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ALT: Left: Green Plamer amaranth next to a green sunflower. Right: Green plant with green, spiny structure at leaf base.

Palmer Amaranth: Now Is the Time to Scout

South Dakota State University (SDSU) Extension encourages farmers, ranchers and other landowners to start scouting for Palmer amaranth, a weed that has been rapidly spreading north into the United States and is likely to be glyphosate-resistant.

Red-brown colored weevil with bent antennae originating on the elongated mouthparts.

Red Sunflower Seed Weevils Are Active

Red sunflower seed weevils are active in South Dakota sunflowers. We noticed that many fields at R5 stages are already being sprayed, but scouting should still continue in those fields after application, and it should begin for fields that will reach the R5 stage within the next week.

Small black beetles covering a partially defoliated leaf.

Flea Beetles Causing Issues in Canola

Large flea beetle populations in canola have been observed in neighboring states and within South Dakota. The hot, dry and sunny conditions that we have been experiencing throughout 2021 have been ideal for flea beetle populations.

Cream-colored moth with a dark brown band in the middle of its body.

It’s Time To Start Scouting For Banded Sunflower Moths

Sunflowers throughout South Dakota are quickly approaching the R3 growth stage, which means it’s time to start scouting for banded sunflower moths. Banded sunflower moths are capable of reducing yields due to their caterpillars feeding on the bracts, florets and seeds.

Gray beetle with long antennae that are alternating white and black pattern on green leaf petiole.

Dectes Stem Borer May Be More of an Issue During 2021

Dectes stem borers are an annual pest of sunflower in South Dakota. During most years, they do not cause major issues in sunflower. However, we have observed increased issues with this pest during dry years.

Small, black beetle with a long snout.

Headclipping Weevils in Sunflower

Headclipping weevils have been active in some sunflower fields and in ornamental sunflower throughout South Dakota. Although the headclipping weevil is considered a minor pest of commercial sunflowers, it can cause a lot of problems for individuals trying to maintain sunflowers in their yards and gardens.

Green and brown grasshoppers on the leaves of a sunflower plant.

Grasshoppers Already Moving Into Sunflower Fields

With grassland food sources being depleted earlier than usual due to drought, grasshoppers are moving into nearby crops in search of vegetation. In parts of western South Dakota, grasshopper nymphs have already been observed feeding on young sunflower plants.

Light colored fly with dark pattern on wings sitting on a green leaf.

Sunflower Receptacle Maggot Flies Spotted in Sunflower

Quite a few sunflower receptacle maggot flies have been spotted in South Dakota sunflower fields. The adults don’t feed on sunflower, but the larvae of this insect are considered minor pests of South Dakota sunflower.

Caterpillar with a red stripe on its back sitting on a green leaf. Bottom: Mottled gray caterpillar sitting on a green leaf.

Cutworms in Sunflowers

In South Dakota, some late-planted sunflower fields are having some cutworm pressure. Although most cutworm activity should be wrapped up by now, it is possible that some populations may have been feeding up until the beginning of July.

Canola leaves with irregular holes.

Flea Beetles Still Feeding in Canola

Large populations of flea beetle adults have been observed on canola this week. In one field we scouted, flea beetle populations were large and causing significant amounts of defoliation.