Posts Tagged ‘17:8’

Timber Rot, White Mold or Sclerotinia Rot in High Tunnels

Friday, May 8th, 2009

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

The fungus Sclerotinia sclerotiorum causes disease on hundreds of plant species. Timber rot or Sclerotinia rot is becoming a very serious problem in tomatoes (and other crops) grown in high tunnels. Even when a high tunnel is moved between seasons, the disease can be severe because the fungus overwinters both in and around the tunnels. Usually the primary source of inoculum is outside of a high tunnel. In the spring when the soil is moist, the fungal fruiting bodies emerge and spores (ascospores) are released. These ascospores will be released continually throughout the spring and are carried on wind into the doors or raised sides of nearby high tunnels. Ascospores are usually carried or dispersed less than 330 feet. Therefore it is important to use sanitation within 330 feet of a high tunnel. No plants, leaf clippings, potting mix, or soil from the tunnels should be discarded within this area.

The biocontrol Contans has been effective in managing Sclerotinia diseases in the field. Contans, which is a formulation of the fungus Coniothyrium minitans, parasitizes the survival structures of S. sclerotiorum. If it is sprayed on the area around the high tunnel and watered into the soil, it may help reduce ascospore formation in future years. Because the product is living, it must be handled carefully prior to use. Contans would be a good choice to try in fields or areas around high tunnels, which are used repeatedly for a susceptible crop. See the Contans label for additional information.

Other products labeled for Sclerotinia timber rot are Endura, which is labeled for field use, and Botran, which is labeled for greenhouse use.

The black sclerotia on the small tomato fruit will overwinter and result in ascospore formation in future years. The fruit should be either buried or discarded more that 330 feet from the high tunnel.

 Sclerotinea rot on a small tomato fruit.

Tomato fruit infected with Sclerotinia sclerotiorum.

Downy Mildew and Alternaria of Cole Crops

Friday, May 8th, 2009

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

Symptoms of downy mildew on cole crops include purple to yellowish-brown spots on upper leaf surfaces. A grayish-white spore mass will develop and cover the underside of leaves under ideal temperatures (night temperatures of 46 – 61°F and day temperatures below 75°F). Downy mildew can kill young plants. Heavily infected leaves may drop providing entry points for bacterial infections (black rot and soft rot).

Symptoms of Alternaria on infected leaves include small, expanding circular lesions with concentric rings that may have a ‘shot-hole’ appearance as lesions age. Heavily infected seedlings may result in damping-off.

Control of downy mildew and Alternaria begins with preventative fungicide applications. Use one of the following at the first sign of disease and continue every 7 to 10 days: (Please refer to the pesticide table on page F21 of the 2009 Delaware Commercial Vegetable Production Recommendations to determine which fungicide is labeled for each specific crop.)
● Quadris (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08F/A
● chlorothalonil (M5) at 1.5 pt 6F/A or OLF
● Cabrio (pyraclostrobin, 11) at 12.0 to 16.0 oz 20EG/A
● Endura (boscalid, 7) at 6.0 to 9.0 oz 70WG/A
● maneb (M3) at 1.5 to 2.0 lb 75DF/A or OLF
● Ridomil Gold Bravo (mefenoxam + chlorothalonil, 4 + M5) at 1.5 lb 76.5WP/A (14-day schedule)

For Alternaria only, apply:
Switch (cyprodinil, 9) at 11.0 to 14.0 oz 62.5WG/A

For downy mildew only, apply:
Actigard (acibenzolar-S-methyl, P1) at 1.0 oz 50WG/A (Begin applications 7-10 days after thinning and re-apply every 7 days for a total of 4 applications per season.)
or
Aliette (fosetyl Al, 33) at 3.0 to 5.0 lb 80WDG/A (on a 14-day schedule).

For more information please see the 2009 Delaware Commercial Vegetable Production Recommendations.

Tomato Bacterial Spot and Speck

Friday, May 8th, 2009

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

Tomato transplants with suspected bacterial spot or speck symptoms can be treated with streptomycin (Agri-Mycin 17, Agri-Strep, 25) at 1 lb/100 gallons, or 1.25 teaspoon per gallon every 4 to 5 days prior to transplanting. Additionally, Kocide 3000 (copper hydroxide, FRAC code M1), the updated formulation from DuPont, has a greenhouse label for speck and spot control in the greenhouse. Apply 0.5 to 1.5 tablespoons per 1000 sq ft every 5 to 10 days. Remember, phytoxicity is an important issue when applying copper in enclosed structures; see label for cautions, restrictions and liabilities.

After transplanting, apply Actigard at 0.33 oz 50WG/A (see label for use), or fixed copper (M1) at 1 lb a.i./A plus a mancozeb (Dithane, Manzate, Penncozeb, M3) at 1.5 lb 75DF or OLF, or ManKocide (M1 + M3) at 2.5 to 5.0 lb 61WP/A on a 7-day schedule.

