Pest & Crop Newsletter

Hessian Fly Infestation Should be Monitored This Fall Even Though Populations Remained Low in Indiana Wheat in 2002- (Sue Cambron)

Hessian fly infestation was low in wheat trials sampled in Indiana in 2002, however, precautions should be taken to minimize the establishment of the fly in plantings this fall. The Hessian fly is present in wheat-growing areas throughout Indiana and often survives, although in lower numbers, in wheat stubble or grasses during the summer. However, there is potential for rapid increase of fly populations as a result of weather conditions or cropping practices that favor survival of eggs and young larvae in the fall.

Insecticidal control of the fly once infestation has occurred is poor, and generally not economically feasible. Management practices that prevent or delay build-up of fly populations, such as planting of resistant varieties and seeding after the fly-free date, provide the most cost effective means of control for wheat growers.

Much of the fall fly population can be avoided by planting after the fly-free date. This is key to avoiding subsequent infestation by the spring brood. Additionally, it has been shown that following the fly-free date will help reduce wheat disease problems and reduce winter kill from excessive growth. To determine the fly-free date for your area of the state, refer to the following map. Crop rotation, where wheat following wheat is avoided, also is one of the key management strategies for reducing Hessian fly problems. The Hessian fly passes the summer in the stubble of the current wheat crop. Plowing the stubble results in the destruction of the pest. Volunteer wheat, the wheat seedlings sprouting in the fall from grain left in the field during threshing, germinates and begins growing just in time for the fall emergence of the Hessian fly. These plants are readily infested resulting in a rapid build-up of the population. The use of resistant varieties, in combination with the above pest management strategies, increases the chance for a fly-free crop.

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Barley Yellow Dwarf Virus Infection at a Record Level High in Indiana Small Grains in 2002– (Sue Cambron)

Barley Yellow Dwarf Virus infection, which is vectored by aphids, was at a 20 year high during the 2001-2002 growing season. The mild fall led to a high aphid population, and a longer time for feeding and transmission of the virus. There are few oat or wheat cultivars that offer good resistance to the virus.

Specific characteristics and yield potential of varieties presently grown in Indiana can be determined by consulting Purdue Station Bulletin “Performance of Public and Private Small Grains in Indiana - 2000”, web access: <http://shawdow.agry.purdue.edu/agronomy/ext/smgrain/variety/sm~var.htm> or talk to your seed dealer.

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Rootworm Beetles Late in the Season– (John Obermeyer, Rich Edwards, and Larry Bledsoe)

Western Corn Rootworm Feeding on Weed Pollen

Astute pest managers are still reporting some very large numbers of western corn rootworm beetles in various crop and non-crop situations. This may have to do with the late growing season, as the western corn rootworm beetle variant initiated its movement between corn and soybean about two weeks later this year. These reports of late-season activity are mainly coming from areas where large numbers of beetles were seen in corn during pollination.

The potential impact of beetle infestations in September and early October is not known. However, it is expected that while alive, beetles will continue to lay additional eggs. In years past, it has been noted by many producers in west central and northwestern Indiana counties that beetles have been all over the combine while harvesting soybean fields. Why hoards of beetles would be in mature, weed-free soybean fields is a mystery, as there is no green plant material to feed on. Should you experience this phenomena in your area, we would appreciate you calling and providing the following: 1) positive rootworm beetle identification, 2) presence (species) or absence of weeds, 3) approximate distance from corn, and 4) intensity of beetles (number covering a square foot area on a combine). Please call 765-494-4563. If you get voicemail, please leave the requested information, as well as your name, business, location, and phone number.

In areas where large numbers of western corn rootworm beetles are still active, the potential for larval damage in next year’s corn exists. Crop, or non-crop areas, where green plants (e.g., forages, weeds, vegetables, etc.) are present and where corn will be planted in 2003, should be monitored now for rootworm beetles.

