Volume 7, Issue 13                                                                                            June 25, 1999

Vegetables

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

Lima Beans.

As soon as the earliest planted fields begin to flower and set pods, fields should be sampled for lygus bugs and stink bugs. Treatment should be considered if you find 15 adults and/or nymphs per 50 sweeps. Lannate should be used if both species are present.

Melons.

Unfortunately, mite control with registered products has been variable this season. If you have sprayed for mites and need a second or third application, it is important to consider using an insecticide with a different mode of action to reduce the chances of developing insecticide resistance. In addition, sprays will need to be applied 5-7 days apart if population levels are high at the time of treatment and numerous eggs are present. Dimethoate has not been used in many fields this season, because it has only provided poor to fair control in the past. However, the addition of a penetrant like LI-700 has been shown to improve the performance of dimethoate. Recent applications of Kelthane have provided good control for one week after application. Control with Agri-Mek has been more variable compared to the 1998 season. A sticker similar to Plex should be used if Agri-Mek is applied by air.

Peppers.

Although corn borer BLT catches are currently low, the five day average in the Bridgeville, Greenwood, Harrington, Milford, and Rising Sun areas still warrant a 7-10 day spray schedule on peppers if fruit is -inch in size. 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).

Potatoes.

If Admire was not used at planting and you see a significant increase in second generation adult activity in the next week (50 per 100 plants), Provado should be used. Fields that are 2 weeks from harvest will not need to be treated for aphids until you find 10 or more aphids per leaf. Fields that are more than 2 weeks from harvest should be treated if you find 4 aphids per leaf. Monitor or Provado will provide green peach aphid control. Lannate or Provado will provide melon aphid control.

Snap Beans.

In the Bridgeville, Greenwood, Harrington, Milford, and Rising Sun areas, snap beans should be sprayed for corn borer. Processing snap beans that are in the bud to bloom stage should receive an Orthene treatment. If corn borer catches increase to the 2 to 5 per night range in your area, a second treatment of Orthene will be needed on processing beans at the pin stage. Once corn borer trap catches reach 2 to 5 per night in your area, fresh market snap beans should be sprayed 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. 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).

Sweet Corn.

Fresh market silking sweet corn should be sprayed on a 3-4 day schedule throughout the state. If corn earworm can be found in pre-tassel stage corn, a spray should be applied at tassel emergence and again in 3-4 days. At this time, the majority of the first generation corn borers have tunneled into the stalk or midribs of the leaves. We should start to see an increase in corn borer moth activity by next week. 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


Fresh Market Tomatoes - Ed Kee, Extension Vegetable Crops Specialist, kee@udel.edu

Approximately 2,200 acres of fresh market tomatoes for commercial sale are planted in Maryland and 100 acres planted in Delaware. Most are sold locally, although some do get shipped to terminal markets and to private market operators in other states. Others are also sold to regional chain stores and more distant chain stores.

Quality, uniform ripeness, and uniform size are critical to satisfying buyers and generating continuing repeat business. Understanding the ripeness stages of tomatoes is critical, yet there is always some confusion among growers and buyers about these stages.

Tomatoes should be harvested when physiologically mature, which is a range when the tomatoes reach mature green through to the red stage. At physiological maturity, the seeds can germinate.

The table below lists the stages and describes each stage:

Stage

Days From
Mature Green

Description
Immature Green

--------

Dull green, seeds won’t germinate
Mature Green

0

Bright to whitish green. Seeds imbedded in gel. Fruit not easily cut. Seeds will germinate. Fruit will ripen with right conditions. A Shipping Stage.
Breaker

2

Pink at Blossom End.
A Shipping Stage.
Turning

4

Pink Extending from Blossom End to cover 10 to 30% of Fruit.
Local Shipping Stage.
Pink

6

Pink to Red. 30 to 60% of fruit is covered with color.
Local Use, Local Shipping.
Light Red

8

Pink to Red. 60 to 90% of fruit is covered with color.
Local Use, Local Shipping.
Red

10

Red covers at least 90% of fruit.
Local Use, Local Shipping.

