Volume 15, Issue 23 August 31, 2007




Vegetable Crop Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu



We continue to find economic levels of beet armyworm, cabbage looper, and diamond back moth larvae and harlequin bugs. Be sure to apply treatments before larvae move deep into the hearts of plants.


Lima Beans

With the continued heavy moth flight, continue to sample fields for corn earworm. Higher rates will be needed if population levels are high and worms are large at the time of treatment. As trap catches continue to increase, multiple treatments may be needed for earworm control. At this time of year, we have also found soybean loopers in lima bean fields. If soybean loopers become a problem again this year, remember that they are a migratory pest, difficult to control and pyrethroid resistance has been documented in states to our south. Therefore, you will need to consider an application of Lannate LV at the higher rate for soybean looper control. The following is the link to the Lannate label (http://www.cdms.net/LDat/ld183006.pdf) be sure check the label for rates and days from last application to harvest.



In areas where corn borers are being caught in local traps, fields should be sprayed on a 7-day schedule for corn borer control. In areas where corn borer catches are above 10 per night, a 5 to 7-day schedule may be needed. Since trap catches can increase quickly at this time of year, be sure to check local moth catches in your area at http://ag.udel.edu/extension/IPM/traps/latestblt.html. With the continued high corn earworm pressure, you will also need to watch for corn earworms infesting peppers. Be sure to select a material that will control corn borers and corn earworm as well as beet armyworm if they are present.


Snap Beans

At this time, you will need to consider treatments for both corn borer and corn earworm from the bud stage through harvest on processing snap beans. After the pin sprays, you will need to check our website for the most recent trap catches to help decide on the spray interval between the pin stage and harvest for processing snap beans (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/snapbeanecbthresh.html). The highest labeled rates of insecticides may be needed if population pressure is heavy in your area. Remember, Orthene will not provide effective earworm control. Be sure to scout fields at least twice a week for corn earworm to be sure that a tighter schedule is not needed between the pin spray and harvest. Once pins are present on fresh market snap beans, a 5 to 7-day schedule should be considered for corn borer and corn earworm control.



Be sure to watch for both webworms and beet armyworm moths as soon as plants emerge. Controls should be applied when worms are small and before they have moved deep into the hearts of the plants or produced webbing. Remember that both insects can produce webbing on the plants. Generally, at least 2 applications may be needed to achieve control of webworms and beet armyworm. If both species are present, Intrepid or Confirm are labeled for both species.


Sweet Corn

With the high corn earworm catches throughout the state, all fresh market silking sweet corn should be sprayed on a 2-day schedule.



Cucurbit Downy Mildew Update Bob Mulrooney; Extension Plant Pathologist; bobmul@udel.edu


The forecast for downy mildew transport and survival on cucurbits is moderate for Friday and low risk from Saturday through Monday. Preventative fungicide applications should be continued. We saw a dramatic increase in downy mildew in our unsprayed fungicide trial plots in the last week.



Downy Mildew on Pumpkin Kate Everts; Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu


Downy mildew has been confirmed on pumpkin near Salisbury, MD. Although downy mildew has been a problem in cucumbers for over a month, this is the first confirmed occurrence of downy mildew on another cucurbit. Now that downy mildew is on pumpkin, fungicides targeted specifically for downy mildew should be applied in addition to the general spray program for other pumpkin diseases. (Remember that powdery mildew is present at high levels, so also protect plants for that disease.) Fungicides that have performed well in fungicide trials around the region on downy mildew include Ranman, Previcur Flex, Curzate and Tanos.


Tank mix one of the following products with a protectant such as chlorothalonil:

Ranman 2.1 2.75 fl oz (FRAC 21)

Previcur Flex 1.2 pt (FRAC 28)

Curzate 3.2 oz (FRAC 27)

Tanos 8 oz (FRAC 11 + 27)


Fungicide sprays should be applied on a 7-day schedule and materials with different FRAC codes (fungicide resistance code) should be alternated.



Agronomic Crops


Agronomic Crop Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu



Be sure to watch for defoliators, including corn earworm, armyworms and webworms. Economic levels can be found and controls should be applied before significant defoliation occurs. Defoliators can be destructive in last cuttings, especially during drought conditions. When defoliators are present, early harvest may eliminate the problem. Although there are no specific thresholds, as a general guideline if the crop is more than 2 weeks from cutting and 25 to 30 percent of the terminals are damaged, treatment is suggested.


