Summer Insect Scouting - A Worthwhile Walk

Summer Insect Scouting

Summer is here. Your crops are looking good. Weeds and diseases are under control. Mother Nature is doing her part. All that is left is to sit back and watch your crops mature before you start prepping your equipment for harvest. Not so fast.

Insect issues can creep up mid-season or late season. That is why it is important to scout your fields each week. Checking your crop for insects helps you maximize yield potential and profitability, an ROI that is definitely worth the effort.

Here are some helpful tips when scouting your corn and soybean fields:

  • Walk in a zigzag pattern when scouting to cover more crop, although this may be more difficult when plants get taller later in the season
  • Check for patterns of field damage near field edges or in previous weed areas
  • Examine the soil beneath the surface for any subsurface insects; conduct soil testing as needed
  • Investigate areas where plants have not emerged or where there’s uneven emergence
  • Depending on the crop, use a shake cloth and/or sweep net for an accurate insect threshold count
  • Estimate the percentage of total leaf surface damage or defoliation caused by insects

“You should also check both sides of the plant leaf, as some insects attack the bottom of the leaf. Many times the top plant leaves will have noticeably more defoliation than the ones toward the bottom. You need to check leaves on the entire plant to determine the extent of defoliation,” says Malin Westfall, soybean marketing manager for Crop Science. “Insect activity also can be heavier in reduced tillage systems.”

Threshold levels can vary based on defoliation, geographic location, growth stage and crop. Growers should examine insects caught during scouting to determine threshold populations and the presence of any beneficial predators or parasites. Beneficials feed on crop-damaging insects. Checking insect size can aid in making control decisions. “The more large insects you have, the faster yield-impacting crop damage can occur,” says Westfall.

For instance, with soybeans, four or more foliage-feeding larvae ½ inch or longer per row foot can cause 20 percent defoliation, while eight or more of the same size larvae can cause 35 percent defoliation. During bloom and pod fill, foliage loss of 20 percent or higher can decrease yield. Whereas when soybeans have matured and pods have fully developed, 35 percent foliage loss will typically not reduce yield.

In addition to scouting, other insect management recommendations include:

  • Document your Integrated Pest Management (IPM) plan and update that plan with scouting numbers and actions taken on fields
  • Select a hybrid/variety for targeted pests in your fields
  • Use crop rotation
  • Choose insecticides for targeted pests
  • Rotate insecticide modes of action and use proper rates to prevent resistance

“Once done with scouting and analysis, growers must determine if an insecticide application is necessary based on threshold levels,” says Jody Wynia, corn marketing manager for Crop Science. “Insecticides are a critical element to any IPM plan, but you should not rely on them as the only method to control insects.”

According to Mississippi State University, management tactics applied against one pest may be favorable or unfavorable to the development of other pests. In addition, treatments applied during one part of the season may affect future pest populations, or even your ability to control those pests later during the season or in future years.

One thing is certain, if your fields exceed threshold levels, take prompt action to prevent yields from being compromised. “The old adage ‘Time is money,’ applies in minimizing insect damage,” says Wynia. “Insecticide applications, even later into the season, have been proven to help guard your crop from yield-damaging insects.”

A mid-to-late season application of an insecticide such as Leverage® 360 helps protect yields by delivering a quick knockdown to stop insect feeding and a long-lasting residual for broad-spectrum control with minimal risk to beneficial insects.

Growers are encouraged to discuss insecticide application timing and tankmix options with their crop consultant, Extension agent or Crop Science representative.

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