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C.O.R.N. Newsletter : 2019-24
A more normal pattern ahead into AugustAuthor(s): Jim Noel
June and July together for Ohio will go down as 1-2 degrees warmer than normal and rainfall will go down on average as 100-175% of normal. However, details and timing matter. Looking at July only, rainfall will go down as 75-100 percent of normal over the southwest part of the state while the northern and east will down down as 100-150% of normal.
Over the next two weeks rainfall will be at or slightly below normal in the 1-2 inch range. Rainfall is expected into Tuesday July 30. After that rain event, the next will not occur until about August 6 or 7. The good news is temperatures will be close to normal over the next two weeks. There will be a burst of above normal temperatures this coming weekend though.
NOAA/Climate Prediction Center 6-10 Day Temperature Outlook
NOAA/Climate Prediction Center 6-10 Day Rainfall Outlook
Two week rainfall totals are expected in the 1-2 inch range as attached graphic shows.
The outlook for August is near normal temperatures and precipitation.
Western Bean Cutworm: Peak time to scout for egg massesAuthor(s): Amy Raudenbush, Kimberley Gault, Mark Badertscher, Lee Beers, CCA, Amanda Bennett, Bruce Clevenger, CCA, Sam Custer, Tom Dehaas, Allen Gahler, Jason Hartschuh, CCA, Andrew Holden, Stephanie Karhoff, , , David Marrison, , Sarah Noggle, Les Ober, CCA, Eric Richer, CCA, Kaitlin Ruetz, Garth Ruff, Clint Schroeder, Jeff Stachler, Mike Sunderman, , Curtis Young, CCA, Chris Zoller, Andy Michel, Kelley Tilmon
Results from week five of The Ohio State University Western bean cutworm (WBC) monitoring network has resulted in an overall increase of moths captured across Ohio. Meaning, last week (July 22 – 28) marks our peak week in adult WBC flight to date. A total of 26 counties monitored 79 traps across Ohio and resulted in a 2842 WBC adults (up from 2001 total last week) and a statewide average of 36.0 moths/trap (up from 25.3 average last week) (Figure 1). Since 2016, peak adult WBC emergence has typically occurred during the second or third week in July; however, with the cooler temperatures and increased rainfall the 2019 WBC peak week was delayed (Figure 2). If your county is averaging over 7 moths per week, now is the time we recommend scouting for WBC egg masses. You can view our scouting video here.
Scouting and management.
Check pre-tassel corn approaching tassel fields first – females prefer these fields to deposit eggs.
- To scout for eggs or larvae, choose at least 20 consecutive plants in 5 random locations (scout different areas of the field that may be in different growth stages).
- Inspect the uppermost 3–4 leaves.
- Threshold (when to consider treatment):
- Field corn, if >8% of inspected plants have eggs or larvae.
- Sweet corn, if >4% of inspected plants have eggs or larvae for the processing market or on >1% of plants for fresh-market.
What you are looking for.
WBC egg masses are often found on the upper leaf surfaces in clusters. Eggs laid by WBC are round and first appear white, then tan and then a dark purple. Once eggs turn purple, they will hatch within 24 to 48 hours (Figure 3). WBC egg masses can be easily confused with stink bug egg masses; however, stink bug eggs are larger in size and are more barrel shaped with a ring of hairs around the top.
If infestations exceed threshold, many insecticides are available to adequately control WBC, especially those containing a pyrethroid. However, as with any ear-burrowing caterpillar pest, timing is critical. Insecticide applications must occur after egg hatch, or after tassel emergence, but before caterpillars enter the ear. If eggs have hatched, applications should be made after 95% of the field has tassel. If eggs have not hatched, monitor for the color change. Hatch will occur within 24–48 hours once eggs turn purple. To search for larval injury after it has occurred, search the corn for ears having feeding holes on the outside of the husks.
