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)

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

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

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

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.

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)

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

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

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

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

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