Weekly Crop Update

University of Delaware Cooperative Extension

Volume 5, Issue 21

August 21, 1997

 

Field Crops:

Grain Marketing Highlights -

Carl German, Extension Specialist, Crops Marketing

clgerman@udel.edu

 

Commodity traders are currently turning their attention to export news and the levels of exports for the current and next marketing year. For the moment, weather related information has been discounted (bid into) commodity prices. The Pro Farmer crop tour is underway this week with corn yield estimates of 111.7, 115.5, and 116.6 bushels per acre reported for Indiana, Ohio and Illinois. These estimates are running about 10 bushels per acre below the August USDA U.S. corn yield projection. Tour pod counts for soybeans tend to indicate yield estimates to be in line with USDA's August estimate. High yield variability, within fields, and district to district is being noted, which adds uncertainty to the actual yield estimates. Crop maturity, being well ahead of last year and the five year average, has tour participants wondering if recent beneficial rains can have much impact on improving yields, particularly for soybeans. It will be interesting to note how much weight the futures market places on the crop tour reports?


The Future of Crop Yields: What's the Limit? Wheat

Richard W. Taylor, Extension Agronomist

rtaylor@udel.edu

 

I read an article this week about modern agriculture's challenge to keep up the pace of food production so the world's increasing population can be fed. Some people fear that the steady increase in crop yields over the past few decades has slowed or reached a plateau. For wheat, the article stated that neither the United States nor Mexico has seen any improvement in wheat yields for 13 years. Globally, wheat yields rose an average of 2.1 percent yearly from 1960 to 1990 but have increased just 0.1 percent in the past 10 years.

 

Will wheat yields continue to stagnate? No. Several avenues for improvement exist. The first, changes in starch (captured sun energy) partitioning, is under way in rice. Plant breeders are changing the rice plant's architecture so that a greater share of the plant's carbohydrates are moved into the grain and a lesser share goes to stems and leaves. If this approach is taken in wheat, yields can again increase.

 

A second avenue currently under development is to maximize the benefits of hybrid vigor (heterosis) in new wheat cultivars. Although not commercially economical at this time, the development of a chemical treatment to sterilize the male part of the wheat flower to prevent self-pollination and allow inexpensive production of a first-generation hybrid wheat is under way. Measurements of the hybrid vigor of such a wheat hybrid show yield increases of 20 percent. Current seed available to you, the grower, represents seed from the 7th to 10th generation of a hybridization. This means that little to no hybrid vigor is being expressed as increased yield potential.

Another area that may reinvigorate wheat yields is irrigation. Many growers have or are considering irrigation systems and could grow wheat/double-crop soybeans in their rotations. We know that double-crop soybean yields can be increased dramatically (up to the 40 to 50 bu/A range) with irrigation. I hope to begin work this coming year on managing irrigation on wheat to discover if wheat yields can be increased and how best to irrigate to accomplish this goal.


Field Crop Diseases -

Bob Mulrooney, Extension Plant Pathologist, bobmul@udel.edu

Wheat.

The Following table reports resistance reactions to wheat spindle streak mosaic virus. This is s soil borne virus that is transmitted by a root infecting fungus. If you know wheat spindle streak mosaic virus has been diagnosed in a field, choosing a resistant wheat variety would be the preferred control measure. Wheat spindle streak mosaic can be a problem during cool, wet springs like we experienced this past season. These ratings were reported by Dr. Don Hershman at the University of Kentucky and are useful for us because they grow soft red winter wheat also. Another source of resistance information is your seed supplier. Be sure to check for virus resistance to the three common viruses that we see here in Delaware: wheat spindle streak mosaic, wheat soilborne mosaic, and barley yellow dwarf.

See Page 5 for the Report from University of Kentucky on Wheat Varieties Reactions to WSSM.


Vegetable Crops:

Vegetable Crop Insects - Joanne Whalen, Extension IPM Specialist

joanne.whalen@mvs.udel.edu

 

Cabbage.

Although diamondback (DBM) and cabbage looper (CL) are the predominant insect species found at this time, fall armyworm(FAW) populations are also starting to increase. A combination of a Bt plus a pyrethroid has provided good control if worms are small at the time of treatment and the predominant species are DBM and CL. However, if FAW are being found then Monitor ( 1qt/a) or Lannate LV (1.5 pt/a) plus a Bt should be used.

 

Lima Beans.

Although earworm , stinkbug and lygus populations have been light in many fields, be sure to continue checking fields twice a week for this insect complex. Corn earworm moths can now be found flying in fields and laying eggs. Since populations can explode quickly, corn earworm size at the time of treatment can vary from to 1 inch in size. If most of the worms are greater than an inch at the time of treatment , at least 2 pt/A of Lannate LV will be needed to provide control. However, if treatment is delayed, 3 pt/A will be needed.

 

Peppers.

All peppers should be sprayed on a 7 day schedule for corn borer, corn earworm, fall armyworm and aphid control. Since corn borer catches remain high in the Bridgeville, Harrington and Leipsic areas, a 5 day schedule is needed. Orthene or Lannate are the preferred materials at this time.

