Pest Management & Crop Development Bulletin • No. 13/ June 20, 1997

Hot Topics!

European corn borer injury and larvae found in central Illinois. larvae have been detected in the whorl leaves of corn plants in Macon County. In addition to early instars, fresh egg masses were found in the same field. Moth flights have been reported throughout the state; and, in some pheromone traps, moth captures were impressive. Growers are encouraged to accelerate their scouting activities for potential firstgeneration corn borer injury during the next several weeks. Even for those growers who planted transgenic Bt corn, we suggest a scouting trip or two across these fields. This page.

Corn rootworm eggs have hatched. Our colleagues at Purdue Uni- versity indicate that corn rootworm egg hatch has occurred. The hatch is about 1 day behind last year’s hatch. So, the trend of delayed hatches continues. Growers who planted in early to mid-April and used a soil insecticide should be alert to potential larval injury. Simi- FOR IMMEDIATE RELEASE lar to last season, we anticipate that larvae will extend their root- No. 13/ June 20, 1997 feeding activities well past mid-July. This will increase the likelihood of performance problems for some soil insecticides. Producers Executive editor: Kevin Steffey, should be alert for signs of larval injury such as lodging of corn Extension Entomologist plants. Page 111.

Web subscriptions available: http://www.ag.uiuc.edu/cespubs/pest/ For subscription information, phone Hot INSECTS 217.244.5166, or e-mail Topic [email protected]

European Corn Borer Moth In This Issue Captures Impressive in Some Sites ❏ European Corn Borer Moth Cap- The 1997 European corn borer season lurched forward during the tures Impressive in Some Sites, 109 past week! Steve Wendzel with Crop Production Services, Galesburg, ❏ Western Corn Rootworm Eggs Illinois, is monitoring the corn borer flight with 19 pheromone traps Have Hatched! 111 located in western counties. Beginning in early June, moth captures ❏ Egg Counts in East-Central Illi- were common in many of Steve’s traps; and, by June 5 through June nois Soybean Fields, 112 13, numbers were very respectable in some traps. Wayne Buhler, an ❏ The Good Guys Are Here! 112 entomologist with Purdue University, is using numerous pheromone ❏ WorldWide Web Addresses for traps in an experiment located in east-central Illinois and, during the IPM, Environmental, and second week of June, collected 195 moths in one of his traps. Wayne Pesticide-Related Issues, 113 indicated that he caught moths for the first time this season in Benton ❏ IPM Adoption: How Far Along the Continuum Are We? 113 County, Indiana, on June 4. Doug Gucker, Piatt County Extension Service, reports that he has been observing European corn borer ❏ Preharvest Weed Control Treat- ments for , 114 moths since June 5 in action sites. Dave Feltes and Jim Morrison, ❏ Replanting Herbicide-Resistant/ Extension Service educators, also have observed moths in northwest- Tolerant Soybeans, 114 ern Illinois counties since approximately June 4. On June 17, Howard ❏ Controlling Waterhemp in Large Brown, an agronomist with Pioneer Hi-Bred International, Inc. re- Corn, 115 ported that a cornfield near Niantic, Macon County, had whorl-feed- ❏ One More Caution, 115 ing injury and active early instar European corn borers in the whorls. ❏ Scab of Wheat, 115 Howard also found egg masses on several plants. Corn borer season ❏ Pesticide Safety Education Pro- is under way! gram Information, 116 109 Pest Management & Crop Development Bulletin • No. 13/ June 13, 1997

Table 1. Projected degree-day accumulations (developmental threshold of 50o F) from initial capture of moths in the spring to first occurrence of life stage or activity of first-generation European corn borers (from European Corn Borer: Ecology and Management, NCR Publication no. 327, Iowa State University, Ames).

