Insect Pests of Corn

1. Insect Pests of Corn Kelly V. Tindall Area Extension Entomologist Twin Falls County

3. http://www.entsoc.org/Pubs/Books/Handbooks/Corn.htm

4. http://www.entsoc.org/Pubs/Books/Handbooks/Corn.htm

5. Planted Seed Feeding Insects Fire ants Seedcorn beetles Seedcorn maggot Slugs Thief ant Wireworms

6. Seedcorn Beetles Light brown/yellow brown body with broad dark stripe on each wing Black head Can be beneficial/ predacious BUT when prey is unavailable or limited, it feeds on seeds

7. Seedcorn Maggot Adult: gray, smaller and more slender than a house fly Larvae: damaging stage, creamy white body, tapered at the front end, no visible head or legs Biology: sporadic pest, more problematic when: germination is slow, high levels of decaying organic matter (plants or manures) Injury: tunneling in the seed decreases vigor or causes complete destruction/decay, rarely foliar symptoms

8. Slugs Description: gray to pale cream; like a snail without a shell; 1-2 in Biology: wide host range including living or dead and decaying plant tissue; plant residue favors population build-up; prefer tender leaves of seedling-stage plants; primarily feed at night or overcast days but often leave slime trials; eggs need a moist habitat to develop Monitoring: place bait stations throughout the field to establish activity and numbers; look for slime trails and interveinal feeding; may need to bait more than once if populations are large and weather is particularly wet and cold.

9. Wireworms Description: cylindrical, light tan to reddish tan larvae, usually hard bodied Biology: prefer porous, well drained loam soils; injury more severe when corn follows pastures, small grains and other forage crops Injury: feed on seeds before or during germination, bore in to seedlings below soil surface

10. Baits for Wireworms Hole aprx. 4 X 10 inches 1-3 wk before planting Place in grassy areas or areas of previous infestations

11. Baits for Wireworms Hole aprx. 4 X 10 inches 1-3 wk before planting Place in grassy areas or areas of previous infestations � cup of mixture of non-treated wheat and corn seed, soak seed in water for 24h

12. Baits for Wireworms Hole aprx. 4 X 10 inches 1-3 wk before planting Place in grassy areas or areas of previous infestations � cup of mixture of non-treated wheat and corn seed, soak seed in water for 24h Fill remainder of hole with soil and mound

13. Baits for Wireworms Hole aprx. 4 X 10 inches 1-3 wk before planting Place in grassy areas or areas of previous infestations � cup of mixture of non-treated wheat and corn seed, soak seed in water for 24h Fill remainder of hole with soil and mound Cover with a 3ft black plastic square, put soil on top to prevent wind removal (? soil temp and germination)

14. Baits for Wireworms Hole aprx. 4 X 10 inches 1-3 wk before planting Place in grassy areas or areas of previous infestations � cup of mixture of non-treated wheat and corn seed, soak seed in water for 24h Fill remainder of hole with soil and mound Cover with a 3ft black plastic square, put soil on top to prevent wind removal (? soil temp and germination) Minimum of 5-10 bait stations per 25-30 acre field Check 2-3 days prior to planting � 1 per bait = economic infestation

15. Summary of Wireworm Trials: Increase in Stand

16. Summary of Wireworm Trials: Reduction in Damage

17. Root Feeding Insects Carrot beetle larvae Cornfield ant Corn root aphid Corn rootworm larvae Grape colaspis larvae Sugarcane beetle Symphylans Whitefringed beetle larvae White grubs

18. Carrot Beetle Larvae Adult: reddish-brown with stout legs, robust, and about 1/2 inch long; Adult damage: economically, damaging stage; feed on seedlings just below soil line making gouge-like wounds destroying the growing point Larva: C-shaped and white, resembling common white grubs with brown head Larval damage: feed on roots, usually not an economic threat Biology: overwinter as adults in the soil; potential for infestation is greater no-till fields

19. Cornfield Ant 1/12 � 1/10 inch Brown to very dark 1 segmented waist Sporadic pest Relationship with corn root aphids (CRA) � and CRA retard growth; plants turn yellow or red, then brown and die; small ant mounds usually found near injured plants Ants may tunnel along roots; plants rarely die from ants

