NDSU Extension - Burke County


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Good Bugs and Bad Bugs

County Agent News
Dan Folske
August 24, 2020


Good Bugs and Bad Bugs

            Imagine a little black and orange bug about one half inch long that looks rough and scaly like an alligator  Something that ugly has to be bad. Right?  Actually no, what I am describing is the larvae of the ladybug beetle. It may be ugly but it is very beneficial, consuming lots of aphids and other unwanted pests.  I sat down in the field to change a sickle section on my hay conditioner last week and was overwhelmed with pale green aphids but as I watch there were a few Ladybugs and lots of their ugly larva (click here to see it in action!). I found this awesome video by Russel Kogan on YouTube at https://www.youtube.com/watch?v=ws_D5nXOAJg (or just google The Stunning Life Cycle of a ladybug).



            Mention wasps and most people get nervous and start looking around for yellow jackets if they are outdoors. And yes, some wasps do sting and the stings can be very painful.  Actually most wasps are beneficial and either consume other harmful insects like aphids or they lays their eggs on or near the eggs or larva of other insects which are more harmful to or crops and food supply. Many are quite small and barely noticeable. Others are larger and very scary looking. There are several non stinging wasps which resemble yellow jackets but are larger and have a long ovipositor which looks like a huge stinger. Even yellow jackets which can be a painful nuisance at a picnic or on a deck are actually quite beneficial in helping to control other insects.



            Wheat Stem Sawflies on the other hand are a serious threat to wheat and durum crops. The wheat stem sawfly produces one generation per year. Adults emerge in late May or early June and are generally active when winds are calm and field temperatures are above 50° F. The adult wheat stem sawfly (Figure 1) is about ¾ of an inch long with smoky-brown wings. It is wasplike in appearance, with a shiny black body with three yellow bands around the abdomen. When not in flight they often are found on wheat stems, positioned with the head pointed downward.

            Females lay eggs immediately upon emergence and typically live about one week. The adult emergence and flight period continues for 3-6 weeks. The eggs are inserted into the wheat stem where the larva feed and the cut a vee into the inside of the stem causing the stem to break and lodge. The long adult emergence and egg laying period makes control with insecticides very difficult.

            Sawfly infestations are generally heaviest along field edges or in fields that were planted on wheat stubble which had infestations the previous year. Rotation to crops other than small grains or planting solid stem varieties are the only feasible options. Early identification of infestations can provide the option of swathing prior to lodging occurrence. Often only the outside few rounds would need to be swathed.





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