Grass Hay Fields

We have received a report of economic levels of true armyworm in a few fields in Kent County. Be sure to watch for larval feeding which can quickly defoliate an entire field. Earlier this summer, Mustang MAX received a label on grass forage, fodder and hay. Please see the label for the grasses included, rates, days to harvest after application and other restrictions (http://www.cdms.net/LDat/ld67J028.pdf).



Corn earworm populations remain high in Sussex County (well above threshold in many fields) and economic levels can be found in fields throughout the state. Economic levels continue to be found in both double crop fields as well as full season fields, especially ones that were drought stressed. Although open canopy blooming fields will be the most attractive to egg laying moths you should check all fields to be sure you do not miss an infestation. In many cases, a field right next to a heavily infested field will not have economic infestations. In addition, like with all insects, population levels will vary within a field so you need to do a representative sample so that you do not under estimate or over estimate the population level. Bottom line is that all fields need to be sampled since each field may be different. In some fields, we can also find a mixture of corn earworm and beet armyworm. If economic levels of both are present, be sure to pick a product that will control both insects. We can also find economic levels of defoliation by green cloverworm and soybean loopers. Experience from the south indicates that beet armyworm and soybean loopers (both migratory pests) typically have some levels of resistance to the pyrethroids.


You will also need to continue to scout for soybean aphids. With the recent cooler weather, we are seeing economic levels of aphids in a few fields in Kent and New Castle County. As a general guideline, treatment is needed through the R5 stage (seed is 1/8 inch long in the pod of one of the four uppermost nodes on the main stem) of soybean development if economic levels are present. It may also be beneficial to spray through R6 stage (pods containing a green seed that fills the pod cavity at one of the four uppermost nodes on the main stem) reports vary as to the benefit of spraying once plants reach the R6 but in some years and some situations there has been an economic return. Spraying after R6 stage has not been documented to increase yield in the Midwest. The suggested treatment threshold from the Midwest is still 250 aphids per plant with 80% of the plants infested with aphids. This number should provide a 5 to 7 day lead time for treatment to avoid economic loss.


We continue to find economic levels of stinkbugs. You will need to continue to scout for stinkbugs in fields that are in the pod development and pod fill stages. Economic damage is most likely to occur during these stages. You will need to sample for both adults and nymphs when making a treatment decision. Available thresholds are based on beans that are in the pod development and fill stages. We are currently following the same guidelines that are being used in Virginia. Thresholds are also based on numbers of large nymphs and adults, as those are the stages most capable of damaging pods. As a general guideline, current thresholds are set at 1 large nymph/adult (either brown or green stink bug) per row foot if using a beat sheet, or 2.5 per 15 sweeps in narrow-row beans, or 3.5 per 15 sweeps in wide-row beans.


Be sure to check all labels for the rates, days from last application to harvest as well as other restrictions.



Agronomic Crop Diseases Bob Mulrooney; Extension Plant Pathologist; bobmul@udel.edu


Soybean Rust Update

I thought I would pass along an update on soybean rust written by Dr. Arv Grybauskas, Extension Field Crops Plant Pathologist at the University of Maryland. It is a good synopsis of the current soybean rust situation and is applicable to Delmarva.


As you are all aware, thanks to the drought of 2007 there hasn't been much of a threat of soybean rust to keep you up-to-date on. But the situation has been changing and we are not out of the woods, yet.



The onset of soybean rust in commercial soybeans in the Gulf States was delayed somewhat by two factors. The first was the Easter period frost that knocked back kudzu growth. Kudzu is the primary alternative host for soybean rust in the US and is the live host on which the soybean rust pathogen survives winters. Frost knocked back the population of the fungus so that re-infection of kudzu and introduction into soybean fields was delayed. The second factor has been the drought which has been very significant throughout the soybean production areas of the US. The soybean rust pathogen needs moisture to survive transport, cause infection on new hosts and reproduce. The drought also changed the planting of soybeans so that many full-season soybean acres in the South were planted late and there was also a significant increase in double-crop soybeans after wheat. The result of this change in planting pattern was that many of the commercial acres in the South came into peak susceptibility later in the season.


