Volume 6, Issue 3 April 10, 1998


Vegetable Crops

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

Cabbage.

Begin to watch early planted fields for diamondback larvae moving into the hearts of the plants. Since larvae can quickly cause damage by feeding in the hearts and Monitor is no longer available for cabbage, early detection will be even more critical. At this time, the Bt insecticides are the only available products for DBM moth control on cabbage. These materials should be applied when larvae are small and early in the morning to allow them to work during the heat of the day.

Sweet Corn.

As soon as plants emerge from the ground be sure to scout for flea beetles and cutworms. Warmer winter conditions have increased the potential for damage from flea beetles. In fields where cover crops were used and are not completely plowed under, cutworm levels have been higher in recent years. Even though Counter and Furadan can provide good control, weather conditions can affect the performance of these materials. The treatment threshold for flea beetles is 5% infested plants. At the one-two leaf stage, the cutworm threshold is 3% cut plants or 10% leaf feeding damage. If both insects are present, Asana, Ambush, Pounce or Warrior will provide control of both. Sevin also provides flea beetle control.

 Peas and Snap Beans.

Seed corn maggot flies can still be found laying eggs, especially in fields where a green cover crop has been plowed under close to planting or where manure has been used. The use of diazinon 50W as a planter box treatment is labeled on both crops and has provided the most cost effective control in recent years. The use rate is oz per bushel of seed. It should also be combined with oz of graphite to reduce friction and a fungicide to reduce the chances of phytotoxicity. v

 

Afila Peas - Ed Kee, Extension Vegetable Crops Specialist ; kee@udel.edu

The Afila, or semi-leafless pea, is a recent development. This genetic trait was discovered years ago. Commercial varieties have been on the market for at least a decade. In afila varieties, leaflets are converted to tendrils. Adjacent plants hold each other erect to harvest and plants don't lodge. This creates a more open structure and keeps pods higher. It is also thought to improve pea color because the pods are more exposed to direct sunlight than standard varieties.

While estimates indicate between 30 and 40% of the national acreage are now planted to afila types, harvestability and rate of maturity have been issues here on Delmarva. Past experiences have resulted in poor harvest recovery. We are cooperating with seed companies and processors and have established seven test sites in commercial fields to evaluate ease of harvest, maturity rates, and yield. Harvest will occur in June. v

 

Vegetable Diseases - Kate Everts, Extension Plant Pathologist, University of Maryland and University of Delaware ; everts@udel.edu

White Mold On Peas, Snap and Lima Beans.

White mold (also called Sclerotinia rot on many vegetables) was severe in 1997 in some pea, lima bean and snap bean fields. The fungus which causes this disease is Sclerotinia sclerotiorum. It produces sclerotia (overwintering structures) which are highly resistant to adverse environmental conditions. Unfortunately that means that inoculum in affected fields is likely to be high this year. There are several strategies that can be used to minimize the disease pressure in your 1998 crop. Plant these crops in fields that have been rotated out of legumes for 3 years. Make sure your seed is clean and free of sclerotia (black, irregularly shaped hard structures which range from the size of a mustard seed to inch in length, or more). Avoid excess fertilizer, narrow row spacings, high plant populations and excess irrigation. Varieties with upright architecture, or afila types will be less affected because aeration between the rows is better. Planting the rows in the direction of the prevailing winds may also increase air movement down the row.

There are some chemical controls for lima and snap beans (not peas). A fungicide should be applied if conditions favor sclerotial germination. The sclerotia of white mold germinate and form small mushroom like structures called apothecia when the soil has been wet for 6 to 10 days prior to bloom. If these conditions occur, apply Benlate 50WP (1.5 - 2lb/A), Rovral 50WP (1.5 - 2 lb/A), or Topsin M 85 WDGA (1.5 - 2 lb/A) when 70 - 80% of the blossoms are open. Ronilan 50DF is also available (for snap beans only), and is applied at a rate of 1 lb/A. v

 

Vegetable Diseases - Bob Mulrooney, Extension Plant Patholgist ; bobmul@udel.edu

Asparagus.

Our friends in New Jersey have suggested the following for establishing a new production field. Use disease free crowns. The vigorous New Jersey hybrids are recommended especially Jersey General, Jersey Giant, and Jersey Knight. Select well-drained soils without a history of asparagus or that have been out of production for at least 8 years to minimize the occurrence of Fusarium root rot. Also, apply Nemacur 3SC as a spray into the bottom of the furrow before dropping the crowns. Research in NJ has shown an increase in vigor of the planting and reduction of Fusarium root rot.

Potatoes.