20. Corn Rootworms

21. Western Corn Rootworm Larva: creamy white body, up to � in., dark brown head and anal plate on last abdominal segment Adults: light yellow to light green, 3 black stripes on wings (size of stripes vary) Corn is the only known crop host; therefore, rotations have been effective in control HOWEVER, evidence suggests 2 biotypes � one that lays eggs only on corn and one that will lay on soybeans � making corn/soybean rotations ineffective

22. Summary of CRW Trials% Reduction of Injury

23. Symphylans AKA: garden centipede Immatures: 6 pairs of legs; gain 1 new pair with every molt Adult: 12 pairs of legs Infrequent pest, often spotty damage Damage occurs with 50-100/plant Damaged plants are stunted and purple

24. White Grubs In PNW � Phyllophaga spp. C-shaped and up to 1 inch Orange-brown to brown head 3 pairs of legs Dark posterior Injury: occasional pests; apparent when plants are 2-6in tall; plants turn yellow or tan, wilt and die; may turn purple from lack of phosphorous uptake

25. White Grubs vs Annual Grub

26. White Grubs vs Annual Grub

27. Foliage Feeders: Seedlings Armyworms Billbugs Carrot beetle adult Chinch bug Corn leafhopper Cutworms False chinch bug Flea beetles Hop vine borer Leafrollers

28. Armyworms Four species cause significant injury Armyworm Beet armyworm Fall armyworm Yellowstriped armyworm In PNW � Armyworm Beet armyworm Bertha armyworm Western yellowstriped AW

29. Armyworm Larva: vary in color from dark greenish-brown to black; long, pale white, orange, and dark brown stripes along the side of the body; yellowish brown head; dark band on the outer side of each proleg; aprx. 1.5 in Adult: tan to light brown, tiny white spot centered on each forewing Biology: eggs are laid in rows or groups on leaves of host plants; females tend to roll the leaf blade around the egg mass; may build-up in grassy areas

30. Beet Armyworm Larva: light to dark green with a 2 light and 1 dark stripes running the length of the body; usually a dark spot above the second pair of legs; inverted "Y� on front of head Adult: Front wings light brown to gray marked with dark brown and white scales, round cream colored spot � may be cream with an orange center Biology: eggs are covered with scales Injury: infrequent pest of corn; can damage leaves and ears; feed in the whorl and at the base of expanded leaves

31. Carrot Beetle Adult Adult: reddish-brown with stout legs, robust, and about 1/2 inch long; Adult damage: economically, damaging stage; feed on seedlings just below soil line making gouge-like wounds destroying the growing point Larva: C-shaped and white, resembling common white grubs with brown head Larval damage: feed on roots, usually not an economic threat Biology: overwinter as adults in the soil; potential for infestation is greater no-till fields

32. Cutworms Variegated cutworm Western bean cutworm Damage and management is the same

33. Black Cutworm Larva: body gray with light brown stripe down the back; greasy appearance; inside pair of tubercles is about one-third to one-half the size of the outside pair; pebbly skin texture; dark brown or black head; 1.6 in long. Adults: brownish-gray with a light silvery band on the wings Biology: overwinters as a pupa; adults emerge in April and lay eggs; larvae are underground of surface feeding during late March - early June; two overlapping generations/year; 2nd generation adults emerge in Aug. and Sept. Monitoring: seedling stage; 2-3 wilted or cut plants or leaves in 10 ft at several sites in field = insecticide application; insecticides most effective on young larvae

34. Bronzed Cutworm Larva: dark brown body with bronze sheen with 3 yellowish strips on body; tan head color, 1.75 in Adult: Bronze sheen on purple forewing Biology : overwinters as eggs; feed on crowns of grasses and cut plants; major pest when corn is planted behind sod or pasture grass

35. Dingy Cutworm Larva: resembles black cutworm but the skin textures differ; pale gray with ting of red; V-shaped marking on abdominal segments, pale brown-gray head; dingy CW has smooth skin; the tubercles are of similar size, Adult: forewings are dark brown with bean-shaped markings Biology: overwinter as late instars; begin feeding Mar. or Apr.; regarded primarily as leaf feeders and rarely cut plants; not considered an economic threat; frequently occur in fields planted after clover or alfalfa

