Volume 7, Issue 10                                                                                                     June 4, 1999


Vegetables

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

Cabbage.

If you are growing cabbage varieties that are susceptible to thrips, be sure to watch for an increase in feeding activity. A treatment should be applied when 20% of the plants are infested. Dimethoate, Metasystox-R, Spintor or Warrior will provide control.

Snap Beans.

Fresh market and processing snap beans should be monitored for leafhopper and thrips activity. A treatment is needed if you find 5-6 thrips per leaflet or 5 leafhoppers per sweep. If both insects are present, the threshold of each should be reduced by the level for each insect. In seedling beans, fields should be treated if plants are drought stressed and you can find leafhopper nymphs feeding on plants. Lannate should be used in fresh market snap beans and Lannate or Orthene in processing snap beans.

Peppers.

No corn borer controls will be needed until -inch size fruit are present. Sprays will be needed on a 7-10 day schedule when corn borer catches are above 2 – 5 per night in local blacklight traps. Currently, corn borer trap catches are averaging 2-5 per night in most areas except in the Harrington and Greenwood areas where catches are 15 and 10 per night respectively.

Potatoes.

Economic levels of corn borers, potato leafhoppers, and CPB larvae can be found in fields where Admire was not used at planting. Corn borer larvae can now be found in the terminals of the earliest planted fields. Furadan or Monitor will provide the best control once larvae are in the terminals. Potato leafhopper populations have also increased this past week. With the consistent hot weather, you can expect to see egg hatch in the next few days and nymphs can damage fields quickly. The treatment threshold for potato leafhoppers is one leafhopper per sweep or one nymph per 10 leaves. Furadan, Provado or a pyrethroid will provide leafhopper control.

Sweet Corn.

European corn borer whorl infestations have increased to 20 –25 % infested plants in the earliest planted fresh market sweet corn fields. The treatment threshold is 15% infested whorls or tassels. If you plan to wait and treat just as tassels are emerging, timing of sprays will be important. Treatments must be applied just as tassels are emerging from the whorls to be effective. Since we can find a range in the size of larvae, the majority of the larvae may not have pupated before tassel emergence and will have a chance to make it into developing ears. Also, once larvae begin to bore into the midribs you will not get control. Ambush, Baythroid, Pounce, Penncap-M or Warrior will provide the best control. If bees are foraging in the area, Penncap should not be used.

 

New Publication on the Web.
Delaware's 1999 Commercial Vegetable Production Recommendations are now on the web. It includes all of the information found in the printed version. You can access this publication at http://www.rec.udel.edu . It can then be found by going to the Publications section.

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

LATE BLIGHT REPORT

DSV accumulations as of June 1, 1999 are as follows:

Location/

Emergence Date

DSV’s

June

1

DSV’s

May 27

Recommendation
Baldwin – 4/19

33

33

10-day, low rate
Jackewicz – 4/30

35

35

10- day, low rate
Art Wicks – 4/26

35

35

10-day, low rate
Ken/Chris Wicks – 5/3

32

32

10-day, low rate

Conditions have not been favorable for late blight.

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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

Spinach .

The weather conditions have been favorable for white rust development. Continue application of copper fungicides to minimize development or spread. To reduce risk of phytotoxicity, switch to Aliette when the field is close to harvest.

 

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 August 5-12. Any questions please call Phil Shields at (410) 742-8788 or e-mail: ps136@umail.umd.edu

EFI Values for 1999

Location

5/27

5/28

5/29

5/30

5/31

6/1

6/2

U of M, LESREC
Salisbury,MD

0

0

1

1

2

2

0

Wootten Farms, Galestown,MD

1

0

1

2

3

4

3

Mark Collins,
Laurel, DE

0

0

0

1

2

2

0

Vincent Farms Laurel, DE

0

0

0

0

1

1

0

D C Farms,
Bridgeville, DE

0

0

0

2

3

1

1

Balvin Brinsfield,
Vienna, MD

0

0

0

0

0

2

0

Charles Wright,
Mardela Springs, MD

0

0

0

1

2

0

0

DE U of D, REC Georgetown, DE

0

0

0

0

0

0

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 fields carefully for leafhoppers. Scouting should begin within one week of harvest for potato leafhopper adults and nymphs. With the consistent hot weather, you can expect to see egg hatch in the next few days and nymphs can damage fields quickly. When alfalfa is 3-inches or less in height, the treatment threshold is 20 per 100 sweeps. In four to six-inch tall alfalfa, the treatment threshold is 50 per 100 sweeps. In alfalfa 7 –11 inches tall the threshold is 100 per 100 sweeps. Ambush, Baythroid, Dimethoate, Pounce or Warrior will provide effective control.

Field Corn.

As the earliest planted fields reach 18-inches in height, begin checking fields for the presence of European corn borer larvae, especially fields where Bt varieties were not planted. Low levels of corn borers and southern corn stalk borers have been detected in the earliest planted non-Bt fields. Since we rarely treat for the southern corn stalk borer, be sure to pull out the whorls of 10-20 plants per field to determine which insect is causing the damage. Southern corn stalk borer larvae will appear spotted compared to the cream colored body of the corn borer. In irrigated corn, a corn borer treatment should be considered if 50% of the whorls are infested with live larvae. In non-irrigated corn, the treatment threshold is 75 -80 % infested plants. Ambush, Pounce, Penncap-M or Warrior will provide the best control. If bees are foraging in the area, Penncap should not be used.

