July 14, 2021

CANOLA QUIZ – What’s in my sweep net?

Sweep nets are required scouting tools for lygus bugs. Their economic thresholds are based on sweep net counts. Here are five questions related to sweep netting and other timely insect management topics this week.

1. The current recommended threshold for lygus bugs is ____ adults and instars (with darkening wing pads) per 10 sweeps? (Fill in the blank.)
2. Sweep netting can show the biodiversity of insects in the flowering canopy of a canola field. The bottom arrow points to a lygus nymph with developing wings. You include these in your threshold counts along with adults. The top arrow points to a beneficial insect looking like its about to eat a diamondback moth larva (middle arrow). What is that beneficial insect?

3. Grasshoppers might show up in your sweep net, but grasshopper thresholds are not sweep-net based. They are based on counts per square metre. The nominal threshold for grasshoppers in canola is ______ per square metre. (Fill in the blank.)
4. Insecticides have restrictions on the number of applications per year on a field. If you sprayed deltamethrin (Decis, for example) on flea beetles earlier in the season, can you spray it again on grasshoppers?
5. Lygus bugs and grasshoppers are out in higher numbers with the dry conditions, which is why we're focused on them this week. One of these insects will move long distances, so repeat sprays may be necessary to protect a crop. Which one is more mobile?

 

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