Strawberry Disease Control

Friday, May 8th, 2009

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

Anthracnose Fruit Rot
Strawberry anthracnose can be extremely destructive during warm, wet weather, causing significant fruit rot. Symptoms of anthracnose include blackish-brown circular spots on maturing green fruit and soft, sunken (flat) circular lesions on ripe fruit. On ripe fruit, lesions can expand rapidly and are often covered with a pinkish-orange spore mass. Spores are spread from infected to healthy fruit with splashing water. Control of anthracnose always begins with a 7 to 10-day preventative spray program initiated no later than 10% bloom and/or prior to disease development.

For control apply the following combinations:
Application #1

captan (M3) at 4.0 lb 50WP/A plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23.0 oz 38WG/A
Application #2
captan (M3) at 4.0 lb 50WP/A plus
Abound (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08SC/A
or
Cabrio (pyraclostrobin, 11) at 12.0 to 14.0 oz 20EG/A
Application #3
Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A

For subsequent applications, alternate:
Abound (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08SC/A plus captan (M3) at 4.0 lb 50WP/A
or
Cabrio (pyraclostrobin, 11) at 12.0 to 14.0 oz 20EG/A plus captan (M3) at 4.0 lb 50WP/A
or
Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A

To help manage fungicide resistance development, do not make more than two consecutive applications of either; Pristine (pyraclostrobin + boscalid, 11 + 7), Cabrio (pyraclostrobin, 11) or Abound/Quadris (azoxystrobin, 11) before switching to another fungicide chemistry.

Botrytis (Gray Mold) and Blossom Blight
Botrytis can cause serious losses in strawberry plantings in high tunnels and the field if not controlled properly. Development is favored by moderate temperatures (59-77°F) with prolonged periods of high relative humidity and surface wetness. Control of gray mold begins with preventative fungicide applications. Apply at 5-10% bloom and every 10 days until harvest. During periods of excessive moisture, spray intervals of 5 to 7 days may be necessary. Rotate fungicide chemistries to aid fungicide resistance management.

Application #1
captan (M3) at 4.0 lb 50WP/A plus Topsin M (thiophanate-methyl, 1) at 1.0 lb 70WP/A
or
Switch (cyprodinil, 9) at 11.0 to 14.0 oz 62.5WG/A
Application #2
Elevate (fenhexamid, 17 – See restrictions) at 1.1 to 1.5 lb 50WDG/A
or
Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23.0 oz 38WG/A
Application #3
captan (M3) at 4.0 lb 50WP/A plus Topsin M (thiophanate-methyl, 1) at 1.0 lb 70WP
or
Switch (cyprodinil, 9) at 11.0 to 14.0 oz 62.5WG/A

For subsequent applications, alternate any of the following:
● captan (M3) at 4.0 lb 50WP/A
● Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A
● Switch (cyprodinil, 9) at 11.0 to 14.0 oz 62.5WG/A
● Pristine (pyraclostrobin + boscalid, 11 +7) at 18.5 to 23.0 oz 38 WG/A
● Thiram (M3) at 4.0 to 5.0 lb 65WSB/A

Strawberry Leather Rot
For additional information on leather rot see the article titled Controlling Leather Rot of Strawberry in the April 10, 2009 issue of WCU.

In New Plantings:
Aliette (fosetyl-Al, 33) at 2.5 to 5.0 lb 80WDG/A. Begin 14 to 21 days after planting and continue on a 30 to 60 day interval as long as favorable disease conditions occur.
or
Ridomil Gold (mefenoxam, 4) at 1.0 pt 4E/A. Make one application at transplanting plus an additional application at fruit set or 30 days before harvest.

In Established Plantings:
Aliette (fosetyl-Al, 33) at 2.5 to 5.0 lb 80WDG/A
or
Ridomil Gold (mefenoxam, 4) at 1.0 pt 4E/A
Apply in spring before first bloom and repeat once in the fall.

Potato Late Blight Advisory – 5/8/09

Friday, May 8th, 2009

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

This is the first report for 2009. If you would like a fax or email report please call (302) 831-4865 or email 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 making spray recommendations. Our location this year is:

Shadybrook Farms, Little Creek, Kent County.
Greenrow: May 1

Disease severity values have been accumulating very quickly since the beginning of this rainy period. The threat of late blight from seed infection is low to moderate, but there was some in Maine last season. Be vigilant, given this recent weather pattern. The Wisdom program that is used for calculating the disease severity values will not generate values until one week after greenrow. The way DSVs have been accumulating based on the forecasts, when Friday comes we will have accumulated the necessary numbers to initiate the first spray. The late blight advisory from Skybit has calculated that we have accumulated 21 DSVs to date. My suggestion would be to make a fungicide application when you can get on the field. This is a little early but the weather warrants an application if you reached greenrow on or about May 1. Apply sprays of mancozeb (Dithane, Manzate, Pencozeb, Manex II, Gavel) or Bravo (chlorothalonil) now, and then again before plants canopy down the row.

Fortunately late blight has not been a problem here in Delaware for many years and unless you have seed from an unknown source the risk of late blight is low. However, the weather has been perfect for it if it is present on seed.

