Posts Tagged ‘18:10’

Potato Disease Advisory #3 – May 20, 2010

Thursday, May 20th, 2010

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

We are using the E-WEATHER SERVICE from SkyBit, Inc as we have in the past. The service determines specific requested weather parameters (temperature, relative humidity and rainfall) based on calculations of data from the nearest National Weather Service stations. This weather data is used in the WISDOM software program for predicting late blight and early blight and making spray recommendations.

Location: Art and Keith Wicks Farm, Rt 9, Little Creek, Kent County.
Greenrow: May 6

Date DSV Total DSV Spray Recommendation
5/1 – 5/10 0 0 none
5/11 – 5/12 3 3 none
5/12 – 5/13 1 4 none
5/14 – 5/17 0 4 none
5/17 – 5/19 7 11 none

 

The threat of late blight from seed infection is low, but there was some in Maine last season. Be vigilant anyway, given this recent weather pattern. The first late blight fungicide application is recommended once 18 Disease Severity Values (DSVs) accumulate from green row. Green row occurred approximately on May 6, 2010. Please be vigilant and keep a look out for suspect infections on young plants coming from infected seed pieces! Growers opting not to use the forecast system should put the first late blight fungicide application on when the plants are 6 inches tall, and repeat every 7 days. There are numerous fungicides now labeled for late blight control; however, use of mancozeb (Manzate, Penncozeb, or Dithane), chlorothalonil or Polyram are still very effective early season protective fungicides to use.

The recent wet, cool weather produced 7 DSVs from late Monday night through Wednesday night. This leaves us with only 7 DSVs before the first late blight spray should be applied if it has not already been applied.

The Plant Management Network has just posted an excellent webinar about late blight on potato by Dr. Steve Johnson, Extension Potato Specialist, Maine Cooperative Extension. Steve was an invited speaker at several of our Delaware Vegetable Growers Conference potato grower sessions many years ago. You can find it at: http://www.plantmanagementnetwork.org/edcenter/seminars/potato/PotatoLateBlight

Sweet Corn Vigor

Thursday, May 20th, 2010

Gordon Johnson, Extension Fruit & Vegetable Specialist; gcjohn@udel.edu

Each year we see sweet corn fields with stand and plant vigor issues, especially in early planted fields. There can be many causes for stand loss and weak seedlings: surface compaction and crusting, birds, soil insects, cold soils that delay emergence, soil diseases affecting seeds or seedlings, wet soils, fertilizer injury, deep planting, and herbicide injury are just a few examples.

When checking sweet corn fields with vigor and stand problems, it is important to dig up seeds and affected plants and examine the seed remnants, roots, and mesocotyl (stem that pushes the seed leaf to emerge above the ground). Corn seedling survival and early vigor is directly tied to a healthy seed kernel and mesocotyl from planting through the six leaf stage. Any damage to the seed or mesocotyl during this period can lead to stunted or weak seedlings, and in severe cases, seedling death. This is because the corn seedling depends on the seed for food to grow for several weeks after emergence until sufficient leaf area has been produced and nodal roots have become established. The seed kernel provides the means for early roots to grow and these food reserves are also mobilized and transported through the mesocotyl to grow the first stalk and leaf tissue. The mesocotyl also serves to transport water and mineral nutrients from the seedling roots.

Sweet corn is more susceptible stand loss and poor vigor problems than field corn because the seed has less food reserves. Shrunken types (supersweet and sugary enhanced varieties) have even less stored food than “normal” types and therefore are more susceptible to stand problems.

I have looked at sweet corn fields with stand loss and vigor problems (uneven growth) over the years. Often, when digging up the seedlings and examining the seed remnants and mesocotyls, the kernels will be disintegrated and there will be darkening at the mesocotyl attachment. This means that the seeds will have deteriorated prematurely and therefore the full content of the food reserves in the seed were not available for seedling development leading to the stand and vigor issues. The question that needs to be answered is what caused the seed to deteriorate prematurely?

