Quck answer
To get rid of worms on petunias, follow these steps:
1. Inspect the plants regularly for signs of worms, such as chewed leaves or holes.
2. Remove any affected leaves or plants immediately to prevent the worms from spreading.
3. Use organic insecticides or insecticidal soaps specifically designed for controlling worms on petunias.
4. Apply the insecticide according to the instructions on the label, ensuring thorough coverage of the plants.
5. Repeat the treatment as necessary, typically every 7-10 days, until the worms are eliminated.
6. Encourage natural predators, such as birds or beneficial insects, to help control the worm population.
7. Maintain proper plant hygiene and avoid overwatering to prevent attracting worms.
Garden petunias (Petunia x hybrida) are vibrant and abundant flowers that symbolize summer. However, dealing with worms on petunias can be frustrating. Whether they are grown as perennials in USDA plant hardiness zones 10 and 11 or as annuals in other areas, they bloom for many months. Unfortunately, when a petunia’s flowers have holes in their petals, it means the plant is being attacked by tobacco budworms. Budworms are just one type of insect larvae that can infest petunias. Although they each cause different types of damage, there are organic methods available to eliminate all three types of worms.
Tobacco Budworms: Green Worms
Tobacco budworms are tiny worms that hatch from eggs laid on petunia leaves and buds by night-flying Helicoverpa (Heliothis) virescens moths. On petunias, these worms are light green to blend in with their surroundings. They typically feed on the bases of the flower buds. Signs of an infestation include petals with ragged edges, holes at the bases of the flowers, buds that fail to open, and black waste specks on the buds and leaves.
How to Deal with Tobacco Budworms
If your petunias have a light infestation of tobacco budworms, you can remove them at dusk when they come out from their hiding spots around the base of the plants to feed. Simply pick them off the plants by hand and drown them in soapy water.
If handpicking is too time-consuming, you can use a ready-to-use microbial pesticide called Bacillus thuringiensis var. kurstaki (Btk) or a spinosad pesticide. When the worms consume these pesticides, they stop feeding immediately, but it may take a few hours for them to die. Bt is safe for bees, but spinosad is toxic to bees, so it’s important to follow the label instructions and take precautions to minimize harm to pollinators. To protect honeybees, spray spinosad when bees are unlikely to be foraging, such as in the late evening, at night, or early in the morning. Apply the pesticide to the petunias on a calm, dry day when they are not in direct sunlight.
Shake the pesticide bottle well and thoroughly coat the petunias until all surfaces are dripping. Reapply after rain or according to the recommended interval on the pesticide label until the infestation is under control. When working with pesticides, wear protective clothing, waterproof gloves, safety goggles, and a respirator mask, and always follow the instructions on the label.
Variegated Cutworms: Spotted Worms
Variegated cutworms (Peridroma saucia) are named for the light yellow spots that run along their bodies. These worms chew irregular, large holes in petunia leaves. They only feed at night or in very cloudy weather. During the day, they hide in the mulch or soil around the base of the petunias, where their brownish-black color makes them difficult to spot.
How to Control Variegated Cutworms
Use a flashlight to search for variegated cutworms on the petunias after dark. Pluck them off the plants and dispose of them. During the day, use a garden trowel to create a trench in the soil about 2 or 3 inches away from the stems. The worms will curl up into a C-shape when exposed. Drown them in soapy water. For a hands-off approach to cutworm control, spray the petunias with Btk, following the same method used to eliminate budworms.
Yellow Serpentine Leafminer Worms
Yellow serpentine leafminer worms, scientifically known as Lyromiza trifolii, are the larvae of small flies that have a yellow and black coloration. However, it is highly unlikely to ever come across one. The female flies lay their eggs inside the tissue of petunia leaves, and the worms create meandering, whitish tunnels as they feed and prepare for pupation. The presence of these worms can be detected by the wavy lines formed by their tunnels on the leaves. While leafminers usually cause only superficial damage, heavily infested petunias may experience stunted growth or the loss of affected leaves.
Getting Rid of Leafminer Worms
Chemical pesticides have limited effectiveness against leafminer larvae that are protected within the leaves. To control them, it is advisable to remove and discard infested leaves as soon as the trails of the worms are noticed. Planting annual dill (Anethum graveolens) or perennial yarrow (Achilleum millefolium), which are suitable for USDA zones 4 through 9, near your petunias can attract predatory wasps that feed on leafminers. Another method is to use spinosad, applying it in the same way as for managing budworms.
