Soybean aphid spray day complete

Yesterday my lab finished another successful soybean aphid insecticide spray day. We have evaluated insecticide efficacy to soybean aphid since 2005. I didn't get involved with the program until I started at ISU in 2009, but it's a growing research trial and the largest in the nation. I evaluate a range of products, different chemistries, new formulations, etc. I also compare seed treatments and host plant resistance to foliar insecticides. My program also monitors for genetic resistance to our management tools. Eventually, I expect soybean aphid will develop resistance to pyrethroids and organophosphates, so I want to monitor their response to exposure over time.

Wearing Tyvek for hours is not my favorite thing to do!

This year, we have 35 treatments at the Northeast Research Farm near Nashua and 15 treatments at the Northwest Research Farm near Sutherland. We sprayed at Nashua yesterday and will spray at Sutherland tomorrow. Aphid numbers have been steadily climbing, with populations doubling every 5-7 days. Many commercial fields have reached the economic threshold, and foliar insecticides are going on all over northern Iowa. Typically late-planted fields have higher soybean aphid numbers - so those fields should be your scouting priority.

The spray crew is ready to go with proper PPE! Thanks Greg, Tyler, Eric, Cody K., Cody S. and Mike!

If you are interested in how insecticides perform, I summarize all the results in an annual publication called the Yellow Book. You can access a free copies by year on my website. The 2013 version will be ready for distribution by November.

Meet my lab!

It's about time I talk about humans for once on the blog and not just focus on insects. I wanted to give some big props to the people in my lab that spend all day (every day) outside looking for insects in corn and soybean. My lab has actually grown quite a bit this year and branching out of my usual research comfort zone.

Some of the lab (L-R): Thelma, Greg, Amanda, Eric, Erin, Ezra, Taylor, Tyler, Sarah and Cody. Yes, I am wearing a cockroach t-shirt!

Greg Van Nostrand is my lab technician and makes sure the work gets done
Hometown: Vincent, Iowa
Major: B.S. Entomology, ISU (2009)
Sports and Hobbies: retro/classic video games
What else? has wanted to be an entomologist since he was a kid; likes Windows, Android, classic rock and energy drinks

Thelma Heidel-Baker is a new post-doc in my lab. She is working with pollinators in addition to helping me with extension projects
Hometown: Random Lake, Wisconsin
Major: Ph.D. Entomology, University of Minnesota (2012)
Sports and Hobbies: running and more running, triathlons, photography, traveling, and gardening
What else? she has a 4-month old daughter, Ava

Eric Clifton just recently finished his M.S. degree at ISU and is now working on a Ph.D.
Hometown: Gurnee, Illinois [home to Six Flags Great America]
Major: M.S. Entomology, ISU (2013); Ph.D. Entomology, ISU (2016?)
Sports and Hobbies: frisbee golf, mushroom hunting, dancing, foosball, cross country running, photography, hiking
What else? he believes everyone should watch Billy Murray movies, travel often and eat more tacos to vastly improve quality of life

*******
Amanda is a new undergraduate working with Thelma this summer
Hometown: Muscatine, Iowa
Major: Biology, expected graduation in 2014
Sports and Hobbies: music, biking, reading
What else? wants to get a M.S. degree in teaching and teach high school biology

Cody is a new undergraduate working with Greg this summer
Hometown: Maquoketa, Iowa
Major: Environmental Science, expected graduation in 2014
Sports and Hobbies: running, basketball, fishing, hunting, camping and anything outdoors
What else? wants to get a graduate degree and go into research

Ezra is a new undergraduate working with Thelma this summer
Hometown: Tucson, Arizona
Major: History, expected graduation in 2013
Sports and Hobbies: soccer and football
What else? thinking about graduate school in entomology [bonus!]