The answer of course will change from field to field. Seed deterioration and/or poor vigor seedlings can be due to diseases that cause seed rots, seedling blights and/or root rots. Fungal disease organisms such as Pythium, Fusarium, Rhizoctonia, Aspergillus, and Penicillium are common in soils and many can even be carried on seeds. Fungicide seed treatments are critical to control these diseases. Problems occur where seed treatments are not adequate, where disease organisms are at very high levels, or where soil conditions are too cold and seeds remain in the soil for extended periods before germination and emergence. The risk of seeding infection increases as germination and emergence is extended and protecting seed treatments dissipate.

Cold stress and cold soils is a common stress factor leading to poor stands. Often growers are pushing the limits and are planting sweet corn too early. While field corn will start to germinate at 50°F, many types of sweet corn need much warmer soils. This is especially true of supersweets and other shrunken types which perform best at soil temperatures 65°F or higher. Sweet corn germinates best at soil temperatures above 68°F. When soil temperatures are below 55°F, germination is greatly extended. Food nutrients are mobilized in the seed but are not being utilized rapidly by the plant. The seed then becomes a perfect food source for many soil microorganisms.

Soil insects can cause seed deterioration by feeding on seed contents and causing entrance wounds for disease organisms. Seed corn maggots and wireworms can feed on the seed directly causing stand losses. Grubs feed on seedling roots causing stunting. Wireworms and certain grubs will also feed on the mesocotyl causing seedlings to collapse. Sweet corn that takes more than 10 days to emerge is at great risk of injury due to insects as seed treatments dissipate. In fields with heavy infestations of soil insects seed treatments may not be adequate. Addition of manures or other organic matter sources just prior to early plantings can lead to heavy seed corn maggot populations that overwhelm seed treatments.

Stand issues are often related to the inherent poor vigor of sweet corn. Work with seed suppliers to obtain their best lots for early plantings with the largest seed sizes. Obtain varieties that perform better under cold stress.

The University of Delaware has two separate trials of processing sweet corn varieties from several seed companies that were planted in both early (April) and later (May). Results from these trials will be available later this year for future planning.

Vegetable Crop Insects – May 21, 2010

Thursday, May 20th, 2010

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

Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. We are starting to find cucumber beetles, especially in cantaloupe fields. As soon as we get a day of warm, sunny weather we could see a significant increase in activity. So be sure to scout carefully since damage can occur quickly. Since beetles can continue to re-infest fields as well as hide under the plastic, multiple applications are often needed to achieve control. Foliar products labeled for cucumber beetle control on melons include Assail, a number of pyrethroids, Lannate, Sevin and Thionex. The Actara label only states cucumber beetle suppression. Be sure to check all labels for rates, precautions and restrictions, especially as they apply to pollinators.

Peppers
Continue to sample for thrips and corn borers. On young plants, corn borer larvae can bore into the stems and petioles. In areas where peppers are isolated or corn is growing slowly, moths are often attracted to young pepper plants. Therefore, you should watch for corn borer moths laying eggs in all fields. As a general guideline, treatment may be needed if there is no corn in the area or you are using rye strips as windbreaks. You should also look for egg masses on the leaves. For the most recent trap catches, you can check our website at (http://ag.udel.edu/extension/IPM/traps/latestblt.html) or call the Crop Pest Hotline (in state: 1-800-345-7544; out of state: 302-831-8851).

Snap Beans
Continue to sample all seedling stage fields for leafhopper and thrips activity. The thrips threshold is 5-6 per leaflet and the leafhopper threshold is 5 per sweep. If both insects are present, the threshold for each should be reduced by 1/3. If both insects are present, Lannate, bifenthrin, Proaxis and Warrior (lambda-cyhalothrin) are labeled for both insect pests on snap beans. Be sure to check labels for comments on thrips management. In addition, be sure to watch for bean leaf beetle. Damage appears as circular holes in leaves and significant defoliation can quickly occur. As a general guideline, a treatment should be considered if defoliation exceeds 20% prebloom. A pyrethroid, dimethoate or Sevin are labeled for control.

