Volume 6, Issue 8                                                                                          May 15, 1998

Vegetables

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

Potatoes.

Corn borer populations still remain below 5 per night in all potato growing areas of the state. When trap catches reach 10 per night, you can expect to see an increase in egg laying activity. Now that the rain has finally stopped and with the predicted high temperatures, we should see an increase in moth activity over the weekend. Controls should be applied when you find 25% of the terminals infested with small larvae. If treatments are timed for percent-infested terminals, Furadan or Monitor should be used. In general, two applications of Furadan or Monitor will be needed to achieve corn borer control. If treatments are based on moth catches in blacklight traps, sprays should be applied within one week of finding 25 moths per night in your local blacklight trap. Penncap, Ambush or Pounce will provide control and generally 2- 4 sprays will be needed if timing of applications is based on moth activity.

Sweet Corn.

Begin to watch your earliest planted fields, especially fields that were planted under plastic, for European corn borer larvae. The earliest planted fields will be the most attractive to egg laying moths. Small true armyworm larvae can be found in the earliest planted fields that had a lot of cover incompletely plowed down before planting. The treatment threshold for corn borer or armyworm is 15% infested plants. Ambush, Pounce or Warrior will provide control of both insects. *

 

Cool Temperatures and Wind Damage on Cantaloupe and Watermelon Transplants - Ed Kee, Extension Vegetable Crops Specialist ; kee@udel.edu

Several growers called on Wednesday, when the weather finally cleared after five days of rain, wind, and cold weather. Transplants were wilted down, or flopped over flat. This results from wind whipping the plants around, doing damage to the stems. It is also a result of temperatures dropping into the forties. The plant essentially shuts down under such cold temperatures, unable to translocate water from the roots up into the leaves and stems. The duration of exposure to the low temperature stress determines how severe the damage is. Several hours of temperatures in the forties can do enough so the plants won't come back. With less exposure, many of the plants will straighten up and start to grow with the warmer, sunny conditions expected this weekend. Growers should allow two days of good conditions before spot transplanting replacements. This will allow for a more accurate decision on which plants to replace. *

 

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

Snap and Lima Beans.

To avoid root rot rotate with non-legume crops, avoid poorly drained fields, and plow under previous crop debris. For control of Pythium root rot apply Ridomil Gold 2E in a band over the row. To control Pythium and Rhizoctonia root rot apply Ridomil Gold PC in the furrow at seeding.

White Potatoes.

Pink rot and leak. Early plantings are approaching bud development, which is a reminder that the first pink rot spray if needed, should be applied at flowering and 14 days later. Ridomil Gold MZ should be applied in as much water as possible. I have had excellent results with 30 gallons/acre. Test results have indicated that two applications beginning when the first tubers are nickel-sized also provides very good control. Remember that the new Ridomil Gold MZ, or the older Ridomil MZ72 formulation at the 2.5 lb. rate contains 1.6 lbs. of mancozeb which is enough for late blight control as well.

Cantaloupes.

Keep cucumber beetles controlled to avoid transmission of bacterial wilt.

 

Late Blight Update

DSV accumulations as of May 11, 1998 are as follows:

Location/Emergence Date

DSV's May 7

DSV's May 11

Recommendations

Baldwin - 4/20

21

47

5-day, low rate

Jackewicz - 4/20

21

49

5-day, low rate

Zimmerman - 4/23

23

47

5-day, low rate

Baker - 5/1

18

44

5-day, low rate

These data included continuous period of 90+ R.H. for 84-89 hours, since late Thursday night until this morning (May 11, 1998) when data were collected. All potatoes that have emerged from May 7 and earlier have been exposed to weather favorable for late blight infection. This Thursday will be 7 days since the first favorable weather for late blight occurred and if present, could be seen from this Thursday on. Field scouting potatoes is recommended especially those that were not sprayed before last Thursday. I would suggest 1 lb/A of EBDC for small plants and possibly 1.5 lb./A for larger plants. Bravo (chlorothalonil) rates would be from pt. to 1 pt./A. The Late Blight Report is also posted electronically at the UD Extension IPM website: http://www.udel.edu/IPM *


Field Crops

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

Small Grains.

