Corn Planthopper: How to Spot It and Stop It in Your Mais

It matters because it spreads maize mosaic virus and maize stripe virus. The hoppers pick up the virus while feeding, the virus multiplies inside them, and after a few days they pass it to healthy plants. The virus does not travel on seed.

How to Identify Corn Planthopper

Adult hoppers are greenish or brownish yellow with darker tips on the wings, and the abdomen is smoky with yellow stripes on the sides. Nymphs are whitish, then yellowish, with red eyes. Sooty mold on the leaves shows heavy feeding. Look for stripes on the leaves too. A corn downy mildew plant shows pale stripes as well, but it also has a white growth on the underside of the leaf.

• Small greenish brown hoppers sit in the whorl and on the leaves, and jump when disturbed.
• Honeydew and black sooty mold coat the leaves where they feed.
• Light green to yellow stripes run along the leaves, either thin or 1 to 2 centimeters wide.
• Infected plants are stunted.
• Ears do not form, or they are deformed with few seeds.

How Corn Planthopper Hurts Your Corn

Feeding takes sap and leaves honeydew that grows sooty mold, which blocks light and lowers the sugars the plant needs for grain fill. The bigger threat is the viruses. Plants infected young stay stunted, and the cobs stay small or do not form.

A virus fact sheet from the Pacific notes that infection rates often stay low, at about 1 to 2 percent of plants. That is why spraying the whole field does not pay. We found no sourced yield loss figure for the Philippines.

How to Control Corn Planthopper

1. Pull out plants with stripes and stunting as soon as you see them. Grasp the young leaves together so the hoppers cannot escape, put the plant in a sack and burn it.
2. Weed the field and the edges. Remove itch grass, barnyard grass and goosegrass, which host the hopper and the virus.
3. Sample the field edges, where the hoppers gather, and check the whorls of young plants every week.
4. Rotate corn with a crop that is not a host, so the hoppers lose their food between seasons.
5. Plant resistant varieties where they are sold. Imported maize seed has often come from breeding programs that selected for resistance.
6. Protect natural enemies, which help to hold the hoppers down.

When a Spray Makes Sense

A virus has no cure, so the control is the vector and clean plants. Extension sources say that insecticides are not economical for this disease, since the infection rate is usually low. If hopper numbers are very high on young plants, ask the DA about an FPA registered product. We name no active ingredient here, because our sources named none.

Active Ingredients on Philippine Labels

Keep It Out Next Season

• Pull out striped, stunted plants early: close the young leaves in your hand so hoppers cannot jump, bag the plant and burn it.
• Clear itch grass, barnyard grass and goosegrass from the field and borders. They keep the hopper and the virus alive.
• Rotate corn with a crop that is not a grass, so the hoppers lose their food between seasons.
• Plant at the same time as your neighbors, and use virus resistant seed where it is sold.

Natural Enemies and Biological Help

• Spiders, lady beetles, mirid bugs that eat hopper eggs, and egg wasps keep numbers down. Avoid broad sprays that kill them.
• Beauveria or Metarhizium fungus infects hoppers in humid weather.

Not Sure What You Are Seeing?

Take a clear photo of the insect, the damage and the whole plant, then ask Anee, the smart farm technician in anee.io, in Tagalog or English. Anee tells you what it most likely is and what to do at the age of your crop. You can also put your scouting days on the cropping calendar, so the team knows when to walk the field.

Questions Farmers Ask About Corn Planthopper