Soybeans.

Bean leaf beetles continue to be the main pest feeding on seedling beans. Damage appears as small circular holes in the leaves. In comparison, Mexican bean beetle feeding will appear as a lacey pattern on the leaves. No controls are needed unless you find at least 2 bean leaf beetles per plant and they are reducing the stand by 25 percent. A pyrethroid or Sevin will provide control. Grasshopper nymphs can also be found in no-till fields and along field edges. Treatment of non-crop areas may also help to prevent whole field infestations at a later date. As a general guideline, non-crop areas should be treated if you find 20 or more grasshoppers per square yard. As you begin to plant soybeans after barley harvest, these fields should be checked carefully for grasshopper activity. Early control of nymphs will provide the best control. Once grasshoppers are found in a field, a treatment is needed if you find one grasshopper per sweep and 30% defoliation. Asana, Sevin or Warrior have provided the most consistent control.

Small Grains.

Head clipping and economic levels of grass sawfly and armyworm are still being found in an occasional field. Fields should be checked at least one more time for both of these insect pests. It is generally too late to treat for sawflies if the number of clipped heads is 3 to 4 times the average worm count and most caterpillars are greater than one-inch long. v


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

Wheat.

Dry, dry, dry. Wheat diseases have ground to a halt as the crop rapidly matures. Scab appears to be non-existant this year, which is good news after last years’ problems with scab. Take-all has been identified from a few fields in Maryland. The dry weather will accelerate symptom development of this disease. Look for stunted plants with white heads and a poorly developed root system. The lowest internode will have black streaks once you remove the leaf sheath. v


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

1999 Loan Rates Announced
USDA has announced loan rates for 1999.

For Delaware the rates are:

County

Price (dollars per bushel and/or cwt)

Crop

Barley

Corn

Oats

Wheat

Soybeans

Grain

Sorghum

New Castle

1.43

2.10

1.19

2.67

5.36

3.06 (cwt)

Kent

1.43

2.10

1.19

2.59

5.36

3.06

Sussex

1.42

2.10

1.19

2.54

5.36

3.06


Providing U.S. crop development materializes into normal or better yields with low prices, these rates will become important in 1999 grain and oilseed sales decisions. The deadline to update 7-year Production Flexibility Contracts is August 2, 1999. The deadline to update crop acreage reports is June 1 for wheat, barley, and other fall seeded crops; and August 5, 1999 for corn, soybeans, grain sorghum, and other spring seeded crops. These updates are necessary in order to maintain eligibility for 1999 loan deficiency payments (LDPs).

As for the matter of potential changes in how loan deficiency payments are made. USDA has placed the matter on hold. Possible public hearings are being considered. Hearings are not required.

Commodities Focus on the Weather
The weather now becomes a key factor in determining the direction in the bidding of commodity prices. Talk of a possible downturn in stock prices could eventually bid well for commodity prices, bringing an increased level of speculative funds into commodity bidding. v


Drought-stress and Postemergence HerbicidesMark VanGessel, Extension Weed Specialist; mjv@udel.edu

It is dry and the weeds are robbing valuable moisture, so what is the sure-fire answer for effective control? Sorry, no silver bullets, but here are a few things to consider. Greenhouse studies with soybean herbicides (and field observations) under moisture-stress conditions showed that translocated herbicides like Roundup, Pursuit, and Classic performed better than contact herbicides such as Blazer and Basagran. The effectiveness of all the herbicides was reduced by the moisture-stress, but effectiveness of the translocated herbicides was not reduced as much as the contact herbicides.

Under moisture-stress conditions, use the full labeled rate. Dry weather is not the time to shave rates.

Adding nitrogen fertilizer and ammonium sulfate can increase the effectiveness of herbicides by increasing the plant absorption of herbicides through leaves. However, this also increases the uptake of herbicide by the crop which can lead to increased injury. So expect higher level of crop injury if you include these products. In cases of large weeds and limited soil moisture, the crop injury may be justified in return for improved weed control.

Do not assume that because the weeds do not show signs of moisture stress that they are actively growing. Last season was a good example of common lambsquarters not showing signs of moisture stress (while other weeds were wilted), yet lambsquarters control was reduced as much as other weeds.

Finally, be sure to recheck treated fields for herbicide effectiveness, and if re-treatment is needed, be sure it is done as soon as possible after the field gets some rain. v

 

Yellow Nutsedge Control in Corn –– Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

I have seen a lot of yellow nutsedge this year, which is surprising for how dry the spring has been. The best control in corn is Permit. This treatment not only burns off the leaves but also controls the nutlets. This treatment is superior to other postemergence corn herbicides. Be sure to refer to the label for use rates and restrictions. v


                  Weather Summary

Week of May 27 to June 2

Rainfall:
 

None.

Readings taken for the previous 24 hours at 8 a.m.
Air Temperature:
Highs Ranged from 91F on May 30 to 72 F on May 27.
Lows Ranged from 67F on June 2 to 51F on May 28.
Soil Temperature:
81 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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