Vegetable Crop Insects – 5/8/09

Friday, May 8th, 2009

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

Asparagus
Asparagus beetles adults can be found laying eggs on spears. As a general guideline, a treatment is recommended if 2% of the spears are infested with eggs. Since adults also feed on the spears, a treatment is recommended if 5% of the plants are infested with adults.

Cabbage
Continue to scout fields for imported cabbage worm and diamondback larvae. Larvae can be found and sprays will be needed before they move deep into the heads. As a general guideline, a treatment is recommended if you find 5% of the plants infested with larvae.

Melons
Economic levels of aphids can be found in the earliest transplanted fields. When sampling for aphids, be sure to watch for beneficial insects as well, since they can help to crash aphid populations. We have also been asked about ants being found near melon transplants. In many cases, if ants are present you should look carefully on the undersides of leaves for melon aphids. Ants are commonly found associated with melon aphids in fields. They are often present in fields to collect honeydew from the aphids and can even hinder predation by other insects. As a general guideline, a treatment should be applied for aphids when 20% of the plants are infested, with 5 aphids per leaf. Foliar treatments labeled for melon aphid control on melons include Actara, Beleaf, Fulfill, Lannate and Thionex. These materials should be applied before aphid populations explode. The Fulfill label states that the addition of a penetrating type spray adjuvant is recommended to provide optimum coverage and penetration. Admire and Platinum are also labeled at-planting for aphid control.

Although we do not consider this typical spider mite weather, we are also starting to find an increase in spider mite populations in melons. The threshold for mites is 20-30% infested crowns with 1-2 mites per leaf. Acramite, Agri-Mek, bifenthrin, Danitol, Oberon and Zeal are labeled on melons for mite control. Note – Zeal can only be applied by ground application.

Peas
Continue to sample fields for aphids. On small plants, you should sample for aphids by counting the number of aphids on 10 plants in 10 locations throughout a field. On larger plants, take 10 sweeps in 10 locations. As a general guideline, a treatment is recommended if you find 5-10 aphids per plant or 50 or more aphids per sweep. When sampling dry land peas, you may want to reduce the threshold, especially if they are drought stressed. Be sure to check labels for application restrictions during bloom.

Potatoes
Continue to sample fields for Colorado potato beetle adults, especially if an at-planting material was not used. Low levels of the first emerged adults can now be found. A treatment should not be needed for adults until you find 25 beetles per 50 plants and defoliation has reached the 10% level. Low levels of corn borer moths have been caught in light traps. A corn borer spray may be needed 3-5 days after an increase in trap catches or when we reach 700-degree days (base 50). If you are scouting for infested terminals, the first treatment should be applied when 10% (fresh market) or 20-25% (processing) of the terminals are infested with small larvae.

Sweet Corn
Continue to scout emerged fields for cutworms and flea beetles. As a general guideline, treatments should be applied for cutworms 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.

2009 Wye Strawberry Twilight Meeting

Friday, May 1st, 2009

Thursday, May 21     6:00 p.m.
Wye Research and Education Center
Queenstown, MD

Meet at the farm operations complex, 211 Farm Lane – signs will be posted.

Come See:
● High Tunnel Fall/Spring Fruit Production
● Annual Plasticulture System
● 2nd year carry-over plot using bare-rooted dormant plants in a plasticulture system

University and USDA personnel will speak and be on hand to discuss research and cultural aspects of strawberry production.

The meeting will be held rain or shine (bring rain gear).

Registration is not required. For more information contact Mike Newell (410) 827-7388.

For directions go to the Wye Research and Education Center’s website at http://www.wrec.umd.edu/.

New Castle County Weed ID Workshop

Friday, April 17th, 2009

Tuesday, May 12, 2009     5:00-7:00 p.m.
University of Delaware Webb Farm
508 S. Chapel Street
Newark, DE

What is that weed!? Learning to identify weed species can help with controlling the weed, crop production and your bottom line. Learn to identify a number of weed species that are found locally. Experts will be on hand to answer your questions and help with weed management issues.

Please bring a folding chair.

Pesticide (2) and CCA credits will be available.

This meeting is free and everyone interested in attending is welcome. Please call (302) 831-2506 to register by May 8.

Equine Pasture Walk

Friday, April 17th, 2009

Tuesday, May 19, 2009     5:00-7:00 p.m.
Two Eagles Farm
1311 McQuail Road
Smyrna, DE

Learn about Natural Resource Conservation Services Cost Share Programs and EQIP Eligibility. See on-farm manure storage facility and storm water management projects. Learn about pasture management and managing the diet to avoid injuries and illness. Experts will be on hand form the University of Delaware and the Natural Resource Conservation Service (NRCS) to answer your questions!

Please bring a folding chair.

Nutrient Management (1.75), Pesticide (1) and CCA credits will be available.

This meeting is free and everyone interested in attending is welcome. Please call (302) 831-2506 to register by May 15.