The TV show “Dirty Jobs” put host Mike Rowe in all kinds of nasty situations. He never found his way to a cornfield at tasseling time — but if writers had stumbled across how uncomfortable it is to walk cornfields with corn over the person’s head at tasseling, he might well have found himself shooting a show in a cornfield.
What would he have been doing there? He could have scouted corn for several things, including which insects were present, and whether or not they were clipping silks. This is the time of year when you read about Japanese beetles and corn rootworm beetles clipping silks. Can enough clipping occur to affect yields? Is it really worth playing the Mike Rowe-role and heading into your cornfields?
The Indiana Certified Crop Advisers panel examines this question. Panel members include Jamie Bultemeier, Great Lakes A&L Labs, Fort Wayne; Gene Flaningam, Flaningam Ag Consulting LLC, Vincennes; and Bryan Overstreet, Purdue University Extension ag educator, Jasper County.
Bultemeier: Severe Japanese beetle silk clipping can have a negative impact on corn pollination. If silks are clipped back to less than one-half inch from the husk, with more than 50% pollination to go and beetles are still actively feeding, it is time to treat.
Flaningam: Damage caused by Japanese beetles needs to be reviewed on a field-by-field basis. Usually, silk clipping will start along grassy field borders and grass waterways. Scout these primary areas first. Each field will need to be scouted for pollen shed. Shake 25 plants and determine the amount of pollen left in the field.
Overstreet: Since Japanese beetles feed in clusters along the edges of fields, it may look worse than it really is. Scout five areas in the field that are not along the edges. The economic threshold is when silks are clipped to less than one-half inch, less than 50% of pollination is complete and beetles are still present.
Bultemeier: Silks grow at a rapid rate. A few clipped silks is not a big issue. But if beetles completely remove silks and prevent pollination, yield impacts could be sizable. This assumes there is feeding across a large portion of the field.
Overstreet: I’ve found you get a better reading of silk length if you scout fields in the morning. Silks will grow at night, and beetles will feed on them during the day.
Flaningam: Check silks to see if they are still viable for pollination. Brown silks should be considered pollinated. Fresh silks still have the potential for pollination. Measure the length of clipped silks. Count the average number of beetles per plant.
Overstreet: To check for percentage of pollination, shuck the ear and shake it to see which silks fall off. Once a silk has pollinated a kernel, it will usually fall off the cob when shaken. Bob Nielsen, the Purdue University Extension corn specialist, has demonstrated this shaking method to help assess pollination to hundreds of farmers and agronomists across the state. From this easy test, you can see how much of the ear is pollinated. For more information on silk clipping and Japanese beetles, you can visit this website: https://extension.entm.purdue.edu/fieldcropsipm/insects/corn-japanese-beetles.php.