Once soybeans reached the peak susceptible period, reproductive growth stages, the overriding factor has been rainfall. The center of activity this season has been Texas, Oklahoma and Louisiana. This region experienced several periods of extended and heavy rainfall when even the Florida and Georgia region only got a few scattered showers. With the center of soybean rust activity being further west, the primary concern has been of a direct and relatively early hit in states with large soybean acreage just due north. The only reason this has not happened has been the lack of rain. There is still no sign of rust in Kansas, Missouri or even central Arkansas. Even northern Oklahoma has only a few sites with very low levels of infection.


We are now in a situation where all soybeans that are still green in the US are susceptible. Soybean rust has increased to sufficiently high levels especially in the Texas, Oklahoma, Louisiana region so that there is a greater chance of longer distance transport with survival in greater numbers. And to complete the disease triangle, we are also heading into a period when cooler and wetter conditions are to be expected. We are basically looking at the exponential phase of the epidemic to get started.


What does this mean for us in Maryland and Delaware?

Up until last week we had zero risk of soybean rust due to the drought. Even if spores landed here conditions were not suitable for infection. But there also wasn't a large enough source of spores close to us to really produce a threat to our area. The source is now large enough, but without a hurricane or some other major storm system it is unlikely that we would see any significant volume of spores moving our way in the immediate future. Soybean rust still has to develop a little further north to be a more direct threat. A second avenue for infection could come from the southeastern states.


Soybean rust is increasing in Florida, Georgia, Alabama and once that gets into enough commercial acreage the coastal route that brought soybean rust to our doorstep last year will be a potential avenue this season as well. I estimate that most full-season soybeans will hit R7 in a month if not less. Some early maturing early planted soybeans are already at R7 or the equivalent due to drought stress. In any case the window for infection and for any fungicide response is only about a month. Without a hurricane, if soybeans in the central Midwest become infected in the next two weeks then we could still see soybean rust in full-season beans within this window. With a hurricane the chances go up, but for now there is nothing developing in the Atlantic. Double-crop soybeans have a longer window and thus have a greater chance of getting soybean rust. The big problem will be deciding whether or not there is enough of a yield potential to warrant fungicides if that threat develops. Kansas State University has done a quick economic analysis as their crop is poor and they are at much greater risk of getting soybean rust this season. They estimate that there should be a 15-20 bu/A yield potential to warrant protection with fungicides.

Dr. Arv Grybauskas, Extension Field Crops Plant Pathologist at the University of Maryland


Soybean Charcoal Rot

Charcoal rot was identified this week from an early planted Group II variety. Charcoal rot is favored by dry weather that follows wet weather soon after planting. Usually irregularly sized patches of infected dying plants are seen in the field, but sometimes you can see individual plants in the row infected, and dead or dying. When this happens you see scattered plants dying, either singly or several in a row flanked by healthy ones. Carefully dig up plants and look at the roots and lower stem. They will often be gray, and if you scrape the gray lower stem or roots you can see many small black flecks that look like the tissue was covered with powered charcoal. Often, if the plants are dead and you split the stems, the pith is full of these tiny microsclerotia as well. Rotation will help to prevent the disease to some degree, as will planting later maturing varieties. I am surprised that we have not seen more charcoal rot, but since most of the acres had so little rain from planting onwards there was no time for infection early in the season, except for these early planted Group II varieties. This disease will always be a threat to this maturity group when planting in fields previously cropped to soybeans if a season is wet early and then the crop is drought stressed during pod-fill like this year.



Unknown Cyst Nematode Discovered on Corn in Tennessee Bob Mulrooney; Extension Plant Pathologist; bobmul@udel.edu


Delmarva farmers and agronomists are well aware of soybean cyst nematode (SCN), the plant-parasitic nematode that is widespread throughout all the major soybean growing areas of the country and can seriously reduce soybean yields. But most crop professionals probably are unaware that there is a corn cyst nematode that has been in the northeastern United States since 1981. And just recently, a new cyst nematode species that reproduces on corn was discovered in Tennessee.