Expect cornfields pollinating well into AugustAuthor(s): Peter Thomison
According to the National Agricultural Statistics Service for the week ending July 28, 2019, 32% of the state’s corn was silking compared to 75% for the 5-year average. Given the wide range in corn planting dates this year, most corn will not achieve tasselling and silking until we are well into August. The pollination period, the flowering stage in corn, is the most critical period in the development of a corn plant from the standpoint of grain yield determination. Stress conditions (such as hail damage and drought) have the greatest impact on yield potential during the reproductive stage. The following are key steps in the corn pollination process.
Most corn hybrids tassel and silk about the same time although some variability exists among hybrids and environments. On a typical midsummer day, peak pollen shed occurs in the morning between 9:00 and 11:00 a.m. followed by a second round of pollen shed late in the afternoon. Pollen may be shed before the tassel fully emerges. Pollen shed begins in the middle of the central spike of the tassel and spreads out later over the whole tassel with the lower branches last to shed pollen. Pollen grains are borne in anthers, each of which contains a large number of pollen grains. The anthers open and the pollen grains pour out in early to mid morning after dew has dried off the tassels (see figure). Pollen is light and is often carried considerable distances by the wind. However, most of it settles within 20 to 50 feet.
Pollen shed is not a continuous process. It stops when the tassel is too wet or too dry and begins again when temperature conditions are favorable. Pollen stands little chance of being washed off the silks during a rainstorm as little to none is shed when the tassel is wet. In addition, silks are covered with fine, sticky hairs, which serve to catch and anchor pollen grains.
Under favorable conditions, pollen grain remains viable for only 18 to 24 hours. However, the pollen grain starts growth of the pollen tube down the silk channel within minutes of coming in contact with a silk and the pollen tube grows the length of the silk and enters the female flower (ovule) in 12 to 28 hours. A well-developed ear shoot should have 750 to 1,000 ovules (potential kernels) each producing a silk. The silks from near the base of the ear emerge first and those from the tip appear last. Under good conditions, all silks will emerge and be ready for pollination within 3 to 5 days and this usually provides adequate time for all silks to be pollinated before pollen shed ceases.
Pollen of a given plant rarely fertilizes all the silks of the same plant. Under field conditions, 97% or more of the kernels produced by each plant may be pollinated by other plants in the field. The amount of pollen is rarely a cause of poor kernel set. Each tassel contains as many as 2 million or more pollen grains, which translates to at least 2,000 pollen grains produced for each silk of the ear shoot. Shortages of pollen are a problem under conditions of extreme heat and drought; they may also occur in fields characterized by uneven emergence in later emerging plants. As noted above, poor kernel set is more often associated with poor timing of pollen shed with silk emergence – with silks emerging after pollen shed (poor “nick”). However, modern hybrids rarely exhibit this problem unless they experience extreme drought stress. Some of the new drought tolerant hybrids have shorter “anthesis silking intervals”, i.e. pollen shedding and silk emergence are more closely synchronized than hybrids more susceptible to drought. This shorter anthesis silking interval mitigates the impact of drought stress during pollination.
2019 Ohio Wheat Performance Test
Yield results from the 2019 Ohio Wheat Performance Test are online at: https://www.oardc.ohio-state.edu/wheattrials/default.asp?year=2019 Disease information will be available soon.
The purpose of the Ohio Wheat Performance Test is to evaluate wheat varieties, blends, brands, and breeding lines for yield, grain quality, and other important performance characteristics. This information gives wheat producers comparative information for selecting the varieties best suited for their production system and market. Varieties differ in yield potential, winter hardiness, maturity, standability, disease and insect resistance, and other agronomic characteristics. Selection should be based on performance from multiple test sites and years.