Accumulated First General activity Projected date Projected date Projected date degree-days occurrence for Northern for Central for Southern of event Illinois Illinois Illinois (first (first moth (first moth moth capture, capture, 6/7) capture, 6/1) 5/24) 212 Egg hatch Pinhole leaf feeding June 19 June 15 June 7 (first instar) 318 Second instar Shot-hole leaf feeding June 24 June 20 June 14 435 Third instar Midrib and stalk boring June 29 June 25 June 19 567 Fourth instar Stalk boring July 5 June 30 June 24 792 Fifth instar Stalk boring July 15 July 9 July 2 1,002 Pupa Changing to adult July 23 July 17 July 10

In an earlier issue of this Bulletin (no. These projections are based upon heat units by June 15. This projection 11, June 6), we provided a table that average historical temperatures for matches very nicely with Howard offered some information on European each of these regions of the state. The Brown’s observation in Macon corn borer lifecycle events based upon information that Scott has provided County. accumulated degree-days. Bob Scott, appears to be right on track. For in- Illinois State Water Survey, has pro- stance, we should expect to find first- How do I scout for the first generation vided (Table 1) some projections for instar larvae and egg hatch in central of European corn borers? When corn these corn borer development events Illinois by June 15. This is based upon plants have an extended leaf height of based upon first captures of moths in an initial capture of moths on June 1 15 inches, scouting should begin in northern, central, and southern Illinois. and a projected accumulation of 212 earnest. If possible, examine at least

Figure 1. Management worksheet for first-generation corn borer.

110 Pest Management & Crop Development Bulletin • No. 13/ June 20, 1997

than sprays for controlling first-gen- eration corn borer larvae in the whorls, unless the sprays can be directed right over the rows.

Mike Gray and Kevin Steffey, Extension Entomologists, (217)3336652

Hot Topic

Western Corn Rootworm Eggs Have Hatched!

Figure 2. Body lengths and prothoracic shield widths for instars of the Euro- John Obermeyer, an entomologist with pean corn borer. Purdue University, confirmed recently that corn rootworm eggs have hatched in Indiana. Entomologists at Purdue 20 consecutive plants in each of five you should fill out a management have used root-staining techniques for random areas for every 40 to 50 acres worksheet and make the appropriate many years to spot first-instar corn within a field. In very large fields, it decision (Figure 2). rootworm larvae feeding internally will be more practical (although less within corn roots. Egg hatch this sea- precise) to examine 25 consecutive In using Figure 1, keep these points in son occurred approximately one day plants in each of five random areas for mind. Prothoracic width is preferable later than last year’s delayed egg hatch every 80 acres. It’s also a good idea to for determining instars because less of June 12. This shouldn’t be a sur- walk at least 100 feet into the field variation is associated with this mea- prise, based upon the slow accumula- before sampling. If more than one surement than body length. Note that tion of soil heat units that we have variety of corn is being grown or if the unshaded portion of the body- reported in several earlier issues of different planting dates occurred length scale represents the upper range this season’s Bulletin. The following within the same field, it is important to in length of each instar. Also, note the equation might be worth paying close consider each section as a separate brackets around stages 4 and 5; these attention to. field when scouting. Plants should be two instars usually are found tunneling checked for fresh whorl-feeding dam- in the stalks. Consequently, they can- Early Planting + Delayed Corn age, and the percent of infested plants not be controlled with insecticides. Rootworm Egg Hatch + Cool, Wet calculated. For every 20 to 25 plants Spring + Extended Larval If control of an infestation of Euro- examined, remove the whorl leaves Feeding Period = Potential pean corn borers is justified, you can from two plants and check for the Soil-Insecticide Problems select among several insecticides presence of live borers (Figure 1). (Table 2) that provide essentially Growers should examine root systems This allows you to estimate the aver- equivalent control. Remember, for the presence of corn rootworm age number of borers per infested granulars are usually more effective larvae later this month and look for plant. After the field has been scouted, any signs of root injury throughout early July. Several soil insecticides are Table 2. Suggested insecticides for first-generation European corn borer in field corn. labeled for use as cultivation rescue treatments and include: Counter CR, Insecticide Amount of product per acre Placement Dyfonate II 15G, Force 1.5G and 3G, *Ambush 2E 6.4 to 12. 8 oz broadcast Furadan 4F, Lorsban 15G and 4E, and Dyfonate II 15G 4 to 8 oz per 1,000 ft row over whorls Thimet 15G and 20G. Cultivation Dyfonate II 15G 5 to 6.75 lb broadcast treatments generally perform less Lorsban 4E 1-1/2 to 2 pt broadcast Lorsban 15G 5 to 6.5 lb broadcast satisfactorily than planting-time treat- Lorsban 15G 3.5 to 8 oz per 1,000 ft row over whorls ments; however, this season, with corn *Penncap-M 2 pt over whorls development lagging and a delayed *Penncap-M 3 to 4 pt broadcast *Pounce 1.5G 6.7 to 13.3 lb broadcast corn rootworm egg hatch in progress, *Pounce 3.2EC 4 to 8 oz broadcast rescue treatments may be required in *Warrior 1EC 2.56 to 3.84 oz broadcast some fields.

