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I am a field crop extension entomologist at Iowa State University. This blog provides real-time updates on field crop insect IPM.
Updated: 37 min 19 sec ago

Bee yard visit and maybe the best day of the summer

Mon, 08/04/2014 - 15:51
Today my post-doc, Thelma, and I got to go on an adventure and visit a honey bee yard. It's maybe a little embarrassing to say it was my first time seeing hives, maybe because you would assume entomologists get to see this stuff all the time. Well, not so much for this field crop bug girl. I did have a tiny bit of anxiety about the visit. Random questions to myself before the trip...

First thought: Am I going to freak out with all the buzzing and swarming? I imagined a deafening sound of a thousand bees landing on me and not sure if that was going to send me running back to the car.

Second thought: Am I going to get stung and by how many bees? Note: I hate being bit by mosquitoes, ticks or anything, really. My last bee sting swelled up substantially and I wasn't looking forward to a puffy welt.

Third thought: Am I going to get really sticky? I just had an idea of a bee hive being messy with dripping honey everywhere. Not sure why? Note: I don't really like to be covered with sugar.

Fourth thought: Am I going to sound like an idiot? I know I don't know anything about honey bees, but was very curious. Would I sound and look like a moron? You decide on my look!

Bee suits aren't very flattering, but I felt protected with the cool head gear!
Thelma and I arranged this meeting with Andy Joseph (IDALS State Apiculturist) and Robin Pruisner (IDALS State Entomologist). They took some time off from their usual jobs to look at a few hives east of Ankeny and talk about honey bees. They both personally own honey bees and have a lot of practical experience raising successful bees in Iowa.

The colorful boxes hold honey bee colonies. Each tower has it's own queen, workers, and drones.
Andy and Robin showed us various stages of brood and honey production. Rearing healthy and productive honey bees takes a lot of work. Plus it's like they were using another language to describe the process (my entomological background was only mildly helpful). It was also apparent that a beekeeper needs a bunch of specialized tools! The buzzing was surprisingly not bad. I didn't feel like they were out to get me, even though we were popping open "supers" and looking at their babies and potentially taking their food.

Andy lightly smokes the super before pulling out the frames. I almost sound like I know what I am talking about!
Andy typically only wears the hat with mesh veil. Obviously, he's been working with bees for a long time!
An example of a nicely progressing frame. The queen should start laying eggs in the middle and work her way around. Note the capped cells in the middle and pure honey in the upper right corner. 
They seemed to know right away if the bees were making the right pattern. It wasn't as obvious to an untrained eye. Some frames were very organized and others looked like they were created by bees with ADHD. We got to taste some honey straight from the hive. Woot! I am now officially a honey snob and I never EVER want to buy honey from a store again. 
Worker bees forage on pollen and nectar for the colony. Once their bellies are full, they pack extra pollen on their hind legs. Note the bright, yellow pollen balls on these ladies!
Entrance hole for foraging bees. Workers live for a few weeks after emerging from capped cells. 
Final thoughts: didn't freak out, didn't get stung, it wasn't sticky and I only kinda sounded ignorant. Overall, a great experience! I can't wait to visit again, perhaps during the honey extraction for an extra tasty adventure!

Maggots and armyworms

Wed, 06/11/2014 - 10:08
It is that time of year when I hear about maggots and armyworms in field crops. At least that means people are out there looking for insects! I don't always get great photos of the insect activity or injury, but this week is the exception. Keep 'em coming, everyone!

Brian Lang, ISU Field Agronomist in northeast Iowa, has already found a soybean aphid (actually he almost always finds the first ones every year) AND he found a few prevent plant fields with seed corn maggot in soybean. He seemed to notice more plant feeding in fields that were planted to oats last year compared to radish. He also noted it was a field with mostly naked soybean seed (no insecticidal seed treatment).


Seedcorn maggot and pupae at the base of an emerging soybean plant. Photos by Brian Lang, ISU. 
Tom Hillyer, a crop consultant in Iowa, always sends me interesting photos. He manages to stump me on a regular basis with insect identification. But his recent photos included some developed armyworms feeding on corn. He also found a few bean leaf beetle on soybean despite my earlier prediction for high mortality this year. 
Yellowstriped armyworm. Photo by Tom Hillyer.
Armyworm. Photo by Tom Hillyer.
Bean leaf beetle. Photo by Tom Hillyer. 

