Crop Sciences

Soil management may help stabilize maize yield in the face of climate change

Published September 20, 2016
cover crops
Winter cover crops (oat on left, oilseed radish on right) on Lily Lake Farm, in Lily Lake IL
  • Given that predicted climate changes are expected to affect maize yields, many researchers and companies are focusing on improving maize varieties to withstand more stressful environments.
  • A new study shows that climate effects on maize yield can be mitigated by soil water holding capacity and soil organic matter.
  • Cover cropping and other methods of improving soil organic matter may result in a more stable maize crop in future climates.

URBANA, Ill. – How will we feed our growing population in the face of an increasingly extreme climate? Many experts suggest the answer lies in breeding novel crop varieties that can withstand the increases in drought, heat, and extreme rainfall events predicted in the not-too-distant future. But breeding is only part of the equation, according to new research from the University of Illinois and several collaborating institutions across the Midwest.

“It might not be necessary to put all the stress of climate adaptation and mitigation on new varieties. Instead, if we can manage agroecosystems more appropriately, we can buffer some of the effects of climate instability,” says U of I and USDA Agricultural Research Service ecologist Adam Davis.

To find the management tool that could ameliorate the effects of climate instability, Davis and his collaborators had to go beyond the traditional field-scale experiment. “We had to think at a much broader spatial scale,” he notes.

The team obtained weather, soil, and yield data from every county in four states—Illinois, Michigan, Minnesota, and Pennsylvania—across a span of 15 years. They then used a new analytical approach, which borrowed from economic concepts, to determine the effects of weather and soil properties on maize yield.

“The things that were most effective at buffering against the different forms of yield instability were soil organic matter and water holding capacity,” Davis says. This pattern was true across all years and all study locations.

Greater water holding capacity, which increases with more soil organic matter, gives crops an advantage in hot, dry climates. They can continue to take up water from the soil, which means continued growth and strong yields even in adverse climates.

The good news for farmers is that they may be able to manage for improvements in water holding capacity, giving them a potential tool to support novel maize varieties. “In locations with coarse soils, you can see really quick and gratifying responses to soil organic matter amendments,” Davis says.

Davis suggests a number of practices to increase soil organic matter, including using cover crops, avoiding excessive soil disturbance, increasing crop rotation length, and adding composted manures. He points out that cover crops might be the best choice for some farmers.

“Cover crops are a great way for improving soil organic matter; even small amounts of cover crop biomass seem to have soil organic matter benefits,” Davis explains. “They also can have weed suppressive benefits, so cover crops may represent a win-win scenario.”

No matter which amendment practice farmers choose, he says, “soil organic matter amendments are an important place to start building a cropping system resilient to climate change.”

The study, “Soil water holding capacity mitigates downside risk and volatility in US rainfed maize: Time to invest in soil organic matter?” is published in the journal PLOS One. Funding was provided by the Agriculture and Food Research Initiative of the USDA’s National Institute for Food and Agriculture. The full article is accessible at the journal’s website.

News Source:

Adam Davis, 217-333-9654

Sustainable Student Farm open house and field tours

Published September 13, 2016

URBANA, Ill. – The University of Illinois Sustainable Student Farm (SSF) and Woody Perennial Polyculture (WPP) project will host an open house on Friday, Sept.16, from 3 to 6 p.m. at their site just south of the main Urbana campus.

The SSF serves as a production farm to provide U of I residence halls with locally grown, low-input sustainable food. In addition, the farm acts as a living laboratory to connect students, community members, and the state at large with regional, small-scale food systems.

The WPP project, located near the SSF, is the first large-scale, university-funded research site studying a savanna-based agroecosystem. Founded in 2012, the WPP site hopes to lay the foundation for a scientific understanding of the potential agricultural and ecological benefits of woody polyculture systems.

During the open house, U of I Dining Services will be serving delicious and free food and drink prepared from SSF produce. The SSF, the WPP, and the U of I Community Garden Plots will be giving tours throughout the afternoon.