Sweet Corn
Continue to sample for cutworms and flea beetles. As a general guideline, treatments should be applied if you find 3% cut plants or 10% leaf feeding. In order to get an accurate estimate of flea beetle populations, fields should be scouted mid-day when beetles are active. A treatment will be needed if 5% of the plants are infested with beetles. Small corn borer larvae can be found in the whorls of the earliest planted fields. A treatment should be applied if 15% of the plants are infested. Corn earworms can also be found in light traps and pheromone traps. In sweet corn planted under plastic, silk sprays will be needed for corn borer and corn earworm as soon as ear shanks are visible. For the most recent trap catches, you can check our website at (http://ag.udel.edu/extension/IPM/traps/latestblt.html) or call the Crop Pest Hotline (in state: 1-800-345-7544; out of state: 302-831-8851).

Livestock Pasture Walk

Friday, May 14th, 2010

Wednesday, June 9, 2010     6:00 – 8:00 p.m.
DSU, Hickory Hill Research Farm
Route 42, West of Cheswold, DE

Come learn techniques for good pasture management for livestock!

Experts will be on hand from the University of Delaware, Delaware State University and the Natural Resource Conservation Service (NRCS) to answer your questions!

Please bring a folding chair.

NM and CCA credits will be available.

This meeting is free and everyone interested in attending is welcome.

To register, request more information or if you require special needs assistance for this meeting, please call our office in advance at (302) 831-2506.  Call to register by June 7.

See you there!

Anna Stoops
NCC Extension, Agricultural Extension Agent

Soybean Cyst Nematode Workshop

Thursday, May 6th, 2010

Tuesday, August 3, 2010  8:30 a.m.- 1:30 p.m.
Delmarva Poultry Industry Building
(former UD office building)
16684 County Seat Hwy.
Georgetown, DE 19947

Soybean cyst nematode (SCN) is a widespread and serious pest of soybeans on Delmarva. First discovered in the fall of 1979 it has been causing increased problems for growers in recent years. This workshop will cover some basics about the biology of SCN and it management and the results of the recent Delaware Soybean Board sponsored survey of SCN in Delaware. The workshop will also include visiting a small research plot to see SCN first hand and discuss symptoms, diagnosing SCN from root samples with a hand lens, and proper soil testing procedures. The workshop is suggested for agricultural professionals on Delmarva who advise soybean growers and growers who want to know more about this important pest.

Pesticide recertification credits and CCA credits in pest management will be offered for attendees.

The cost of the program is $10 per person with lunch included. The registration deadline is Friday, July 23. A registration form is available here: http://www.rec.udel.edu/Extension/Agriculture/SCN.pdf

Looking for an Enterprising Vegetable Grower

Thursday, May 6th, 2010

We have the land!  Do you have the passion?

We have created one of the most exciting new communities ever to be built in New Castle County just north of Middletown, Delaware on 1,600 acres.  There are 3,000 homes planned on our land and approximately 2,000 homes planned on neighboring lands.  We would like to incorporate locally grown produce as an integral part of our new community—The Village of Bayberry.  We have the land, an ag well, and the perfect location for an entrepreneurial farmer who loves growing and selling fresh produce.  A new farm stand building with plenty of parking will be built by us and would be included in the lease.  There is presently no competition in the area and the land is available immediately.

If interested, please call Jeff Seemans, RLA, at 302-254-0100, X214, or email him at JSEEMANS@BLENHEIMHOMES.COM.  Lease terms are negotiable as is amount of land.

Agronomic Crops Twilight Tailgate Session

Thursday, May 6th, 2010

Wednesday, May 26, 2010     6:00-8:00 p.m.
UD Cooperative Extension Research and Demonstration Area
(3/4 mile east of Armstrong Corner, on Marl Pit Rd. – Road 429, Middletown)

Join your fellow producers and the UD Extension team for an overview of University of Delaware’s Demonstration Plots at the Marl Pit Road Demonstration Site. We’ll cover highlights on grain marketing, nutrient management and pest management, as well.

We will apply for DE Pesticide and Nutrient Management re-certification credits and Certified Crop Advisor credits.

This meeting is free and everyone interested in attending is welcome.

Bring a tailgate or a lawn chair.

To register, request more information or require special needs assistance for this meeting, please call our office in advance at (302) 831-2506. Please call to register by May 25.

See you there!
Anna Stoops, New Castle County Extension
Agricultural Extension Agent

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, disability, age or national origin.