Hailey is a new undergraduate working with Greg this summer
Hometown: Urbandale, Iowa
Major: Biology and Accounting, expected graduation in 2015
Sports and Hobbies: softball, camping, fishing, playing with animals
What else? loves ice cream and her favorite color is blue

Joe is a new undergraduate working with Thelma this summer
Hometown: Ankeny, Iowa
Major: History, expected graduation in 2013
Sports and Hobbies: golf and tennis
What else? after college, he wants to move to Oregon or Washington

Kiley is a new undergraduate working with Eric this summer
Hometown: Buffalo, Minnesota
Major: Forestry, expected graduation in 2013
Sports and Hobbies: brewing tea, tying shoelaces and the pursuit of adventure
What else? she wants to breed a bevy of homing pigeons to help communication in southern Canada

Sarah is a new undergraduate working with Eric this summer
Hometown: Belleville, Illinois
Major: Animal Ecology and Biology, expected graduation in 2014
Sports and Hobbies: photography, watching baseball, and visiting classic car museums
What else? she is allergic to oranges

Sydney is a new undergraduate working with Greg this summer
Hometown: Pleasantville, Iowa
Major: Biology, expected graduation in 2014
Sports and Hobbies: hiking, photography, hanging with friends, traveling and dog (Winston)
What else? wants to get a graduate degree and conduct field research as a wildlife biologist

Taylor has been working for us since 2012; she is working with Greg again this summer
Hometown: Sioux City, Iowa
Major: Animal Science, expected graduation in 2015
Sports and Hobbies: movies, swimming, fishing, hiking
What else? aphids are awesome! [obvious brown-nosing attempt, but that is the correct answer!]

Tyler has been working for use since 2012; he is doing an independent study in grapes this summer
Hometown: Williamsburg, Iowa
Major: Horticulture (Fruit Production), expected graduation in 2014
Sports and Hobbies: hockey, trap shooting, golf, disc golf, boating, bonfires
What else? after college, he hopes to own his own vineyard in the midwest and make beer and wine

Aphid numbers quickly building in Iowa - try Speed Scouting!

In a recent ICM News article, I reviewed scouting and management tactics for aphids in field crops. They seem to be popping up in Iowa corn and soybean, especially in the northern counties. Soybean aphid populations are doubling every few days in my small plot efficacy evaluation trial at the ISU Northeast Research Farm. Populations will likely exceed the economic threshold of 250 per plant next week and we plan to make our foliar applications when that happens. It always raises a red flag to me when most plants within a field have some soybean aphid - even just a couple on most plants. A week of favorable temperatures can allow them to have exponential growth. We also know that soybean aphids generate more winged adults after soybean bloom and are highly mobile short and long distances.

Now is the time for soybean aphid. Turn over leaves and estimate aphids per plant. 

Have you ever tried Speed Scouting to make treatment decisions for soybean aphid? In an area with lots of soybean aphid, this sampling method can greatly reduce the amount of time it takes to decide if an application is needed. I've got blank Speed Scouting forms available here. Or you can take a look at a blank form below.

It's easy to use and most importantly can save a lot of time (hence the name!). You only have to count to 40. Once you get to 40 - stop and consider that plant infested. Look at 11 plants to get started and then use the decision matrix to get the sampling decision. Most of time you will know if you should treat or not in less than 15 minutes.

Learn how to identify Japanese beetle females

Recently, I had a crop consultant ask me to verify his male/female specimens of Japanese beetle. He squished them to look for eggs (which is highly diagnostic of a female!). I thought there might be an easier and less messy way to determine the sex. But after spending some time online and reading through my textbooks, I only found a few external characteristics that were different. I was somewhat disappointed because sometimes beetles have drastically body features. When males and females of the same species look different - that is called sexual dimorphism.

Western hercules beetles on ash; note male horn on top and size difference. Photo by Alex Wild. 

Depending on how good your eyesight is, you will be able to tell male from female Japanese beetle. Look at the first pair of legs and focus on the tibia. The tibia is the late large segment before the tarsus, or "feet." You may need a hand lens to see the tibia. The male will have spikes on the tibia and the female will have more spoon-like paddles. 

Male Japanese beetle. Photo by Tom Hillyer. 

Female Japanese beetle. Photo by Tom Hillyer. 

Or just use the squish test to look for eggs in female Japanese beetle. Photo by Tom Hillyer. 

For more information (with drawings), visit these websites: University of Tennessee Extension and NAPPFAST. 

Thinking about treating corn rootworm adults? Read this first.