Also included in the open house:

  • The Fresh Press will be on hand for information about its new fiber garden and possible demonstrations.
  • The U of I Architecture Department will be talking about farm stand display pieces and a washing/packing/shed complex members of the department built for the SSF.
  • The Student Sustainability Committee, along with other affiliated groups will be on hand with information about projects happening on campus.
  • College of ACES researchers will give presentations on current projects at the SSF and WPP.

Currently the SSF operates between 45 to 48 weeks per year, occupying 6 acres for outdoor field production and nearly 10,000 square feet of year-round high tunnel production. In addition to selling the majority of its produce to the residence halls, it also markets its produce directly to consumers on the U of I quad each Thursday from May to November.

The Sustainable Student Farm was created through a grant from the Student Sustainability Committee and is made possible by the continued support of the University of Illinois Dining Services, the Department of Crop Sciences, and the Student Sustainability Committee.

The farms are located at Lincoln Avenue and Windsor Road, just south of the main U of I campus in Urbana.

For more information about the Sustainable Student Farm, visit Find out more about the WPP research project at

News Source:

Matt Turino

New corn disease identified in DeKalb County

Published August 26, 2016
bacterial leaf streak
Foliar symptoms of bacterial leaf streak showing long lesions with wavy margins and halo visible with backlighting. Photo courtesy of Nicole Furlan, PPQ technician, USDA-APHIS-PPQ

URBANA, Ill. A positive sample of bacterial leaf streak was found in a corn field in DeKalb County, Illinois, its identification verified yesterday by the USDA. With this presence in Illinois, bacterial leaf streak has been identified in 9 states:  Colorado, Iowa, Illinois, Kansas, Minnesota, Nebraska, Oklahoma, South Dakota, and Texas.  DeKalb is the only county in Illinois that has been verified to have the disease. 

“Because this is a bacterial disease, fungicides cannot be expected to control or suppress it,” says Suzanne Bissonnette, University of Illinois plant clinic director and assistant dean for agriculture and natural resources with U of I Extension.

U of I Extension commercial agriculture educator Dennis Bowman adds, “Crop rotation and tillage are the best short-term management strategies if the disease is present in a field.” 

Bissonnette says if growers suspect bacterial leaf streak in their field, they can submit a sample to the U of I Plant Clinic.

“We’d like to get a comprehensive idea of distribution in the state,” Bissonnette says. “Although there are currently no known methods to prevent it, differences in varietal susceptibility may point the way to sources of resistance.”

Bacterial leaf streak is caused by the pathogen Xanthomonas vasicola pv. vasculorum. The disease causes the formation of linear lesions between the veins on a corn leaf. The lesions look similar to gray leaf spot symptoms – although GLS lesions tend to be shorter, more rectangular, and to stay within their veinal borders.

“Bacterial leaf streak lesions are more irregular, often thinner and longer,  will ‘bleed’ over the veinal border, and may have a halo when held up to the light,” Bowman explains.

In many Great Plains states where the disease has been found, symptoms first appear on the lower leaves and infection progresses up the plant. Typically these fields have been under pivot irrigation.  Later infections may occur and show up primarily in the upper canopy. This was the case for the positive DeKalb County sample found in the survey of approximately 340 randomly selected fields in transects across 68 of Illinois’s 102 counties. The survey was conducted by APHIS-PPQ (Animal Plant Health Inspection Service), IDA (Illinois Department of Agriculture), CAPS (Illinois Natural History Survey’s Cooperative Agricultural Pest Survey) and U of I Extension.

Bissonnette says there is currently very little known about this disease. Further research is needed to develop a complete understanding of this disease, its impact, and strategies for long term management.  However, APHIS notes it is not believed to present a health risk to people or animals.

For information about the biology, symptoms, or management of Xvv, visit or





Workshop and field day will raise awareness of local grains and local markets

Published August 25, 2016

URBANA, Ill. - The potential for regionally adapted grains to serve growing local and regional markets is the topic of an upcoming workshop at the University of Illinois. Illinois Extension, along with the departments of Natural Resources and Environmental Sciences, Crop Sciences, and Food Science and Human Nutrition will host “Illinois Local Grains and Local Markets” on Sept. 9 in the Monsanto Room of the ACES Library, Information and Alumni Center.

