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2006

Iowa State University

Agricultural Science

Series

Entomology

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Aphids In The Air: What Is The Risk For 2007?, Wayne Ohnesorg, Matthew E. O'Neal, Marlin E. Rice Dec 2006

Aphids In The Air: What Is The Risk For 2007?, Wayne Ohnesorg, Matthew E. O'Neal, Marlin E. Rice

Integrated Crop Management News

The 2006 growing season has come to a close and with it another year's worth of experience with the soybean aphid. For many, it was a quiet, "low aphid" year with few reports of economic outbreaks within Iowa. Reflecting these low populations in the field, we observed fewer aphids within our suction traps (Figure 1) compared to the 2005 growing season when the traps collected nearly 100 times more aphids (Figure 2). For the last two years, the Iowa suction trap network (Figure 3) has been part of a larger network of suction traps located in nine states throughout ...


Bt Rootworm Corn Failures: Understanding The Issues, Jon J. Tollefson, Marlin E. Rice Nov 2006

Bt Rootworm Corn Failures: Understanding The Issues, Jon J. Tollefson, Marlin E. Rice

Integrated Crop Management News

Genetically engineered corn that produces a Bt toxin effective against corn rootworms is now readily available and was widely planted in Iowa during 2006. Several seed companies have registrations, or will have shortly, and they will add additional Bt events and varieties to the choices for corn rootworm management. Does that mean that our corn rootworm management decisions are over, and we don't have to worry about rootworm injury? No. Bt corn rootworm hybrids are another insect management tool that must be thoughtfully incorporated into corn production practices.


A Roller Coaster Season, Richard O. Pope Sep 2006

A Roller Coaster Season, Richard O. Pope

Integrated Crop Management News

Like most years for Iowa farmers, 2006 was a weather roller coaster ride. The graph shows the weekly departure from 30-year average degree day accumulations from May through September. One way to read the chart is to consider a 1- to 3-week time period and look at the slope of a line at that time. If it was warmer than normal, the line rises; if cooler than normal, the line falls; and if the weather is at the average, it will neither rise nor fall.


Sudden Death Syndrome Prevalent This Summer, X. B. Yang Sep 2006

Sudden Death Syndrome Prevalent This Summer, X. B. Yang

Integrated Crop Management News

As the summer ended, sudden death syndrome (SDS) of soybean has been found in many fields in Iowa. Widespread infestation has been reported by producers and agronomists in eastern and central Iowa, and the disease also has been found in western Iowa. This year, the disease showed up in early July with many reports before the first week of July. Cooler temperatures this summer may have contributed to its occurrence. In central Iowa, the incidence of infested fields is high, but the severity is not. In most fields where SDS is spotted, the disease occurs in small areas with limited ...


August Angst, Richard O. Pope Aug 2006

August Angst, Richard O. Pope

Integrated Crop Management News

August 2006 began where the rest of the season left off, warm and fairly dry. Sporadic thundershowers were the rule, with considerable local variation in rainfall. A storm system rolled through northwest and north-central Iowa, dropping 4 to 5 inches of rain in some areas. However, straight-line winds leveled corn and some soybeans in a narrow band from Plymouth to Dickinson County. Rain concerns continue in nearly all parts of Iowa. Aphid populations can be found in nearly all counties, but to date the only populations nearing threshold are located along the border with Minnesota.


Bean Pod Mottle Virus: Back With A Vengeance, John H. Hill, Palle Pedersen, Jeffrey D. Bradshaw Aug 2006

Bean Pod Mottle Virus: Back With A Vengeance, John H. Hill, Palle Pedersen, Jeffrey D. Bradshaw

Integrated Crop Management News

As stated in an earlier article in the ICM Newsletter (May 15, 2006), bean leaf beetles are back with a vengeance this year. Based on observations from agronomists across the state, this year seems to have the highest level of bean leaf beetles since 2002. This also has resulted in an apparent high incidence of bean pod mottle virus disease in Iowa fields. Infected plants can be characterized by the leaves, which show a yellow to green blotchy appearance called leaf mottle. Sometimes leaves have a raised or blistered appearance.


The Heat (Has Been) On!, Richard O. Pope Jul 2006

The Heat (Has Been) On!, Richard O. Pope

Integrated Crop Management News

It should come as no surprise that the week of July 23 was a hot one in all of Iowa. We effectively gained an extra day and a half of heat compared with long-term averages in all parts of Iowa. Mind you that as corn and soybean are in the fill stage, degree days themselves aren't as important as they were in the leadup to pollination. Now we look at stresses on plants, and we do have variable moisture and accompanying heat stress in many parts of Iowa.