Just to let you know, we will be operating the late blight weather monitoring stations again this season. Enough funds are now available to run this important service. Thanks to all those that are responsible. More on this later. Potato growers will be receiving a special mailing soon, outlining the procedures for this season. The report will be made available in Crop Update whenever we get close to reaching the threshold of 18 disease severity values. v

 

Field Crops

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

Field Corn.

Last season, black cutworm populations were higher than normal, reaching economic levels in many fields. This was generally a result of later planting and the presence of heavy weed growth before planting. Since this insect overwinters in the soil and winter conditions were mild, many are assuming that cutworm population will again be higher than normal. Although this makes sense, you should also consider the fact that soil conditions were saturated with water for much of the late winter. This could result in death of pupae (overwintering stage of the black cutworm) due to disease organisms. In 1997, pheromone trap catches in April provided a good indication of where black cutworm problems would most likely occur. The most recent pheromone trap data for 1998 (see table on last page of newsletter, information provided by Terra Inc., Bridgeville, DE) indicates that cutworm moth activity is starting to increase on the shore. Although no precise thresholds are available, 7 to 15 moths per 7 day period has been associated with a moderate to high potential for cutworm outbreaks. Moth catches of 5 per night for at least 2 nights in a row has also indicated a high potential for problems. Moth activity alone may not always mean that you will have a cutworm problem. Field conditions attractive to egg laying should also be considered including heavy chickweed/ broadleaf weed growth before planting, no-tillage planting, late plowing of cover crops, late planting, and poorly drained fields. The pyrethroids (Asana, Ambush, Pounce or Warrior) tanked mixed with herbicides pre-emergence have provided effective control. Force, Fortress and Lorsban will also provide control but they must be t-banded to be effective.

Unfortunately, the Special Local Need 24C label for Mesurol 50 HBT was pulled by EPA right after the newsletter was printed last week. Gowan will still be working towards a full registration; however, it will probably not be available for use this season.

Small Grains.

Aphids and CLB eggs can still be found in many fields. Aphid populations have increase slightly; however, beneficial insect activity, especially lady beetles, is still preventing population explosions of aphids. Cereal leaf beetle adult activity and egg laying has also increased. However, lady beetles can also be found feeding on cereal leaf beetle eggs. If conditions remain cooler, we should not see any cereal leaf beetle egg hatch before the third week in April.

Alfalfa.

Alfalfa weevil larvae can be easily found feeding in the tips of alfalfa plants. Once you see tip feeding, a full field sample should be taken. Randomly collect 30 stems throughout a field, placing them upside down in a bucket and shaking the stems to dislodge larvae from the tips. Once alfalfa reaches 12-inches tall, the treatment threshold is one per stem. In 13 to 15-inch tall alfalfa, the threshold is 1.5 per stem and in 16-inch tall alfalfa the threshold is 2 per stem. Baythroid, Furadan, Imidan or Warrior will provide effective control under a wide range of environmental conditions. v

 

 Options for Triazine-Resistant Lambsquarters and Pigweed - Mark VanGessel, Extension Weed Specialist ; mjv@udel.edu

Triazine resistant weeds are a wide spread problem in Delaware. Atrazine at 1 to 1.5 lbs/A is an effective treatment if the weeds are not triazine-resistant, but will not have effect on triazine-resistant weeds. If lambsquarters and pigweed are not effectively controlled with the atrazine applied preemergence but other species are controlled, you should be concerned about triazine-resistant biotypes and control the lambsquarters postemergence. Atrazine is in many pre-mixtures with residual grass herbicides including: Bicep, Bullet, Harness Xtra, and Surpass 100.

Python (the Broadstrike portion of Broadstrike + Dual) can be used on late planted corn (soil temperatures greater than 60F), planted at least 1.5 inches deep, and soil organic matter at least 1.5%. If the restrictions are not met when using Python, then use an IMI-corn hybrid. Other soil applied herbicides have not provided consistent control.

Control of triazine-resistant lambsquarters is often dependent upon postemergence applications. Postemergence control of lambsquarters and pigweed (triazine-resistant and susceptible) can be achieved with the following options. Basis (1/3 oz/A) plus a non-ionic surfactant applied early postemergence (up to fourth leaf stage). Banvel (4 to 8 oz/A) up to 36 inch tall corn (Banvel is a component of Marksman as well). Exceed (1 oz/A) plus Banvel (2 to 4 oz/A) plus a non-ionic surfactant can be applied up to 36 inch tall corn. Basis and Exceed both have restrictions when Counter is used - be sure to read the label. v

 

Field Crop Diseases - Bob Mulrooney, Extension Plant Patholgist ; bobmul@udel.edu

Barley Diseases.