Mike Gray, Extension Entomologist, * Use restricted to certified applicators only. (217)333-6652 111 Pest Management & Crop Development Bulletin • No. 13/ June 13, 1997

what otherwise would have been a big mate. The greatest density (2 eggs per Egg Counts in East-Central rootworm problem all over again. Our pint) of western corn rootworm eggs Illinois Soybean Fields on-farm research indicates otherwise. in a soybean field was found near Producers who are cooperating in a Are producers going to experience Loda in Iroquois County. Bottom line: large on-farm investigation with us severe western corn rootworm larval Egg laying continues to occur in some had very little root injury (first-year injury in first-year cornfields across soybean fields in eastern Illinois, and corn) last season in their check strips east-central Illinois this season? For the potential economic threat remains. (no soil insecticide used). Either egg many growers who used a soil insecti- Until the larval feeding period is over densities of western corn rootworms cide at planting and failed to leave a (late July), we won’t know for sure were low to begin with or larval estab- check strip, this question can’t be how this season compares with the lishment was poor in saturated soils answered very well, unless the product previous 2 years. Drs. Eli Levine and last year. Where do we stand for 1997? of their choice fails to perform ad- Joseph Spencer, with the Illinois Natu- ral History Survey, provided egg- equately. Then at least we know that Preliminary egg-sample data suggest sampling data for this article. rootworm pressure is a reality. In that densities of western corn root- about 50 percent of continuous corn- worm eggs in certain soybean fields Mike Gray, Extension Entomologist, fields, rootworm densities never reach last fall were lower than in adjacent (217)333-6652 economic importance despite the fact cornfields in east-central Illinois that nearly 90 percent are treated an- (Table 3). All egg-sample data pro- nually. We don’t have estimates such vided in Table 3 were obtained by Good Guys Are Here: Natural as these for first-year corn yet. using a golfcourse cup cutter to re- Enemies of Insects! move soil to a depth of 4 inches dur- Recall that corn rootworm pressure in ing October and November of 1996. In How often have you wondered about 1996 was considerably less than in general, egg densities of 5 eggs per the correct identification of an insect 1995 across east-central Illinois. Many pint of soil are considered of potential during your troubleshooting efforts in have suggested that the increase in soil economic importance. However, there a field? Is an insect beneficial, or is it insecticide use during 1996 masked is some flex associated with this esti- a pest? Michael Jeffords, Susan Post,

Table 3. Western corn rootworm egg samples taken in corn and soybean fields during the fall of 1996.