36. Glassy Cutworm Larva: glossy, semi-translucent greenish-white or grayish white, lacks body markings reddish brown heads; aprx. 1.5 in Adult: nondescript, medium sized grayish miller moth with a scattering of dark markings Biology: most subterranean of the cutworms; overwinters in the crowns of grass as small larvae and mature in the spring; adults emerge in late June � August; eggs are laid on the soil near grass plants; larvae hatch and feed on crowns before overwintering; 1 generation/yr

37. Pale Western Cutworm Larva: they are grayish-white to a grayish-green color with no distinct markings on its body; amber to black head; 1.25 in Adult: gray to brownish white, heavy-bodied; no distinct markings on the wings; distinctive characteristic is the white under-sise of the wings Biology: overwinters as an egg; larvae emerge and feed throughout spring; prefers dry loose soils; irrigated fields are rarely injured

38. Redbacked Cutworm Larva: light brown ot gray with 2 red stripes down back bordering median stripe; yellow-brown head; aprx. 1.5 in Adults: pale clay-yellow to dark red Biology: overwinters as eggs in soil; severe pest in Canada

39. Sandhill Cutworm Larva: light tan, semi-translucent with several pale, chalky white, longitudinal stripes; tan to dull red-brown head; 1.3 in Biology: overwinters as a partially grown larva; only occurs in very sandy soil ; feed almost entirely beneath the surface of the soil, so they usually cut the seedlings off below the growing point

40. Spotted Cutworm Larva: dull gray-brown black wedge-like markings begin half way down the back toward the end � �spotted appearance�; whitish head; aprx. 1.5 in Adult: brown forewings with red or purple ting, pinkish trianglular spot on the outer margin and a moon-shaped spot near the center of each wing Biology: climbing cutworm; night feeders; overwinter as larvae; prefers vegetable crops

41. Variegated Cutworm Larva: green-yellow to tan to nearly black, pale yellow marks on segments 4-7; W or crown shape on last abdominal segment; 2 in Adult: faintly outlined spots on dark purple/brown forewing Biology: regarded primarily as leaf feeders and do not present a significant economic threat; frequently present in fields planted after clover or alfalfa

42. Western Bean Cutworm Description: young larva � dark brown with faint diamond shaped markings; older larvae � pale tan, gray-brown to pink gray with 3 short dark stripes along the first segment behind the head ; 1.5 in Adult: dark brown with white stripe on the outer edge of the wing Biology: eggs laid on the upper surface of corn leaves; larvae hatch and feed in the whorl, silks or kernels; can reduce kernels by 50-60%; overwinter as prepupae Threshold: 8% of plants have eggs and larvae when corn is at 95% tassel (Nebraska-grain yields)

43. Summary of Cutworm Trials: % Increase in Stand

44. Summary of Cutworm Trials: % Reduction in Damage

45. General Cutworm Information

46. False Chinch Bug Nymphs: ash-gray with brown-white mottling on the back and red mottling on the abdomen Adults: dirty gray with brown and black markings; 1/8 in Biology: unpleasant smell; prefer mustard and beets; rarely pests of corn; may be problematic in times of drought; gregarious Injury: excessive fluid removal salivary toxins causes wilting or death of leaf tips or whole plant

47. Leafrollers Spotted fireworm

48. Slugs Description: gray to pale cream; like a snail without a shell; 1-2 in Biology: wide host range including living or dead and decaying plant tissue; plant residue favors population build-up; prefer tender leaves of seedling-stage plants; primarily feed at night or overcast days but often leave slime trials; eggs need a moist habitat to develop Monitoring: place bait stations throughout the field to establish activity and numbers; look for slime trails and interveinal feeding; may need to bait more than once if populations are large and weather is particularly wet and cold.

49. Stink Bugs Description: shield shaped; multiple colors Biology: primarily seed feeders but will feed on foliage if seeds are limited; some predaceous species Injury: common in fields associated with winter annual weeds; stunted plants; production of tillers; wrinkled leaves; holes, either scattered or in repeating patterns up to 1 in; holes may be outlined by a yellow to brown color; whorl leaves unable to expand; may occur on mid-whorl-stage plants but most common on seedlings up to 4th true-leaf stage; Insecticide control is rarely warranted because most injury is seen and it is too late.

50. Good and Bad Stink Bugs General rules of good vs bad BAD � rounded shoulders GOOD -spines on the shoulders THERE ARE EXCEPTIONS!!!