Spider Mites, Soybean Aphids, And Summer Temperature, Marlin E. Rice Jul 2006

Spider Mites, Soybean Aphids, And Summer Temperature, Marlin E. Rice

Integrated Crop Management News

Temperatures in the high 90s and low 100s have prompted questions about how this will affect pests in soybeans. Spider mites typically flourish in hot, dry weather. Fungal pathogens that suppress spider mites during high humidity and mild temperatures are less effective against mites during very dry and hot conditions. Therefore, spider mites may be a greater concern this year during early August than soybean aphids.


Location, Location, Location!, Richard O. Pope Jul 2006

Location, Location, Location!, Richard O. Pope

Integrated Crop Management News

The biggest factor determining the crop condition in late July is not a new one. If your location has caught some of the sporadic rainfall in the past month, you are likely in reasonable shape. If not, your crops are beginning to struggle. The driest areas in terms of rainfall deficit from normal since May 1 are northwest, west-central and south-central, which are all around 50 percent of normal rainfall. That said, corn and soybean both are hanging in pretty well, and late July and August rainfall will work wonders--if and when it comes.


Soybean Aphids Down In July, Marlin E. Rice Jul 2006

Soybean Aphids Down In July, Marlin E. Rice

Integrated Crop Management News

Reports from extension field crops specialists across Iowa on July 24 indicate that soybean aphids have not reached the economic threshold of 250 aphids per plant in most fields. Soybean aphids can be found, but it appears that overall the populations range from just a few aphids per plant up to 30-50 per plant. There was a report of several fields being sprayed in northwest Iowa near Emmetsburg, but no aphid counts were given for these fields so the population size relative to the economic threshold is unknown.


Rotation-Resistant Corn Rootworms In Iowa, Patricia L. Prasifka, Jon J. Tollefson, Marlin E. Rice Jul 2006

Rotation-Resistant Corn Rootworms In Iowa, Patricia L. Prasifka, Jon J. Tollefson, Marlin E. Rice

Integrated Crop Management News

There are variants of both corn rootworm species in Iowa that are resistant to crop rotation. The northern corn rootworm overcame the annual rotation of corn with another crop by developing a two-year life cycle. This variety of the northern corn rootworm (known as extended diapause) became common and caused extensive damage to rotated corn in the late 1980s in northwest Iowa. Since then it has spread throughout Iowa and is probably found in every county.


These Are The Dog Days, Richard O. Pope Jul 2006

These Are The Dog Days, Richard O. Pope

Integrated Crop Management News

The traditional dog days of summer roughly range from July 4 through about August 10. Although they were named for the time when the dog star, Sirius, rose with the sun, dog days for us is the time when row crops are pollinating and the first half of grain fill. The week starting July 10 was about average in degree day accumulation, and especially in the southern two-thirds of Iowa, some welcome rain fell. Moisture remains a concern, but the week's rainfall coincided with pollination, which is a very good thing.


Protect Pollinating Bees From Pesticides, Chuck Eckermann, Joyce Hornstein Jul 2006

Protect Pollinating Bees From Pesticides, Chuck Eckermann, Joyce Hornstein

Integrated Crop Management News

A pesticide applicator is required to notify all owners of registered beeyards (apiaries) within a 2-mile radius of the site of application if the pesticide is labeled as "toxic to bees." Notification is required at least 24 hours and no more than 72 hours before the application. This enables beekeepers to move or otherwise protect their bees from harm. This notification is required by the Iowa Administrative Code rule IAC 21-45.31(206).


Mite Watch 2006, Carol Pilcher, Richard O. Pope Jul 2006

Mite Watch 2006, Carol Pilcher, Richard O. Pope

Integrated Crop Management News

Whenever hot, dry weather persists, spider mite populations may develop on both corn and soybean. Twospotted spider mites, Tetranychus urticae, are serious pests of many crops throughout the United States. Producers in areas of Iowa where the weather remains dry should be on the lookout for spider mite infestations.


July Picks Up Where June Left Off, Richard O. Pope Jul 2006

July Picks Up Where June Left Off, Richard O. Pope

Integrated Crop Management News

The first week of July was slightly cooler than normal statewide, and again, unfortunately, drier than normal. Corn is starting to tassel across Iowa, and moisture stress is a growing concern. Fortunately, crop breeding has provided us with varieties with improved drought tolerance; however, that only works to a point. Monitoring for pests is important, and grasshoppers and spider mites are two key insects to watch for.


