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A review of USDA crop yield forecasting methodology

Published August 10, 2015

URBANA, Ill. – The USDA’s National Agricultural Statistics Service (NASS) will release the first survey-based yield and production forecasts for the 2015 corn and soybean crops on August 12.  A comprehensive review of the NASS forecasting methodology was provided in a Marketing and Outlook Brief in 2011and NASS provides a very detailed description of the methodology in the publication Understanding USDA Crop Forecasts. In addition, a summary of survey and estimation methodology is included with each Crop Production report.

“Even though a description of the NASS crop production forecast methodology is widely available, there always seem to be some misconceptions about how NASS makes corn and soybean yield forecasts,” said University of Illinois agricultural economist Darrel Good.

Good provided the following overview of the methodology and said that while the summary does not do full justice to the very comprehensive forecasting methodology, he presents it to assist in placing the upcoming yield forecasts in the proper perspective.

NASS corn and soybean yield forecasts are made in August, September, October, and November. The final yield estimate is released in January after harvest based on the comprehensive December Agricultural Survey of producers. Two types of surveys are used to collect data for the monthly NASS forecasts in August through November. The monthly Agricultural Yield Survey (AYS) of producers is conducted in 32 states for corn and 29 states for soybeans with a total of about 25,000 producers surveyed for all crops in August. The Objective Yield Survey (OYS) is conducted in 10 states for corn and 11 states for soybeans. The surveys are generally conducted in a two-week period ending about a week before the release of the forecasts.

For the AYS, a sample of farm operations to be surveyed is drawn from those who responded to the acreage survey in June. Although the sample of operations to be surveyed changes from year to year, for any particular year the same operations are interviewed each month from August through November. Survey respondents are asked to identify the number of acres of corn and soybeans to be harvested and to provide a forecast of the final yield of each crop. Based on these responses, average yields are forecast for each survey state and for the United States.

The goal of the OYS program is to generate yield forecasts based on actual plant counts and measurements .The sample of fields (1,920 for corn and 1,835 for soybeans) for the OYS survey is selected from farms that reported corn (soybeans) planted or to be planted in the June acreage survey. A random sample of fields is drawn with the probability of selection of any particular field being proportional to the size of the tract, and two plots are randomly selected in each field.

Data collected from each corn plot during the forecast cycle are used to measure the size of the unit and to measure or forecast the number of ears and grain weight. These data include (as available based on maturity) row width, number of stalks per row, number of stalks with ears or ear shoots per row, number of ears with kernels, kernel row length, ear diameter, ear weight in dent stage, weight of shelled grain, moisture content, total ear weight of harvested unit, lab weight of sample ears, weight of grain from sample ears, and moisture content of shelled grain from sample of mature ears. Corn yield is forecast based on the forecast (or measurement if maturity allows) of the number of ears, the weight per ear, and harvest loss.  

Data collected from soybean plots (as available based on maturity) include row width; number of plants in each row; number of main stem modes, lateral branches, dried flowers and pods, and pods with beans; weight and moisture content of beans harvested by enumerator; and weight and moisture content of harvest loss. The data collected are used to forecast yield based on a forecast (or measurement if maturity allows) of the number of plants per acre, the number of pods with beans per plant, the average bean weight, and harvest loss.

For both corn and soybeans, the state average yield forecast based on the OYS is the simple average of the yields for all the sample fields. In addition, a state yield forecast is also made by first averaging the forecast or actual yield factors (such as stalk counts, ear counts, and ear weight) and then forecasting the state average yield directly from these averages. This forecast is based on a regression analysis of the historical relationship (15 years) between the yield factors and the state average yield. State average yields are combined to forecast the U.S. average yield.  

The NASS corn and soybean survey and forecasting procedures produce a number of indicators of the average yield. In August, these indicators include: average field level yields from the OYS, average state-level counts from the OYS, and the average yield reported by farmers in the AYS. Each of the indicators provides input into the determination of the official yield forecasts by the USDA’s Agricultural Statistics Board.

“The accuracy of the USDA yield forecasts relative to the final yield estimates varies from year to year, but as would be expected, improves each month through the forecast cycle as the crops become more mature,” Good said. “A year ago, we provided a comprehensive analysis of the NASS yield forecasting accuracy for corn and soybeans.”


Fall and winter tree care

Published August 10, 2015

URBANA, Ill. - When the cool weather of fall arrives, the desire to work outdoors is enticing. The heat and humidity of summer are past, and the changing colors of leaves are pleasing and relaxing. The impulse to clean up plants and make sure that the gardens are put to bed before snowfall can be strong, and often people pull out pruning tools and begin to prune trees too late in the season, said a University of Illinois Extension horticulture educator.

Kari Houle explained that pruning trees in late summer and fall encourages new growth that won’t have time to harden off before winter arrives. “Hardening off” means that the plants have time to prepare for the coming freeze. “The only reason that pruning should occur in the fall is to remove dead or damaged branches to minimize stress on the tree,” she said.