51. Good and Bad Stink Bugs General rules of good vs bad BAD � rounded shoulders GOOD -spines on the shoulders BAD - long thin mouthparts GOOD � short stout mouthparts

52. Thrips Description: very slender, tan in color; adults with two pairs of feathery wings; rasping mouth parts; 1/16 in Biology: sporadic pest; infestations more severe in drought conditions and near weedy hosts Injury: rasp plant tissue and suck plant juices; leaves appear sand-blasted; whitish in color with yellow streaking; can resemble diseases; insecticide rarely applied

53. Webworms Description: usually pale gray-brow with black spots and coarse hairs; aprx. 1 in Biology: several species in US; usually worse in fields following sod Injury: sporadic pest; defoliate leaves, feed on leaf margins; sometimes feed just below soil surface killing the growing point

54. Wireworms Description: cylindrical, light tan to reddish tan larvae, usually hard bodied Prefer porous, well drained loam soils More severe injury when corn is planted behind pastures, small grains and other forage crops Injury: feed on seeds before or during germination, bore in to seedlings below soil surface

55. Plant-fluid Feeding Insects Aphids Chinch bugs Corn delphacid False chinch bug Leafhoppers Spider mites Stink bugs Thrips Twolined spittlebug

56. Aphids Six species in North America on corn Bean Aphid Bird Cherry-Oat Aphid Corn Leaf Aphid Corn Root Aphid Greenbug Potato Aphid Most have worldwide distribution All aphids have cornicles (tube-like projections at the end of their abdomen) Feed on plant juices Some transmit disease

57. Bean Aphid 1/16-1/8 inch Olive green to black Considered a minor pest Individuals of old colonies may develop a white waxy pubescence Potential vectors of maize dwarf mosaic virus (MDMV) and barley yellow dwarf virus

58. Bird Cherry-Oat Aphid Adults 1/16 � 3/32 inch Dark olive to green with an orange, red, rust-colored patch near the cornicles Usually found on husks, leaves or lower stalks Significant loss of corn yields Transmits barley yellow dwarf virus, which is relatively harmless to corn but corn can be a reservoir for the virus, aiding the spread to cereal grains.

59. Corn Leaf Aphid Pale blue-green; black cornicles with black spots on the abdomen at the cornicle base As they age, they change colors: a dark green to black. Do not overwinter north of Texas, but they migrate as far north as Canada Occasional pest Primary vector of maize dwarf mosaic virus (MDMV), causing stunting and mottling of plants.

60. Greenbug Pear-shaped body; yellow-green to blue-green with dark green strip down the middle of the back; cornicles are pale with dark tips Not considered a pest of corn; is a problem in sorghum; a new biotype may develop that is injurious to corn Found on the underside of leaves; inject salivary toxins that cause a variety of plant responses Transmits barley yellow dwarf virus and may transmit maize dwarf mosaic virus

61. Potato Aphid Pear-shaped; 1/16-1/8 inch; usually green, but may be yellow, pink or magenta; have distinctive red eyes Problematic in vegetables, only a minor pest of corn Transmits maize dwarf mosaic virus

62. Spider Mites General: pierce leaf tissue feeding on cell contents; drought stressed plants more prone to infestation Two-spotted spider mite Produces copious webbing Food balls concentrated on the sides of the abdomen Chlorotic tissue evenly distributed across leaf Uniformly distributed on the plant Banks grass mite Green food balls around periphery of abdomen Chlorotic tissue begins near the midrib and spreads to the basal portion of leaf Concentrated on lower 1/3 of plant and density decline as move up the plant

63. Stink Bugs Description: shield shaped; multiple colors Biology: primarily seed feeders but will feed on foliage if seeds are limited; some predaceous species Injury: common in fields associated with winter annual weeds; stunted plants; production of tillers; wrinkled leaves; holes, either scattered or in repeating patterns up to 1 in; holes may be outlined by a yellow to brown color; whorl leaves unable to expand; may occur on mid-whorl-stage plants but most common on seedlings up to 4th true-leaf stage; Insecticide control is rarely warranted because most injury is seen and it is too late.

