Volume 10, Issue 21 August 16, 2002

Vegetables

 

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

 

Cabbage.

Continue to sample fall planted fields for diamondback and cabbage looper larvae. We can find economic levels of both insects in recently planted fields. If both species are present, Avaunt (3.5 oz/acre), a Bt, Proclaim (3 oz/acre), or Spintor (4-5 oz per acre) will provide control. If cabbage looper is the predominant species, a pyrethroid or Confirm (8 oz/acre) will also provide control.

 

Lima Beans.

Be sure to sample fields carefully for corn earworm, lygus and stinkbugs. A treatment should be applied if you find one corn earworm per 6 foot of row or 15 tarnished plant bugs and/or stinkbugs per 50 sweeps. Lannate, Mustang or Capture can be used to control all 3 insects on lima beans. Spider mites are still present in drought stressed fields. Kelthane or Capture will provide control. If Capture is used for insect control, Kelthane should be considered for mite control to provide a rotational material.

 

Peppers.

At the present time, all peppers should be sprayed on a 7-day schedule for corn borer, corn earworm, and beet armyworm control. Orthene or Address will not provide satisfactory earworm control. A pyrethroid or Lannate will be needed for earworm control. If beet armyworms are present, Avaunt, Spintor, Confirm or Lannate will provide the best beet armyworm control. Depending on the pest complex present, a combination of products will be needed.

 

Snap Beans.

Processing snap beans in all areas of the state should be treated at the bud and pin stages for corn borer control. Orthene or Address should be used at the bud and/or pin stages for corn borer control. In all areas, a pyrethroid should be combined with Orthene at the pin spray for earworm control. After the pin stage, Lannate, Capture or Mustang should be used. Sprays will be needed on a 5-day schedule from the pin spray until harvest. Since this can change quickly, be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in processing snap beans (http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/snapbeanecbthresh.html). You should treat fresh market snap beans for corn borers on a 7-day schedule from the pin stage until harvest. Lannate, Capture or Mustang should be used.

Spinach.

Fields should be scouted at emergence for webworm and beet armyworm larvae. Controls should be applied when worms are small and before they have moved deep into the hearts of the plants. Also, remember that both insects can produce webbing on the plants. Since beet armyworms are more difficult to control and populations are high in Virginia, identification of larvae will be important. Since Lannate cannot be applied before plants are 3-inches in diameter and it only provides control of small larvae, Confirm or Spintor will be needed for beet armyworm control. If webworms are the predominant species, Ambush, Pounce, Confirm (6-8 oz/acre) or Spintor (4-8 oz/acre) should be used. Generally, at least 2 applications are needed to achieve control of webworms and beet armyworm.

 

Sweet Corn.

Fresh market silking sweet corn should be sprayed on a 2-3-day schedule in all areas of the state. Since this can change quickly, be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in fresh market sweet corn.

(http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/silkspraythresh.html ).

 


 

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

 

MELCAST for Watermelons.

From the University of Maryland and University of Delaware

Latest EFI values from local weather stations

Any questions please call (410) 742-8788

 

EFI Values (Environmental Favorability Index)

Do not use MELCAST if there is a disease outbreak in your field, it is a preventative program.

Location 08/14/02 08/13/02 08/12/02 08/11/02 08/10/02 08/09/02 08/08/02 08/07/02

Bridgeville, DE 0 2 2 2 1 1 0

Charles Co. 0 0 0 0 0 0 0

Collins Farms 1 3 2 1 1 1 1

Galestown, MD 1 3 2 1 1 1 0

Georgetown, DE 0 1 0 1 0

Glenville, MD 0 0 0 0 0 0 0

Hebron 1 3 3 1 1 1 1

Hog Creek Rd. 0 0 0 0 0 0 0

Salisbury, MD 0 3 2 1 1 1 1 0

Vincent Farms 1 3 4 1 1 1 1

Westminster 0 0 0 0 0 0 0

White Marsh 0 0 0 0 0 0 0

The first fungicide spray should be applied when the watermelon vines meet within the row. Additional sprays

should be applied using MELCAST. Accumulate EFI (environmental favorability index) values beginning the

day after your first fungicide spray. Apply a fungicide spray when 30 EFI values have 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 0 and start over. The first and last day listed above can be partial days so use the larger EFI value

of this report and other reports for any specific day.

