You should be able to prevent this by spraying when you hit the one nymph per sweep threshold. Keep in mind that most fields will have kudzu bugs at some level. 

As discussed in the first paragraph, even if you can see insects when you peel back the canopy, you might not have a threshold-level population or you might start picking them up as they get older. Kudzu bugs take a long time to develop relative to other insects, so this will not happen overnight. 

Some tips for using the sweep net are to:

• Take 15–20 sweeps per sample away from field edges. Ideally, keep the same number of sweeps per sample and per field to compare them.

• Try to get the net as low as possible between sweeps to hit the middle portion of the plant. More than half the insects are located this section of the plant. I like to imagine that I’m stripping the bugs off the main stem, which hopefully buries my net pretty deep in the canopy.

• Sweep at a comfortable pace that you can maintain throughout the sampling bout.

• Kudzu bug is more active from 11a.m. to 2 p.m, resting near the bottom of the plant in quiescent times in the morning and late afternoon and evening. To facilitate capture and reduce the chance of underestimating the adult population, scout during the mid-day period above.

• Look closely at the bottom of the sweep, net because nymphs cluster in this section of the net.

For both visual samples and sweeping, you can check field edges to see if the bugs are present. However, this, insect congregates much more heavily on these edges.

The insect is also attracted to structures with height, often aggregating on taller plants, fence posts, or volunteer corn plants in a field. 

Treatment decisions should be based on field interiors of average sized plants. Start sampling at least 50 feet into the field, being sure to visit several parts of the field.

(Sampling information is from Alejandro Del Pozo-Valdiva, NCSU Department of Entomology PhD student).

 

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