Field location Total WCR egg count Average WCR egg count

Northern Champaign County, Field 1, corn 24 eggs in 12 pints of soil 2.0 eggs per pint Northern Champaign County, Field 1, soybean 0 eggs in 12 pints of soil 0 eggs per pint Northern Champaign County, Field 2, corn 9 eggs in 12 pints of soil 0.75 eggs per pint Northern Champaign County, Field 2, soybean 1 egg in 12 pints of soil 0.08 eggs per pint Central Champaign County, Field 3, soybean (30 years continuous soybean) 0 eggs in 12 pints of soil 0 eggs per pint Iroquois County, Loda, corn 73 eggs in 18 pints of soil 4.06 eggs per pint Iroquois County, Loda, soybean 42 eggs in 21 pints of soil 2.00 eggs per pint Champaign County, Dewey, corn 23 eggs in 12 pints of soil 1.92 eggs per pint Champaign County, Dewey, Soybean Field 1 3 eggs in 18 pints of soil 0.17 eggs per pint Champaign County, Dewey, Soybean Field 2 (field was isolated) 7 eggs in 12 pints of soil 0.58 eggs per pint

112 Pest Management & Crop Development Bulletin • No. 13/ June 20, 1997

and Robert Wiedenmann, entomolo- Provided is a list of WorldWide Web gists with the Illinois Natural History addresses for several home pages that IPM Adoption: How Far Along Survey, along with Clifford Sadof of concentrate on topics related to IPM, the Continuum Are We? Purdue University, have just created a environmental issues, and pesticides. Several years ago, the Clinton Admin- set of laminated cards with color pho- These web addresses were gleaned istration challenged the IPM commu- tographs of beneficial insects. A card from the report and represent only a nity to implement pest management is about the size of a baseball card and small fraction of those presented by practices on 75 percent of the nation’s includes pertinent information about a Charles Benbrook and his coauthors. managed acres by the year 2000. How given beneficial insect on the flip side. For our readers who access the web well are agricultural clientele doing in Instead of batting averages, facts site (http://www.ag.uiuc.edu/ meeting this objective? The answer to about the insect’s life cycle and behav- cespubs/pest/) of this Bulletin, we this question depends to a large extent ior are offered. Although the authors thought you might like to visit these on how IPM is defined. In the Con- of these cards indicate they were de- homepages. sumers Union Report, Pest Manage- signed primarily for use by home ment at the Crossroads, authored by gardeners, I believe they would be a Home page titles and WWW ad- dresses Charles Benbrook and others, IPM is valuable component of any field-crop defined along a continuum. Each of scouting kit as well. Photographs of Interactive Identification of Adult four categories describing the manage- the following beneficial insects found Insects: ment of pests has its own unique char- commonly in field crops are featured: http://www.ento.vt.edu/Facilities/ acteristics. After reading the descrip- lady beetle, tiger beetle, ground beetle, OnCampus/idlab/id/id-adg1.html tions provided below, ask yourself soldier beetle, green and brown lacew- Biological Control Virtual Information which category describes most accu- ing, assassin bug, ambush bug, damsel Center: rately pest management actions in bug, minute pirate bug, predatory stink http://ipmwww.ncsu.edu/biocontrol/ Illinois field crops? bug, robber fly, hover fly; spiders, biocontrol.html predatory mites, and many more. In No IPM all, photographs of 30 beneficial in- Environmental Working Group, Water sects are provided. For more informa- Quality: • proper calibration, operation, and tion about the cards, give me a call. If http://www.ewg.org/pub/home/ cleaning of spray equipment Water/Water.html you would like to order a set, please • scouting for pests call (217)333-6833. A set of cards The Extension Toxicology Network, costs $8. EXTOXNET: • sanitation and good agronomic http://ace.ace.orst.edu/info/extoxnet/ practice Mike Gray, Extension Entomologist, (217)333-6652 Pesticide Action Network North Low-level IPM America, PANNA: http://www.panna.org/panna/ • scouting plus application in accord WorldWide Web Addresses The Pesticide Properties Database with thresholds (PPD): for IPM, Environmental, • avoid or delay resistance and sec- http://www.arsusda.gov/ppdb2.html and Pesticide-Related Issues ondary pest problems Environmental Working Group, Pesti- In 1996, the Consumers Union, Yon- cides: • optimally time applications kers, New York, published a lengthy http://www.ewg.org/pub/home/ report entitled Pest Management at the • some preventive practices (short reports/CAMBMemo/MBIntro.html Crossroads authored by Charles M. rotations, resistant Benbrook and others. The Consumers Biocontrol and IPM, Related Patents: Union is a nonprofit membership http://www.inform.umd.edu:8080/ • varieties, cultivation) EdRes/Topic/AgrEnv/AltFarm/ organization chartered in 1936 “to Medium-level IPM (Multitactic ap- Patents provide consumers with information, proaches) education and counsel about goods, Information Systems for Biotechnol- services, health, and personal fi- ogy: • limit or remove pest habitat and nances; and to initiate and cooperate http://www.nbiap.vt.edu/ augment biodiversity with individual and group efforts to National IPM Network National • resistant varieties, use of cover maintain and enhance the quality of Server: crops and longer rotations life for consumers.” A review of this http://ipmwww.ncsu.edu/nipmn/ report provided some very interesting states/National.html • enhance beneficials, use of soil reading about a wide variety of issues Mike Gray, Extension Entomologist, amendments, disease affecting those of us working within (217)333-6652 the pest management arena. 113 Pest Management & Crop Development Bulletin • No. 13/ June 13, 1997

