The Weekly Schedule Begins – April 4, 2003

 

This newsletter is designed to provide subscribers with the latest information on disease and insect problems, weed control information, crop progress reports, and other timely topics related to agronomic and vegetable crop production in Delaware.  University of Delaware Extension Specialists and Agents provide information for the newsletter.  The weekly issues will begin on April 4, 2003 and continue through the month of September.  The Weekly Crop Update can be obtained by mail, fax (subscription cost is $30) or from the Internet at http://www.rec.udel.edu/TopLevel/Publicat.htm for free.  Use the enclosed form to subscribe. We also offer a weekly email reminder to those of you who wish to receive one.  Please forward your email address on the enclosed form or to my email address below.  I ask those of you who plan to access the newsletter from the Internet to please notify me of any problems you may encounter during the season.  Please forward any comments or concerns to me at

302-856-7303 or at wootten@udel.edu .

 

 

Has the Winter Weather Affected Insect Populations? - Joanne Whalen, Extension  IPM Specialist;   jwhalen@udel.edu

 

Entomologists are often asked if extremely cold or mild winter weather has an impact on insect populations in the spring. Most would agree that there is no one answer to this question. Although mild weather conditions enable some overwintering insects to survive, winter weather has little or no impact on other species.

 

If you look at the major insects that attack field and vegetable crops, some general principles can apply ---

(a)    Overwintering Stage: Insects that overwinter in the soil in the egg stage are generally not affected by cold winter temperature. The best example is the corn rootworm. In comparison, insects that overwinter in the adult stage, especially beetles can be more affected by cold winter temperatures. However, the heavy snow cover can negate these affects because it offers some degree of insulating protection.

(b)    Overwintering Location: Insects that overwinter deep in the soil -- like grubs and wireworms -- are generally not affected by the cold winter temperatures. Spring conditions including early planting followed by cool, wet weather can favor damage from these pests.

(c)    Natural Protection: The European corn borer (ECB), which overwinters as a full grown larva, has an antifreeze type material in its body that protects them from cold winter weather. Vacillating temperatures (from very cold to very warm) in the winter can have a greater impact on reducing overwintering ECB populations.

(d)    Migratory Species: Obviously, winter conditions in our area have no affect on migratory species like the potato leafhopper, cabbage looper and beet armyworm.

So, predicting the potential for infestations based on winter weather conditions is often not very accurate. It has been the experience of most entomologists that spring weather conditions have the greatest impact on insect populations and determine if an insect will become a pest problem. The only way to know if you have a problem is to understand which cropping systems favor certain pests and plan to scout fields on a routine basis in-season.

 

Fruit

 

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

 

Peaches.

A Section 18 Emergency Use request was again submitted to EPA in February for the use of Provado on stone fruit to control aphids that vector the Plum Pox Virus. There is also a possibility that the full Section 3 federal registration may come through before this use season. We will let you know as soon as we get a response from EPA.

 

 

Vegetables

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

 

Seed Corn Maggot (SCM).

With the recent cool, wet weather, SCM management should be considered in most spring planted vegetables including cabbage, peas, snap beans, spinach and sweet corn.

 

Peas and Snap Beans.

The only available control options are a seed applied Lorsban SL treatment (must be done by a commercial treater) or a hopper box treatment of diazinon 50W. Gaucho is no longer labeled on snap beans for seed corn maggot control. In recent years, diazinon 50W has provided good SCM control. It should be applied at a rate of ½ oz per bushel of seed and graphite added to prevent bridging in the planter.  As of November 2002, this is the only diazinon formulation registered for use on peas and snap beans. We will have this label until July of 2004, but it is in jeopardy of being lost. We will need to hear from growers and processors interested in maintaining this registration. Documentation and information regarding the importance of this material for your operations will be needed. Please contact Joanne Whalen at

302-831-1303 for more information.

 

Spinach.

The only available option is a broadcast application of 3 qts/A of diazinon applied right before planting and immediately incorporated 2-3 inches deep. Diazinon should not be incorporated too deeply and the ground should only be worked once after application.

