Switchgrass

Symptoms: caterpillars feeding at ear tips; chewed kernels and frass inside husk; damaged silks; worse in later-season plantings

• CulturalPlant early and choose tight-husk varieties●●●Strongstrong evidence — extension confidence

  Set out early plantings, which face lower earworm pressure, and choose tight-husked varieties whose long, snug husk slows larvae from reaching the ear.

  Source: Clemson HGIC: Insect Pests of Sweet Corn; UMN Extension: Sweet corn pests

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• OrganicApply oil-Bt drops to silks●●Moderatemoderate evidence — extension confidence

  About five to six days after silks emerge, apply a few drops of vegetable or mineral oil (mixed with a labeled Bt per the label) to the silk at each ear tip to smother young caterpillars in the silk channel.

  Always follow the product label — it is the law.

  Source: Clemson HGIC: Insect Pests of Sweet Corn

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Symptoms: leaves skeletonized between veins; lacy chewed foliage; metallic green-bronze beetles clustered on plants; feeding worst in warm midsummer sun

• CulturalHandpick into soapy water· every 1 days · ~4 wks●●●Strongstrong evidence — extension confidence

  In early morning when beetles are sluggish, knock them into a bucket of soapy water; daily removal also reduces the scent that draws in more beetles. Skip the lure traps, which tend to attract more beetles than they catch.

  Source: UMN Extension: Japanese beetles; PennState Extension: Japanese Beetles in the Home Garden

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• CulturalCover plants past bloom●●Moderatemoderate evidence — extension confidence

  On crops that have finished flowering and set fruit, drape a row cover or netting to keep beetles off without blocking pollination during bloom.

  Source: UMN Extension: Japanese beetles

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Unusual this time of year.

Symptoms: stunted plants with dark dull green leaves; reddish or purplish tint on leaves and undersides; delayed maturity and poor fruiting; symptoms worst in cold spring soils; older leaves affected first

• CulturalCheck soil test and soil temperature●●●Strongstrong evidence — extension confidence

  Purpling in cold spring soils is often temporary, since cold roots can't take up phosphorus that's actually present; warm weather usually resolves it, so confirm a true shortage with a soil test before adding phosphorus.

  Source: UMN Extension; Missouri Botanical Garden

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• OrganicAdd phosphorus only if the test calls for it●●Moderatemoderate evidence — extension confidence

  If low phosphorus is confirmed, work a phosphorus source into the root zone per the test recommendation, and keep soil pH in range since extreme pH ties up phosphorus.

  Always follow the product label — it is the law.

  Source: UMN Extension

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Unusual this time of year.

Symptoms: patchy poor germination; seedlings die in stretches; tunneled holes in potatoes and root crops; hard shiny orange-brown worms in soil; thinning stands after sod or grass

• CulturalRotate away from grassy ground●●●Strongstrong evidence — extension confidence

  Avoid planting susceptible crops right after sod, pasture, or grass cover, where wireworms build up; rotate to a less-favored crop and let infested beds dry out between plantings.

  Source: UMass Extension: Wireworms; UC IPM: Wireworms

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• CulturalBait-trap to monitor· every 5 days · ~3 wks●●Moderatemoderate evidence — extension confidence

  Bury pieces of carrot or potato or a handful of soaked wheat seed as bait when soil reaches about 50F, check after several days, and remove the worms you find to gauge and reduce pressure.

  Source: UMass Extension: Wireworms

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Symptoms: clusters of tiny soft-bodied insects on new growth and undersides; sticky honeydew or sooty mold; curled distorted new leaves; ants tending them

• CulturalBlast off with water· every 3 days · ~2 wks●●●Strongstrong evidence — extension confidence

  Knock colonies off with a strong jet of water in the morning; repeat every few days. Light infestations rarely need more.

  Source: UC IPM: Aphids

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• OrganicInsecticidal soap - label use only· every 1 wk · ~3 wks●●Moderatemoderate evidence — extension confidence

  For persistent colonies apply insecticidal soap to undersides per label. Avoid open flowers.

  Always follow the product label — it is the law.

  Source: UC IPM

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Symptoms: swollen silvery-white galls on ears, tassels, or stalks; galls darken to a black sooty spore mass; worse after wounding, hail, or heavy nitrogen

• CulturalCut out galls before they open· every 1 wk●●●Strongstrong evidence — extension confidence

  Watch through the season and cut out smut galls while still firm and white, before they rupture into black spores; remove them from the garden and bury or trash them rather than composting.

  Source: Clemson HGIC: Sweet Corn Diseases; UMN Extension: Common smut on corn

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• CulturalClean up debris and ease off nitrogen●●Moderatemoderate evidence — extension confidence

  Remove crop debris after harvest rather than tilling it under, and avoid excess nitrogen and plant wounding, both of which favor smut.

  Source: Clemson HGIC: Sweet Corn Diseases; UMN Extension: Common smut on corn

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