• forecasting models Are the goals set forward by the Con- tems: 7 days for 1 pint of 2,4-D ester, sumers Union realistic? Are the goals 30 days for 2 pints. There are no soy- Biointensive IPM (Reliance on pre- worth striving for? Questions to pon- bean planting restrictions if Roundup ventive measures to limit pest pressure der. Ultra was used as a preharvest treat- and enhance beneficials) ment. Mike Gray, Extension Entomologist, • multiple steps to enhance plant (217)333-6652 What if the wheat was previously health and soil quality treated with some other herbicide? • focus on conservation of Soybeans may be planted 60 days after beneficials and habitat an application of Harmony Extra, 10 months after an application of Peak, • microbial biocontrol of root patho- and 10.5 months after an application of gens WEEDS Stinger.

• release of beneficials Aaron Hager and Marshal McGlamery, Department of Crop Sciences, (217)333- Specific recommendations were made Preharvest Weed Control Treat- 4424 in the Consumers Union report regard- ments for Wheat ing IPM adoption along this con- With the wheat crop nearing maturity tinuum. in southern portions of Illinois, some Replanting Herbicide-Resistant/ Tolerant Soybeans By the year 2010, 75 percent of crop- producers may consider applying a land should be under Medium or High preharvest herbicide treatment to con- Prolonged cool soil temperatures and (biointensive) IPM, including nearly trol weeds that could make harvesting abundant moisture have contributed to 100 percent of fruit and vegetable operations difficult. There are, how- areas of some soybean fields having to acreage. ever, only two herbicides that are be replanted (often the perennial “wet labeled for this type of application. hole”). Undoubtedly, some of these By the year 2020, all acreage in Roundup Ultra may be applied using fields were originally planted with a American agriculture should be man- herbicideresistant/tolerant soybean aged under biointensive IPM. either ground or aerial application equipment. Applications must be made variety. The supply of seed for replant In urban, suburban, household and after the harddough stage of grain of these particular varieties may be in other indoor pest management, (30% or less grain moisture) and at short enough supply to force producers biointensive IPM should be nearly uni- least 7 days before harvest. Do not into replanting the “wet holes” with a versal by the year 2010. apply more than 1 quart per acre for conventional soybean variety, not a preharvest applications, and do not resistant/tolerant variety. If this is the By using the IPM continuum provided treat wheat being grown for seed as a case, weed control strategies will need by the Consumers Union, most Illinois reduction in germination or vigor may to be modified somewhat. growers fall into the No IPM or Low occur. Additionally, do not apply to Roundup Ready and STS soybeans are IPM categories. A survey of central wheat with a legume underseeding. Illinois growers in eight counties currently the only commercially avail- raised for me several questions that I Some formulations of 2,4-D ester are able herbicide-resistant/tolerant variet- offered in an issue (no. 24, 1996) of labeled for preharvest applications in ies. Roundup Ultra would be the pre- this Bulletin last year. Those questions wheat. Use rates vary somewhat by ferred choice of growers with were as follows: product but usually fall in the range of Roundup Ready soybeans; but if areas 1 to 2 pints per acre. Applications of a field were replanted with non- 1. Why are more than one-third of should be made after the wheat is in Roundup Ready soybeans, weeds in central Illinois farmers scouting the hard-dough stage, but not to wheat these areas would have to be con- their fields only two or three times with a legume underseeding. trolled by some option other than per growing season? Roundup. Synchrony STS is labeled If wheat harvest is timely and mois- for use only on sulfonylurea-tolerant 2. Why are two-thirds of central Illi- ture conditions remain favorable, soybeans (STS), so if areas of STS nois farmers not using economic double-crop soybeans could likely be fields are replanted with a non-STS thresholds for insect management planted in many wheat-stubble fields. variety, Synchrony should not be ap- decisions? If a preharvest application of 2,4-D plied to the non-STS soybeans. ester was made in the preceding wheat 3. Is the use of economic thresholds a What can be done for weed control if viable weed-management approach crop, planting soybeans should follow the time intervals set for preplant the replanted areas are not the same or if so few farmers (9 percent) ever a similar resistant/tolerant variety was use them? applications of 2,4-D in no-till sys-

