The following article is from Matt Montgomery who is the University of Illiniois extension specialist to the Menard-Sangamon counties in Illinois.

The information relates to questions regarding effectiveness of Poncho products and Grub pressure. Please note the red printed underlined area in the article. This may explain why some areas have shown grub evidence without affecting the corn.

TEX

GRUBS AND PONCHO

Poncho 250 and Poncho 1250* treated seed has largely been the “seed rule” in many area cornfields, and with such widespread use comes performance questions. If one used Poncho but still found healthy grubs, would that find be proof that the product was not working?

Poncho 250 and Poncho 1250 are different rates of the same insecticide seed treatment. The insecticide is termed chlothianidin and it belongs to a larger group termed nicotinoids (also termed neonicotinoids/chloronicotinyls). Nicotinoids are nerve poisons. They inhibit receptors on dendrites of the nerve cell. Those receptors should accept chemicals that signal the nerve to “fire.” By blocking those receptors, nicotinoids cut off the essential flow of information in the nerve. Nicotinoids move systemically within the plant. In order for these insecticides to work, the target must feed on nicotinoid-laden tissue (i.e. no consumption of tissue equals no death of the target). The insecticide moves within the plant NOT within the soil. One could thus note healthy grubs in proximity to root material if those grubs did not feed on root tissue because those grubs would not have come into contact with the insecticide at all.

Grubs are the larval stage of many different beetles. In our area, three major species are noted in the field. The annual white grub, Cyclocephala lurida, has a one-year lifecycle and is the immature stage of a beetle termed the southern masked chafer. The true white grub, Phyllophaga spp., is the larval stage of several different beetles, which are commonly termed May/June Beetles. These grubs have a three-year lifecycle. The Japanese Beetle grub also has a one-year lifecycle.

Of these common field grubs, two species are often noted for “diverse” feeding habits. Those two are the annual white grub and the Japanese Beetle grub. They are known to feed on roots and/or organic material in the soil. Roots can thus go unscathed while intense grub populations exist nearby because these grubs can feed on organic mater rather than roots. Healthy, well-fed grubs could exist near roots without feeding on those roots thus resulting in exceptional grubs numbers near chlothianidin-laden root tissue.

Product names are property of their respective companies. No promotion of product is intended.

Tex Young, CCA
Sales Agronomist
Great Lakes Hybrids

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