For Randy S. - better late than never!
Back in college when I was an intern for the no longer American Cyanamid, I attended a field day about white grubs. As part of my internship, I was also charged with writing a paper about what I learned. Long story short, I never wrote the paper, I felt like I didn’t really get any answers other than use seed treatments.
A couple of days latter my uncle called me, he had some pretty severe stand loss. After scouting it was determined that in one area of the field he had 2-3 white grub larvae per sq ft. In addition to root feeding, raccoons had managed to dig up the remaining corn in search of the grubs.
So ten years later I am writing about white grubs.
At the field day I attended we looked at white grub damage with thresholds in the 4-5 per sq foot range. The field was on a side hill, with a grassy tree filled creek at the bottom. This was very similar to the field my uncle had problems with.
What do we know about the white grub?
White grubs are the larvae of scarab beetles, otherwise known as June Bugs.
White grubs feed on fibrous-rooted plants, such as corn and grass.
Larval infestations are greatly influenced by soil type or texture. Infestations by white grub are reported to be more common in light, sandy soils that are well-drained than in poorly drained, heavy clay soils.
White Grub normally takes three years to complete its life cycle in most areas.
The June beetles fly from willow and poplar tress to grassy areas to lay their eggs. The eggs hatch and over winter. In the second year the most damage is done.
Preventative insecticides are not recommended, and shelter belt removal is foolish. Planting tolerant crops and tillage (exposes grubs to birds) might be an option.
What have I learned after 10 years of thinking about a project I never completed and no one missed? Proper fertility is actually key to white grub management. In soils that have low calcium and soil with an imbalance of soluble salts, grasses like foxtail can predominate, regardless of herbicides use.
Soil with proper pH and proper calcium insure herbicides control foxtails, and reduces weed vigor, making a poor environment for the June beetle to lay eggs. Sounds too simple I know, but in most cases the simplest solution is usually the best.
Visit http://www.ag.ndsu.nodak.edu/aginfo/entomology/entupdates/whitegrub/whitgrub.htm for more info on white grubs.
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