Two fungal spots of barley are common in Delaware. The first is the spot form of net blotch, caused by the fungus Pyrenophora teres. Sounds confusing, it is. We used to see net blotch in the 70s up to the early 80s, then I started seeing dark brown elliptical to round spots, no longer did we see the typical net-like symptoms made of thin dark brown striations that crossed each other like a net. The new form of net blotch is called the spot form of net blotch. The fungus overwinters in debris from the previous crop and infection is favored by wet weather, and high nitrogen levels. The most economical control if you have problems with the spot form of net blotch is to plant resistant varieties.

The second common leaf disease of barley is scald. This has been seen in Delaware fields this spring. Scald is pretty easy to identify once you learn the symptoms because they are distinct and not much else looks like it. Symptoms begin as dark or pale gray lesions which later turn watersoaked. As the infection progresses the centers of the lesions dry out and bleach, turning light gray, tan, or white. The edges become distinctively dark brown and wide. The lesions often expand to become very large and not delimited by the leaf veins. The disease gets its name because it looks like someone poured boiling water on the leaves. Not really, or you just need the right imagination. The controls are the same as for net blotch and planting resistant varieties is the most economical control. Nomini is susceptible and that is the variety on which it has been seen this season so far. If it shows up in our variety test plots I will have ratings for these two diseases.

Wheat.

Powdery mildew is present in wheat at low levels in most fields. Since most wheat is rapidly approaching or past growth stage 6 (jointing), now is the time to be scouting your fields.

Novaritis Crop Protection has applied for a section 24C registration in Delaware for applications of Tilt up to the heading stage (Feekes GS 10.5). I have supported this registration because it allows growers to wait to see if disease conditions warrant an application. Later applications on susceptible varieties, under most conditions, will carry the crop through flowering. This new labeling also gives growers greater flexibility in planning their disease control program. This registration is pending and we will have to wait for EPA approval.

Soybeans.

Soybean severe stunt disease which has only been identified in Sussex County can be managed in several ways. Once this disease has been identified it can be managed by planting a non-host crop such as corn, sorghum, or vegetables, or plant a resistant soybean cultivar. We have identified several cultivars with resistance to SSSV. Group IV varieties with resistance include Delsoy 4710, Chesapeake, Corsica, Cisne, Agripro AP4400, Stine S4650 and S4790. The only resistant group V cultivar has been Choska which is very new from Nebraska and is not available yet. Of these varieties only Delsoy 4710 has resistance to SSSV and the soybean cyst nematode races 3, 14. Our variety trial work has been partially funded by the Delaware Soybean Board and we are grateful for their support. This virus disease is soilborne and thought to be transmitted to soybeans by the dagger nematode. Yields from infected areas run anywhere from 5 to 20 bushels/A. Usually only small areas have plants that show the typical stunting and curling of infected leaves. The internodes are very short, and the leaves are crinkled and mottled. Infected areas can enlarge over time if the disease is not identified. It could be misdiagnosed as herbicide injury or early in the season you may think the plants have been grazed by deer, but on closer inspection you can see the dramatic symptoms. v

 

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

April 1998 USDA Crop Report: Executive Summary

U.S. soybeans take the spotlight in this month's report with a 20 million bushel decrease in projected ending stocks. The net effect of the reduction in soybean stocks is likely to be minimal when we consider the March 31, 1998 planting intentions report and the large Southern Hemisphere crop being harvested.

Projected Stocks for U.S. Corn, Wheat, and Soybeans

* Ending stocks for U.S. corn projected at 1.209 billion bushels, increased 260 million bushels

* Ending stocks for U.S. wheat projected at 726 million bushels, increased 52 million bushels

* Ending stocks for U.S. soybeans forecast at 235 million bushels, reduced 20 million bushels

* Ending stocks for U.S. soymeal stocks were increased 25 million tons, while soyoil stocks decreased 280 million pounds

Projected World Ending Stocks for Corn, Wheat, and Soybeans

* World Ending Stocks for Corn were increased by 7.7 million metric tons to 80.47

* World Ending Stocks for Wheat were increased 3.5 million metric tons to 134.75

* World Ending Stocks for Soybeans were decreased slightly

Summary

The above comparisons are based upon the changes in projected stock levels from the March to the April 1998 USDA Crop report. The numbers indicated in this month's report are not expected to have much impact on 1998 crop prices. Both world and domestic grain and oilseed stocks are adequate. Major strenthening in 1998 crop prices is not expected unless a major weather development occurs.