The workshop runs from 8:00 a.m. to 12:00 p.m., with presentations starting at 8:30 a.m. Speakers include Bill Davison from Illinois Extension, Allison Krill-Brown from the Department of Crop Sciences, Harold Wilken from Janie’s Farm, Frank Kutka from the Northern Plains Sustainable Agriculture Society, and Julie Dawson from the University of Wisconsin-Madison.

Presentations by Kutka and Dawson will showcase participatory breeding efforts taking place in other regions. This event will be of interest to researchers, breeders in the region, bakers, and brewers who want to source locally produced grains, and farmers interested in conducting trials.

Kutka is a plant breeder and the co-coordinator of the Northern Plains Sustainable Agriculture Society Farm Breeding Club. In his current work, he is developing a yellow dent corn that has the ability to prevent cross-pollination with GMO corn. This work builds on approximately 20 years of experience with corn breeding for the organic farming sector.

Dawson is an assistant professor of horticulture at the University of Wisconsin. Dawson’s background is in organic wheat breeding and participatory research. She has conducted research on value-added grains for regional food systems at Cornell University, and she helped create a participatory wheat breeding program with an association of organic farmer-bakers in France.

A field day will be held on Sept. 10 at Janie’s Farm in Danforth, Illinois. Presentations will be given by Harold and Ross Wilken on their experience with on-farm selection and milling at Janie’s Farm. Fred Kolb and Allison Krill-Brown will speak on U of I efforts to develop wheat varieties suitable for Illinois. A discussion on participatory crop breeding will be led by Frank Kutka.

Lunch will be prepared by chefs from Hendrick House Catering with foods made from locally sourced grains. The cost is $12 for pre-registered participants. A limited number of lunches will be available for $15 for on-site participants.

The Agroecology and Sustainable Agriculture Program at the University of Illinois, and the Illinois Organic Growers Association are also co-sponsors for these events. For more information about the workshop, contact Carmen Ugarte at or Bill Davison at You may consider participating in one or both events; registration is required for the field day.


News Source:

Carmen Ugarte

News Writer:

Leanne Lucas, 217-244-9085

Recycled leaves make inexpensive mulch

Published August 17, 2016

URBANA, Ill. – Rather than bagging or removing fallen leaves, University of Illinois Extension horticulture educator Rhonda Ferree suggests using them in your yard.

“The tree leaves that accumulate in and around your landscape represent a valuable natural resource that can be used to provide a good source of organic matter and nutrients for use in your landscape,” Ferree says. “Leaves contain 50 to 80 percent of the nutrients a plant extracts from the soil and air during the season. Therefore, leaves should be managed and used rather than bagged or burned.”

Ferree says adding a 2-inch layer of leaf mulch adds approximately 150 pounds of nitrogen, 20 pounds of phosphorus, and 65 pounds of potassium per acre. Due to natural soil buffering and breakdown in most soil types, leaf mulch also has no significant effect on soil pH. Even oak leaves, which are acid (4.5 to 4.7 pH) when fresh, break down to be neutral to slightly alkaline.

According to Ferree, there are four basic ways leaves can be managed and used in the landscape.