114 Pest Management & Crop Development Bulletin • No. 13/ June 20, 1997

planted originally? Obviously, many Similar to atrazine, many sensitive condition, a “little” drift may options exist for chemical and postemergence herbicides use dicamba cause a great deal of corn injury. nonchemical control. A soil-applied as a tank-mix partner. Use rates vary Aaron Hager and Marshal McGlamery, herbicide may provide sufficient con- according to the label of the tank-mix Department of Crop Sciences, (217)333- trol to eliminate the need for a herbicide, but generally do not exceed 4424 postemergence herbicide application. 8 fluid ounces of Banvel or Clarity. If a postemergence program is desired, Applying these treatments with drop products other than Roundup Ultra or nozzles would be beneficial with re- Synchrony STS could be used in the spect to enhancing coverage of the non-resistant/tolerant replanted areas target vegetation and reducing the or across the entire field. If Roundup potential for crop injury. PLANT DISEASE Ultra or Synchrony STS is to be used, make sure the replanted areas are Some formulations of 2,4-D allow application with drop nozzles to larger clearly defined so these products are Scab of Wheat not applied to the non-resistant/toler- corn and can provide control or sup- ant soybeans. pression of waterhemp. Rates vary Wheat scab is beginning to show up in somewhat by formulation and drop many fields in southern and south Aaron Hager and Marshal McGlamery, nozzles should be used to apply 2,4-D central Illinois. Although at a low Department of Crop Sciences, (217)333- when corn is larger than 8 inches. 4424 level, this disease has prompted some Aaron Hager and Marshal McGlamery, calls about the appearance of white Department of Crop Sciences, (217)333- heads in the field. Scabbed heads are 4424 Controlling Waterhemp in Large commonly found scattered throughout Corn a field; and the numbers will vary, depending on the genetic resistance of The prolonged cool weather delayed One More Caution the plant and the time of flowering. the emergence of waterhemp in some Because wheat scab infects only the corn fields across central Illinois; but, With the cool and wet growing condi- open flowers when weather conditions with the slow development of the tions encountered across much of favor the disease, it is quite common crop, waterhemp has been able to Illinois, the corn crop remains “ten- to see differences among wheat variet- come on strong. What can be done to der” and is fairly susceptible to injury ies planted on the same farm if the control waterhemp in large corn? from herbicides drifted from flowering times are different. postemergence applications in soy- Many postemergence products can be bean fields. In particular, drift of Scab (also known as head blight, pink tank-mixed with atrazine, but corn- Roundup Ultra and the postemergence mold, or white-heads) is caused by height restrictions (12 inches) may grass herbicides used in soybeans are several fungi in the genus . limit the use of this treatment. Addi- of particular concern due to the inher- The principal pathogens are Fusarium tionally, late applications of atrazine ent sensitivity of corn to these prod- graminearum, F. avenaceum, and F. may raise concerns about potential ucts. culmorum (synonymous name for all rotational crop injury. three is F. roseum f. sp. cerealis); and Any herbicide is subject to drift if F. nivale. These fungi produce only Dicamba (Banvel or Clarity) can pro- applications are made when conditions asexual spores with limited genetic vide control or suppression of larger favor off-target movement. Nearly all diversity. The sexual stage is known as waterhemp. When used alone, broad- postemergence herbicides have label zeae. cast applications may be made until statements about not making applica- the 5-leaf (8 inches) stage. After this, tions during conditions that favor off- Scab infects all small-grain cereal drop nozzles are needed to keep the target movement. Symptoms that drift crops, corn, and many other grasses, herbicide out of the corn whorl. Ac- has occurred are more apparent with including spelt, emmer, cheat, wildrye, cording to the label, a late some herbicides than with others. several foxtails, quackgrass, crabgrass, postemergence application of up to 0.5 Much has been made about label state- and bluegrasses. Other plants that may pint of Banvel (not Clarity) may be ments indicating that applications be attacked include clovers, alfalfa, made to corn between 8 and 36 inches should not be made when winds are in pokeweed, sweet potato, and several tall, or 15 days prior to tassel emer- excess of, for example, 5 miles per members of the parsley family. In gence, whichever comes first. Do not hour. In the reality of the Illinois, the fungi that cause scab and apply Banvel when soybeans are “postemergence spray world,” days related diseases are most widespread growing nearby if they are more than with wind speeds less than 5 mph are and damaging on wheat, , rye, 10 inches tall or have begun to bloom. almost the exception rather than the and corn. Scab can be severe in wheat norm. However, with corn in a very sown in the residue from a previous host crop such as corn. 115 Pest Management & Crop Development Bulletin • No. 13/ June 13, 1997

