Wheat disease updates in Illinois

Wheat development in most in Southern Illinois fields is between Feekes growth stage (FGS) 9-10.5.1. Wheat in the central portion of the stage varies from FGS 6-9.

Stripe rust was detected in Eastern Madison County as of 5.5.20, and conditions are favorable for disease development and spread.  This is a cool season disease that loves wet weather and temperatures in the high 40’s through the mid 60’s.  Fields should be scouted for the disease, keeping in mind that it often starts in small pockets, or epicenters in a field, and may not be widespread.

Remember that products for head blight suppression also work on stripe rust (example for a late-arriving epidemic below).  If disease arrives prior to heading on a susceptible variety, you may need to consider

Example of fungicide effects on a wheat variety susceptible to stripe rust. Different letters within a column indicate significant treatment differences using Tukey’s HSD (0.05).   In this trial conducted at the Wye, MD, stripe rust signs and symptoms began at the start of heading, and cool wet weather persisted well past flowering. From Kleczewski, 2017.

Wet weather is elevating the Fusarium head blight (FHB) risk for highly susceptible , flowering wheat.  Cool temperatures in the forecast may reduce FHB risk for flowering wheat in many areas. For an update on Fusarium head blight click here.


New maps for tracking Southern rust in corn (repaired link)

Southern rust is caused by a fungal pathogen that does not overwinter in Illinois.  Instead, it blows in from warmer regions during the growing season.  When conditions favor spread and development of this disease significant damage can occur, especially if it arrives before tasseling (VT).  For more information on Southern rust, check out the Crop Protection Network publication by clicking here.  Yesterday our colleagues detected this disease in Southeast Missouri.  With the hurricane/tropical storm remnant pushing northward, and warm weather forecast, there is a good chance we could see some movement into the Southern / Western  part of the state within the next 7-10 days, and there may be some in Southwest Illinois already.  Scouts should be keeping their eyes out for this disease, as things can escalate quickly.  Suspect samples should be sent to the University of Illinois Plant Diagnostic Clinic for confirmation.  Images can also be sent to me via twitter @ILplantdoc, or email at  nathank@illinois.edu.

We have a new tracking system for rusts in corn that we are using this year.  To access the maps click here.  These maps are very useful for tracking a disease that does not overwinter in the area as it needs to spread, establish, and produce more spores to move, unlike diseases that overwinter on residue, alternate hosts, etc.  That means you can see the disease spread and know if you are at risk for it moving into your area.  If your fields are at a critical point in growth, and the disease is detected nearby, in season management can be considered, and unneeded treatments avoided.  We also have a tar spot map.  This disease overwinters in the region, and little is known about disease movement and spread within a season.  Data indicate it can move at least from field to field; however, after last season there is reason to believe it may move longer distances, but we simply are speculating at this point.  This map therefore can tell you when the disease is starting to be detected in certain regions, and also if the disease has been detected in new counties.  For more on tar spot click here.

Locations where tar spot was confirmed in 2018. This map shows incidence not severity at county level. Severity in general was highest in Northern Illinois and extremely low in central Illinois

 

 


New mapping system to monitor corn rusts

This season we will be using a new system to monitor and  track southern rust in Illinois #corn.  We will be operating and managing a site that clientele can access and view in real time.  I will provide information pertaining to the site once it is operational in a few days.

Why do we need to monitor rusts?  Because rusts are obligate fungal pathogens.  This means they need a living, green host to grow and reproduce.  Rusts do not survive our Illinois winters and instead overwinter in warmer southern locations.  Once temperatures increase, spores from the south are blown north.  Corn planted in the United states can then be infected as the pathogen infects new corn, produces more spores, and moves on air currents to new areas and fields.  Therefore, by tracking rusts we can determine if and when fields may be at risk.  This information can help make timely fungicide applications or avoid unneeded applications.   This process takes time and often rusts do not reach our corn until later in the season, once yield has been made.  However, due to our late planting throughout the state we may see these rusts infect plants at earlier stages in growth and development, which may result in greater potential yield impact if disease occurs.  This is why scouting your corn this year will be especially important.  

 

Example lifecycle of Southern rust. Note that it blows in from warmer, southern regions.

In the meantime, any growers, consultants, ag professionals in Illinois that observe rust on corn should send a picture to myself at nathank@illinois.edu OR tweet a picture to me @ILplantdoc and @corndisease with #southernrust hashtag.  Southern rust, common rust, and other diseases may not be easily identified by images, and may require expert analyses.  Samples of corn rust can be sent to the UIUC Plant Diagnostic clinic– instructions found HERE.

Common vs Southern rust in corn. Due to late planting we may see both earlier than normal during the season, but tracking the diseases and their progress is critical for rusts.


What effect will cold temperatures have on pests and pathogens?

Nathan Kleczewski Research assistant Professor and Extension Field Crop Pathologist

Nick Seiter- Research Assistant Professor and Extension Field Crop Entomologist

 

Many in the Illinois agricultural community are wondering what effects the recent extreme cold might have on pests and pathogens. While it would be nice if the cold temperatures we are experiencing could help to reduce our potential for pest damage, past experience tells us that the most serious pests we deal with are unlikely to be impacted much by these conditions.

Many of the pathogens and insect pests that commonly affect field crops in Illinois are well adapted to survive our winter conditions.  In many cases, pathogens produce recalcitrant survival structures (e.g. cysts in soybean cyst nematode, oospores in Phytophthora, sclerotia in white mold).  These structures allow the pathogen to survive extreme conditions including cold, drought, and flooding. Different species of insects overwinter in different life stages, including eggs (for example, western corn rootworm), larvae (Japanese beetles), pupae (corn earworm, though they do not survive the winter in most of Illinois), or adults (stink bugs). The overwintering stage has characteristics that help these insects to survive the winter, either by adjusting its physiology to better survive the cold, seeking out an overwintering site that protects it (such as soil, tree bark, or leaf litter), or both. The overwintering sites that insects find mean that they are not experiencing the same temperatures that we are when we venture outside. Wind chill has little effect for this reason (even though it has a major, unpleasant effect on us).

Extreme cold temperatures can impact some insects and plant pathogens, particularly those that may not overwinter as well (e.g. powdery mildew).  When cold weather pushes into the Southern regions of the country it can push certain diseases, such as rusts, further south, delaying disease onset in Illinois and other regions further north. The same is true of migratory insects, such as black cutworm and fall armyworm, which do not usually overwinter in Illinois; colder temperatures during winter often delay the arrival of these insects, and may ultimately lead to lower numbers. The opposite is also true – warmer than normal temperatures during the winter can allow these migratory insects to become a problem earlier in the season.

Although cold temperatures may not impact most of the diseases we encounter in Illinois field crops, fluctuation between conditions of cold and warm may have a negative impact on some diseases.  Dormancy by fungi can be broken by environmental conditions such as higher temperatures.  This is similar to what occurs in plants, where warm weather may result in trees flushing out buds and flowers.  Consequently, the wide swings in temperature that we have experienced during the 2018/19 winter may negatively impact some diseases. While some insects (such as stink bugs) can also break dormancy during brief warm periods, many of our most serious pests will stay “hunkered down” until the spring and avoid these fluctuations. Unfortunately, insects and plant diseases are unlikely to suffer as much from the recent cold as we have. The best way to reduce the impact of insects and pathogens on those cold days is to stay inside, grab a hot cup of coffee, and curl up to the latest UI Extension recommendations or UI applied research results guide.