  1. A light covering of leaves can be mowed. Simply leave the shredded leaves in place on the lawn. This technique is most effective when a mulching mower is used. In fact, during times of light leaf drop or if there are only a few small trees in your landscape, this technique is probably the most efficient and easiest way to manage leaf accumulation.
  2. Mulching is a simple and effective way to recycle leaves and improve your landscape. Leaves can be used as a mulch in vegetable gardens, flower beds and around shrubs and trees. Leaves that have been mowed or run through some other type of shredder will decompose faster and are much more likely to remain in place than unshredded leaves. Unshredded leaves also tend to mat together, which can impede water and air infiltration. Ferree uses a chipper/shredder/vacuum to pick up her leaves, which she uses instead of purchased mulch in her landscape beds.
  3. Leaves can be collected and worked directly into garden and flowerbed soils. A 6- to- 8-inch layer of leaves tilled into a heavy, clay soil will improve aeration and drainage. The same amount tilled into a light, sandy soil, will improve water and nutrient-holding capacity. A recommended strategy for using leaves to improve soil in vegetable gardens and annual planting beds is to collect and work them into the soil during the fall. This allows sufficient time for the leaves to decompose prior to spring planting. Adding a little general purpose fertilizer to the soil after working in the leaves will hasten their decomposition.
  4. Try composting your leaves. Compost is a dark, crumbly, earth-smelling form of organic matter that has gone through a natural decomposition process. If you have a garden, lawn, trees, shrubs, or even planter boxes or houseplants, you have a use for compost. For additional information composting, visit the University of Illinois Extension website.

Ferree also recommends jumping in the pile of leaves “at least once.”

News Source:

Rhonda Ferree, 309-543-3308

News Writer:

University of Illinois Extension

Benefits of fall core aeration for the lawn

Published August 16, 2016

URBANA, Ill. - Although it’s true that core aeration relieves soil compaction in the lawn, a University of Illinois Extension horticulture educator says coring has several more benefits for the grass plant soil profile, microbial activity in the ground, and thatch management.

“When the soil beneath the lawn is compacted, grass roots grow poorly,” says Richard Hentschel. “They stay nearer to the surface and are more readily affected by droughts. Coring allows the soil to relax and expand into the vacated core. This allows deeper roots. To encourage deeper roots, the core allows more soil oxygen into profile along with water. Both of these promote deeper rooting of your lawn grasses, which allow better disease resistance, for example.”

Another benefit is the lawn’s ability to remain green and actively growing during a brief drought. “If any topdressing is done with quality black dirt or using well-composted organic matter, this material will find its way into the core as well, improving the soil profile,” he says. “Any kind of organic matter will also support the microbial life in the ground, improving the symbiotic relationship between the grass root system and the microbes in the soil. Research shows that if the soil is in good health with teaming microbial activity, it in turn supports good grass growth by providing critical elements to the grass plant.”

According to Hentschel, core aeration can also maintain thatch levels under one-half inch.

“Homeowners hear the word ‘thatch’ and often think the worst,” Hentschel says. “In fact, having some thatch has benefits to the lawn. Thatch acts as insulation protecting the crown of the grass plant from quick changes in the weather, such as a sudden drop in temperature. Thatch also provides a cushion from foot traffic, protecting the grass plant crown from being crushed or damaged. Coring breaks through the thatch layer opening up those opportunities for air and water movement. When the core is ejected by the machine, there is also a plug of soil that is left on the surface. That soil containing those microbes can now begin to break down the thatch layer.”

Hentschel cautions that when the thatch layer is well over one-half inch in depth, using a dethatching machine will often result in the loss of the entire lawn. Coring is a way to recover the lawn without such a drastic measure. “This will not happen in one season and other management activities, such as high rates of fertilizers, should be modified.”

Core aeration alone will benefit the health of the lawn, Hentschel concludes. “Combining topdressing with any re-seeding or over seeding along with regular watering for at least three weeks will really turn the lawn around. Bluegrass lawns have two peak growing cycles in our climate. The greening and rapid growing in the spring is the first one. The second flush or growth is more about the root system expanding and storing food reserves in the cooler temperatures of fall. There is still growth above ground and mowing should continue well into late fall with a sharp mower blade.”

News Writer:

University of Illinois Extension

Digging and storing cannas

Published August 15, 2016

URBANA, Ill. - Now is the time to devise a plan for digging and storing cannas, says University of Illinois Extension horticulture educator Nancy Kreith.

“To successfully overwinter cannas indoors, the bulbs should be dug up after the first light frost has killed the top of the plant,” she explains. “Although technically they are not bulbs, but rhizomes, cannas need to be treated as tender bulbs and must be dug up to survive the winter. Some gardeners have reported success with cannas overwintering in the ground in micro-climates or against south facing walls due to the radiant heat from the building.”