As soon as fields are dry, be sure to check for grass sawfly and true armyworm activity. Most grass sawflies are still small and will be most easily detected with a sweep net. Once larvae are found, you need to examine 5 linear foot of row in 5 – 10 locations for larvae and head clipping. Be sure to include an edge sample in your sampling sites since larvae will often be detected in rank areas on field edges. Sawflies are also spotty in their distribution throughout a field so a representative sample is necessary. In comparison, armyworms are nocturnal feeders so they are generally found at the base of the plants during the day. Be sure to carefully examine the area around the base of the plants in 5 linear foot of row for armyworm larvae. Armyworm larvae now range in size from to inch long. The treatment threshold is one to two armyworms per foot of row. Sawfly populations generally peak by the end of May. Also, if you find twice the number of clipped heads compared to sawfly larvae it is usually too late to treat.

Hessian Fly in Wheat.

During the past 2 weeks, we have encountered a number of fields in New Castle County, DE and Cecil County, MD with varying levels of hessian fly damage. We are still sampling fields to see if infestations are widespread. In some situations, the entire field has been infested and is not worth keeping. These fields have been generally planted in continuous wheat and/or were in no-till situations with volunteer small grains present at the time of planting. In other cases, infestations are spotty and plants appear very stunted or shorter than normal for the growth stage and are generally the result of spring infestations. All of the infested fields were planted after the "fly-free date"; however, with the warm winter conditions it appears that we had 2 generations last fall and/or an early spring generation. As you check fields for other pests during the next week, be sure to take note of any stunted plants. If you pull up a stunted plant, you should find tiny white maggots and/or the puparia or "flaxseed stage" in the crown of the plants or at the base of the leaf sheaths. There are no control options that can be applied at this time except for the destruction of the stubble to prevent the flaxseed-stage flies from infesting fields planted in wheat this fall. The stubble must be plowed under, disked under completely or burned to provide effective control; however, this is not very practical in most situations. Crop rotation will also help reduce populations but it must be done on an area wide basis to be effective. We will keep you informed about any additional management strategies that can be applied this fall.

Field Corn.

Be sure to watch newly emerged fields carefully for cutworm activity. Larvae range in size from to 1 inch long and both leaf feeding and cut plants can be found. Bird damage can also be found in fields so be sure that you do not confuse the damage. Small cutworm leaf feeding damage will initially appear as small, irregular shaped holes in the leaves. Larvae will eventually cut plants at or below the soil surface and should easily be found due to the moist soil conditions. Rescue treatments with a pyrethroid should be very effective since cutworms are feeding close to the soil surface. Bird damage can sometimes look like cutworms, especially in moist conditions when they often just cut off the tops of plants. If you look closely, you will also see an occasional plant pulled out of the ground and plants missing for long distances in a row. *

 

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

Small Grains.

There has been an outbreak of bacterial kernel blight in barley. This bacterial disease is not common in this region and as of this writing I don’t think it has been reported before. The disease can be identified by the spotting and discoloration of the glumes surrounding the seed. The basal kernel blight symptom begins with the discoloration beginning at the end closest to the rachis (seed attachment to the stem). Brown discoloration with a reddish brown border can be seen. Recent samples from other fields are showing a spotting of the glumes that is on the tip of the seed. Bacteria isolated from these discolored areas have been identified as Pseudomonas syringae, but have not been identified to pathovar yet. These bacteria commonly survive as ephiphytes (live on the surface of grass leaves), and during periods of very wet weather can become pathogens. They can be splashed or driven by wind blown rain into the creases of spiklets or at the base of the glume joints. It is enough to know that if you see discolored barley heads you may be led to believe that is might be glume blotch or some other fungal disease. The heads should be checked carefully to determine the cause of the discoloration. If the infection occurred early, no seed may have formed, but seeds that form and are discolored may be infected with the bacteria. Fields that have a significant amount of bacterial kernel blight should not be saved for seed. The infected seeds pose no threat to animal or human health. This may be a case of a common bacteria just needing the right set of environmental conditions to become a barley disease. No chemical controls are possible and avoiding infected seed is recommended. I would be interested to know if anyone has seen these symptoms and would submit a sample to their county agent. Please include the name of the variety with the sample.