Adult corn rootworm emergence is in full swing all around Iowa. Actually seeing adults is a good reminder to assess for larval injury before too much root regrowth obscures feeding. Questions about adult management are popping up from ISU field agronomists, crop consultants, and farmers. My answer is not automatic - it really depends on the field history and ultimate goal for long-term production. Ask yourself:

#1. Are adults interfering with pollination? Adults aren't considered an economically important life stage unless they clip silks and prevent pollination. The late planting of many fields this year is coinciding with adult emergence. Silk feeding is certainly happening around Iowa. They are strongly attracted to green silks and will "chase" silks in neighboring fields. Target late-planted or late-maturing hybrids for your scouting efforts. After pollination is complete, they will feed on corn leaves, but that is considered minimal.

Consider a foliar treatment if: 5 or more beetles per ear AND silks have been clipped to less than 1/2 inch AND pollination is not complete. The threshold of 5 beetles is for drought-stressed corn; the threshold can be increased to 15 beetles per ear for fields with adequate moisture. Also keep in mind other silk feeders that may interfering with pollination (e.g., Japanese beetle, corn earworm, etc.).

Corn rootworm prefer to eat corn silks. Photo by John Obermeyer, Purdue University Extension. 

#2. Is pollination complete? If the goal is try and reduce the egg deposition and potential larval damage the next season, then my response gets a little more complicated. First determine if action should be taken by estimating adult density. If scouting reveals 1-2 beetles per plant in continuous corn, it is recommended to take some sort of action; see the table below for more specific numbers. Taking action means targeting adults this year or larvae at planting the following year.

To try and do an effective job of adult control requires an intense scouting effort and well-timed foliar treatments. We must understand adult emergence in order to apply insecticides to gravid females (mated and mature eggs). Plan for at least two applications, about 7-10 days apart.

To estimate more specifically, a biofix is established and is defined as the first adult found in that field. After reaching the biofix, emergence of the remaining population is based on accumulating air temperature (i.e., degree days). Calculating accumulating degree days is easy = [(max daily temp + min daily temp)/2]- 53 (lower developmental threshold). So for example, if the maximum temp for the day was 95 and the minimum temp was 50, the calculation would look like this: [(95 + 50)/2] - 53 = 19.5.

To answer how long adults will emerge depends on the temperatures following the biofix. Warmer days will mean adults emerge faster. It could happen in three weeks or be extended to five weeks during a cooler summer. ISU entomologists studied how long it takes for adult corn rootworm to emerge and in general: males emerge first and westerns develop faster than northerns. Here is a table that more specifically summarizes emergence based on degree days following the biofix:

#3. How do you know when females are gravid? Again, targeting applications to gravid females is critical. But first you have to distinguish the males from the females. Females are typically larger and have three distinct, black lines on the forewings. Males have a smudgy, black marking on the forewings. See if you can spot the male in the photo above. Gravid females will have swollen abdomens that extend past the end of the forewings. Or consider a looking for mature eggs by expressing them from the abdomen. 

Use the "squish" test to look for mature eggs. Photo by Purdue University Extension. 

#4. What are the long-term management goals? If larval root injury is evident and adults are abundant, that should be concerning no matter what management strategy (or strategies) is implemented. Larval root pruning will reduce yield and make plants unstable. I strongly encourage diversifying management to avoid increasing activity during the next growing season. Plus, resistance to Cry3Bb1 and mCry3A is confirmed in Iowa and is a real threat to Iowa's corn production. We need to be more strategic on how we use this technology in order to prolong the efficacy.

Crop rotation is the single, most effective suppression tool. Corn rootworm larvae will not eat soybean (or other non-corn hosts), and starvation is eminent. I've summarized other management ideas in a publication with ISU corn entomologist Aaron Gassmann - read it and pass it on!

Sorry so long, but this is a complicated topic. Hope it helps, Erin

Corn silk feeders are worth scouting right now

I saw my first corn tassels of the season and it got me thinking about silk feeders out and about now. But then again, I saw some corn that was only 18 inches tall and looked a long way from tasseling. It's been a crazy summer!

Of course many of you are noticing Japanese beetles flying around (and maybe hitting your windshields) this week. They are definitely attracted to green silks and can interfere with pollination. Japanese beetles mate and feed in groups. It is not uncommon to see them aggregated on plants, especially along the edge rows. They are highly migratory and are constantly moving around the landscape. Adults have a wide host range (>300 plants) and are likely to find something they like to eat.

