Volume 7, Issue 12                                                                                 June 18, 1999

Vegetables

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

Potatoes.

In fields where Admire was used at planting, we are starting to see low levels of small and medium size Colorado potato beetle larvae. If economic levels are being found and Admire was used at planting, Spintor (4-6 oz/acre), Kryocide/cryolite (8 –10 lb per acre) or Agri-Mek (8 oz/acre) should be used.

Peppers.

Corn borer sprays are needed on a 7-10 day schedule if peppers fruit is -inch in size or larger. If Orthene is used, a 10-day schedule will be adequate. If a pyrethroid or Lannate is used, sprays should be applied on a 7-day schedule.

Snap Beans.

Processing and fresh market snap beans in all areas should be treated for corn borer. Processing snap beans that are in the bud to bloom stage should receive an Orthene treatment for corn borer control. If corn borer catches remain above 2 – 5 per night, a second treatment of Orthene will be needed on processing beans at the pin stage. Corn borer sprays on fresh market snap beans should begin at the pin stage with Lannate. If corn borer catches remain above 5 per night, sprays should be applied on a 7-day schedule until harvest.

Sweet Corn.

Corn borers, corn earworms and low levels of fall armyworms can all be found in whorl stage sweet corn. The treatment threshold is 15% infested plants. If the predominant species are corn borer and corn earworm, Ambush, Baythroid, Pounce, or Warrior should be used at tassel emergence and again in 3-4 days. Corn earworm catches have recently increased so most fresh market silking sweet corn should be sprayed on a 3-4-day schedule for corn earworm control except in the Middletown area where sprays are needed on a 5-6 day schedule. Be sure to check the Crop Pest Hotline on Tuesday and Friday for the most recent BLT catches (1-800-345-7544 – in-state; 1-302– 831– 8851 – out of state; www.udel.edu/IPM). v


Stewart’s Wilt on Sweet Corn - Ed Kee, Extension Vegetable Crops Specialist, kee@udel.edu

Stewart’s wilt has been noted in several fields of sweet corn where the variety is rated tolerant. Sweet corn in the 1 to 3 leaf stage is more susceptible than later stages, even if a variety has good levels of tolerance to this bacterial disease. An outbreak of flea beetles, which spread the bacteria, can overcome the genetic tolerance inherent in the variety when the corn is in the 1 to 3 leaf stage. Corn infected at this early stage is more likely to be seriously affected and even die. Fortunately, for the most part 5% or less of the plants in these fields were affected. v


Pea Yields - Ed Kee, Extension Vegetable Crops Specialist, kee@udel.edu

Pea yields in the driest parts of the state have been adversely affected by dry weather, even with irrigation. In some of these cases, irrigation systems could not keep up with the water needs of the pea crop, which uses inch per day from blossom through pod fill. Yields in these fields have been about 2,000 pounds/acre, below the state average of 3,500. However, many fields that caught a few showers, or irrigation was not limited, have reached the 4-5,000 pound level. Harvest is near 60% complete. v


Watermelon Sales - Ed Kee, Extension Vegetable Crops Specialist, kee@udel.edu

A recent survey conducted by the National Watermelon Association of produce retailers indicate that lack of uniform size in a load reduces sales. Consumers react negatively if a mix of sizes is displayed, apparently intuitively thinking quality varies within the display. Consequently, produce buyers insist on size uniformity and will reject watermelons that fall outside of the normal size of a load or display. This has implications for our local watermelon industry, which has done a good job over the years of loading loads within the stated size limits of each wholesale transaction. The importance of meeting the size filters right through the market chain to the consumer, and consequently can filter back to the grower with negative results if proper sizing is not insured. v


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

LATE BLIGHT REPORT

DSV accumulations as of June 17, 1999 are as follows:

Location/

Emergence Date

DSV’s

June

13

DSV’s

June

17

Recommendation

P-Day

Value for Early Blight Prediction*

Baldwin – 4/19

44

48

7-day, low rate

400/ 427

Jackewicz – 4/30

40

45

7-day, low rate

348 / 375

Art Wicks – 4/26

40

44

7-day, low rate

367 / 395

Ken/Chris Wicks – 5/3

36

40

7-day, low rate

331 / 358

*bold is current value/ regular is previous report value.

The recent high humidity and scattered showers has provided conditions to accumulate some severity values. Maintain your fungicide spray program at the recommended interval. All sites have surpassed the 300 p-day spray interval for early blight control. Early blight susceptible varieties may benefit from an alternating spray program utilizing Quadris and an EBDC or Bravo, or using SuperTin plus an EBDC at this time. Research in other states has shown both products to work well when early blight has been difficult to control. Fortunately for us early blight has not been hard to control on most varieties. v


Vegetable Diseases - Kate Everts, Extension Vegetable Pathologist, University of Delaware and University of Maryland; everts@udel.edu and Phil Shields University of Maryland; ps136@umail.umd.edu

MELCAST for Fungicide Application on Watermelons.