Septoria leafspot is now being seen on the lower leaves of wheat. Both Septoria fungi are being seen. The leaf spot pathogen is Septoria nodorum and can infect the heads and is referred to as glume blotch. The other Septoria leaf disease is Septoria tritici and is often referred to as speckled leaf blotch from the numerous dark fruiting bodies of the fungus that are imbedded in the dead centers of the spots. They can occur together or in some years one predominates over the other. In any case, they both need ample rainfall which we have had to infect and spread. Most wheat has developed beyond the need for fungicides, but those that have been sprayed with Tilt, mancozeb, or Bayleton and Benlate should see some control of Septoria leaf and glume blotch. Late wheat or in New Castle county there may be fields that are flowering now that might benefit from an application. Check the 1998 Pest Recommendations for Field Crops for more information. *

 

What Is In Those Soybean Herbicide Pre-mixes? -Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

The following is a summary of the products in commonly used pre-mixes for soil-applied soybean herbicides. This is meant as a reference point to compare the amount of various products based on the use rate that is appropriate for you.

.Pre-Mix Products
Authority Broadleaf 56.3 DF at 5.1 oz 2.4 oz sulfentrazone + 1.95 oz Classic 25 DF
Broadstike SF + Dual 7.72 L at 1.75 pt 0.8 oz Python 80 WDG + 1.63 pt Dual 8E
Broadstrike/Treflan 3.65 L at 1.5 pt 1.0 oz Python 80 WDG + 1.27 pt Treflan 4E
Canopy 75 DF at 4 oz 3.43 oz Lexone/Sencor 75DF + 1.95 oz Classic 25 DF
Canopy XL 56.3 DF at 5.1 oz 2.4 oz sulfentrazone + 1.95 oz Classic 25 DF
Detail 4.1 EC at 1 qt 2.8 oz Scepter 70 DG + 1.2 pt Frontier 6E
Squadron 2.33 E at 3 pt 2.8 oz Scepter 70 DG + 1.82 pt Prowl 3.3E
Steel 2.59 E at 3 pt
  1. oz Scepter 70 DG + 1.4 oz Pursuit 70 DG

+ 2.0 pt Prowl 3.3E

Triscept 3 E at 2.33 pt 2.8 oz Scepter 70 DG + 1.5 pt Treflan 4E

*

 

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

Agricultural Options: A Marketing Tool for Weather Markets.

The use of agricultural options is a way for some farmers to make a percentage of their sales decisions in the midst of weather markets. Options have provided farmers with a limited use marketing alternative since being re-introduced to farmer use in 1984. The reason the alternative is limited is because the price of the commodity being sold, the option premium, and market conditions all have to agree with using options as a pricing mechanism, at given points in time. Many times, the cost of the option premium can be prohibitive when considering the use of the option as a sales alternative. In the case of using put options for price risk protection against growing crops, price level of the commodity also becomes an important factor. It is generally easier to make money on the put option when the price of the commodity is in its upper third of the prevailing price range, assuming declining prices. Simultaneously speaking, when commodity prices are in their upper third of the prevailing price range the forward cash contract is often times the favored marketing alternative.

Why consider the put option as a price risk reducing marketing alternative? There are several possible scenarios that might make this alternative worth considering. Given here, we will consider two of the most common for using the put option: 1). For making growing crop sales decisions, once 50 % contracted on expected production 2). When needing to make sales on a percentage of the crop, as part of prudent business-management, and higher prices are anticipated above present levels.