There has been a lot of marketing about controlling Japanese beetles this year. I don't think it is wise to treat for adults BEFORE tasseling. I have preliminary research that shows foliar insecticides do not have a long residual, regardless of the chemistry. Most broad spectrum insecticides will kill adults if the droplets make contact on the body. That application won't have a 7-day residual for immigrating beetles.

But if beetles are actively feeding when silks are present, determine densities to make smart treatment decisions. Consider an insecticide if: 3 or more beetles per ear AND silks have been clipped to less than an inch AND pollination is not complete. Again, do not expect a long residual with any product, so continue to scout until pollination is over. If a second spray is warranted, alternate chemistries to reduce the chance of developing resistance.

The tricky part of managing this pest is if you have sweet corn that may have staggered planting dates or late-maturing hybrids. This summer is a good example of field corn at various growth stages, too. Be aware beetles will continue to move to green silks throughout the summer.

Japanese beetles at the ISU Johnson Research Farm in 2012. 

The second most common type of silk feeder is adult corn rootworm. Emergence has started in southern Iowa and it won't be too long before we see them all over the state. Like Japanese beetle, they are strongly attracted to green silks and like to feed and mate in masses. Silk feeding can interfere with pollination, so it is important to scout during this period to ensure kernel formation later this summer. Consider an insecticide if: 5 or more beetles per ear AND silks have been clipped to less than an inch AND pollination is not complete. The threshold can be bumped up to 15 per plant if the field is under adequate moisture conditions.

Adult corn rootworm can clip silks. Photo by John Obermeyer, Purdue University.

Grasshopper nymphs and adults can also occasionally eat corn silks. They are usually found around field borders first and then can infest the field interior later in the summer. Since grasshoppers are so mobile, it is very difficult to try and estimate densities. So as with the Japanese beetle and corn rootworm, it is important to watch for silk clipping and take action if they are interfering with pollination. Because grasshoppers tend to move short distances and attack border rows first, a border treatment may be a cost effective decision. 

The differential grasshopper is common in Iowa field crops. Photo by David Cappaert, www.ipmimages.org.

The fourth potential corn silk feeder in Iowa is the corn earworm. The larvae have highly variable body color, ranging from yellow, to green or orange, or brown and even purple. There are alternating dark and light stripes running the length of the body. Larvae have a textured appearance, with many spines coming out of small bumps. This is unlike black cutworm or fall armyworm that have smooth bodies. 

Female moths deposit eggs on green silks during the night. First instars will feed on silks and eventually move down inside the tip of the ear. Older larvae will destroy developing kernels. Since trying to kill the larvae once inside the ear is almost impossible, I recommend monitoring adults. The University of Illinois has a nice website that summarizes how to properly time a foliar treatment for corn earworm, depending on the type of corn grown. 

Corn earworm larvae can feed on silks before they enter the ear to feed on kernels. Photo by Frank Peairs, www.ipmimages.org.

Lots of Japanese beetle look-alikes out there

Based on a soil temperature prediction model, Japanese beetles should be emerging all over Iowa now. We've seen them at nearly all of our ISU Research Farms. Ok, it helps when we use pheromone traps because they are especially attractive. But we like to be able to catch the first adults of the season!

At the same time these beautiful beetles are moving around, many other close relatives are coming out, too. Japanese beetles and other "scarabs" belong in the beetle family called Scarabaeidae. There are about 30,000 scarabs around the world. Even though they are highly diverse and abundant, they have a couple things in common: stout bodies, clubbed antennae, and many have broad front legs for digging. Some scarabs can be metallic or brightly colored, while others blend into the landscape. Adults can be active during the day or night depending on the species. Because of their relative size and body weight, they are clumsy fliers that move short distances. Some scarabs are scavengers that feed on dung, carrion or decomposing organic materials; others are significant plant pests. The larvae are distinctive because they are ALWAYS in a c-shape and commonly called grubs.

Grubs are immature scarab beetles. Note they have three pairs of true legs but lack the fleshy abdominal legs commonly seen on caterpillars. Grubs can be white or transparent, and will always be in a c-shape. Photo by David Cappaert, www.ipmimages.org. 

