Unit 3: Corn Insect Diseases

1. Unit 3: Corn Insect Diseases

2. Unit 3: Corn Insect Diseases • European Corn Borer & Southwestern Corn Borer • Can cause 3% yield loss/corn borer/plant • Sweet corn 8% • Bore • Stalks • Tassels • Cobs • Ear • Mature larvae ~1” long (ECB), .4” long (SWCB)

3. Unit 3: Corn Insect Diseases • Mature adult overwinters in stalks, stubble, cobs, etc. • Pupate from April to July • Emerge as moths 2-3 wks later • Prevention • Complete destruction of all winter cover substances • Early planting • Improves plant vigor & ability to withstand damage

4. Unit 3: Corn Insect Diseases • Treatment • Chemical applications • Must get them before they bore into the stalk • Sweet corn – may treat every 5d • Bt corn • How might it be managed

6. Unit 3: Corn Insect Diseases

7. Unit 3: Corn Insect Diseases • Corn Rootworm • Bore into seedlings & ruin bud or growing point • Feed on roots of older, established corn • Control • Corn/SB crop rotation used to provide good control • Beetles are laying eggs in the SB fields anticipating corn the next season

8. Unit 3: Corn Insect Diseases • Use chemical treated seed and/or soil-applied insecticide • Bt corn is also effective • Don’t forget the refuge area! • Why is it important • Corn Earworm • Causes the most direct damage to the ear • ~2% of the corn crop is victim to this pest • 1-2 generations/yr. in our area • Maybe 7 in southern U.S.

9. Unit 3: Corn Insect Diseases • Overwinters 1-9” in the soil (pupae stage) • Moth emerges in spring • Lay ~1000 eggs each • Full grown larvae ~1/2” • Eats developing kernels • Entry point for molds, and other insects • Prevention • Plant varieties w/ heavy husk covers (protects ear)

10. Unit 3: Corn Insect Diseases • Early tillage can also destroy the pupae before they have a chance to emerge • Treatment • Chemical treatment is effective, if you catch them before they get into the ear • Chinch Bug • Can destroy entire fields in severe cases • Greatest risk is late-planted corn next to a small grain

11. Unit 3: Corn Insect Diseases • Can migrate by foot from wheat in June/July as wheat begins to ripen • Prevention • Spray a barrier strip around the field for protection • May be ineffective if they are able to fly • Plant resistant varieties

12. Unit 3: Corn Insect Diseases • Nematodes • 10 species can cause damage in corn • Root injury, poor plant color, stunted growth, reduced yields • Symptoms of nematode damage can often be confused w/ other problems • Root rot, nutritional deficiencies, climatic stresses • Must have a soil analysis to determine

13. Unit 3: Corn Insect Diseases • Weevils • Most commonly infest stored grain • May fly to the fields in the South and damage standing corn • Heavy husks help prevent infestation • Most species cannot or will not penetrate the husk to lay eggs • Fumigation is the only way to treat infested corn

14. Unit 3: Corn Insect Diseases • Cutworms • Sporadic problem pests • Cut plant off at the ground • Nocturnal feeders • Can be controlled w/ barrier chemical applications • Armyworms • Most damage on late-planted corn • Most devour leaves, but also will damage growing point