The Fusarium fungi may cause a blast light brown to pink or grayish white, to 10 days after infection, salmon pink of the spikelets (usually called head depending on the time of infection and masses of conidia form at the base of blight or scab); a rot of the root, the weather conditions. the diseased spikelets. These conidia crown, or foot; and stem blight. The are carried by the wind to the heads of fungi also cause a seedling blight and Occasionally, the may girdle other cereal and grass plants, in turn a rot of the stalk, root, and ears on and kill the spike or rachis of a grain producing new, secondary infections. corn. The stand, yield, quality, and head, causing the parts beyond to die. The process is repeated as long as the feeding value of the grain may all be The result is no grain at all or small, spikelets are susceptible and the moist seriously affected by scab. The disease shriveled kernels that are separated out weather prevails. has been reported from most of the in the process of harvesting or thresh- humid and semihumid areas of the ing. If the weather remains warm and Secondary infections may result from world where cereals and corn are moist, spikelets on heads infected the long-distance spread of airborne grown. The severity of scab infection early become speckled by harvest time conidia. are usually pro- on cereal grains varies greatly from with superficial, spore-producing duced too late in the season to func- year to year. Severe infection occurs bodies (perithecia) that are a dark tion as secondary inoculum but persist during the flowering stage and shortly purplish black. in crop residue and can contaminate seed. afterward, when the weather is warm Disease cycle. The scab fungi and moist. If the weather is dry after overseason and propagate in and on Seedling infections result primarily the head emerges, small grains are the soil as spores, mycelium (thread- from seedborne mycelium and spores. nearly scab-free. like mold growth), and fruiting struc- When the soil temperature is above ° Symptoms. In the field, the earliest tures known as perithecia, which 60 F, seedlings from clean seed may and most conspicuous symptom of produce ascospores. Light pink to become infected from mycelium in scab infection occurs soon after flow- orange-colored masses of conidia or decaying crop residues on or in the ering. Diseased wheat spikelets be- “summer” spores are produced in soil. Head and stem infections occur come a bleached, light-straw color and tremendous numbers during warm, independently of seedling blight and ripen prematurely, while healthy moist weather. Ascospores (often root rot (because the fungi cannot spikelets are still a normal green. called “winter” spores) produced grow for any distance within the ce- Diseased wheat kernels are grayish within the perithecia are discharged real plant). However, the fungi may brown and lightweight. Scabinfected into the air during warm, moist live for several years within infected rye kernels are dark brown to carmine weather in the spring and early sum- kernels. mer. Air currents and rainsplash carry red. If the entire head is infected, H. Walker Kirby, Associate Professor, barley spikes are dwarfed; diseased the ascospores and conidia to the Department of Crop Sciences, (217)333- spikelets are compressed rather than young spikelets. The spores germinate 8414 spreading. Scab-infected spikelets of in a film of moisture and first invade oats are ash gray; those of barley, light the flower parts, frequently spreading brown. One or more spikelets may be to the glumes and other parts of the infected, or the entire head may appear head. Infections are most frequent and prematurely bleached. The dead serious at anthesis. At this time, an- “whiteheads,” which are sterile or thers and pollen may serve as a food SAFETY contain only partially filled seed, are base for pathogens. Blight symptoms often rapidly colonized by secondary develop within 3 days after infection, when temperatures range between 77° black molds. Pesticide Safety Education Pro- and 86°F and moisture is continuous. gram Information During warm and moist weather, In areas that otherwise are too dry for masses of light pink to salmoncolored scab development, sprinkler irrigation The 1996–1997 annual report on mold (composed of mycelium and may predispose plants to the disease. Illinois’s Pesticide Safety Education “summer” spores or conidia of the Programs is now available. The 20- Conidia and ascospores may also fall fungi) may form on infected glumes page document highlights program on crop residues. These spores soon and lemmas of the spikelets, espe- goals and mission, program structure, germinate, resulting in mycelium, cially near the base of the kernel. This benefits of our program, and major which produces large numbers of is an excellent diagnostic sign. In- accomplishments, including educa- conidia. Both the ascospores and fected kernels are generally shrunken, tional material development, pesti- conidia are capable of producing in- wrinkled, and light in weight, with a cide-container recycling, commercial fection if they land on the head of a rough and flakyto-scabby appearance. PAT programs, private PAT programs, cereal or grass plant during or shortly These kernels range in color from Worker Protection Standard (WPS), after the blossoming period. Within 7