Kreith says the most important thing to do when digging up rhizomes, tubers, or any tender bulb is to be careful not to wound these fleshy underground structures. “Wounds and bruises serve as entry points for diseases, which can cause rotting and loss in storage. This is true for any tropical plant with fleshy underground structures, such as elephant ears and caladiums.”

Kreith suggests following these simple steps to properly overwinter cannas indoors.

Start by cutting back the foliage to 4 to 6 inches above ground in order to see the base of the plant. Dig several inches away from the base of the plant, avoiding the underground structures. Carefully loosen the soil using a spade shovel. Remove the large clump of multiple structures from below the soil level. Separate the clumps and remove most of the soil by hand, and wrap each individual structure in newspaper. Finally, layer them in a crate or large tote with the lid off.  This is how they will remain stored until the following spring.

Be sure to monitor the bulbs every month for rotting pieces and pests. If found, remove infected pieces right away, Kreith recommends.

“Often times these structures multiply underground during the growing season,” Kreith explains. “Even though you may have only planted three to five bulbs the past summer, you could have well over that number by the fall. As the structures multiply, plan to incorporate cannas into more parts of your landscape or share them with friends and neighbors.

“As you read through the literature available, other sources will have varied recommendations for storing methods,” Kreith adds. “Some horticulturalists have been successful in overwintering cannas in an unheated garage or shed. Some tend to allow bulbs to cure and dry out for one to three days before storing. Others recommend removing all of the soil once dried and storing in peat moss or sawdust. I prefer to recycle newspaper. It acts as an aid in the curing process. The newspaper serves as a barrier that protects the structures from excess moisture. The main take-home point is to keep bulbs cool, dry, and out of freezing temperatures.”

To get a head start on the growing season, help bulbs emerge while indoors, Kreith says. Once the following spring comes around (about 4 to 6 weeks before the last average frost date) cannas can be planted in containers of professional potting mix. Unwrap the structures and plant them with the pointed side facing up. When using a large container (12 inches in diameter or more) multiple bulbs can be planted in the same pot.

Finally, place them in a sunny window or under artificial lighting and treat them as houseplants. The cannas can be planted outside after the danger of frost has passed.

Kreith has been successful at storing container-grown cannas by bringing in the whole container and storing them in a dark hallway closet. To do this, simply cut back the foliage after a light frost and place the container indoors. Let them remain dormant until the next spring and then put them in a sunny location. “Amazingly, as they receive more sunlight, signs of leaf growth will begin,” she says. “Over the past two years, my cannas have multiplied in the container and leave little to no room for planting other flowers. This container is now devoted solely to cannas, but over time, these structures will need to be divided and thinned out.”

Kreith says cannas are an easy-care tropical plant that provides beautiful foliage and long-lasting blooms. Repeated blooms are encouraged by deadheading spent flowers. “This versatile plant comes in a variety of leaf colors and can range from 1 foot to more than 6 feet tall. For the greatest foliage color and fullest blooms, place cannas in full sun with plenty of water and healthy soil.”

News Source:

Nancy Kreith, 708-679-6889,

News Writer:

University of Illinois Extension

Tip-back and the 2016 corn crop

Published August 5, 2016
Signs of tip-back on ears of corn.

URBANA, Ill. - Although crop condition reports and yield prospects for the 2016 Illinois corn crop continue to be good, there has been some recent discussion about unfilled ear tips and whether or not this might mean lower yields than the appearance of the crop leads us to believe, says a University of Illinois crop scientist.

Corn ears with kernels missing at the outer end of the ear are often said to have “tip-back.”

“The term is a little obscure, but the idea is that something happened to cause the ear to adjust its kernel number downward so it won’t have as many kernels to fill. That exposes the end of the ear,” says Emerson Nafziger.

The missing kernels can be aborted kernels—ones that were fertilized but stopped developing—or can be kernel initials that weren’t fertilized due to problems with the pollination process. Low sugar levels in the plant before, during, and after pollination are often associated with such loss of kernels.