 

Processing Snap Beans.

Corn borer treatments are needed at the early bud and early pin stages. Corn earworm control will also be needed at the pin stage. Since Orthene will not provide effective corn earworm control, a combination of Orthene (1.33 lb/a) plus Asana (6 oz/acre), should be applied at the pin stage. After the pin spray, sprays should be applied on a 5-6 day schedule except in the Bridgeville, Harrington and Leipsic areas where sprays are needed on a 4 day schedule. Since corn borer and corn earworm are both potential problems, the high rate of Lannate is the material of choice.

 

Spinach.

As soon as plants emerge, begin scouting for small webworms feeding in the hearts of plants. Controls must be applied when worms are small and before webworms have produced significant webbing and are no longer exposed to an insecticide application. Since Lannate can not be applied before plants are 3 inches in diameter, Ambush, Pounce or a Bt insecticide (20 gallons water per acre for the BT application) should be used. Generally, 2 insecticide applications are needed to get effective webworm control.


Lima Bean Weed Control -

Ed Kee, Extension Vegetable Specialist

kee@udel.edu

 

Several growers have asked about using the material Reflex on lima beans. It is not labeled on lima beans. Reflex does have a Section 18 Emergency label for green beans in Maryland and Virginia. Indications are that a full national label may be in use by next season for Reflex on green beans, although that remains to be seen. If not, Delaware will apply for a Section 18 for Reflex on green beans in 1998.

 

Previous research at Delaware indicated significant injury can occur on lima beans, especially Fordhook lima beans, at the rates need to achieve morningglory control. This work was conducted in small plot work, and in a commercial setting. While further research may be needed, there are strong indications that significant crop injury may occur on lima beans, which are a different crop species than green beans or string beans.

 

Reflex is useful for controlling morningglory and other weeds, but currently it is only labeled for green beans, as well as soybeans.


Vegetable Crop Diseases -

Kate Everts, Plant Pathologist, University of Maryland and Delaware

everts@udel.edu

 

Cucurbit Diseases.

Powdery mildew (Sphaerotheca fuliginea) is now present in many squash, cucumber, muskmelon, and pumpkin fields on Delmarva. This disease is controlled by use of systemic fungicides. Unfortunately, the fungal population contains individuals which are resistant to the chemicals we use most widely: benomyl (Benlate) and triadimefon (Bayleton). In a recent bioassay conducted in plots at the REC in Georgetown, fungal colonies were able to grow on plants which

had been treated with benlate, bayleton, and both chemicals. This bioassay, which was conducted before either chemical was applied to these plots, indicates that resistance is present even before we apply systemic chemicals! Fungicide usage can impact how quickly fungicide resistance increase over the growing season. To minimize resistance build up, scout fields and do not apply systemic fungicides before one lesion is detected on 50 old leaves. Use systemic fungicides in combination with protectant fungicides like copper or chlorothalonil (Bravo or Terranil). Alternate systemic chemicals, and limit their usage over a season. Since resistance can build up rapidly, prolonged use will result in reduced effectiveness of systemic fungicides. In making planting decisions for 1998, try to use resistant varieties when available.

 

Weather Summary
University of Delaware,
Georgetown
Week of August 15 to August 21, 1997
Rainfall:
0.03 inches: August 18
0.07 inches: August 19
1.35 inches: August 21
Readings taken for the previous 24 hours at 8 a.m.

Temperature:
Highs
Ranged from 97 F on August 17 & 18 to 75 F on August 21.
Lows
Ranged from 83 F on August 17 to 56 F on August 19.

Soil Temperature:
74 F. Average for the week.

http://laurie.rec.udel.edu

 

Compiled & Edited By:

Tracy Wootten

Extension Associate - Vegetable Crops

 

Resistance Reactions to Wheat Spindle Streak Mosaic Virus for Wheat

University of Kentucky

 

Variety

WSSM Reaction

Variety

WSSM Reaction

Beck 103

MS

Becker

MS

Caldwell

S

Cardinal

MS

Clark

R

Clemens

MS

EK 102

S

EK 114

S

EK 309

S

Elkhart

S

Ernie

MS

Featherstone 520

S

FFR 523

S

FFR 525

VS

FFR 555

MS

FFR 558

S

Foster

MS

Glory

R

Hopewell

MR

Jackson

S

KAS Justice

MS

KAS Patriot

MS

Madison

R

NK Coker 9543

MS

NK Coker 9663

S

NK Coker 9704

S

NK Coker 9803

MS

P2510

R

P2540

R

P2548

VS

P2568

R

P2552

R

P2684

MS

P2737

MR

Patterson

MR

Pocahantas

S

Terra SR 204

MS

Terra SR 205

MS

Terra SR 211

MS

Verne

MR

Voris 6044

MS

Wakefield

S

Ratings are based on observation of replicated plots and/or multiple field observations.

R=resistant, MR=moderately resistant, MS=moderately susceptible, S=susceptible, VS=very susceptible.

 

Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State College and the United States Department of Agriculture cooperating. Richard E. Fowler, Director. Distributed in furtherance of the Acts of Congress of March 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, color, sex, handicap, age or national origin.