Corn Cyst Nematode Known in United States Since 1981

The corn cyst nematode, Heterodera zeae, initially was reported in India in 1970. It was first discovered in the United States in Kent County, Maryland, in 1981. The corn cyst nematode has been found only in four counties in Maryland (Cecil, Harford, Kent, and Queen Anne's) and in Cumberland County, Virginia. The fields known to be infested with the corn cyst nematode were quarantined by the United States Department of Agriculture in 1981, but the quarantine was lifted in 1996. Delaware was sampled as part of the original effort to determine the range of the corn cyst nematode and it was not found in Delaware.


The biology of the corn cyst nematode is similar to that of SCN. The life cycle takes 18-21 days under ideal conditions, and several generations can occur in a growing season. The ideal temperature for the corn cyst nematode is 86F, which is considerably higher than the 78F optimum temperature for SCN. All of the numerous corn hybrids tested in the 1980s in Maryland were susceptible to the corn cyst nematode. Other host plants of the corn cyst nematode include barley, oats, rice, sorghum, sugarcane, wheat, and several grass weeds.


New Species of Cyst Nematode Discovered on Corn in 2006

On July 29, 2007, at a scientific conference, university nematologists from Missouri, Nebraska, and Tennessee and USDA nematologists announced that a new cyst nematode species was discovered on corn. Juveniles and cysts (egg-filled, dead females) were discovered in a soil sample taken from a field of stunted corn in northwestern Tennessee (Obion County) in 2006. University of Missouri nematologists made the discovery and verified reproduction of the nematode on corn and also found no reproduction on soybean in greenhouse tests. The nematode reproduced well on many different corn hybrids but poorly on other monocots. No dicots were found to be hosts. The cysts of this nematode look different than those of the corn cyst nematode discussed above, and genetic analyses confirmed that the nematode was not the corn cyst nematode. The nematode appears identical to a cyst nematode discovered on goosegrass, a weed, in Lauderdale County, Tennessee, in 1978.


Will New Cyst Nematode Species Affect Corn Production on Delmarva?

It is difficult to predict whether the new cyst nematode discovered on corn in Tennessee will move into other states and eventually reach Delmarva. But in the 11 years since the quarantine was lifted on the fields infested with the corn cyst nematode in Maryland and Virginia, the nematode has not been found in any other state.


It also is unclear how damaging the new cyst nematode discovered in Tennessee would be to corn if it moved to Delmarva. The corn cyst nematode, H. zeae, causes significant yield reductions only in hot environments, such as in India and Pakistan. Currently, it is not possible to predict how the new cyst nematode discovered on corn in Tennessee might affect Delaware corn yields because details such as the length of the nematode life cycle, number of generations per season, optimum temperature, survival in frozen soil, and ability to damage corn are not available.


New Cyst Nematode Species on Corn Would Hinder SCN Field Sampling and Research

Spread of this new cyst nematode on corn into fields locally would seriously hinder field soil sampling as well as research on the biology and management of SCN. Currently, no other cyst nematode species commonly exist in Delmarva corn and soybean fields, and eggs recovered from cysts extracted from Delmarva soils are assumed to be SCN eggs. But eggs of SCN and other cyst nematodes look similar and cannot be distinguished by appearance. Determining SCN egg population densities for management or research purposes would be impossible using current techniques if other cyst nematodes were present. A stain that is specific for SCN eggs currently is not available, and developing such a stain likely would take years.


Based on an article by Dr. Greg Tylka, Iowa State University Cooperative Extension


For pictures and more info see http://www.ipm.iastate.edu/ipm/icm/2007/7-30/nematode.html and http://www.pestalert.org/viewNewsAlert.cfm?naid=46



Lodging in Corn Gordon Johnson, Kent County Extension Agriculture Agent; gcjohn@udel.edu


As I was looking at the UD dryland corn variety trials in Smyrna, some varieties showed significant lodging in the lower stalk. I have already looked at a number of droughted fields that have considerable lodging. We have the potential to see a lot more lodging this year because stalks are weak due to the drought. Downed corn could be a major problem if any storm of significance comes through. In addition to stalk lodging, weak root systems can lead to root lodging and corn stalks pulling out of the ground during harvest, especially if we get any wet weather to soften up the soil. Ear shanks are also very weak and premature ear drop and ear drop during harvesting can be expected.