“Because kernel number is closely related to yield, missing kernels on an ear suggests that yield has been lost,” Nafziger explains. “Drought stress, loss of leaf area to hail or disease, or lack of nitrogen all result in stress that lowers photosynthesis which decreases the sugar supply. So we associate low kernel numbers with stress.

“While low kernels numbers per acre and low yields do go together, it’s important in a year like this to consider the overall condition of the crop and to focus on how many kernels are present before worrying about how many kernels seem to be missing. We often see some amount of tip-back even in good years, and this may have no effect on yield if kernel numbers are still high,” he adds.

As an example, under outstanding pollination conditions in 2014, Nafziger says almost no tip-back was seen; ears were filled out to the very end of the cob. “There was much more tip-back in 2015, but kernel counts per acre and yields were as high in many areas in 2015 as in 2014. While we don’t think that having some tip-back is necessary to show that the ear had ‘extra’ room in case it was needed it, it’s much more common to see some tip-back than to see none. We certainly don’t consider tip-back to be a problem if kernels numbers are high,” he says.

Nafziger adds that what matters for yield is the number of kernels per acre that fill, along with the ability of the crop to fill them completely. “So 34,000 ears each with 16 rows of kernels and 35 kernels per row should produce yields in the vicinity of 220 bushels, even if most cobs have ‘room’ on the end for another 50 or 100 kernels. At high yield levels when all of the nutrients the plant produces go to fill kernels, having more kernels may mean that kernels stay smaller, and yield may not change much,” he says.

Nafziger says he is seeing some signs that kernel numbers in some fields may not be as high as expected. In one field on South Farm near Urbana he found tall plants and green leaves, but ears with fewer than 400 kernels per ear, or yield potential of perhaps 160 bushels per acre. In another field with similar soil planted at the same time with slightly lower population, plants were not quite as tall, stalks were larger in diameter, and ears were more uniform in size. Ears show a small amount of tip-back, but with an average of about 600 kernels per ear, this field should yield 225 bushels per acre or more, he says.

“There are no obvious reasons why similar fields planted at about the same time should have such different kernel numbers and yield potential,” Nafziger explains. “The field with lower yield potential has a number of different hybrids and most seem to show some degree of the same problem, so hybrid doesn’t appear to be the main difference. Both fields emerged well and have had good uniformity and dark green leaves from the beginning.

“Variability in ear size and placement suggests that plant-to-plant competition began early and increased during vegetative growth, eventually showing up as non-uniform ear development and lower kernel numbers. Temperatures in May and June were warm and there was a lot of sunshine. Rainfall both months was near normal, but the latter half of June was dry, which could have meant more underground competition,” he says.

The crop appears to have used a lot of resources to grow the plant, including roots as they grew deeper during dry weather in the weeks before pollination. Uniformly warm air and soil temperatures and rapid growth during that period might have meant some diversion of sugars away from ear growth and kernel set, Nafziger says. “It’s also possible that uptake of water was slightly lower in some soils due to texture or root growth and uptake, and that the crop in such soils experienced a little more stress.

“Although we can’t do anything to change kernel numbers now, it is worthwhile to visit each field to note kernel number and other plant characteristics that can help explain what happened in different fields. While the Illinois corn crop condition overall remains good, some fields may have disappointing kernel numbers even on plants that continue to look very good. Note which hybrids show this, but given that this may be a one-time phenomenon, be cautious about discarding hybrids, especially those that have been top-yielding in the past,” he adds.

Palmer amaranth and non-crop environments

Published August 5, 2016

URBANA, Ill. - Palmer amaranth (Amaranthus palmeri) has garnered much attention recently in both academic discussions and popular press releases, and with good reason, says University of Illinois weed scientist, Aaron Hager.

Among the weedy species of Amaranthus, Palmer amaranth has the fastest growth rate and is the most competitive with the crops common to Midwest agronomic cropping systems, Hager explains. Soybean yield losses approaching 80 percent and corn yield losses exceeding 90 percent have been reported in the peer-reviewed scientific literature.