Western Bean Cutworm In 2006, Richard O. Pope, Marlin E. Rice Jul 2006

Western Bean Cutworm In 2006, Richard O. Pope, Marlin E. Rice

Integrated Crop Management News

A network of pheromone traps has been placed throughout the state to assist in scouting efforts for western bean cutworm. Iowa State University Extension is cooperating with Pioneer Hi-Bred agronomists to survey for western bean cutworm emergence. Most traps are now in place and results are being posted on a western bean cutworm website. Traps cannot be used to predict which fields should be sprayed; rather, they can indicate those areas that have significant moth flights and where fields should be scouted.


Fungicides: Safety And Restrictions, Daren S. Mueller, Joyce Hornstein Jul 2006

Fungicides: Safety And Restrictions, Daren S. Mueller, Joyce Hornstein

Integrated Crop Management News

Reading through a pesticide label will give you most of the needed information concerning safety for both yourself and others while spraying field crops. Below is a synopsis of some of the dangers and restrictions for some common fungicides. For details on a specific fungicide, please follow the label's directions for mixing and application along with the instructions for safe use.


Rain, Rain, Come Again!, Richard O. Pope Jul 2006

Rain, Rain, Come Again!, Richard O. Pope

Integrated Crop Management News

July fires off with soybeans flowering and corn starting to work on tassels in most of Iowa. Crops are mostly in good condition, but additional rainfall would help now, especially as flowering and seed set progresses. Since May 1, all parts of Iowa are below normal rainfall, with northeast Iowa down by only about 11/2", and north-central, central, south-central and west-central Iowa with over 4" of rain deficit. Northwest and southwest are seasonally around -3".


Warm And Dry, Richard O. Pope Jun 2006

Warm And Dry, Richard O. Pope

Integrated Crop Management News

June is finishing as it started--slightly warmer than average--so we have gained heat on the season and are drier than usual. The extra warmth has led to relatively rapid crop growth and also rapid development of some pests. For example, western bean cutworm emergence is about 10 days to 2 weeks earlier than usual, so if you are cooperating in the pheromone trapping program with ISU, please set up your traps as soon as possible!


Western Bean Cutworm Flight Starts--Early!, Marlin E. Rice Jun 2006

Western Bean Cutworm Flight Starts--Early!, Marlin E. Rice

Integrated Crop Management News

Adult western bean cutworms were first collected at two locations in Iowa on June 23--the earliest date they have ever been collected in the state. Single adults were captured in blacklight traps near Correctionville (Woodbury County) in western Iowa and Ames (Story County) in central Iowa. A blacklight trap in Boone County captured 19 adults on June 26. A historical look of western bean cutworm captures for Woodbury County is shown in the table.


Soybean Aphids Scattered Across Iowa, Marlin E. Rice, Matthew E. O'Neal Jun 2006

Soybean Aphids Scattered Across Iowa, Marlin E. Rice, Matthew E. O'Neal

Integrated Crop Management News

Soybean aphid populations remain at low densities in monitored fields across the state, but the known distribution for 2006 now covers most of Iowa. On June 19, Extension field crops specialists reported soybean aphids from northeastern (Allamakee, Clayton, Winneshiek counties), southeastern (Lee County), central (Story County), and northwestern Iowa (Cherokee County). Aphid densities were less than one aphid per plant in all counties. In the June 5 newsletter, we reported an aphid colony containing 40 insects, but two weeks later when 80 plants were inspected in the same field, only a single plant was found with only four aphids on ...


Summer "Officially" Arrives!, Richard O. Pope Jun 2006

Summer "Officially" Arrives!, Richard O. Pope

Integrated Crop Management News

Summer arrives on June 21, but the below-normal rainfall and mostly above-normal temperatures have been with us since the finish of planting. The week of June 12 was slightly above long-term averages in degree day accumulations, marking the third consecutive warm week. Row crops are in generally good condition across Iowa, but questions about the growing deficit in topsoil moisture are common. We have lost little yield potential so far, even though corn has rolled in the afternoon in scattered areas. Ample subsoil moisture is working like a moisture bank now that crop roots are rapidly growing. As we near ...