The first scenario, primarily applies to dry land crop production because of the risk involved in cash contracting anticipated production over of what one expects to grow. The put option can be used to contract the other 50 % of production, taking sales up to the 100% sold level of anticipated production, if prices and conditions warrant. The reason is that the portion of the crop priced using put options does not have to be delivered. The option position may be offset, allowed to expire, or exercised. In the event that crop production does not measure up to contracted expectations, the option position(s) being held would either be allowed to expire worthless or offset for any premium value in the option.

In the second scenario, our strategy may sound a bit more speculative, yet the put option is a way to sell commodities, and take advantage of higher prices that may develop later on. Of course, the per bushel cost of the premium is foregone once this strategy is chosen, and hindsight would suggest that one should have just waited to make the sale in the first place. Anyone interested in getting further information on using agricultural options in their marketing program should contact Carl German at 302-831-1317. For some the call option can come in handy, those recommendations are generally made on an individual personal contact basis only. *

 

Yellowed Emerging Corn - Richard W. Taylor, Extension Agronomist ; rtaylor@udel.edu

In many fields, corn that has emerged appears yellow instead of the usual light green color we expect to see. Several factors are responsible for this including cold soils, excessive rainfall, nitrogen (N) leaching, and slow root growth. Banded starter N probably has been leached deep into the soil and this combined with slower than normal root growth means that the plants may have sub-optimum tissue N concentrations. Even in manured fields, plants may appear N deficient. The low soil temperatures and higher than normal rainfall have either delayed the release of N from organic sources or moved released N below the root zone.

Should you be worried about this? It depends on how long the symptoms last. The corn should begin to green up soon after warmer, drier weather allows the soil temperature to rise. If N has not leached too deep, corn roots will quickly grow into the starter band and pick up N for the crop. On manured fields, the warmer soil temperatures will increase microbial activity releasing plant available N from organic sources.

In some situations, little N may remain in the immediate rooting zone. Lighter soils are especially sensitive to leaching during periods of heavy rainfall. Flooded or ponded areas in fields may loose N through denitrification. Whenever the yellowing persists past the third or fourth leaf stage, you should be concerned. [Remember, the third leaf stage is when the leaf collars of three leaves are visible although you may be able to see the leaf blades of as many as five or six leaves.] When the crop does not green up, consider an early sidedress N application. Between the third and fifth leaf stage, some components of yield are being determined. Since yield potential can be limited by inadequate nutrition even at this early growth stage, an early sidedress may be needed. *

 

From Sussex County… - Derby Walker, Sussex County Extension Agricultural Agent; derby@udel.edu

Wheat and Barley.

Three farms have been identified with Loose Smut, a fungus disease that is seedborne, and is normally controlled with the proper systemic seed treatment. We know the wheat fields were not treated. The barley field was seed treated. The outbreak of loose smut could have been due to the use of an incorrect fungicide, too low a rate or incomplete coverage of the fungicide on the seed. Neither grower saw much loose smut last year. Normally we see less then 1% of the heads infected, these fields had 5 to 10% of the heads infected. The smutlevel was high enough to spot through a windshield survey. Heads are only infected during flowering. Wet and cool to moderate temperatures favor infections. A week after flowering, heads become resistant to infection. The certified small grains that they planted looked "clean" of loose smut. However, a few heads in what appears to be a clean field can be major problem the next year.

Small grain seeds must be treated with a seed treatment that contains Vitavax, Baytan 30, Dividend (wheat only) or Raxil-Thiram to prevent loose smut. The treatment must be applied correctly to be effective. Fields with any smut should not be used for seed unless they are treated.

Beneficials in Small Grains.

What are those large flies that look like black and yellow bees in small grain fields? These are not sawflies, they are adult syrphid flies. A very beneficial insect, the larvae eat a lot of aphids. A sawfly is a wasp, not fly.