* a metric ton of wheat and soybeans = 36.7433 bushels

**a metric ton of corn = 39.3678 bushels v

 

How Well Do You Treat Your Hay

Richard W. Taylor, Extension Agronomist ; rtaylor@udel.edu

Large round bale production can offer significant savings with respect to manual labor requirements especially for larger operations that use substantial quantities of hay. Many of us have heard about the deleterious effects of storing the small rectangular bales directly in contact with the ground outside, but we may have the false impression that the losses will be less for the larger round bales.

Work done at Michigan State University shows us that the losses can be even greater on improperly-stored large round bales. Their data indicate that 4 inches of spoiled hay on the outer shell of a 5 foot diameter round bale (it weighs approximately 1,000 pounds) represents a 25 percent loss in volume. The researchers, T. M. Harrington and J. R. Black, calculated for 4 foot diameter (600 pound bale), 5 foot diameter, and 6 foot diameter (1,400 pound bale) round bales the volume and value loss associated with each inch increase in depth of spoiled hay. The volume and value losses were as follows:

 4 FT BALE

Depth of

Spoiled Hay

%

Volume

Losses

$ Losses

/Bale*

2 inch

16

$ 2.88

3 inch

24

$ 4.32

4 inch

31

$ 5.58

5 inch

37

$ 6.66

6 inch

44

$ 7.92

* Loss per bale based on a $60 per ton hay price and hay fed free-choice.

 5 FT BALE

Depth of

Spoiled Hay

%

Volume

Losses

$ Losses

/Bale*

2 inch

13

$ 3.90

3 inch

19

$ 5.70

4 inch

25

$ 7.50

5 inch

30

$ 9.00

6 inch

36

$ 10.80

* Loss per bale based on a $60 per ton hay price and hay fed free-choice.

 6 FT BALE

Depth of

Spoiled Hay

%

Volume

Losses

$ Losses

/Bale*

2 inch

11

$ 4.62

3 inch

16

$ 6.72

4 inch

21

$ 8.82

5 inch

26

$ 10.92

6 inch

31

$ 13.02

* Loss per bale based on a $60 per ton hay price and hay fed free-choice.

The actual value lost per bale will vary with the price per ton of hay and on the assumed use of the hay. For example, the value lost will be less for animals fed free-choice than when bales are mixed in a totally mixed ration and fed to high-producing dairy cows.

What can you do to minimize you losses? The least costly but also the least effective method is to set bales on pallets or other material so they are not in contact with the ground. This does not prevent the spoilage of loose outer layers of hay. To do that, you need to protect bales from weather during storage either using a permanent structure or a plastic bale wrap system. The permanent structure has low maintenance costs but the initial cost of investment is high. For the plastic bale wrap system, the initial investment cost is much lower but there is the cost of the plastic wrap material and additional labor costs that are added to the overall investment in the system. Be sure you understand the costs and benefits of each storage option and calculate how much you can afford to invest before choosing among them.

To get started, go out now and measure the depth of spoiled hay on your bales stored since last summer. You can use this information to estimate your losses and by using a table the authors of the study constructed, you can calculate the break-even investment point for a storage building or a plastic wrap storage system. If you would like a copy of their break-even investment table and an explanation on how to interpret and use the table, please e-mail me with your request or call me with your name and address at (302) 831-1383 and request the information on hay storage. v

 

National Corn Growers Association Entry Forms Are Now On-Line - Richard W. Taylor, Extension Agronomist ; rtaylor@udel.edu

I recently was notified that the National Corn Growers Association has released the entry forms for the 1998 National Corn Yield Contest. The on-line PDF-formatted entry forms are available at their world wide web site at the following address:

www.ncga.com/08profits/entryform.htm

Dr. Bob Nielsen in the Agronomy Department at Purdue University has also added a few new timely links from Iowa State University and Ohio State University on the Chat ‘n Chew Cafe page. The address for this site is as follows:

www.agry.purdue.edu/agronomy/ext/corn/chatchew.htm

When you have a few minutes to spare over lunch or a mid-day snack, log-on and see what’s new about corn at the Chat ‘n Chew Cafe. v

 

Frost Effects on Winter Wheat -

Dr. Richard W. Taylor, Extension Agronomist, rtaylor@udel.edu

Most fields of winter wheat have reached the jointing stage of growth when wheat is rapidly growing. Frost or freeze damage can occur from now through heading if three basic conditions are present. First, the wheat must be in a sensitive growth stage (from Feeke’s growth stage 6 to 11). Second, air temperatures must drop to a certain critical level. The third and final condition is that the temperature must remain at the critical level for at least 2 to 3 hours. Most often we see this occurring on calm, clear nights or in isolated pockets protected from wind by woods or other natural barriers.

