Posts Tagged ‘18:6’

Strawberry Disease Control

Thursday, April 22nd, 2010

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

It won’t be long before strawberry growers will need to deal with several important diseases. Here are the latest recommendations from the 2010 Commercial Vegetable Production Recommendations.

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 no later than 10% bloom and/or prior to disease development. For control apply the following combinations:

First Application
Captan (M3) at 4.0 lb 50WP/A plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23.0 oz 38WG/A

Second Application
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

Third Application
Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A

For subsequent applications, alternate:
● Captan (M3) at 4.0 lb 50WP/A plus Abound (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08SC/A
● Cabrio (pyraclostrobin, 11) at 12.0 to 14.0 oz 20EG/ A plus captan (M3) at 4.0 lb 50WP/A
● 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 2 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 gray mold and blossom blight can cause serious losses in strawberry plantings in high tunnels and the field if not controlled properly. Development is favored by moderate temperatures (59 to 77°F) with prolonged periods of high relative humidity and surface wetness. Control of gray mold begins with preventative fungicide applications. Apply at 5 to 10 percent 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.

First Application
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

Second Application
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

Third Application
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:
● 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

Weed Control in Succulent Beans

Thursday, April 22nd, 2010

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

There is some overlap of herbicide options for snap beans and lima beans, but you need to pay particular attention that a product is labeled for snaps or lima beans and do not assume if it is labeled for one, it is labeled for both.

Snap Beans
Weed control in snap beans starts with a good soil-applied program. The regional recommendations include Eptam, Treflan or Prowl applied pre-plant incorporated; Dual, which can be applied preemergence or pre-plant incorporated; or Command or Sandea applied preemergence. Early postemergence treatments for broadleaf weeds include Basagran, Reflex, or Sandea. Select Max, Targa/Assure II, or Poast are labeled for postemergence grass control. UD research has seen consistent control with Dual used at planting followed by a timely (1 to 2 trifoliate stage of the beans) application of Reflex and Basagran. If there are concerns about timely application of the postemergence herbicides, consider use of a broadleaf weed herbicide at planting.

Lima Beans
The biggest difference from snap bean herbicides is that Reflex cannot be used for lima beans since they are very sensitive to Reflex and severe injury will occur. A soil-applied herbicide program for lima beans is very important due to the lack of effective postemergence herbicides. Herbicides listed in the regional vegetable guide for lima beans include:

Pre-plant incorporated: Prowl or Treflan
Pre-plant incorporated or preemergence: Dual or Pursuit
Preemergence only: Sandea
Postemergence: Basagran or Raptor for broadleaf weeds; Select Max or Poast for grasses.

Hollow Heart in Watermelon

Thursday, April 22nd, 2010

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

The first watermelons will be transplanted in the field the last week in April. One problem with seedless watermelons that can cause significant loss of marketable fruits is hollow heart. This interior separation of fruit storage tissue is most common on crown sets in the first harvests.

In the past, the cause for hollow heart was thought to be related to rapid growth of the fruit where the rind expanded faster than the internal flesh leading to separation of the three internal fruit compartments and an open area between. Excess nitrogen and over-watering along with favorable growing conditions were implicated in higher incidence of hollow heart.

There is growing evidence that hollow heart is not directly tied to nitrogen and water management but is related to pollination and weather conditions during pollination. Plant hormones are thought to be important in this effect. Several researchers have found no increase in hollow heart with increases in nitrogen; even in varieties know to have hollow heart problems. It is thought that with inadequate pollination, there is reduced release of the plant hormone that controls the development of storage tissue leading to hollow heart.

The first flowering and fruit set in watermelons often occurs in periods of stress with cold conditions. Cold, rainy weather during pollination will also reduce bee flights and may be a causal factor. In addition, some varieties are more susceptible to hollow heart, although hollow heart is wide spread across varieties in some years.

What can watermelon growers do to reduce hollow heart? First, it is important to choose varieties that are less prone to hollow heart for early plantings. Second, make sure that pollinizers in early plantings are in synch with the seedless varieties (there is plenty of pollen for the early sets). A higher pollenizer to seedless ratio may be warranted for the earliest plantings. Third, make sure that you have strong honey bee colonies and consider increasing colonies in the early plantings.

Insecticide Update: Supplemental Label for Belay

Thursday, April 22nd, 2010

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

Belay (clothianidin) – A supplemental label was recently approved by EPA. Crops included on the supplemental label include number of vegetable crops (brassicas, cucurbits, fruiting vegetables, and leafy vegetables) as well as peaches. In addition to the label on the pesticide container, you must also have a copy of the supplemental label in your possession to use Belay on these new crop additions (http://www.cdms.net/LDat/ld8J6008.pdf).

Vegetable Crop Insects

Thursday, April 22nd, 2010

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

Asparagus
Be sure to check for asparagus beetles laying eggs on asparagus spears. As a general guideline, a treatment is recommended if 2% of the spears are infested with eggs. Since adults will also feed on the spears, a treatment is recommended if 5% of the plants are infested with adults.

Cabbage
Continue scouting fields for imported cabbage worm and diamondback larvae. As a general guideline, a treatment is recommended if you find 5% of the plants infested with larvae.

Peas
Be sure to sample for pea aphids on all stages of peas. 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. Be sure to check labels for application restrictions during bloom.