64. Thrips Description: very slender, tan in color; adults with two pairs of feathery wings; rasping mouth parts; 1/16 in Biology: sporadic pest; infestations more severe in drought conditions and near weedy hosts Injury: rasp plant tissue and suck plant juices; leaves appear sand-blasted; whitish in color with yellow streaking; can resemble diseases; insecticide rarely applied

65. Foliage Feeding: Tissue Removal Armyworms Cattail caterpillar Cereal leaf beetle Corn earworm Corn rootworm adult Cutworms European corn borer Flea beetle Grape colaspis adults Grasshoppers

66. Armyworms Four species cause significant injury Armyworm Beet armyworm Fall armyworm Yellowstriped armyworm In PNW � Armyworm Beet armyworm Bertha armyworm Western yellowstriped AW

67. Cattail Caterpillar Description: yellow, orange, and black markings; tufts of black and white hairs on orange bumps on the body; black head with white spots on the �face�; aprx. 1.75 in Injury: rarely reaches pest status; small larvae windowpane feeding; large larvae eat all foliage except the midrib

68. Cereal Leaf Beetle Description: Adult - elytra (wings) shiny blue, black body and head, red pronotum, red to orange legs with black tarsi; Larva � pale yellow to orange, cover body in mucous and fecal matter appearing shiny black Biology: invasive species; infrequent pest, usually around small grains; adults feed between the veins on upper leaf surface of corn; excellent control from parasitoids

69. Corn Earworm Larva: Vary in color from yellow, brown, red, to green with prominent bands of cream, pink, green or yellow; dark yellow or orange head; 1.6 in Adult: brown to olive green forewings with dark spot near the center of the wing Biology: pest of several crops; in corn � consumes leaves, tassels, silks, and kernels

70. Corn Rootworm Adults

71. Cutworms Variegated cutworm Western bean cutworm Damage and management is the same

72. Grasshoppers Four economically important and all are present here

73. Redlegged Grasshoppers Description: brownish red; pinkish-red or bluish tibia on the jumping leg; has a line of black spines on the hind margin of the tibia; �" � 1" long Biology: widely distributed; wide host range but prefers dense stands of weeds and grasses; may severely damage alfalfa, clover, soybeans, small grains, various legumes, corn, vegetables and tobacco; wasteful feeder, leaving as much as 75% of the plant clipped but unconsumed

74. Differential Grasshopper Description: yellowish or greenish gray; the femur of the hind leg is marked with black chevrons; adults are 1 �" � 1 �� Biology: frequently found in the west in various habitats of mixed vegetation; prefers forbes; nymphs can be a pest in small grains, alfalfa and other hay crops; as adults they may fly into corn, large populations will destroy a young cornfield in 3-4

75. Two-striped Grasshopper Descriptions: grayish or brownish green with two distinct yellow strips extending from the head to the wing tips; have a distinct black band on the top of the femur of the hind leg; relatively large grasshoppers 1�" � 2�� Biology: eats a wide variety of different plants; can cause extensive damage in small grains, alfalfa, soybeans and corn; is a wasteful feeder, not consuming most of what is clipped; may completely destroy the crop

76. Migratory Grasshoppers Description: brown to gray with a distinctive black mark behind its eye; has a slight hump behind the spine on its underside, between the middle pair of legs; about 1" long Biology: damages crops more than any other species of grasshopper; prefers to feed on weeds and forbes can be a pest in small grains, alfalfa, clover, corn, and vegetables; strong flier and disperses readily

77. Leafrollers Spotted fireworm

78. Mormon Cricket Description: Adults - black with small useless wings; females have a long ovispositor; aprx. 1 in. Young nymphs- black with white markings; older nymphs � green to black Biology: large host range; feed on edges of corn leaves moving inward; overwinter as eggs; passes through 7 instars in 60-90 days

79. Description: larva � pale-green to yellow white; 0.25 in Biology: eggs laid on corn leaf surfaces, larvae hatch, larvae tunnel into corn leaves, feeding internally, scraping green leaf tissue, leaving behind transparent mines; can complete its life cycle in 3 wk Injury: 7-leaf corn � =35 % leaf area destroyed = no yield loss; ~50 percent leaf area destroyed = 2 % loss; 10-leaf corn � =20 % leaf area destroyed = no yield loss; ~50 percent leaf area destroyed = 6% yield loss Foliage Feeders: Miners

80. Stem-Boring Insects European corn borer Lesser cornstalk borer Mexican rice borer Neotropical corn borer Southern cornstalk borer Southwestern corn borer Sugarcane borer Stalk borer