In fall 2018, wheat was planted at three out of the five locations within two weeks of the fly-free date. Due to poor soil conditions, wheat was planted in Marion and Wayne County 16 and 23 days after the fly-free date, respectively. Wheat entered dormancy in good to excellent condition. Early season wheat growth and development were slower than the previous years due to cool temperatures and above average precipitation. However, harvest conditions were favorable and harvest dates average. Results from the Marion County were not included in the 2019 report due to extreme field variability caused by high rainfall. Overall, grain test weight averaged 55.0 lb/bu (compared to an average test weight of 55.5 lb/bu in 2018). Across the Wood, Wayne, Darke, and Pickaway locations, grain yield averaged 85.9 bu/acre.
Summer Corn and Soybean Scouting Night in Crawford CountyAuthor(s): Jason Hartschuh, CCA
Tuesday, August 13th, 5:00 P.M
2019 has been a trying year. Monitoring disease and insect pressure will be crucial this year with our crops maturating later than normal. Anne Dorrance, Pierce Paul, Mark Loux, Kelley Tilmon, and Andy Michel will be joining us for hands on discussion to help us better understand which diseases and insects we need to be on the lookout for this fall to maximize crop yields and/or profit. https://crawford.osu.edu/sites/crawford/files/imce/Program_Pages/ANR/2019Prog/Scouting%20aug%2013%20flier.pdf To register please call the Crawford County Extension office at 419-562-8731.
Mid-season diseases and managementAuthor(s): Anne Dorrance
The rains last week around Wayne County (5+ inches) provided for saturated soil conditions. Cultivars with low resistance to Phytophthora sojae are now developing Phytophthora stem rot. These fields were planted the first week of June and the stands were good but are now beginning to thin out. This has been the pattern, it takes 1 to 2 weeks for above ground symptoms to develop on cultivars with resistance packages that are no longer effective. Phytophthora sojae has one host, soybean, and can adapt to some of the types of resistance that is bred into soybeans to manage this pathogen. Scout fields of soybeans 1 to 2 weeks after a rain to look for symptoms. If you find a plant or two, probably don’t worry but if you easily find dozens of plants and the canopy is thinning due to loss in stand – look at the resistance package of the soybean. It is time for something new.
Another thing is that plants that were planted in this first week of June were in flower. For those of you that have whitemold annually, there is an app developed by colleagues at University of Wisconsin. Sporecaster is the name (https://ipcm.wisc.edu/apps/sporecaster/). Just to be clear, this has not been validated under Ohio conditions. Last year, it was only 50% correct in predicting. This year is going to be very strange as we don’t know what the late planting and all of the rain will impact whitemold, but if you try it – keep notes and go back and check to see if whitemold does develop. Most important, what is the resistance rating for the variety? The higher the resistance, the less likely that white mold above the yield loss levels will develop.
Frogeye leaf spot reports were low the last two weeks. For those fields now hitting the R2 growth stage, it is time to scout. For fields of soybean, known to be susceptible to this leaf spot, the fungicide timing is R3. There are lots of very effective materials available. We have begun our surveys for leaves with frogeye leaf spot to determine if the fungicides are still effective. If you would like to participate we would greatly appreciate the samples.
Japanese Beetles and Other Defoliators
We have been hearing reports of increasing numbers of Japanese beetles in corn and soybean, and sporadic infestations of various caterpillars in soybean. Japanese beetles are large with a shiny copper and green color. Foliage feeding in corn is almost never economic, though economic damage from silk clipping is possible (though rare). Consider a rescue treatment when silks are clipped to less than ½ inch and, fewer than 50% of the plants have been pollinated, and the beetles are still numerous and feeding in the field.
Japanese beetles will also feed on soybean foliage. While the damage might look startling, it is very rare that this reaches economic levels from Japanese beetle. A rescue treatment is advised when defoliation levels reach 30% in pre-bloom stages, and 20% in bloom to pod fill. These defoliation levels apply to the plant as a whole, not just certain leaves. Damage is often worst at the top of the canopy but on closer examination most of the plant is relatively unharmed. Make your decision based on the average condition of whole plants, not a scan of the top canopy. Also, defoliation tends to be worse on field edges, so make your assessment based on the field as a whole, including interior.