Wheat tissues are most vulnerable to freezing when in an active state of cell division or cell elongation. The risk is especially high during stem elongation (Feeke’s growth stage 6 through 9) and heading (Feeke’s growth stage 10.1 and 10.5). Temperatures in the range of 20 to 24 F. can kill segments of the elongating stem or sections of the seed head that are caught in the act of cell division or cell elongation at the time of the freeze.

Wheat leaves can tolerate even colder temperatures, 15 to 20 F, after beginning active growth in the spring depending on the variety and age of the leaves. The older or more mature leaves are more sensitive to cold than the new or developing leaves. Seed heads (consisting of spikelets and flowers) can be injured at temperatures as mild as 27 to 29 F.

Frost damage to young, developing heads is usually not recognized until after heading is complete but may have occurred anytime after jointing began (Feeke’s stage 6). If the growing point is killed before heading then the main stem or tiller will die but may be replaced by the development of a new shoot from the crown of the plant. Heads damaged by frost are empty and bleached white but the entire head is not always affected. From boot (Feeke’s stage 10) to early heading, frost damage can affect the entire head, the tip only, the base only, both the tip and the base, or occasionally the middle section only. Empty heads can also be caused by freezing of the elongating internodes during stem elongation (Feeke’s stage 6 to 9). To identify this latter kind of frost damage, peel back the leaf sheaths to expose the stem internode region. A damaged internode is evident as a thin, often collapsed, and sometimes brownish section of the stem that is 1 to 3 inches long.

Can you make a freeze damage evaluation based on the overall visible symptoms of a field? No, the visual symptoms can sometimes be misleading since even fields that visibly appear to have minor freeze damage (little leaf burn, good color, plants standing well) can have extensive head and stem damage on closer inspection. Wait at least 5 to 7 days after the freeze to make a valid assessment. This allows the temperatures to warm up and active growth to begin again. In cases where conditions (wheat growth stage and temperatures) were marginal, you may need to wait up to two weeks to make an evaluation. This will allow enough new growth so you can more easily identify damaged and undamaged plant tissue.

Next week, I will cover what to look for to identify head, stem, and leaf damage. v

 

Planting Update - Tracy Wootten, Extension Associate - Vegetable Crops; wootten@udel.edu

The majority of Delaware potato growers have 50-75% of their crop in. Pea planting is currently on schedule although we had a late start this year due to the rain. The recent warm weather has enabled growers to catch-up, with 40% of the pea crop planted. Sweet corn planting began one week earlier this season due to warm temperatures. Estimates are that 10-15% of the approximate 20,000 acres of processing sweet corn on Delmarva is in. Early plantings of sweet corn for fresh market are in. Planting of field corn began this week. v

 

Black Cutworm Pheromone Trap Counts – March 27 through April 3, 1998

Trap Counts Provided by Terra Inc., Bridgeville, DE

Location

# Moths per 7 Days

Location

# Moths per 7 Days

American Corner, MD

2

Lewistown,MD

1

Argos Corner, DE

1

Magnolia,DE

2

Atlanta, DE

1

Milford, DE #1

4

Berlin, MD

1

Millsboro,DE

1

Bucktown, MD

2

Newark,MD #1

1

Denton, MD

3

Pocomoke,MD #1

2

Eldorado,MD

1

Preston,MD

1

Ellendale, DE

1

Reliance, MD

7

Georgetown, DE

1

Ridgely,MD

1

Goldsboro, DE

1

Rhodesdale,MD

4

Harmony,MD

2

Seaford,DE #1

1

Hurlock ,MD #1

3

Seaford,DE #2

3

Hurlock.MD # 2

3

Selbyville,DE #2

1

Laurel,DE #2

1

Vernon,DE

1

Leipsic, DE

1

Wyoming,DE

1

 


 

Week of April 3 to April 9

Rainfall:
0.13 inches: April 4
1.23 inches: April 5
0.30 inches: April 9
Readings taken for the previous 24 hours at 8 a.m.
Air Temperature:
Highs Ranged from 79 F on April 3 & 9 to 46 F on April 5.
Lows Ranged from 48 F on April 9 to 31 F on April 6.
Soil Temperature:
53.3 F average for the week.
(Soil temperature taken at a 2 inch depth)

  


Compiled & Edited By:

Tracy Wootten

Extension Associate - Vegetable Crops

 


Cooperative Extension Education in Agriculture and home Economics, University of Delaware, Delaware State College and the United States Department of Agriculture cooperating, John C. Nye, Dean and Director. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, sex, disability, age or national origin.


Hit Counter