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Black Light Trap Catch Report

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Soybean Sudden Death Syndrome- (Gregory Shaner)

Over the past couple of weeks, more and more soybean fields in Indiana have shown symptoms of sudden death syndrome (SDS). Affected areas may be extensive in a field, or confined to a few patches. The disease is most likely to show up earlier and be more severe in compacted areas. With the planting problems this spring, compaction is a greater problem than normal, and this has probably contributed to the widespread outbreak of SDS. Often the areas of SDS run parallel to the edge of a field and in about 30 ft. These are likely areas that are compacted because of extra traffic in the field.

The late appearance of symptoms would not normally be cause for concern about yield and quality of the crop, but because of the later than normal development of soybeans this year, there may be significant yield damage in affected areas of a field. Plants affected after pods are well developed may produce small seed.

I have not been able to conduct a survey of sudden death syndrome throughout the state, but it appears that the disease is more severe in northern and central Indiana, in areas that received heavy rains sometime during early grain filling.

Growers should make note of which fields show SDS and map the locations of affected areas. This can be useful information for future planting decisions in those fields. Where SDS is a problem, growers should avoid early planting of soybeans and use a variety with some resistance to the disease. It’s also a good idea to make note of varieties that show severe symptoms of SDS, even if this is only in a few isolated patches in a field. Susceptible varieties should be avoided when planting a field that has any history of the disease.

It is more difficult to identify resistant varieties. If one field, planted with a particular variety, has SDS, but a nearby field, planted with another variety, has little or no SDS, one cannot necessarily conclude that the second variety is resistant. Planting date and field history have a strong influence on disease severity.

The best way to determine if a variety has resistance is to test it in replicated yield trials in several locations and years under severe and uniform SDS pressure. Scott Abney, with the USDA-ARS at Purdue, has been conducting such tests for several years and has identified several varieties that have a useful degree of resistance.

More information about sudden death syndrome of soybean can be found at <http://www.btny.purdue.edu/Extension/Pathology/CropDiseases/Soybean
Soybean.html#suddendeathsyndrome> or in Purdue extension publication BP-58 Sudden Death Syndrome in Soybeans.

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Preharvest Assessment of Indiana Corn Crop- (Charles Woloshuk)

There is great concern about this year’s corn crop.  We have experienced delayed planting and endured many days with temperatures above 90 degrees and rainfall below normal.  I am starting to hear reports of aflatoxin contamination occurring in some areas of Illinois.  So what is the situation in Indiana?

Every year I assess the corn crop in two ways, road trips and a statewide survey.  Looking at the corn near West Lafayette, I have found no need for concern about mycotoxins.  Last week, I made road trips to as far south as Posey County and to as far east as Adams County.  On my trip south, I stopped at a number of fields between Terre Haute and just south of Sullivan.  I found no more than normal amounts, which is very little, of ear/kernel rots that are frequently associated with mycotoxins.  In the area around Vincennes, I found fields with severe drought stress that had ears infected with the aflatoxin-producing fungus, Aspergillus flavus.  The affected corn crop appeared scorched and the ears were only about 3 inches long.  Finding Aspergillus ear rot in this area is no surprise, because the sandy soils increase the potential for drought stress, one factor making the plants more susceptible to the disease.  In fields starting north of Princeton, going east of Princeton, south to Poseyville and to just north of Mt. Vernon, I was not able to find any evidence of Aspergillus flavus infections or evidence of higher than normal ear/kernel rot. 

A second road trip began in Carroll County north of Delphi, passing to the south of Logansport and Peru, north of Marion, across northern Blackford County, up into Bluffton in Wells County, and then back to West Lafayette along Highway 26 from Portland.  The corn was still green along this route and much farther from maturity than that in southern Indiana.  We did not detect much ear/kernel rot.  Many fields in Wells, Adams, and Jay Counties had extremely stunted plants.  To my surprise, we could not find any evidence of Aspergillus flavus. 

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