Did this winter kill all the corn rootworm eggs?

Wed, 06/04/2014 - 14:52
Insect mortality happens every winter, even under ideal conditions. However, this winter was the 9th coldest in 121 years and I’ve been getting questions about how the harsh conditions may have impacted overwintering corn rootworm eggs. Maybe we don’t need to care rootworms this year if all the eggs froze to death? We’re probably not so lucky. Many factors besides cold air temperatures influence successful overwintering of insects in Iowa, including our most important field crop pest.
Cold temperatures can kill rootworm eggs; temperatures below 18.5°F can be lethal to eggs (Woodson and Gustin 1993). We know the eggs are deposited into soil cracks and crevices and are somewhat protected to air temperatures. Mike Gray (University of Illinois) provided a nice blog summary of research involving soil temperatures, egg depth and survivorship. To see how cold it really was this winter, I was able to extract a graph showing soil temperatures at three depths near Ames (1 November 2013 – 1 May 2014). There were several dates where the temperature was cold enough to kill eggs in the top 12ʺ of the soil in central Iowa and likely other places throughout the state. 

Soil temperature data courtesy of Iowa Environmental Mesonet, ISU Department of Agronomy.
Egg deposition is highly variable within and between species, but in general eggs have a better chance of surviving if they are placed deeper in the soil. Western corn rootworms tend to lay most eggs 4-8ʺ below the soil surface, compared to northern corn rootworms that tend to lay most eggs in the top 4ʺ (Gray and Tollefson 1988). So the odds are in favor of more westerns surviving the winter just because of where females put the eggs.
Crop residue and snow cover can significantly improve egg survivorship (Godfrey et al. 1995). However, just how much residue/snow cover is needed is not fully understood. Tillage and tillage timing does not significantly reduce egg populations (Gray and Tollefson 1988). Soil texture did not appear to influence egg mortality in a Nebraska study (Godfrey et al. 1995).
Saturated soils do not kill corn rootworm eggs, but they can negatively impact larvae. When soil is saturated, oxygen can be limited and cause suffocation. About 50% of third instar western corn rootworm larvae die in saturated soils after 24 hours (77°F); survivorship is increased in saturated soil with decreasing temperatures (Hoback et al. 2002). So later this summer, saturated soils could reduce larval populations but don’t count on it for eggs.
The bottom line is all these factors had some impact on overwintering egg mortality. There was probably more egg death this winter compared to more normal winter temperatures. I do think some corn rootworm eggs survived in Iowa. In a recent ICM News article, I estimated corn rootworm egg hatch is happening now if they survived. This prediction is solely based on growing degree days in the soil. Research has demonstrated about 50% of the eggs hatch when they accumulate 684-767 degrees (base 52°F, soil). It makes sense that egg hatch starts in southern Iowa every year, with the average hatching date for the state around 6 June. Predicted egg hatch is important because larvae will feed on corn roots for about 3 weeks. I encourage everyone to assess corn root injury as larvae finish feeding. Remember, one node of injured roots means a 15% yield loss (Tinsley et al. 2012). It's called the billion dollar pest for a reason!

Map data courtesy of Iowa Environmental Mesonet, ISU Department of Agronomy.
ReferencesGodfrey, L.D., L.J. Meinke, R.J. Wright, and G.L. Hein. 1995. Environmental and edaphic effects on western corn rootworm overwintering egg survival. Journal of Economic Entomology 88: 1445-1454.
Gray, M.E., and J.J. Tollefson. 1988. Influence of tillage systems on egg populations of western and northern corn rootworms. Journal of the Kansas Entomological Society 61: 186-194.
Hoback, W.W., T.L. Clark, L.J. Meinke, L.G. Higley, and J.M. Scalzitti. 2002. Immersion survival differs among three Diabrotica species. Entomologia Experimentalis et Applicata 105: 29-34.
Tinsley, N.A., R.E. Estes, and M.E. Gray. 2012. Validation of a nested error component model to estimate damage caused by corn rootworm larvae. Journal of Applied Entomology 137: 161-169.
Woodson, W.D., and R.D. Gustin. 1993. Low temperature effects on hatch of western corn rootworm eggs. Journal of the Kansas Entomological Society 66: 104-107.