Do not use MELCAST if there is a disease outbreak in your field, it is a preventative program. Below are the EFI values from weather stations located on the Eastern Shore June 9-16. Any questions please call Phil Shields at (410) 742-8788 or e-mail: ps136@umail.umd.edu

EFI Values for 1999

Location

6/9

6/10

6/11

6/12

6/13

6/14

6/15

6/16

U of M, LESREC
Salisbury,MD

3

0

0

1

3

5

2

2

Wootten Farms, Galestown,MD

4

3

1

1

4

5

5

1

Mark Collins,
Laurel, DE

2

0

0

0

4

5

4

2

Vincent Farms Laurel, DE

2

1

0

1

4

5

2

1

D C Farms,
Bridgeville, DE

2

1

1

1

4

4

4

0

Balvin Brinsfield,
Vienna, MD

2

0

0

1

4

4

3

1

Charles Wright,
Mardela Springs, MD

2

0

1

1

4

6

2

1

U of D, REC Georgetown, DE

0

0

0

0

3

4

2

0

Watermelon Fields should be sprayed with a fungicide when 30 EFI values have been accumulated by the weather station nearest your fields. Add 2 points for every overhead irrigation. After a fungicide spray, reset your counter to 0 and start over. If a spray has NOT been applied in 14 days, apply a fungicide and reset the counter to zero. The first and last day above can be partial days so use the larger EFI value of this report and other reports for any specific day. v


Field Crops

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

Alfalfa.

Continue to watch for potato leafhopper adults and nymphs, especially in spring planted fields. Once you see yellowing you have already experienced a yield loss. We are starting to see an increase in nymphs. Nymphs (immature forms) do not fly and can be found moving "sideways" on the leaves. It is this stage that can quickly cause damage. Remember that a sweep net is needed to get an accurate sample of both stages. An early cutting can be used as a control option if the field is 60% or more in bud and it has been 35-40 days since your last cutting. If economic populations were found before cutting, be sure to re-sample the field with in one week of cutting.

Field Corn.

Cereal leaf beetle adults can be found feeding on field corn, especially along edges bordering wheat fields. In general, the damage is not economic and plants outgrow the damage. No treatments will be needed unless you find 10 or more beetles per plant and 50% of the plants exhibit feeding damage throughout the entire field. In some cases, an edge treatment may be needed. A pyrethoid will provide control.

Soybeans.

Before the recent rains, economic levels of thrips and leafhoppers could be found on seedling soybeans. Fields with economic populations before the rain should be re-checked to determine if these insects are still active. A treatment will be needed if you find 8 thrips per leaflet or 8 leafhoppers per sweep. If both insect pests are present, the threshold of each insect should be reduced by one-third. A pyrethroid or dimethoate will provide effective control of both insects. v


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

Soybeans.

Soybean cyst nematode (SCN) was seen this week on soybeans with two trifoliolate leaves. The white and yellow female cysts were visible on the roots of the infected plants. Cysts can be seen anytime from 28 to 36 days after planting on the roots of susceptible plants. Now would be a good time to check. The early dry weather can increase the damage caused by SCN, which will cause stunted, yellow plants.

Even with the dry weather some Septoria leafspot or brown spot can be found on the unifoliate leaves of soybean at the present time. The common symptoms are brown irregular spots with yellow margins, which can be see on the infected unifoliate leaves and the lower trifoliolate leaves. v


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

Corn Market Update
Early growing season weather appears quite favorable for most of the corn belt. As long as the weather remains non-threatening, corn will have a difficult time sustaining any attempted price recoveries. Producers still have an opportunity to make corn sales locally for new crop '99 corn production at price levels that are well above the loan rate. This opportunity is expected to fade once the market takes off its "summer weather market face".

Soybean & Wheat Market Update

Sales opportunities for new crop soybeans and wheat have evaporated, considering our local loan rates of $ 5.36 for soybeans and $ 2.67 per bushel for wheat. Producers not holding any unique sales premium opportunities for either of these two crops must proceed with marketing them based upon the fact that the loan rates effectively serve as 'premium free' puts. Given that, sales advances are not warranted at this time. Both markets do have some impetus for further price pressure from current levels. Wheat will undergo harvest pressure and soybean prices are likely to be further pressured from the abundant supply of all competing oils.v


Regrowth of Perennials in Corn Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

A number of corn fields with perennials weeds were treated earlier and regrowth is starting. Most of the corn is too tall to retreat. For those fields with short corn or planted late, consider what your objective is for weed control. If yield is the only consideration, the need for respraying is often low. But if the objective is to reduce the weed population for future years, you may want to consider another application. But keep in mind, the effectiveness of the re-spray is dependent on the size and vigor of the regrowth, the less regrowth, the more effective it will be.


