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Insect Update

This time of year it is important to be scouting fields for insects and the damage they cause in our agronomic crops.  Crops like peanuts, cotton, corn, soybeans and sorghum can all be attacked by insect pests that can decrease yields and cause other problems in harvested commodities.   Stink bugs are one pest that cotton scouts and consultants are on the lookout for right now.  Cotton in most fields is in a susceptible stage for damage from stink bug feeding.  They use their piercing/sucking mouth parts to feed internally on the seed.  This causes damage to the seed, and can introduce bacteria and fungi that lead to boll rot.

Internal Stink Bug Damage

We don’t often see many stink bugs when walking through cotton fields, so we look for the damage.  By selecting bolls between a dime and a quarter in diameter we can look for internal damage.  During weeks 3 – 5 of bloom we use a threshold of 10-15% damage.  as we move further into the season we can handle a bit more damage.

Since it has been hot and dry spider mites are also beginning to flare up in spots.  This is important to know especially when making spray decision for other pests.  Using a broad spectrum insecticide when a small mite problem exists usually creates a large mite problem.  Hopefully afternoon showers over the weekend will help slow down the spread of any mite infestations.

spider mites and damage to cotton leaf

On soybeans, kudzu bugs are back.  Last year we saw quite a few but a fungus ended up wiping out most infestations.  We will need some wetter weather if we expect the same to happen in 2019.

Just because we see adults by the thousands does not mean we have to spray.  The official threshold is 1 immature kudzu bug per sweep using a net.  I prefer to just visibly inspect the plants.  If you have high adult populations and nymphs are readily found throughout the field it probably warrants a spray.  The fields i was in yesterday had thousands of adults and probably many more eggs, but there were no immature bugs.  In that case we will monitor the field to see if the little guys in the picture make it through the week.  they are not fast and don’t scare other insects so they often don’t make it to see their birthdays.  When the canopy is still open immature kudzu bugs usually have trouble surviving.