With several scarabs emerging at the same time, proper identification can be difficult. Here is a quick review of the most common scarabs out in Iowa right now:

Japanese beetle: Adults are just over 1/2 inch in length. These scarabs have one generation per year. They are visually distinct because of the metallic green head and bronze forewings that do not fully cover the abdomen. They also have white tufts of hair along the sides of the abdomen. Adults have a wide host range (>300 plants), including roses, fruit and shade trees, grapes, corn and soybean. Japanese beetles skeletonize leaves by feeding between the veins.

Japanese beetles are metallic, with clubbed antennae and white tufts of hair. Photo by Dorothy E. Pugh. 

Japanese beetles aggregate to feed and mate, leaving skeletonized leaves. Photo by Mark Licht.  

False Japanese beetle. Sometimes called a sandhill chafer, this species is commonly mistaken for Japanese beetle. They are similar in body shape and size (1/2 inch in length), but is not metallic green and bronze. They can have white hair along the sides of the abdomen, but it is more evenly dispersed instead of in tufts. False Japanese beetles have one generation per year. Adults feed on flowers, fruits and leaves of many plants, but are not considered a field crop pest.

False Japanese beetles are hairy scarabs, but not metallic. Photo by Marlin E. Rice.

Masked chafers. There are several species of masked chafers in Iowa. These scarabs have one generation per year. Adults are 1/2 inch in length and oval in shape. Body color can range from dark yellow to tan with dark markings on the head. They can have hairy bodies, wings and legs. Masked chafers are not known to be field crop pests in Iowa. 

Northern masked chafers are hairy and tan scarabs. Photo by Mike Reding and Betsy Anderson, www.ipmimages.org. 

May/June beetles. There are several scarabs with the common names of May or June beetles. Most have a life cycle that takes 2-4 years. Adults are usually larger (1 inch in length) and oval in shape. Body color ranges from red to brown. Adults feed on a wide variety of plant foliage, but they are not considered field crop pests in Iowa. 

June beetles are attracted to street lights at night. Photo by Steven Katovich, www.ipmimages.org.

Just a few other scarabs that you could find out this summer. None would be considered field crop pests. 

Ten-lined June beetle. Photo by Eugene E. Nelson, www.ipmimages.org.

Little bear. Photo by Whitney Cranshaw. 

Bumble flower beetle. Photo by David Cappaert, www.ipmimages.org. 

Corn rootworm larvae are hungry

Today, I put out an ICM News article on predicted corn rootworm egg hatch in Iowa. It has a map of the soil  degree day accumulation for the year. Entomologists can predict most insect development based on temperature and we estimate about 50% of corn rootworm eggs should hatch between 684-767 soil degree days (base 52F). The Muscatine area is approaching that important benchmark and many other areas in southern Iowa will in the next week. If we continue to have warm days, expect all insect development to speed up quickly.

Soil degree day accumulation as of 14 June 2013. 

This egg hatch prediction is behind the average date of 6 June and way behind numbers for 2012. People that track egg hatch in Indiana and Illinois also reported delayed egg hatch, due in part to the extreme drought in 2012. Mike Gray, Illinois extension entomologist, said sometimes females will lay eggs deeper into the soil profile in drought conditions. The delayed corn planting throughout much of Iowa means larvae will have a smaller root system to feed on and potentially damage. I've also had people ask me about saturated soils killing rootworms this year. It is possible to suffocate the larvae, but the eggs probably survived water-logged soil. 

I encourage all you scouts and farmers to check your corn roots mid July to assess any corn rootworm injury. It will help determine the ongoing strategies for this unruly beast. Unexpected corn rootworm is possible with all Bt traits in continuous corn production. To read more about corn rootworm management, read this short ISU publication Aaron Gassmann and I wrote over the winter. 

Aphids in corn?!

I saw something new for the first time today - aphids on V4 corn. Actually, my summer crew found them while scouting for early-season pest activity in a small plot trial at the ISU Johnson Farm just south of Ames, Iowa. Nice job scouting today - way to go!

Meet part of the 2013 crew. I hope to post something just about our lab personnel soon. 