 

Sweet Corn.

In addition to hopper box treatments, a number of seed applied treatments including Lorsban SL, Gaucho and Cruiser are available for sweet corn. Soil insecticides including Force, Lorsban, Fortress, Furadan and Counter are also labeled for SCM control in sweet corn.  Under heavy pressure, a soil insecticide and a seed treatment may both be needed. Furadan and Counter are the only two soil insecticides that will also provide flea beetle control. Gaucho and Cruiser will also provide flea beetle control.

 

 

Sandea Herbicide Receives Federal Label for Several Vegetable Crops – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

 

In December, EPA granted a federal registration for Sandea, a broadleaf weed herbicide for use on cucumbers, cantaloupes, pumpkins, tomatoes, winter squash, and asparagus as post-plant preemergence or post-emergence treatments.  It is also labeled for use in the row middles for peppers and summer squash.

 

Sandea provides excellent control of yellow and purple nutsedge, as well as many other broadleaf weeds.  Pre-emergence applications require 0.5 to 1.0 ounce per acre.  Post-emergence applications should be applied at the 2-5 leaf stage, with the 3 leaf stage being ideal.  Rates for post-emergence applications are 0.5 to 0.66 ounce per acre with a non-ionic surfactant.  Irrigation should be delayed until 2 to 3 days after application and cultivation until 7 to 10 days after application.  Both applications should be applied in a minimum of 15 gallons of water per acre.

 

Sandea does not control grasses.  Therefore, herbicides that control grasses should be used as part of the weed control program.  The selection of the grass herbicide will vary with the crop.

 

Please read the label carefully before purchasing and using Sandea.  More details about Sandea on a crop by crop basis will be published in future Weekly Crop Updates.

 

 

Pictsweet Frozen Foods Changes Plans – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

 

In early March, Pictsweet Frozen Foods chose not to exercise its option on land south of Bridgeville, Delaware.  The company had been planning to build a raw product receiving and cooling station to receive lima beans, peas, and possibly sweet corn.  Pictsweet was also developing plans to build a complete frozen food factory at some point in the future.

 

While these plans have been dropped, the company is committed to contracting and receiving 3,000 acres of lima beans this year and in the foreseeable future.  Pictsweet is contracting with growers for delivery of raw product in Delaware, then cleaned and cooled for shipment to their plant in Bells, Tennessee.  With the investment required in harvesting equipment, it is also foreseeable that peas, which are harvested by the same equipment as lima beans, may be handled in the future.

 

While the news is disappointing in light of the company’s original plans, Pictsweet’s interest in procuring lima beans from Delaware is a strong positive.  Delaware grower’s ability to produce lima beans efficiently and consistently is why this new “book of business” has found its way to Delaware.

 

 

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

 

Stewart’s Wilt of Sweet Corn.

For control of Stewart's wilt, which is vectored by the corn flea beetle, it is important to control the flea beetle. Plant resistant varieties and control the beetles early. The following index predicts conditions favorable for overwintering flea beetle populations not the abundance of the bacteria. The prediction has its limitations including the influence of snow cover on survival, but indicates that flea beetles should be reduced compared to most seasons. The question always becomes how much bacteria is available for them to spread. It’s interesting to note how cold this period was compared to previous seasons, in case you had not noticed.

 

Winter Temperature Index For Predicting Stewart’s

Wilt in Delaware Sweet Corn, 1994-2003.

 

Average monthly temperatures in ^oF at Georgetown, DE. REC. 1994-2003

	2002-03	2001- 02	2000-01	1999-00	1998-99	1997-98	1996-97	1995-96	1994-95
December	36.7	43.2	31.2	40.3	41.3	39.3	42.0	33.5	43.0
January	28.9	40.0	33.8	33.9	39.5	42.6	35.0	33.5	39.0
February	33.8	39.9	38.8	39.7	38.7	40.6	41.5	34.7	33.8
INDEX	99.4	123.1	103.8	113.9	119.5	122.5	118.5	101.7	115.8

 

Average monthly temperatures in ^oF at