made by filling shallow containers with beer and placing each container in a hole in the soil so that the rims are level with the soil surface. These pests are attracted by the yeasty smell and will fall in and drown. Before putting down the traps, water the area to encourage slug and snail activity that night. Alternatively, placing a board on the ground, raised about one inch, is another trap option. It provides a daytime hiding place for these pests that you can then lift to locate and dispose of them.

Protect plants by sprinkling diatomaceous earth around the plants. Diatomaceous earth is very sharp and scratches the skin of these soft-bodied critters, resulting in dehydration and death. It must be reapplied after rain or watering.

Products containing metaldehyde (3 percent) bait can be used to control snails and slugs in the home landscape. However, newer products are available that contain iron phosphate. Iron phosphate will stop feeding by the snails and slugs quickly and is much less harmful to pets, birds, and non-target animals than metaldehyde. Any unconsumed iron phosphate bait adds nutrients (iron and phosphorus) to the soil. Consult the label for information on the rate. See Table 3 for examples of products containing these slug and snail baits. As with all pesticides, read and follow all label instructions and precautions.

Other Problems

Short Blooming Period: Pansies grow and flower best in cool conditions when temperatures are below 75 °F. Weather that is too hot will cause pansies to fade and die out. Plant pansies in the cool conditions of fall or early spring and prolong blooming by pinching off the older flowers (deadheading). This prevents the plant from making seeds and encourages more flowers to form. Cutting back the plants by one-third will also stimulate new growth and extend the blooming period.

Spindly Growth: Pansies will produce lanky growth when light levels are too low. They require strong filtered light and flower best in full sun during cool weather.

Warty Growths on Stems: Pansy stems and flower stalks may be covered with small, wart-like bumps. This condition is caused by too much water inside of the plant and not by an insect or disease. When a plant gets too much water, the pressure inside the plant builds up, and water ruptures from the stems and leaves. This condition is called oedema. Wet soil combined with cool, cloudy conditions are ideal for this to occur. Prevent this problem by allowing the soil to dry between each watering, and always plant in well-drained soil. Promote drying of the soil by not applying too much mulch around plants and not setting plants too close together.

Nutrient Deficiencies: Pansies grow best with a pH of 5.4 to 5.8 in soil-less mixes for containers and 5.6 to 6.0 for in-ground plantings; therefore, in the typical residential landscape, the beds will probably not need a lime application. The landscape soil should be tested annually to determine both the soil pH and the various nutrient levels.

If the pH is higher than 5.8, then a boron or an iron deficiency may occur. A boron deficiency will stop the growth of the main shoot, and the small developing foliage will remain small and become thickened and cupped. An iron deficiency also may occur if the pH is above 5.8, and the symptom is interveinal chlorosis of the leaves, which is yellowing between the leaf veins. This will occur primarily on the youngest leaves. To correct for both a boron and iron deficiency in a landscape bed, apply a micronutrient product, such as Southern Ag Essential Minor Elements, which contains both iron and boron, along with several other micronutrients. Additionally, it will lower the soil pH to help prevent a reoccurrence of these deficiencies. Apply 1 cup per 10 square feet of beds. Always apply this product when the foliage is dry and water the granules into the soil. Additionally, the use of a small amount of leaf compost mixed into the soil (10% by volume) will provide the boron that plants require.

A magnesium deficiency may occur if the landscape soil pH drops below 5.4 or if there is a high level of calcium in the soil, such as with the excessive use of leaf compost or mushroom compost. The symptom of a magnesium deficiency is interveinal chlorosis of the fully expanded younger leaves, but not of the developing foliage that is still becoming larger. This deficiency can be corrected by the addition of Epsom salts (magnesium sulfate). Water the plants with a solution of 1 tablespoon of Epsom salts per gallon of water.

Table 1. Control of Pansy Diseases

Active Ingredient Examples of Brands & Products
Chlorothalonil Bonide Fung-onil Concentrate; & RTU2
Ferti-lome Broad Spectrum Landscape & Garden Fungicide Concentrate; & RTU2
GardenTech Daconil Fungicide Concentrate; & RTU2
Hi-Yield Vegetable, Flower, Fruit & Ornamental Fungicide Concentrate
Ortho MAX Garden Disease Control Concentrate
Southern Ag Liquid Ornamental & Vegetable Fungicide Concentrate
Tiger Brand Daconil Concentrate
Copper Fungicides Bonide Liquid Copper Concentrate (a copper soap); & RTU2
Camelot O Fungicide/ Bactericide Concentrate (a copper soap)
Natural Guard Copper Soap Liquid Fungicide Concentrate; & RTU2
Bonide Copper Fungicide Spray or Dust (copper sulfate); & RTU2
Monterey Liqui-Cop Copper Fungicidal Garden Spray Concentrate (copper ammonium complex); & RTS1
Southern Ag Liquid Copper Fungicide Concentrate (copper ammonium complex)
Monterey Liquid Copper Fungicide RTU2 (a copper soap)
Espoma Organic Copper Soap RTU2
Mancozeb Bonide Mancozeb Flowable with Zinc Concentrate
Southern Ag Dithane M-45 (concentrate)
Potassium Salts of Phosphorous Acid Monterey Garden Phos (concentrate)
Organocide Plant Doctor (concentrate)
Agrisel Biophos Pro (concentrate)
Thiophanate Methyl Cleary’s 3336-WP Turf & Ornamental Fungicide (a wettable powder)
Southern Ag Thiomyl Systemic Fungicide (a wettable powder)
1 RTS = Ready to Spray (a hose-end sprayer)
2 RTU = Ready to Use (a pre-mixed spray bottle)With all pesticides, read and follow all label instructions and precautions.