Lodged corn


In fields where lodging potential is high, early harvest is imperative. With low yields expected in many fields, limiting harvest losses will be very important. If lodged corn is encountered there are several options to improve harvest recovery:


         If lodging is primarily in one direction (due to wind coming primarily from one angle) then harvesting in one direction often is done.

         In severely downed corn lodged in one direction you might consider harvesting at the angle that the corn is lodged rather than with the row.

         In corn that is badly lodged, deteriorated, with weak roots, using a soybean platform may be the best option.

         Use corn shields that mount on the outside row snouts of the corn head to help catch ears that can drop to the ground or bounce off the corn head from the outside rows when stalks hit the gathering chains.

         Use plastic snouts and plastic gatherer shields to help corn slide into the gathering chains

         Use ear savers.

         Slow combine travel speed to reduce the amount of missed ears.

         Keep gathering snouts as low as practical to pick up downed ears.

         Speed up the gathering chain and rollers if possible (this reduces plugging).

         Use attachments such as reels to pick up the lodged corn and bring it into the combine.


Some sources of attachments for downed corn:


Corn Shields and Plastic Gatherer Shields - GVL Company, 59711 U.S. Highway 12, Litchfield, MN 55355

(888) 657-3664, Fax: (320) 693-6983



The Kelderman Reel - Kelderman Equipment, 2686 Highway 92, East Oskaloosa, IA 52577-9685

(800) 334-6150



The Meteer Corn Reel - Meteer Manufacturing, RR1 Box 221, Athens, IL 62613

(217) 636-8109



Plastic Cone Attachments - The Roll-A-Cone Manufacturing Company, Rt. 2, Box 25, Tulia, Texas 79088

(806) 668-4722



Corn Saver Device - Corn Saver, 5200 N. Columbia St., Plainview, TX 79072

(800) 536-1022



Corn Reel - Minden Machine Shop Inc., 1302 K Road, Minden, NE 68959




Corn Reel - Heritage Machine and Welding, 1001 W. Locust, Bloomington, IL 61701

(309) 828-0400



Corn Reel, Bish Down Corn Reel - Harvs Farm Supply Inc., 508 South D Rd., Giltner, NE 68841

(402) 849-2674, Fax: (402) 849-2293



Corn Reel, Mini Trash Reel - Shelton/Hay LLC, 1524 160th St., Woolstock, IA 50599

(866) 458-5904




Grain Marketing Highlights - Carl German, Extension Crops Marketing Specialist; clgerman@udel.edu


Exports Rule

USDA's weekly export sales report, released this morning, is viewed as bullish for intra-day trading for corn, soybeans, and wheat. However, the report is likely to be discounted into the market in short order due to the early U.S. corn harvest that is now underway.


The last weekly report for the '06/'07 marketing year placed combined export sales of both old and new crop corn at 63.2 million bushels. Pre-report estimates ranged from 27.7 to 47.2 mb. Accumulated U.S. corn exports for the year totaled 2.076 billion bushels, slightly less than USDA's 2.1 billion bushel projection. Shipments at 49.9 mb were well above the 21.3 mb needed to stay on pace with USDA's projections for the '07/'08 marketing year of 2.150 billion bushels.


The weekly report placed total U.S. soybean export sales at 11.8 million bushels. Pre-report estimates ranged from 11.0 to 29.4 mb. Accumulated U.S. soybean export sales for the '06/'07 marketing year totaled 1.098 billion bushels, just shy of USDA's projection of 1.1 billion bushels on the year. Shipments of 11.8 mb were well ahead of the 2.2 mb needed to stay on pace with projections.


The 12th weekly report for the '07/'08 marketing year placed new sales of wheat booked for export at 45.3 million bushels, well above the 11.6 mb needed to stay on pace with USDA's projected annual figure of 1.075 billion bushels. Pre-report estimates for wheat sales ranged from 25.7 to 40.4 mb. Shipments reported at 37.2 mb are well ahead of the 20.4 mb needed to stay on pace with projections.