“The best time to prune trees is during the dormant season. If you don’t end up having time to prune trees during the dormant season, avoid pruning right after trees leaf out in the spring,” Houle said.

Another good habit to get into regarding fall and winter tree care is to provide adequate soil moisture. “Reducing irrigation in fall can cause stress on trees, and it’s best to keep soil moist as long as the ground isn’t frozen as roots will still pull moisture up,” Houle said. “By providing supplemental irrigation, you reduce stress on the tree through the winter.

“This is especially important for evergreens as they can suffer from winter desiccation, which is loss of moisture from intense winter winds and sun,” she added.

Making sure to properly mulch trees helps to also reduce ground temperature fluctuations as well as to assist in maintaining soil moisture. Houle recommends organic-based mulches. “Apply mulch 2 to 4 inches deep and maintain a 2-inch gap between the tree trunk and mulch,” she said.

For many years, it was recommended to wrap newly planted trees or thin bark trees to protect them from sunscald over the winter. Houle said that research has shown that tree wraps do not help to minimize temperature fluctuations but can in fact increase the temperature extremes on the trunk of the tree.

“Tree wraps can also be a perfect place for insects and disease to take up residence,” she said. “If you do need to wrap the trunk of the tree to protect it from animals such as deer, then abstain from use. If using tree wraps for protection, then make sure to use light-colored wraps and wait until as late as possible, removing the wrap early in the spring.”

News Source:

Kari Houle, 217-332-3382

News Writer:

University of Illinois Extension

State Master Gardener conference set for Sept. 17-19

Published August 10, 2015

URBANA, Ill. – Registration is now open for the 2015 University of Illinois Extension State Master Gardener Conference to be held Sept. 17-19 at the Regency Conference Center in O’Fallon, Ill. 

The public is invited to join Master Gardeners and Master Naturalists from Madison, St. Clair, and Monroe counties for three days of tours and classes celebrating the 40th anniversary of Illinois Master Gardeners.  

“This is a great educational opportunity for anyone interested in the environment and/or gardening,” said Monica David, U of I Extension Master Gardener coordinator.  “We have outstanding nationally recognized speakers and some great tours planned that would be interesting for everyone.”

The deadline to register for the conference is Sept. 1. No late or onsite registrations will be accepted. 

The keynote speaker will be Rosalind Creasy. Creasy is an internationally known garden and food writer, speaker, and landscape designer. Her first book, The Complete Book of Edible Landscaping, won the Garden Writers Quill and Trowel award and coined the term “edible landscaping.” Creasy will talk on edible landscaping and heirlooms.

The Saturday general session will feature a presentation by Mike Jeffords on exploring nature in Illinois. Breakout sessions on Friday and Saturday will feature four tracts including plant materials, natives, elements of design, and edibles. 

The plant materials tract will feature talks on hostas by Mark Zilis; grafting fruit and nut trees by Kansas State University Extension specialist William Reid; roses by David Gunn; and amaryllis by Jason Delaney, both from the Missouri Botanical Garden. 

The natives tract will include talks on garden invasives by Chris Evans from the Illinois Department of Natural Resources; dragonflies; native landscaping; and more. The third tract—elements of design—will emphasize downsizing your garden; planting for birds; rain gardens; woodland gardens; and aesthetics and hardscapes in the garden. A fourth tract—edibles—will feature talks on horseradish, culinary herbs, fruit trees, heirloom seeds, and more.

Tours will include:

  • Full-day tour 1 - six Master Gardener and Master Naturalist projects
  • Half-day tour 1 - Gordon Moore Park (hosta garden and rose garden) and the Riverlands Audubon Center
  • Half-day tour 2 – Eckert’s Farm, St. Louis Composting, and Heimos Nursery

Hands-on garden craft classes will also be offered at the same time as the tours.

Register at Visit for more information.

Australia’s seed destructor could be Midwest’s new tool in the battle against weed resistance

Published August 6, 2015

URBANA, Ill. – It’s a piece of equipment that probably isn’t on many Midwest farmers’ radars at this time, but could eventually be a new tool against the growing  herbicide-resistant weed problem, said a University of Illinois crop scientist.

With the effectiveness of many herbicide options being compromised due to the evolution of weed resistance and no new products on the immediate horizon, Aaron Hager said now is the time to look at non-chemical tactics that can be integrated into a management system.

Hager and Adam Davis, a crop scientist at the U of I and the USDA, were recently awarded funding from the USDA to bring the Harrington Seed Destructor, which was developed and is used in Australia, to the U of I South Farms. The seed destructor is a portable mill that attaches to the combine. As the combine collects the chaff at harvest, the pull-behind mill pulverizes the weed seeds, preventing them from growing into new plants the following spring.

The idea is to control the weeds at harvest.

The seed destructor will be on display at this year’s Department of Crop Sciences’ annual Agronomy Day on Thursday, Aug. 20, on the U of I South Farms. Hager and Davis will be on hand to answer questions about the machine.