Postemergence Options in Soybeans Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Spraying Roundup Ultra over the top of Roundup Ready soybeans provides a wider window of application for effective control than with most conventional soybean herbicides. Evaluate conventional soybeans for postemergence sprays 14 to 21 days after planting. The smaller the weeds are the more options you have to control them, and control will be better. Roundup Ready soybeans should be treated three to four weeks after planting, but conventional soybeans should be treated earlier than Roundup Ready soybeans. Most conventional soybean herbicides have residual control that allows you to use them early and not need a second application.


Weed Science Field Days Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

The University of Delaware will hold its Annual Weed Science Field Day on Wednesday June 30, starting at 8:15 am. We will meet in the Grove at the UD Research and Education Center on Rte. 9. Pesticide credits will be awarded. v


What’s the Best Seeding Rate for Double-Crop Soybeans - Richard W. Taylor, Extension Agronomist ; rtaylor@udel.edu; Bob Uniatowski, Extension Associate- Field Cropsbobuni@udel.edu

Last year, the Delaware Soybean Board (DSB) sponsored a project to evaluate the cost and benefits of various seeding rates using a Roundup Ready variety planted double-cropped either dryland or irrigated. Roundup Ready seed are more expensive than the traditional seed. This study was designed to offer growers guidelines for choosing seeding rates when using the more expensive type of seed. For this study, Hoffman brand R366 beans were planted on July 8 and harvested on November 6.

First, keep in mind that the following results are from the first year of the study and may change significantly as more information is obtained. Growing season, rainfall amount, rainfall distribution, sunlight intensity and duration, day and nighttime air temperatures, and others factors that are largely uncontrollable have a great effect on soybean performance.

For 1998, the results showed that for irrigated beans there was a net positive impact on net income up to a seeding rate of 4 pure live seed (PLS) per row foot or about 300,000 PLS per acre. To calculate your seed cost, multiply the number of seed per pound times the percent pure seed (0 to 100) times the percent germination (0 to 100) and divide the result by 10,000 to get the number of PLS per pound. Next, take your seeding rate in thousands per acre and divide that by the number of PLS per pound and divide that by the number of pounds per unit times the cost per unit ($21 in our case). The result is your seeding cost per acre.

There's one other calculation to understand and that is converting from seeds per row foot to seeds per acre. To do this, divide 43,560 by the fraction (row spacing width in inches divided by 12) times the number of seed per foot of row. In this study, we planted on 7 inch rows so 43,560 divided by 7/12 is 74674.3.

In our study, seed size was 2,600 per pound, percent pure seed was 99, germination percentage was 90, and seed cost was $21. Therefore, the last incremental increase in seeding rate that was profitable was going from 2 PLS per foot of row to 4 PLS per foot of row. This cost $2.48 for each extra bushel of yield generated by the increase in seeding rate.

Under dryland conditions, rainfall arrived in time to produce yields close to those under irrigation. Again, the best seeding rate was 4 PLS per foot of row. Going from 2 PLS to 4 PLS per foot of row cost $3.83 for each extra bushel of yield gain. The caution here is that under drought conditions we would expect this to change so several growing seasons will be required to determine the most economical seeding rate to use. Note that in work on single-cropped beans in previous years, the best seeding rate has varied from 1 to 5 seeds per row foot (drilled beans) with no discernable pattern as to when one seeding rate would be better than another. This held true for the equivalent seeding rates on 15- and 30-inch row spacing.

What about even higher seeding rates? Under irrigation going from 4 PLS per foot of row to 8 PLS per foot cost $52.08 for each extra bushel of yield while under dryland conditions the cost was $30.64. At least the first year’s data indicated that there is a limit in how high a higher seeding rate is profitable.

Details of the above studies are available in the January 1999 issue of Soy News or are available from the authors. v


Pesticide BriefsSusan Whitney, Extension Pesticide Educator; swhitney@udel.edu

The next pesticide training sessions are scheduled for October 14 & 15 at the Delaware Department of Agriculture in Dover, Delaware and December 1 & 2 at the University of Delaware Kent County Extension Office in Dover, Delaware. Times for both the October and December are as follows:

Day 1 - 8:30 a.m. to 4:00 p.m., Training

Day 2 - 8:30 a.m.-Noon, Training

Day 2 – 1:00 p.m., Exam v

 


Upcoming Meetings…

The University of Delaware will hold its Annual Weed Science Field Day on Wednesday June 30, starting at 8:15 am. We will meet in the Grove at the UD Research and Education Center on Rte. 9. Pesticide credits will be awarded.


Weather Summary

Week of June 10 to June 16

Rainfall:
0.47 inches: June 13, 1999
Readings taken for the previous 24 hours at 8 a.m.
Air Temperature:
Highs Ranged from 88F on June 14 to 70 F on June 16.
Lows Ranged from 57F on June 10 & 11 to 67F on June 14.
Soil Temperature:
76 F average for the week.
(Soil temperature taken at a 2 inch depth, under sod)

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

http://www.rec.udel.edu


Compiled and 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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