Scouting For Insects in Corn and Grain Sorghum

1. Scouting For Insects in Corn and Grain Sorghum Glenn Studebaker Extension Entomologist

2. Cutworms • Black and Variegated predominant species • Active at night - hide in soil or under debris during daylight • Feed on stem and leaves

3. Bird Damage

4. Chinch Bugs • Adults small black insects • Nymphs red then black with band across body • Adults overwinter in grasses • Migrate into corn • Both nymphs and adults damaging to corn • Feed on roots or stem below soil line

5. Chinch Bugs • Most severe damage comes from adults and large nymphs • Stunted plants • Yellow streaking in leaves • Curled leaves and plant • Plant death occurs under heavy infestations

6. Chinch Bug Damage

7. Corn Leaf Aphid • Blue-green colored aphid with black legs and cornicles • Often found in whorls • Can occur in high numbers early in season • Seldom require treatment unless corn also drought stressed

8. Stink Bugs • Adults are shield shaped insects • Brown stink bug more a problem in corn • Pierce stem and secrete digestive enzymes causing hole in leaves

9. Stink Bugs in Corn • Early season threshold • LA – 1 per 20 feet • GA – 1 per 10 feet

10. Stink Bugs on Corn

11. Stink Bug Damage • Elongated holes in leaves • Caused by feeding before leaf emerges • Does not cause yield loss

12. Ear Damage by Stink Bugs • Caused by feeding during early ear formation • Banana shaped appearance • Shuck formation stops

13. Corn Flea Beetle • Very small beetle with enlarged back legs • Hops like a flea • Feeds on leaves of seedling corn • Vector of Stewart’s wilt disease of corn • Overwinter in grasses and serve as reservoir for disease • Treat when beetles are abundant and affecting vigor

14. Grasshoppers • Several species • Occasional problem • Usually on field borders • Worse in dry years • Treat when heavy defoliation occurs

15. Whorl Feeders • Damage whorl early season • Fall armyworm and/or corn earworm • Corn earworm is cannibalistic - will eat other worms in whorl • Fall armyworm is not

16. Whorl Feeders • Corn can stand some damage with no loss of yield • Treat when 5 - 6 worms per whorl • Usually armyworms at this level

17. Corn Borers Southwestern • Adults • SW – cream color • Euro - light brown to buff colored • Larva feed on corn and other grasses • Moths do respond to pheromone European

18. Corn Borers • Moths lay eggs usually on undersides of leaves • Eggs • 20-50 – European • 2-5 - Southwestern • Flattened and overlap like shingles • Hatch in about 5 days

19. Southwestern Corn Borer Eggs

20. Corn Borers • Larvae hatch and feed on leaves at first • Often move down into whorl and feed for several days • Bore into leaf midrib and/or stem • Impossible to control once inside stem

21. Southwestern Corn Borer • Generally see second generation around first 2 weeks of July • Applications of insecticides with good residual • Intrepid 8 oz (2 wks) • Coragen (2-3 wks) • Bifenthrin (10 days)

22. Corn Borers Southwestern • Yield loss, stalk lodging, ear drop • Treat when • 50% plants infested for European • 25% infested for Southwestern European

23. Stalk destruction reduces population Larvae overwinter in stalks Corn Borer Damage

24. Similar damage as European only more damaging Bore down into lower part of stem Overwinter as larvae in stalk Adults similar in size to European, buff colored Respond to pheromone Lay 2 - 5 eggs/mass Southwestern Corn Borer

25. Southwestern Corn Borer • Scouting is difficult • Can scout for egg masses • Very difficult to find • Scout for pupae • Developed by Dr. Paul McLeod at U. of A. • Works for 2nd generation borers

26. Scouting for SW Corn Borer • Pupae in corn stalks • Split stalks to determine age of pupae • When majority are dark brown color, can spray for 2nd generation about 7 days later

28. Grain Sorghum Insects Glenn Studebaker Extension Entomologist –University of Arkansas

29. Sorghum midge • The most important pest of grain sorghum • Can cause drastic yield losses • Very tiny insect

31. Midge Adult

32. SORGHUM MIDGE • LIFE CYCLE – 11 TO 21 DAYS (16) • ADULT LIVES 24 – 36 HOURS • FEMALE LAYS 50 – 250 EGGS • LARVAE FEED ON DEVELOPING SEED • OVERWINTER AS LARVAE IN SEED HUSK OF HOSTS • FEEDS ON SEVERAL RELATED GRASS PLANTS

33. SORGHUM MIDGE • IMMATURES INJURE DEVELOPING SEEDS – CONTROL BEFORE AND DURING POLLINATION OF GRAIN HEAD • SCOUT DURING BLOOM (YELLOW ANTHERS EXPOSED ON SEED HEAD) 20-90% OF HEADS BLOOMING • APPLY RECOMMENDED INSECTICIDE AT 1 MIDGE PER HEAD AFTER 20-30% OF FIELD HAS BEGUN TO BLOOM • IF ADULTS ARE STILL ACTIVE 3-5 DAYS LATER, APPLY 2ND AND 3RD APPLICATIONS AS NEEDED 3-5 DAYS APART

34. Midge Adults

35. Sorghum Midge Pupal skins

36. SORGHUM MIDGE MANAGEMENT POINTS • PLANT EARLY TO AVOID POPULATIONS • MONITOR CLOSELY DURING FLOWERING • TREAT WHEN MIDGE POPULATIONS REACH 1 – 2 PER HEAD AND 25-30% OF HEADS ARE FLOWERING • LOSSES USUALLY OCCUR TO LATE CROPS • CHECK FIELDS EVERY 2-5 DAYS WHEN BLOOMING

37. Corn Earworm • Feed on head • Treatment level is 2 or more larvae ½-inch in length or longer per head • Pyrethroids work well in controlling this pest

38. Fall Armyworm • Sometimes confused with corn earworm • Same threshold as corn earworm • More difficult to control with pyrethroids • Lannate, Tracer, Sevin

39. Sorghum Webworm • Smaller than corn earworm & fall armyworm • Treat at 5 – 6 webworms per head • Pyrethroids do not work well on this pest either • Lannate, Tracer, Sevin

40. QUESTIONS?