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Ohio State University Extension


C.O.R.N. Newsletter 2010-15

Dates Covered: 
June 1, 2010 - June 8, 2010
Jon Rausch

Potato Leafhopper Time!

It is that time of year to start scouting alfalfa for potato leafhopper.  Most alfalfa is now in its’ second growth cycle, which is the time when leafhoppers start showing up.  Growers should begin scouting for the leafhopper as alfalfa reaches sufficient height for sweep-net sampling. Sampling is done using a sweep net and taking 10 samples throughout the field, with each sample should consist of 10 sweeps.   Both adults and nymphs should be counted, although usually only adults will be seen in early samples. When the average number of both adults and nymphs in a sample is equal to or greater than the average height of the alfalfa stand, insecticide treatment is warranted unless the alfalfa variety is resistant to the potato leafhopper (see next paragraph).  For example, if the alfalfa is 8 inches tall and the average number of leafhoppers 8 or higher, insecticide treatment is warranted. If the average is lower, the grower should re-sample in a few days to check for populations above threshold.   If the alfalfa is over 16 inches, early harvesting should be considered.

If the alfalfa is one of the glandular-haired, leafhopper-resistant varieties of alfalfa, the economic threshold is three leafhoppers per inch of growth (24 leafhoppers for 8” tall alfalfa, for example).  However, if the resistant alfalfa is a new planting this spring, growers might want to use thresholds meant for regular alfalfa during the very first growth from seeding.  Because its resistance improves as the seedling stand develops, research suggests that the threshold for a resistant variety can be increased to 3 times the normal level after its first cutting.

More information on potato leafhopper, including how alfalfa growing conditions might affect the threshold, is available at , while a list of insecticides labeled for control is at .  As mentioned in previous newsletters, it would also be worth your time to keep an eye out for alfalfa weevil larvae that might be limiting alfalfa regrowth.


Twisted Whorls in Corn

Wrapped and Twisted Whorls in Corn often occurs when young corn quickly shifts from a period of slow growth associated with cool, cloudy weather conditions to rapid development or warm, sunny weather. the twisted whorl syndrome is not uncommon, but rarely affects a large number of fields in any given year or a large percentage of plants within a field.

The typical growth stage when this is noticed is late V5 to early V6 approximately knee-high. The lowermost leaves are typically normal in appearance, although although some may exhibit some crinkled (accordion-like) tissue near the base of the leaf blade.

For the complete article by Bob Nielsen,

Grassy Weeds in corn

With the extended wet period in May some producers have yet to apply pre-emergence herbicides and are backed into a corner. Some possible solutions are (1) refer to Ohio and Indiana Weed Control Guide, (2) if Glyphsate tolerant corn or gluphosiante tolerant hybrids you have ready options. For those needing additional options, especially those desiring residual activity refer the chart below from Bob Hartzler, Iowa State University.

  Hartzler Corn Chart

For the full article see:

Western Bean Cutworm monitoring starts June 01 Western Bean Cutworm PSU Ento

Western Bean Cutworm monitoring starts June 01

Western bean cutworm (WBCW) was historically found in the western Corn Belt, where it was a common pest of dry beans and a sporadic pest of corn. Starting in the year 2000, economic damage from this pest was found on corn in Iowa and Minnesota. Since then, this pest has continued to rapidly spread eastward, reaching Ohio in 2006. The easiest way to monitor the presence of this pest is   trapping of the adult moths. In 2006, 3 adults were caught, 6 in 2007, 150 in 2008, and over 500 in 2009. Most moths have been caught in the extreme northwest or west central portion of Ohio.

  The adults emerge in late June–early July after fully grown larvae overwinter inside soil chambers in the soil 3–8 inches deep. The adults are mostly dark brown and black, with three characteristic markings that distinguish them from other moths: (1) a white stripe on the top edge of the forewing, (2) a light brown-tan colored dot, and (3) a comma or crescent-shaped mark behind the dot. Mid-flight of the adults usually occurs in mid-July, with adult flight ending by mid to late August. There is one generation per year.

 During the summer flights, adults mate, and females lay eggs on the uppermost portion of the flag leaf. Eggs are laid in unevenly distributed clusters of 5–200, but averaging about 50 per cluster, and hatch within 5–7 days. Eggs first appear white, then tan and then a dark royal purple. Once eggs turn purple, hatching should occur within 24 hours.

 In pre-tassel corn, larvae will move to the whorl to feed on the flag leaf and unemerged tassel.

Once the tassel emerges, larvae then move to the ear, while feeding on corn pollen, leaf tissue, and silks. By the 4th instar, larvae will enter the ear through the tip, or 7th instar, larvae emerge from the ear and fall to the ground to overwinter in soil chambers. Pupation occurs in May, immediately before adult emergence.

 Corn fields can be easily monitored through simple pheromone traps. Four windows from an empty gallon milk jug are cut, and the jug is tied to a post at least 4 feet high (fig. 5). A bent paper clip is used to attach the lure to the inside lid of the milk jug and the cap is replaced to keep the lure in place. The bottom of the jug is filled with an 4:1; water:antifreeze solution, with a drop of dish soap added. Traps are placed on the edge of a cornfield; one trap per field is sufficient. Traps should be inspected at least weekly. When the first adult is collected or when adults are collected on consecutive nights, scouting for eggs or larvae should begin. Lures can be purchased at either Great Lakes IPM, 10220 Church RD NE, Vestaburg, MI 48891, or  at Gempler’s, P. O. Box 270, 211 Blue Mounds Road, Mt. Horeb, WI 53572. You can also contact your local Extension office for assistance.

 While no eggs have been reported from WBCW in Ohio, a single larva and a single injured ear of corn were found in 2009 in the state. However, economic damage has been reported in Indiana and Michigan, states to the west and north of Ohio, respectively. Ontario is also reporting large adult collections for the first time. For now, scouting remains the growers’ best tool for managing WBCW.

The 2010 Ohio Sustainable Farm Tour and Workshop Series

Will include tours of 15 farms, 3 university research centers, and 10 educational workshops, providing unique opportunities for growers, educators, and conscientious eaters to see, taste, feel, and learn what alternative production systems are all about from the real experts—the farmers and researchers themselves. Each farmer is prepared to share their extensive experience producing and marketing their goods— both successes and failures—with anyone interested in learning more. Market gardeners, grain and livestock producers, processors, future farmers, educators, and discriminating food lovers are encouraged to attend and shake the hands that feed them. All tours are free and open to the public unless otherwise noted. Events will take place rain or shine.

 For more information:

 Here’s a calendar of special events that should be of interest to farmers and allied industry professionals and others interested in production agriculture.



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Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.