Pro Farmer Crop Production Estimates Released

The Professional Farmers of America estimated the '07/'08 U.S. corn crop at 13.109 billion bushels and the soybean crop at 2.658 billion bushels (8/24/07), from average yields of 153.47 for corn and 42 bushels per acre for soybeans. On August 10 USDA estimated the U.S. corn crop at 13.054 billion bushels and the soybean crop at 2.625 billion bushels, from average yields of 152.8 for corn and 41.5 bushels per acre for soybeans. It is fair to point out that the private forecasters have thus far fallen in line with USDA's August production forecasts. The general inclination is to believe that USDA's September yield estimates will be in line with the August forecast for U.S. corn and soybeans give or take a bushel or two.


Marketing Strategy

Dec '07 corn futures put in a double top on August 23 at the $3.70 per bushel level and has not retested that level since. According to Joel Karlin, on average, December corn makes its low around September 23. The average date of the low in years when stocks decline is August 29. In years when stocks rise the average low occurs on October 25. In years of falling stocks the market should bottom sooner. USDA is projecting a 33% increase in ending stocks this year which indicates the low for Dec corn being set around October 4, based upon simple regression analysis. Dec '07 corn futures are currently at $3.46; Nov '07 soybean futures are at $8.89; and July '08 wheat is at $6.12 per bushel.





Smyrna Corn Hybrid Trial

Walk-Through Day

Friday, September 7 Noon 6:00 p.m.

Delaware State University Smyrna Research and Outreach Center (SORC)


All farmers and crop advisors are invited to walk through the University of Delaware corn hybrid variety trials at the Delaware State University Smyrna Research and Outreach Center (SORC) on Friday, September 7th. The plots will be open for viewing from noon until 6:00 p.m. There are major differences due to drought stress! Please park at the picnic pavilion and follow the signs to the plots.


While at SORC you may also view other research going on at the facility by DSU and UD researchers.


Directions to SORC:

Take Rt. 13 toward Smyrna. Just south of Smyrna turn east onto Smyrna-Leipsic Road. Cross over Rt. 1. The SORC farm will be on the south side of the road (white fences). Drive back the lane to the picnic pavilion.



Wye Pumpkin & Sweet Corn Twilight

Wednesday, September 26 4:30 p.m. dark

Wye Research & Education Center

Queenstown, MD


   University specialists will speak about insects and diseases of pumpkin and sweet corn and current research on these crops.


   See 15 varieties of pumpkins.


   Taste four late season BT sweet corn varieties.


Registration is not required. Light fare will be served.


Questions? contact Mike Newell 410-827-7388 or email mnewell@umd.edu







For Current Agricultural Information from the UD Kent Co. Extension Office Visit the Internet Site



Current Topics:

           Sources of equipment for harvesting lodged corn

           Estimating corn harvest losses

           Corn harvesting: more combine considerations

           Corn harvest losses chart

           Corn harvest moisture considerations

           Understanding cation exchange capacity in soils

           Stalk lodging in corn

           Reducing harvest losses in corn

           Calibrating grain drills

           Planting wheat seeding rates

           Minimizing poultry house odors

           Looking for derelict poultry house sites

           Stink bug on the rise in soybeans

           Blister beetles can also be a soybean pest

           More on blister beetles

           What rainfall will do for corn

           Agricultural land leases The Delaware law

           Podworms, podworms, podworms

           Alternaria leaf spot in soybeans

           Late season soybean diseases




Weather Summary

Carvel Research and Education Center Georgetown, DE

Week of August 23 to August 29, 2007

Readings Taken from Midnight to Midnight



no rainfall recorded


Air Temperature:

Highs Ranged from 95F on August 26 to 70F on August 23.

Lows Ranged from 72F on August 26 to 57F on August 29.


Soil Temperature:

80F average.

(Soil temperature taken at a 2" depth, under sod)

Additional Delaware weather data is available at http://www.rec.udel.edu/TopLevel/Weather.htm



Weekly Crop Update is compiled and edited by Emmalea Ernest, Extension Associate Vegetable Crops




Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State University and the United States Department of Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Delaware Cooperative Extension, University of Delaware. It is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, color, sex, disability, age or national origin.