Check Your Hives for New Swarms.

It looks like a good year for bee swarms. I have already caught five from the honey bees we keep here at the U of D Research & Education Center. Last year we had two swarms. Good beekeepers divide their bees or give them more room to prevent swarming. Bees swarm when they run out of room or the queen needs to be replaced. After this cool rainy period you may see swarms. If you call your local beekeeper, they will come to get them. Honey bees do not survive long in the wild because of mites. They need care to protect them from mites and diseases. If you don't know a beekeeper, the county offices and DDA have a list of people who will pickup swarms. *


Upcoming Events…

May 20 -22, 1998

Hopkins Farm Tours for Sussex County Elementary Students

May 21, 1998

Troubleshooting for Small Grains

June 23-24, 1998

Quarterly Pesticide Applicator Training & Testing

Dover, DE For More Information, Contact Delaware Department of Agriculture at 1-800-282-8685. *


Delaware Department of Agriculture Website On-line -

The address is http://www.state.de.us/deptagri/index.htm

*


Weather Summary

FINALLY……

 

    Week of May 8 to May 14     
Rainfall:
0.30 inches: May 8
0.55 inches: May 9
0.22 inches: May 10
0.10 inches: May 11
0.75 inches: May 12
1.02 inches: May 13
Readings taken for the previous24 hours at 8 a.m.
Air Temperatures:
Highs Ranged from 70 F on May 8 to 51 F on May 13.
Lows Ranged from 57 F on May 10 to 40 F on May 14.
Soil Temperature:
55 F average for the week.
(Soil temperature taken at a 2 inch depth, under sod)

Weather Note:

It has rained 10 out of 14 days in the month of May, for a total rainfall of 3.59 inches.


Web Address for the U of D Research & Education Center:

http://www.rec.udel.edu   *


Black Cutworm – Pheromone Trap Catches – 1998 Season

Data Provided by Terra Inc., Bridgeville, DE

Trapping Period : May 1 – May 8, 1998

Location #Moths/7Days Location # Moths/7Days
American Corner, MD

10

Lewistown, MD

30

Argos Corner, DE

12

Magnolia, DE

15

Atlanta, DE

32

Mardela Springs, MD

4

Berlin, MD

0

Marydel, MD

9

Bethel, DE

6

Milford, DE #1

32

Bridgetown, MD

34

Milford, DE #2

-

Bucktown, MD

26

Millsboro, DE

17

Burrisville. MD

4

Milton, DE

19

Cambridge, MD

4

Newark, MD #1

7

Clarksville, MD

7

Newark, MD #2

14

Dagsboro, DE #1

28

New Church, VA

39

Dagsboro, DE #2

2

Oak Orchard, DE

0

Delmar, DE

29

Pocomoke, MD #1

31

Denton, MD

58

Pocomoke, MD #2

15

Easton, MD

28

Preston, MD

22

Eldorado, MD

10

Public Landing, MD

2

Ellendale, DE

2

Queen Anne, MD

11

Farmington, DE

5

Redden, DE

-

Federalsburg, MD

1

Reeds Grove, MD

6

Frankford, DE

29

Reliance, MD

10

Georgetown, DE

23

Rhodesdale, MD

15

Goldsboro, MD

18

Ridgely, MD

5

Greenwood, DE

5

Seaford, DE #1

2

Harmony, MD

47

Seaford, DE #2

30

Hurlock, MD #1

17

Selbyville, DE #1

34

Hurlock, MD #2

15

Selbyville, DE #2

23

Laurel, DE # 1

41

Snow Hill, MD #1

0

Laurel, DE # 2

17

Snow Hill, MD #2

15

Laurel, DE # 3

-

Snow Hill, MD #3

14

Leipsic, DE

10

Trappe, MD

3

Lewes, DE

6

Vernon, DE

28

    Wyoming, DE

16


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.


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