Field Days: Summer Opportunities, Richard O. Pope Jun 2006

Field Days: Summer Opportunities, Richard O. Pope

Integrated Crop Management News

Iowa State University Research and Demonstration Farms will host 14 field days through September. A wide variety of topics related to crops and livestock will be covered. The schedule and topics for the summer and fall field days are listed below; they will take place rain or shine. The public is welcome. Program information for summer field days is subject to change. The information also is available at www.ag.iastate.edu/farms/fielddays.html [2].


A Dry Beginning, Richard O. Pope Jun 2006

A Dry Beginning, Richard O. Pope

Integrated Crop Management News

This week finds Iowa just slightly above the seasonal average in degree day accumulations. The lack of rainfall in many parts of Iowa has been a recent topic of discussion. Posted here are the precipitation deficits by crop reporting district from May 1 through June 11. With the exception of northeast and east central Iowa, it has been a dry start to the growing season. The question, "how critical are the current deficits to the growing crop?" is best answered, "it depends."


Grape Colaspis Damage Occurring In Central Iowa, Benjamin Kaeb, Jon J. Tollefson Jun 2006

Grape Colaspis Damage Occurring In Central Iowa, Benjamin Kaeb, Jon J. Tollefson

Integrated Crop Management News

With the dry weather over parts of the state, grape colaspis feeding has manifested itself as visible injury to corn (stunting, wilting, and discoloration). Without rain, the injury may result in stand loss in seed corn fields in central Iowa. The actual population of grape colaspis larvae does not appear to be higher than those observed in previous years. The lack of moisture is probably the factor that has allowed the symptoms to appear.


Corn Rootworm Larvae Are Actively Feeding On Your Corn, Jon J. Tollefson, Marlin E. Rice Jun 2006

Corn Rootworm Larvae Are Actively Feeding On Your Corn, Jon J. Tollefson, Marlin E. Rice

Integrated Crop Management News

We often use a general rule that "corn rootworm eggs hatch on June 6." On June 7, Jim Oleson, agricultural specialist, Department of Entomology, dug corn plants from our research plots and placed them in Fromm funnels to extract corn rootworm larvae from the soil. The funnels are made of plastic drink cups and fiberglass window screen that hold the plants and soil over water as they dry. As the samples dry, larvae crawl out and fall into the water below. This facilitates the collection of very small, newly hatched larvae. If you would like more information on how to ...


Soybean Aphid Look-Alikes; Don't Be Confused By Alternatives, Matthew E. O'Neal, Marlin E. Rice Jun 2006

Soybean Aphid Look-Alikes; Don't Be Confused By Alternatives, Matthew E. O'Neal, Marlin E. Rice

Integrated Crop Management News

In last week's newsletter, we reported finding low densities of soybean aphids during late May in Story County. Since then, aphids also have been found in northeastern Iowa, near Decorah, by Brian Lang, extension field crops specialist. It is too early to tell if these early reports will develop into populations that will increase to the economic threshold (80 percent of plants infested and the average number per plant at 250 and rising).


Another Warm One..., Richard O. Pope Jun 2006

Another Warm One..., Richard O. Pope

Integrated Crop Management News

A second consecutive warm week means that we are now slightly above normal in heat accumulation across Iowa. Rainfall has been spotty, which is not surprising. Corn is mostly V4 to V6, with some to V8 in southern counties, and soybean is mostly VC to V2 across the state.


First Soybean Aphids Found In May, Marlin E. Rice, Matthew E. O'Neal Jun 2006

First Soybean Aphids Found In May, Marlin E. Rice, Matthew E. O'Neal

Integrated Crop Management News

Our first official sighting of soybean aphids occurred in soybeans on May 31 near Ames in Story County. Students in the Soybean Entomology Research Laboratory found several winged aphids and a few colonies on V3-stage soybeans. One colony had about 40 aphids, indicating that the aphids had probably been there for about a week. The following day, soybeans were inspected at McNay Research and Demonstration Farm, Lucas County, and Northeast Research and Demonstration Farm, Floyd County, but no soybean aphids were found in those research plots.


Ahhhh, Warmth!, Richard O. Pope May 2006

Ahhhh, Warmth!, Richard O. Pope

Integrated Crop Management News

A warm week provided much-welcomed heat for Iowa's crops. Seasonal degree-day deficits largely evaporated over the 7 days from around 50 degree days behind last week to close to average statewide. However, moisture deficits are noted in some areas as well. Sporadic showers over the Memorial Day weekend were welcome, but some localities would welcome additional rain for growing crops.