Hager said while Australia’s problem weed species are different than those in central Illinois, producers in that country have seen similar resistance evolution problems, particularly with ryegrass. However, Australian farmers using the seed destructor are seeing some success. The company that manufactures the machine reports that the seed destructor destroys at least 95 percent of annual weed seeds.

“Their most problematic species in Australia is ryegrass. Here we talk about multiple resistance of waterhemp, but truth be told, theirs is worse,” Hager said. “Based on the success that they’ve seen in Australia, we would be confident in saying that, on some of our larger-seeded species, it would be effective. We need to get a better feel of how it will work on these smaller-seeded species.”

Davis has designed a research project at Urbana to evaluate the impact the machine could have on herbicide evolution in waterhemp. Davis said they hope to find out if they can control herbicide-resistant waterhemp populations in a given year, and if they can reduce the increase of herbicide resistance genotypes in a field over time.

“It’s not Palmer amaranth, but waterhemp is certainly a problematic species that we have. It is similar in seed size to Palmer amaranth,” Hager explained.

Hager said he expects the project could take 2 to 3 years before they have the needed data and an understanding of how effective the seed destructor will be in reducing seed return to the soil. The experiment will also look at how to integrate the machine into a system with other management practices.

“We’ll continue to need herbicides,” Hager said. “Hopefully this will be something that adds another tool by using a technique that we haven’t used much before.”

For now, Hager said they are on a wait-and-see basis to determine how the machine will work against Midwest weed species. Hager, Davis, and their crew are still working to retrofit the seed destructor to a combine to begin the planned research trials.

“For us, it’s new,” he said. “We’re running out of effective herbicide options, and what we see now with resistance may not be the same in 5 or 6 years. It could be much worse. For years, we’ve said that we need to stop controlling weeds and learn how to manage them. This falls into the management idea. Based on what the data will tell us, it could be something very effective.

“Hopefully we’ll get that established, and it will be something that the industry will take from there,” he added.

For more information about this year’s Agronomy Day where visitors can learn more about the seed destructor, go to

Hummingbird moths

Published August 6, 2015
Photo by Deanna Frautschi.

URBANA, Ill. - Small mysterious pollinators have been visiting late-summer and fall-blooming plants in our gardens in order to sip nectar, said University of Illinois Extension horticulture educator Kelly Allsup. With wings as fast as a hummingbird and long tongues like a butterfly, these small moths hover over flowers to gather nectar.

In the fall months in Illinois, hummingbird moths, a member of the sphinx moth species, are numerous and most come out close to dusk, Allsup noted.

“There are 60 species of sphinx moths, and the most common ones are the white-lined sphinx moth, clear-winged sphinx moth, five-spotted hawk moth, and Carolina sphinx. These moths are almost as large as hummingbirds and also fly during the day,” she said.

The color of the white-lined sphinx moth is mottled gray, brown, and white with pink bands. The clear-winged sphinx moth or hummingbird moth, is a large moth much smaller, about 1 inch long, with clear wings that mimic a bee.

“Although cherished as adults, the five-spotted hawk moth and Carolina sphinx incite murderous rage in their larval stage to any gardener trying to grown tomatoes,” Allsup said. The five-spotted moth and Carolina sphinx’s larvae, also known as tomato hornworm and tobacco hornworm, are large green caterpillars that grow about 4 inches long and about as big around as a fat man’s thumb.”

These caterpillars can demolish a tomato plant in just a few days. “The first sign of them is the bare branches and stubs at the tips of the plants that have been stripped by these ferocious eaters,” Allsup explained. “Although they are large, they are just the right color to blend in with the foliage. A small horn at the end of their abdomen distinguishes them from other caterpillars and provides a menacing façade for any predators.”

Allsup added that four weeks after hatching from the egg, the hornworm begins its pupal stage by dropping to the ground to burrow. “This time of year, they will remain in the pupal stage throughout the winter. This is why it is necessary to clean up tomato debris and disc-till the soil in order to destroy them in the pupal stage,” she said.

“There is no need to address hornworms with pesticides. Instead pay the neighbor kid 50 cents a worm to pick them off the plants and feed them to chickens and other birds,” Allsup said.  “Or leave them on the plant and let nature take care of the problem for you.”

Parasitic wasps often lay their eggs on the bodies of the hornworms where their larvae hatch and feed on the hornworm. After the larvae have mortally eaten the caterpillar’s insides, they emerge to decorate the hornworm with their white cocoons.  “If you find a tomato hornworm with white bumps all over it, leave it alone. The parasitized caterpillar will stop feeding and soon die,” Allsup said.

Newly hatched wasps will seek other hornworms in the vicinity to lay their eggs.

Even in their larval stage, they are considered a garden pest, but hummingbird moths are a treat to see in the garden, Allsup noted. “To attract them to your garden, plant lots of fall-blooming perennials, create a water source, and skip the pesticides. Then sit back and watch these lovely pollinators make your fall garden home,” she said.

Learn more about bugs in the garden at University of Illinois Extension Bug Review.

News Source:

Kelly Allsup, 309-663-8306

News Writer:

University of Illinois Extension