“While most concern focuses on Palmer amaranth in agronomic cropping systems, keep in mind that Palmer amaranth also can become established in non-crop areas,” Hager cautions.  “Palmer amaranth populations in non-crop environments obviously do not compete with agronomic crops, but these established plants can produce seeds that ultimately find their way into crop production fields.”

Hager said that crop scientists recently verified the identification of a Palmer amaranth population growing in an area enrolled in the Pollinator Habitat Initiative of the Conservation Reserve Program. The origin of this population remains unknown, but some speculate the forb seed mixture purchased to sow the pollinator area might have been contaminated with Palmer amaranth seed. 

“Regardless of how and where a Palmer amaranth population becomes established, it remains critically important to take all appropriate steps to prevent established Palmer amaranth plants from producing seed,” Hager says. “We strongly encourage all who have established pollinator habitats with a purchased forb seed mixture to scout these areas as soon as possible. 

“If Palmer amaranth is identified, please take steps to remove these plants before viable seeds are produced on the female plants. Plants should be severed at or below the soil surface and carried out of the field. Severed plants can root at the stem if left on the soil surface, and plants can regenerate from stems severed above the soil surface,” he says.

Manage pests on your favorite trees

Published August 5, 2016
Eastern Tent Caterpillar

URBANA, Ill. – University of Illinois Extension horticulture educator Kelly Allsup cautions to watch out for insect pests on favorite landscape trees this late summer and fall. “If you don’t take necessary management actions at the appropriate time, the battle against them may be hard to win,” she says.  

Allsup provides the following information:

Tree pests like fall webworm and oystershell scale have some control management practices that can be implemented in late summer and fall.

Fall webworm (Hyphantria cunea) attacks a large number of tree species but especially hickory, ash, birch, walnut, crabapple, apple, elm, maple, oak, and pecan.

There are two generations of the fall webworm in the southern portion of Illinois. The first generation emerges in late June or July and again in August and September. In the northern portion of Illinois, only one generation emerges in August and September. As far as the overall health of the tree, only the first generation is of concern.

Pale green and yellow caterpillars with thick white hair tufts begin to hatch. They feed for several weeks in tents on the tips of the branches. They can skeletonize leaves and even defoliate trees. After six weeks of feeding, they fall to the ground or find a nice crevice in the bark to pupate.

The adults, which are a pristine white moth (with or without black dots) emerge again in August to lay white egg masses on the bottom sides of leaves. Sometimes she lays them on branches or the trunk and they look like dark brown oval knobs.  At this time, the most efficient method is to prune out webs of caterpillars, scout for, and remove egg masses.

The Pest Management for the Home Landscape says Bacillus thuringiensis var. kurstaki (Btk), among other pesticides, can be applied when caterpillars are young and tents are new for the best efficacy. This bacterial pesticide must be ingested to be effective, so open up the tents and spray on leaves inside.

Or, just let nature take its course. According to Michigan State University Extension, there are over 50 species of wasps that parasitize the eggs or caterpillar and over 30 percent of predators will devour these late-season threats. 

Oystershell scale (Lepidosaphes ulmi) begins to emerge and attack a large species of trees in early May, especially lilac, ash, privet, beech, and viburnum.

Yellow crawlers emerge to feed causing yellowing, stunted foliage, and branch die back. A second generation of this pest can be controlled when Queen Anne’s lace is blooming in August with an insecticidal soap or a summer spray of petroleum oil. Spraying the crawler stage of this pest is best because they have not yet developed the waxy coating that prevents penetration insecticide. Heavily infested branches can be pruned out as the eggs will overwinter under the dead female’s waxy covering. 

Scale are also great attractors of the beneficial insects. If lady beetles and other predators are present, a spray may not be needed.

Ultimately, good tree health is more crucial for tree insect management than any other practice. Good tree management includes watering in times of drought, averting soil compaction, adding mulch ring to prevent weeds, and preventing physical damage by lawnmowers and string trimmers.

News Source:

Kelly Allsup, 309-663-8306

News Writer:

University of Illinois Extension