The Mature Green and Breaker stages are best for shipping any distance. The Turning, Pink, Light Red, and Red stages are best used locally or for local shipping. v


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

LATE BLIGHT REPORT

DSV accumulations as of June 22 , 1999 are as follows:

Location/

Emergence Date

DSV’s

June

20

DSV’s

June

22

Recommendation

P-Day

Value for Early Blight Prediction*

Baldwin – 4/19

60

71

5-day, mid rate

462/ 481

Jackewicz – 4/30

55

65

5-day, mid rate

411/ 428

Art Wicks – 4/26

54

64

5-day, mid rate

430 / 448

Ken/Chris Wicks – 5/3

51

61

5-day, low rate

394 / 411

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

Maintain your fungicide spray program at the recommended interval. DSV’s accumulated from 10-11 over the last period. If you did not have a spray applied within the last 5-7 days, make an application as soon as possible. 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

Pumpkins.

Developing a spray program for foliar diseases of pumpkins is difficult because many diseases (some controlled by different fungicides) must be considered. The following is a schedule that is designed to be effective and take economics into consideration. The core of the program is broad spectrum products, maneb, chlorothalonil, and Quadris. This program will control most diseases of pumpkin, but it is still necessary to scout for development of powdery mildew and downy mildew.

Early in the season, when disease pressure is low and the plant canopy is relatively open, apply Maneb 75DF 2.0 lb/A. When disease pressure begins to build up, or powdery mildew is observed (threshold of one lesion on 45 old leaves), switch to an alternation of fungicides. Alternate chlorothalonil (such as Bravo Ultrex 2.7 lb/A or Terranil 3 pt 6L/A) plus copper (such as Kocide DF 1.5 lb/A) with Quadris 12 oz./A.

These fungicides should be applied at regular intervals depending on the susceptibility of the pumpkin variety. Our preliminary data indicate that maximum yield on susceptible varieties can be achieved only with weekly sprays. However for varieties with some tolerance to powdery mildew (such as Magic Lantern or Merlin) grown on a cover crop (which reduces black rot pressure) a 10 to 14 day schedule does a good job of controlling diseases.

Downy mildew is not usually present here on the Delmarva peninsula until very late in the season (mid- August or September). In some years it is not present at all because it requires high rainfall. Symptoms of downy mildew on pumpkin begin as angular yellow or chlorotic areas on the upper surface of leaves. Sporulation occurs on the underside of leaves and appears as brown to gray. The sporangia can be seen with a 10X hand lens and appear as barely distinguishable black or purple spots. Scout your field for the presence of downy mildew and apply Aliette or Ridomil Gold if it occurs.

Remember that cucurbits are no longer on the Bayleton label, so unless you have material with the old label, it cannot be used.


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 16-23. Any questions please call Phil Shields at (410) 742-8788 or e-mail: ps136@umail.umd.edu

EFI Values for 1999

Location

6/16

6/17

6/18

6/19

6/20

6/21

6/22

6/23

U of M, LESREC
Salisbury,MD

2

2

1

0

1

4

2

1

Wootten Farms, Galestown,MD

1

1

2

0

1

5

2

0

Mark Collins,
Laurel, DE

2

1

2

0

1

6

4

1

Vincent Farms Laurel, DE

1

1

1

0

1

5

2

1

D C Farms,
Bridgeville, DE

0

1

1

0

1

6

2

0

Balvin Brinsfield,
Vienna, MD

1

1

2

0

1

5

2

1

Charles Wright,
Mardela Springs, MD

1

1

1

0

1

4

2

0

U of D, REC Georgetown, DE

1

0

0

0

1

5

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

Field Crops.

Grasshopper populations continue to increase, especially in sorghum; along edges of field corn fields; and in soybeans planted into barley stubble. As a general guideline, non-crop areas should be treated if you find 20 or more grasshoppers per square yard. In corn and sorghum, a treatment is justified if you find 5-8 grasshoppers per square yard. In soybeans, the threshold is one per sweep and 30 percent defoliation. Sevin and Warrior are labeled on all three crops and have provided the most consistent control. Dimethoate is labeled but must be applied when grasshoppers are small to get effective control.

Soybeans.

Spider mites can now be found feeding on soybeans in Kent and Sussex Counties. Be sure to watch carefully for mites feeding on the undersides of the leaves. Damage will first appear at the base of leaves appearing as white stippling on the top surface of leaves. Since we do not have any good miticides available for mite control in soybeans, early detection and application of control materials is critical. If dimethoate is used, high storage temperatures (greater than 95 degrees F) can reduce the effectiveness and it is very susceptible to degradation if the pH and/or iron content of the spray water are high. Buffering agents can be added to the mix to adjust for high pH and iron content. The buffering agent should be added to the spray tank before dimethoate is added.  v


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

Wheat.

