Sunflower Moths Are Flying In

Anitha Chirumamilla

Figure 1: Adult sunflower moth. Photo: North Dakota State University, Extension Entomology

Sunflower moth or head moth is one of the most serious and recurring problems of sunflowers in South Dakota. Each year, adult sunflower moths fly into South Dakota from the south as our winters are too cold for them to survive. Adult moths are about ¾ inch long, tan colored, and are cigar shaped at rest (Figure 1). Blooming sunflowers attract the female moths, which lay their eggs on the florets. Newly emerged larvae feed on florets and pollen while mature larvae feed on seed kernels. Larvae are small caterpillars, (3/4 inch long when fully grown) with alternating white and brown bands running along the length of body (Figure 2).    

Figure 2: Sunflower moth larva and seed damage. Photo: North Dakota State University, Extension Entomology

Damage: Primary damage is caused by moth larvae feeding on florets and seed kernels resulting in yield losses. As the larvae mature, secondary damage is caused by larvae boring and chewing through the receptacle tissue, leaving the sunflower heads vulnerable to head rot fungal infection. Yield losses are higher when larval feeding is coupled with fungal infection due to loss of entire heads. Sunflower heads infested with head moth larvae appear trashy with silk webbing, dry florets, and larval frass (Figure 3). Larvae spin silk threads to lower themselves to the ground where they undergo pupation. Damaged seeds are empty with large round holes at the center or at the distal end of seeds.

Figure 3: Sunflower moth damage, note the silk webbing and frass. Photo: North Dakota State University, Extension Entomology

Scouting: Scouting for sunflower moths should begin when the flowers start blooming and should continue to 80% of pollen shed (R 5.1 to R 5.8). Pheromone traps (Figure 4) are easy to use and are an important tool for monitoring moth activity. A catch of four moths per day per trap is considered the treatment threshold. However, there is no substitute for manual scouting. Pheromone trap efficiency can be limited in high wind and high temperature conditions. The sampling should be done by selecting five random locations, 20 feet away from field margins and counting the number of moths on 20 plants per location (total 100 plants). An average of 1-2 moths per five heads justifies pesticide application.

Figure 4: Pheromone trap. Photo: North Dakota State University, Extension Entomology Management

Options: Considering the migrating behavior of sunflower moth, late planting will help sunflowers escape peak periods of moth flights. Chemical treatment has been the most reliable and effective option in managing sunflower moth infestations in South Dakota. However, timing of insecticide treatments remains very critical for effective control. An early treatment (R 5.1 stage) using contact insecticides will target adult moths and prevent egg laying while a spray at full bloom will kill the early larval instars feeding on the florets.

Source : SDSU