This same defoliation threshold can also be used for general defoliation from other of leaf-feeding insect in soybean, including various caterpillar species, grasshoppers, and Mexican bean beetles. A visual guide to defoliation is useful because it is very easy to over-estimate defoliation in soybean. If there are other foliage-feeding insects present in soybean the same percent defoliation guidelines can be used for all of them collectively.
For more information about Japanese beetle and other defoliating insects visit our factsheet at:
No pigweed left behind - late-season scouting for Palmer amaranth and waterhempAuthor(s): Mark Loux
If you don’t already have to deal with waterhemp or Palmer amaranth, you don’t want it. Ask anyone who does. Neither one of these weeds is easy to manage, and both can cause substantial increases in the cost of herbicide programs, which have to be constantly changed to account for the multiple resistance that will develop over time (not “can”, “will”). The trend across the country is for Palmer and waterhemp to develop resistance to any new herbicide sites of action that are used in POST treatments within about three cycles of use. Preventing new infestations of these weeds should be of high priority for Ohio growers. When not adequately controlled, Palmer amaranth can take over a field faster than any other annual weed we deal with, and waterhemp is a close second. Taking the time to find and remove any Palmer and waterhemp plants from fields in late-season before they produce seed will go a long way toward maintaining the profitability of Ohio farm operations. There is information on Palmer amaranth and waterhemp identification on most university websites, including ours – u.osu.edu/osuweeds/ (go to “weeds” and then “Palmer amaranth”). An excellent brief video on identification can be found there, along with an ID fact sheet. The dead giveaway for Palmer amaranth as we move into late summer is the long seedhead, and those on female seed-bearing plants are extremely rough to the touch. We recommend the following as we progress from now through crop harvest:
- Take some time now into late summer to scout fields, even if it’s from the road or field edge with a pair of binoculars. This would be a good time to have a friend with a drone that provides real-time video, or your own personal satellite. Scouting from the road is applicable mostly to soybean fields, since corn will often hide weed infestations. Scout field borders and adjacent roadsides, areas that flood or receive manure application, and also CREP/wildlife area seedings. The latter can become infested due to contaminated seed produced in states where Palmer amaranth and waterhemp are endemic and not considered noxious. Reminder - ODA will test any seed used for these purposes for the presence of Palmer amaranth.
- Walk into the field to check out any weeds that could be Palmer amaranth, waterhemp, or are otherwise mysterious. If you need help with identification, send photos to us or pull plants and take them to someone who can identify them. Palmer and waterhemp are considerably different in appearance than giant ragweed and marestail, the other two most common late-season offenders.
- Where the presence of Palmer amaranth or waterhemp is confirmed, check to see whether plants have mature seed (in Palmer infestations these are the rough female seedheads), by shaking/crushing parts of the seedhead into your hand or other surface that will provide contrast. Mature seed will be small and very dark. Plants without mature seed should be cut off just below the soil surface, and ideally removed from the field and burned or composted. Plants with mature seed should be cut off and bagged (at least the seedheads) and removed from the field, or removed via any other method that prevents seed dispersal through the field.
- If the Palmer amaranth or waterhemp population is too dense to remove from the field, some decisions need to be made about whether or how to mow or harvest. Harvesting through patches or infested fields will result in further spread throughout the field and also contamination of the combine with weed seed that can then be dispersed in other fields. So consider: 1) not harvesting areas of the field infested with Palmer amaranth or waterhemp, and instead mowing several times to prevent seed production, and 2) harvesting the infested field(s) after all other fields have been harvested, and cleaning the combine thoroughly before further use. This also applies to any infestations that are discovered while harvesting. At least one equipment manufacturer has a good video about how to most thoroughly clean a combine.
- Feel free to contact OSU weed science for help with identification or management of Palmer amaranth and waterhemp. Mark Loux – firstname.lastname@example.org, Bruce Ackley – Ackley.email@example.com. Also – let us know if you would like any of the “no pigweed left behind” magnets and we will get some to you.
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.
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