This find is exceptional for three reasons. First, Iowa corn doesn't always get infested with grain aphids. The overwintering potential in Iowa isn't fully understood, but most people think they have to migrate here from the southern U.S. every year (kinda like potato leafhopper and many other insects). So it can be hit or miss if they land here and establish at all. But grain aphids would rather live on small grains, like wheat sorghum, barely, oats, rye, etc. However, some of these aphids will feed on corn and have been known to build up to extremely high populations after tasseling. There was an corn aphid outbreak in much of northern Iowa in 2011. But finding them in mid-June is very interesting (to an entomologist!).

The second curious part of finding aphids in corn this early is that all conventional corn contains an insecticidal seed treatment. My general thinking is aphids shouldn't like to feed on that or stick around long enough to produce nymphs. But it wasn't hard to find alates (winged adults) and nymphs in this small plot trial.

While looking for cutworms and stalk borers, we found aphids instead!

Alates and first instars were easy to find on V4 corn today. 

 The alate was gone, but left behind at least four nymphs on this plant. 

The third thing that was surprising is I identified them as English grain aphids. Of the many species we can potentially find in Iowa, the two most common species are corn leaf aphid and bird cherry oat aphid. English grains aphids are a little larger than either of them, but not as big as a pea aphid. Adults have dark cornicles (tailpipes on the sides of the abdomen), "knees," and "feet" with a pale cauda (little appendage at the very tip of the abdomen). This species does not alternate between a primary, woody host and secondary perennial host (like with soybean aphid). It is capable of vectoring barley yellow dwarf virus in small grains. It can overwintering on true grasses within the Poaceae family. 

English grain aphid, note the dark knees and feet. Photo by Rothamsted Insect Survey.

I should note we didn't see large colonies on any plant. The alates are migrating to these plots and dropping off a few nymphs. We don't know if they will survive or succumb to the insecticidal seed treatment. Of course we are monitoring these plots weekly and I will post an update if they survive. But in general it means that aphids are around in central Iowa. If colonies persist and are allowed to develop over the growing season, it could be significant feeding that results in yield loss. 

Seeing maggots in your beans?

Well, no two summers are the same. This wet spring has caused some fields to have slug problems. Then other fields are now experiencing some seedcorn maggot problems. Crop consultant in southeastern Iowa, Tom Hillyer provided some excellent photos of recent soybean seedling damage.

  

I don't have much experience with seedcorn maggot, so I extracted some biology and management recommendations from our former extension entomologist, Marlin Rice. Female seedcorn maggots (true flies) deposit eggs in the soil and larvae feed on organic residue. Decaying organic matter, like manure, is especially attractive to females. Larvae overwinter and will complete development in the spring. First generation larvae will feed on germinating seeds and seedlings, and can possibly kill the plant. Several generations are possible in Iowa, but generally are not an economic concern after stand establishment.  

If you suspect seedcorn maggot, carefully dig in the seed furrow and look for evidence. You may not find any maggots, but could see a few feeding scars, tunneling in the seed or stem, or the entire seed destroyed. But the same type of damage could be caused by wireworms, grubs or cutworms. 

Rescue treatments for seedcorn maggot do not exist. Areas with persistent populations should consider using an insecticidal seed treatment to protect corn and soybean fields the following year. Seed treatments are encouraged when planting into cool, wet soils with manure applications. 

It's alive!!

It's been a long time since my last post! But it's ALIVE again...

This cool and very wet spring had impacted planting progress and insect development. So the usual field crop suspects haven't started to show up and are especially behind the 2012 emergence schedule. Some of the questions popping up lately have been with soil-dwelling insects and saturated soils. My general thought on this is that eggs can survive in wet soil, but larvae can't for too long. So if they are small and not very mobile (like corn rootworm larvae), they will probably suffocate. Good news if you like to grow corn!

Cool wet growing conditions in May and June do favor slugs. I wrote up a recent ICM News article today about managing these early-season beasts. Unfortunately, no-till or minimal tillage practices are conducive to slug populations.

Slugs can destroy corn and soybean seedlings. Photo by Brian Lang, ISU.

I will try to post more regular updates about other emerging pest activity. Send some of your observations and pictures my way. Thanks for your continued interest in my blog!