Many fields in Kent and Sussex Counties have black heads at the present time. This dark discoloration is due to the presence of fungi called sooty molds. These fungi are dark and discolor the heads. These are saprophytic fungi, for the most part, that colonize the glumes and are favored by humid weather. They can also discolor seed causing a condition called smudge. Wheat that is weakened from drought, nutrient problems, or damaged in some other way is prone to infection by these fungi and appears sooty. I used to see this problem when 2,4-D was applied after jointing to control garlic. This herbicide damage predisposed the wheat to sooty mold infection. These fungi are not causing the shriveled grain; the dry weather or some other problem has already damaged it. You may see some different amounts in varieties that may indicate some tolerance to sooty mold. If these black heads appear in patches and the wheat is shorter, you may want to check the lower stems for the fungus disease "take-all" as well. Wheat infected by take-all will often be infected by sooty molds too. If take-all is present, rotation away from small grains is recommended for several years. Unfortunately the sooty mold on wheat is indicating how severe the dry weather was in many areas. v


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

Weather Services Play Key Role in Grain Sales and Hedging Decisions
Weather forecasts are never far from the farmer's mind. The same is true for grain traders at the Chicago Board of Trade, specifically from the beginning of spring planting through the fall harvest season.

Years ago commodity traders worked off of a 3 to 4 day weather horizon. Today with the help of weather satellites and the super computers of the National Weather Service, traders work off a 6 to 15 day forecast.

As a producer, you are always most interested in the weather forecast for your farm or ranch, your county and your state. However, as a well-informed, efficient marketer of commodities, a much wider weather perspective is necessary. Scientific national weather forecasts are available from accessible sources of electronic quote and news services, as well as through direct subscription.

The Chicago Board of Trade's web site, www.cbot.com , addresses the importance of weather conditions in the futures market. Included in their web site is a section devoted to various weather services and reports. Many members and customers use this function as a means of knowing ahead of time the anticipated weather patterns for specific regions.

To be an effective manager of commodity price risk a reliable source of ag-weather forecasts is needed. One should avoid forecasters who tend to sensationalize, and keep in mind that weather is not the only factor driving grain markets.

(excerpts taken from an article appearing in the Illinois Agri-News 6/11/99, based on an interview with Ben George, CBOT Member) v


Uneven Soybean Emergence and Herbicide Application Timing Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Due to dry weather at planting, timing of soybean emergence was erratic. Some fields have soybeans ranging from three trifoliates to still emerging. When to spray a postemergence herbicide is not an easy decision. Start with the size of the weeds and determine your herbicide choices. Then select the best herbicide(s) based on crop safety, knowing that the smaller the soybean plants, the more susceptible they are to injury. Herbicide injury can often be minimized but not eliminated. The environment at time of application is a factor. Hot, humid weather is an environment more prone to herbicide injury. Spraying late in the day is one way of minimizing injury. Herbicide injury can be minimized by using non-ionic surfactant rather than crop oil where possible; as well as not using liquid nitrogen or ammonium sulfate. Below is a relative ranking of soybean injury severity for various postemergence herbicides.

Ranking Herbicide
Most injurious Cobra
Stellar
Moderate safety Basagran

Blazer

Flexstar

Pinnacle - (non-STS soybeans)

Raptor

Resource

Fair safety Classic

Pursuit

2,4-DB

Good safety Reflex

FirstRate

Least injurious Assure II

Fusion

Poast/Poast Plus

Select

Roundup Ultra - (Roundup-Ready soybeans)

Touchdown - (Roundup-Ready soybeans)

Classic - (STS soybeans)

Pinnacle - (STS soybeans)

Synchrony STS - (STS soybeans)

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 17 to June 23

Rainfall:
1.00 inch: June 20, 1999
0.11 inches: June 21, 1999
Readings taken for the previous 24 hours at 8 a.m.
Air Temperature:
Highs Ranged from 84F on June 23 to 64 F on June 20.
Lows Ranged from 61F on June 17 to 52F on June 23.
Soil Temperature:
70 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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