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homeowner programs, drift-education copy of the annual report; or view it ing schedules currently shown are all activities, operation-safe fly-in work- on our home page. past. We left them on the page because shops, and many other programs. The there is useful information provided report demonstrates the depth and The Pesticide Safety Education home besides the training dates, such as breadth of Illinois’s safety education page is available at licensing requirements and specifica- programs. Although commercial and www.aces.uiuc.edu/~pse/ This site tions. The training schedules for the private PAT is our first mission, we contains the latest issues of our Illinois 1997–1998 commercial and private also provide quality pesticide educa- Pesticide Review newsletter, the an- pesticide applicator training programs tion to a diverse audience in other nual report just mentioned, fact sheets, will be available this fall. pesticide-related areas. Please contact links to other resources, and our Pesti- Rhonda J. Ferree, Department of Natural Patty Bingaman, (800)244-2363, for a cide Applicator Training schedules. Please note that the dates in the train- Resources and Environmental Sciences, (217)244-4397

The information provided in this publication is for educational purposes only. References to commercial products or trade names do not constitute an endorse- ment by the University of Illinois and do not imply discrimination against other similar products.

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The Pest Management & Crop Development Bulletin is brought to you by the Cooperative Extension Service and Information Services, College of Agricultural, Consumer and Environmental Sciences, University of Illinois at Urbana-Champaign; and the Natural History Survery, Urbana, IL. This newsletter is edited by Mary Overmier and formatted by Jerry Barrett, ACES Information Services.

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