 

If, for some reason, a serious disease outbreak occurs in your field, return to a weekly spray schedule.

More detailed information concerning MELCAST and sample data sheets are available on the web at http://www.agnr.umd.edu/users/vegdisease/vegdisease.htm.

 

 


 

Field Crops

 

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

 

Soybeans.

We are starting to find a few fields with economic levels of corn earworm larvae, especially irrigated fields. In Virginia, high levels are being found and many fields have already been sprayed. In addition to corn earworm, you will also want to be watching for other potential pod feeding larvae. Corn earworm and fall armyworms are the predominant pod-feeders. However, beet armyworm (BAW) populations are also high in Virginia at this time. This insect usually acts as a defoliator, but will begin feeding on pods if populations are high. We can find an occasional BAW larvae in fields throughout the state. This insect is migratory so populations from Virginia could make it to soybean fields in the next few weeks. The pyrethroids have not provided effective control of beet armyworm, so identification will be critical. In general, the body of the caterpillar will be green with wavy white lines and there is a black spot on the side of the larvae above the second set of true legs. Larvin will need to be used if beet armyworms are the predominant species. Although Steward provides very good beet armyworm control, it is not labeled in Delaware at this time.

Therefore, all fields should be scouted for pod feeders as soon as blossoms are present. Since earworms can also act as defoliators, a treatment may be needed if 30% of the plants are defoliated prebloom or 15% of the plants are defoliated during bloom. The treatment threshold for pod feeding is 3 per 25 sweeps in narrow fields and 5 per 25 sweeps in wide row fields (20-inches are greater). A drop (shake) cloth can also be used to estimate populations. The drop cloth should be placed between 2 rows and then the plants are shaken over the cloth in 6 foot of row. A treatment is needed if you find 1-2 larvae per foot of row. When possible, treatment should be delayed until at least 1/3 of the worms at least 3/8-inch long. In addition, watch for diseased worms since the same diseases that attack green cloverworm can also help to reduce earworm population.

 

The following materials will provide corn earworm control in soybeans: Ambush, Asana, Mustang, Pounce, Warrior (all pyrethroids) or Larvin. If population pressure is heavy, the higher rate of the older pyrethroids will be needed. You should use 2.56 of Warrior and 3.2 oz may be needed if mixed size larvae are present at treatment time.

 


 

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

 

Soybeans.

The dry weather is doing more than reducing yields in soybeans; it is also showing soybean cyst nematode infested areas very clearly. Growers and field personnel need to check those yellow areas in fields closely. Not all that stunting and yellowing is mites or manganese deficiency. I am also finding soybean cyst nematode in some spots as well. What is confusing is that at first examination mites are very easily found, but SCN is also present. High initial cyst numbers at planting combined with the dry weather has produced the stunted yellow areas when you can find cysts on the roots. That brings up the next point that during weather like this it is very hard to get a shovel or a soil probe into the ground. This makes finding the cysts on the roots very hard unless you are experienced at finding them in the field. If in doubt, take a soil test and submit it for an SCN test at the county Extension office. This fall it will be important to sample fields that had trouble spots where the beans were stunted and yellow to be sure if SCN was present. Take a sample before any fall tillage from the soybean rows. Instructions are on the back of the Nematode Assay Form that is available from the county Extension offices or on the web at http://ag.udel.edu/extension/information/pp/pp-02.htm. Nematode test bags are $10/ sample.

 


UPCOMING EVENTS:

 

Wicomico Farm & Home Show

 

Winterplace Park

RT 50 & Hobbs Road

Salisbury, MD 21804

 

August 15-17, 2002

 

 


      Weather Summary

Week of August 8 to August 14, 2002

Rainfall:

 

NONE.

 

 

Readings taken for the previous 24 hours at 8 a.m.

Air Temperature:

Highs Ranged from 97F on August 13 to 83F on August 8 & 9.

Lows Ranged from 74F on August 14 to 55F on August 8.

Soil Temperature:

85 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 University and the United States Department of Agriculture cooperating, Robin Morgan, Dean and Director. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. It 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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