Table 2. Control of Pansy Insect Pests & Spider Mites.

Active Ingredient Examples of Brands & Products
Acephate Bonide Systemic Insect Control Concentrate
Bifenthrin Bifen I/T Concentrate
Ferti-lome Broad Spectrum Insecticide Concentrate; & RTS1
Hi-Yield Bug Blaster Bifenthrin 2.4 Concentrate; & RTS1
Martin’s FLEE Ready to Use Yard Spray RTS1
Monterey Mite & insect Control Concentrate
Ortho Outdoor Insect Killer Concentrate
Ortho Bug B Gon Insect Killer for Lawns & Gardens Concentrate; & RTS1 (also with zeta-cypermethrin)
Ortho BugClear Insect Killer for Lawns & Landscapes Concentrate; & RTS1 (also with zeta-cypermethrin)
Talstar P Concentrate
Up-Star Gold Insecticide Concentrate
Cyfluthrin Bayer BioAdvanced 24 Hour Lawn Insect Killer RTS1
Bayer BioAdvanced Complete Insect Killer for Soil & Turf I RTS1
Bayer BioAdvanced Rose & Flower Insect Killer RTU2
Insecticidal Soap3 Bonide Insecticidal Soap RTU2
Espoma Organic Insect Soap RTU2
Garden Safe Insecticidal Soap Insect Killer RTU2
Miracle Gro Nature’s Care Insecticidal Soap RTU2
Natria Insecticidal Soap RTU2
Natural Guard Insecticidal Soap Concentrate
Safer Brand Insect Killing Soap Concentrate
Whitney Farms Insecticidal Soap RTU2
Malathion Bonide Malathion 50% Insect Control
Gordon’s Malathion 50% Spray
Hi-Yield 55% Malathion Insect Spray
Martin’s Malathion 57% Concentrate
Ortho Max Malathion Insect Spray Concentrate
Spectracide Malathion Insect Spray Concentrate
Southern Ag Malathion 50% EC
Tiger Brand 55% Malathion
Lambda or Gamma Cyhalothrin Cutter Backyard Bug Control Spray Concentrate RTS1
Martin’s Cyonara Lawn & Garden Concentrate; & RTS1
Martin’s Cyzmic CS Controlled Release Insecticide
Spectracide Triazicide Insect Killer for Lawns & Landscapes Concentrate; & RTS1
Permethrin Bonide Eight Insect Control Vegetable, Fruit & Flower Concentrate
Bonide Total Pest Control Outdoor Concentrate
Bonide Eight Yard & Garden Ready to Spray RTS1
Bonide Eight Garden & Home Insect Control RTU2
Hi-Yield Indoor/Outdoor Broad Use Insecticide Concentrate
Southern Ag Permetrol Lawn & Garden Insecticide Concentrate
Tiger Brand Super 10 Concentrate
Tau-Fluvalinate Bayer Advanced 3-in-1 Insect, Disease & Mite Control I Conc.; & RTS1; & RTU2 (also contains Tebuconazole – a fungicide)
Bayer BioAdvanced 3-in-1 Insect, Disease & Mite Control Conc.; RTS1; & RTU2 (also contains imidacloprid – a systemic insecticide, and Tebuconazole – a fungicide)
Bayer BioAdvanced All-in-One Rose & Flower Spray Concentrate (also contains Tebuconazole – a fungicide)
Zeta Cypermethrin GardenTech Sevin Insect Killer Concentrate; & RTS1
Gordon’s Bug-No-More Lawn & Garden Insect Control Concentrate
Gordon’s Bug-No-More Large Property Insect Control Concentrate
Ortho Home Defense Insect Killer for Lawn & Landscape; & RTS1 (also contains bifenthrin)
1 RTS = Ready to Spray (a hose-end sprayer)
2 RTU = Ready to Use (a pre-mixed spray bottle)
3 Do not apply insecticidal soaps when the temperature is above 90 °F or to drought-stressed plants. Spray late in the day for best control.With all pesticides, read and follow all label instructions and precautions.

Table 3. Control of Slugs & Snails.

Active Ingredient Examples of Brands & Products
Iron Phosphate Baits Bonide Slug Magic – Makes Slugs Disappear
Brandt Sluggo Max
Espoma Organic Slug & Snail Bait
Garden Safe Slug & Snail Bait
Miracle Gro Nature’s Care Slug & Snail Control
Monterey Sluggo
Natria Snail & Slug Killer Bait
Whitney Farms Slug & Snail Killer
Bonide Bug & Slug Killer Bait (also contains spinosad)
Gardens Alive Escar-Go Slug & Snail Repellent (also contains spinosad)
Monterey Sluggo Plus (also contains spinosad)

Note: Pollinating insects, such as honey bees and bumblebees, can be adversely affected by the use of pesticides. Avoid the use of spray pesticides (both insecticides and fungicides), as well as soil-applied, systemic insecticides unless absolutely necessary. If spraying is required, always spray late in the evening to reduce the direct impact on pollinating insects. Always employ cultural controls first, then use less toxic alternative sprays for the control of insect pests and diseases. For example, sprays with insecticidal soap, horticultural oil, neem oil extract, spinosad, Bacillus thuringiensis (B.t.), or botanical oils can help control many small insect pests and mites that affect garden and landscape plants. Neem oil extract or botanical oil sprays may also reduce plant damage by repelling many insect pests. If soil-applied insecticides are used, make applications immediately after flowering to reduce the amount of insecticide exposure to pollinating insects. For more information, contact the Clemson Home & Garden Information Center.

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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