Volume 8, Issue 20 August 4, 2000
Volume 8, Issue 20 August 4, 2000
Vegetables
Vegetable Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Cucurbits.
Be sure to watch for an increase in aphid populations, especially in seedling stage cucumbers and pickles. Populations are increasing as a result of the cool, wet weather. If the weather turns hot, you can expect to see aphid explosions since beneficials may not be able to keep up. A treatment should be applied if 20% of the plants are infested and before significant leaf curling occurs. Lannate or Thiodan should be used.
Peppers.
At the present time, all peppers that have fruit ½ inch in size or larger should be sprayed on a 7 day schedule for corn borer, corn earworm and pepper maggot control. In the Milford, Harrington, and Frederica areas, sprays should be applied on a 5-7 day schedule. Since corn earworm catches exceed 20 per night in those areas, a corn earworm spray is also needed. Since acephate (Orthene or Address) does not provide effective earworm control, Lannate or a pyrethroid should be used. In all other areas, acephate can still be used on a 7-day schedule. Lannate, Spintor, or a pyrethroid should be used on a 5-7 day schedule. We are also starting to see an increase in aphid populations in peppers. Remember a continuous pyrethroid program should not be used to avoid aphid explosions.
Lima Beans.
Continue to watch for economic levels of leafhoppers that can still be found in fields throughout the state. Remember, most labeled insecticides will only provide 7-10 days of control. In fields with pin pods, you should sample for earworm, lygus and stinkbugs. We have just found our first corn earworm larvae in lima beans in the Georgetown area. A treatment should be applied if you find one corn earworm per 6 foot of row or 15 tarnished plant bugs and/or stinkbugs per 50 sweeps. Lannate or Capture can be used to control all 3 insects on lima beans.
Snap Beans.
Processing snap beans should be sprayed at the bud and pin stages with acephate for corn borer control except in the Milford , Harrington and Frederica areas where Capture or Asana should be added to the mix for corn earworm control. A third spray with Capture or Lannate will be needed 5-7 days from harvest except in the Dover, Milford, Harrington, Frederica and Wyoming areas where you will need 2 sprays between pin and harvest. Fresh market snap beans should be sprayed on a 7-day schedule as soon as pin pods are present.
Sweet Corn.
All fresh market silking sweet corn should be sprayed on a 3-day schedule except in the Milford, Frederica and Harrington areas where sprays are needed on a 2-day schedule. Watch for aphid populations that are increasing on the tassels and silks. Although this feeding does not cause a direct yield loss, it can result in quality problems. A combination of Lannate plus a pyrethroid will help to reduce aphid populations. In areas where corn earworm moth catches are high or populations are increasing, you should not use Lannate alone.
Laurel Farmer's Auction Market Report
July 27 – August 3, 2000
|
Quantity |
Produce |
Price |
|
40,467 |
Cantaloupes |
|
|
|
Athena |
.25-.95 |
|
|
Superstar |
.40 |
|
|
Eclipse |
.40-.50 |
|
10,224 |
Sugar Babies |
|
|
|
Seeded |
.35-1.30 |
|
|
Seedless |
.50-2.10 |
|
1,559 |
Honeydews |
0.30-1.30 |
|
29 |
Crenshaws |
.75-1.15 |
|
170,323 |
Watermelons |
|
|
|
Crimson Sweet |
|
|
|
15 up |
.40-1.00 |
|
|
20 up |
.50-1.55 |
|
|
25 up |
.60-2.45 |
|
|
Sangria |
|
|
|
15 up |
0.50-1.90 |
|
|
20 up |
0.60-1.50 |
|
|
25 up |
1.20-1.80 |
|
|
Celebration |
|
|
|
15 up |
0.75 |
|
|
20 up |
0.75-1.35 |
|
|
25 up |
.80-1.35 |
|
|
Pumels |
|
|
|
20 up |
1.15 |
|
|
Royal Majesty |
|
|
|
20 up |
0.60-1.00 |
|
|
Royal Sweet |
|
|
|
20 up |
.75-1.80 |
|
|
25 up |
1.20 |
|
|
30 up |
1.10-1.30 |
|
|
Seedless |
.40-1.70 |
|
|
Stargazer |
|
|
|
20 up |
1.35 |
|
|
Summer Flavor |
|
|
|
15 up |
.60 |
|
68 |
Peppers |
|
|
|
Green |
4.50-8.50 |
|
2420 |
Tomatoes |
|
|
|
Red |
3.50-13.50 |
|
|
Pink |
3.00-8.00 |
|
|
Orange |
5.00-8.00 |
|
238 |
Sweet Corn Doz. |
.60-1.75 |
|
56 |
Cucumbers |
2.00-10.00 |
|
89 |
Squash |
|
|
|
Yellow |
3.50-15.00 |
|
|
Green |
3.50-8.00 |
|
|
White Squash |
3.00 |
|
79 |
Potatoes |
|
|
|
Red |
3.00-8.00 |
|
20 |
String Beans |
9.00-12.50 |
|
7 |
Eggplant |
3.00-8.00 |
|
2 |
Okra |
3.00-5.00 |
|
7 |
Peaches |
8.00-9.00 |
|
2 |
Pickles |
4.50 |
|
27 |
Lima Beans |
10.00-28.00 |
Late Blight Update - Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
|
Emergence Date |
DSV’s Aug 3 |
Recommendation |
|
April 27 |
164 |
7-day, high rate |
|
May 20 |
116 |
7-day, high rate |
|
May 24 |
116 |
7-day, high rate |
Accumulated 15 DSV’s since the last report.
This will be the last Late Blight Update for the 2000 season. Since many early plantings are maturing and there is no late blight present in the area, spraying is probably not justified. Later plantings that are still growing should be protected at this time. The weather continues to be very favorable for foliage and tuber diseases.
Fortunately Delaware and New Jersey were late blight free once again. To our north I have had reports of late blight on tomatoes in PA and NY.
I just finished harvesting a fungicide test for pink rot control conducted here at the University farm in Newark. I will be sharing that information with you as soon as the data collection is complete. We had plenty of disease on our inoculated plots on Russet Norkotahs.
Vegetable Diseases - Kate Everts, Extension Vegetable Pathologist, University of Delaware and University of Maryland; everts@udel.edu
Cucurbits.
Powdery Mildew – Powdery mildew is present throughout our area on susceptible cucurbits. Fortunately new fungicides have been registered for control of powdery mildew, recently. An excellent article was written by Drs. Meg McGrath and Tom Zitter on fungicide recommendations for powdery mildew and resistance management. The following is excerpted from that article.
Managing fungicide resistance is a critical
aspect of managing
powdery mildew with fungicides.
Fungicides that are systemic or have translaminar
activity are needed to obtain adequate protection of the underleaf
surfaces, where conditions are more favorable for development of the pathogen
than on upper surfaces. Unfortunately,
systemic fungicides are generally at-risk for resistance development because
they have a specific mode of action (single site
of activity), and powdery mildew fungi have exhibited a high
potential for resistance development.
This has been especially true of the cucurbit powdery mildew fungus,
which has developed resistance to Benlate (benomyl), Topsin M (thiophanate-methyl),
and Bayleton (triadimefon) in a short period of time.
Current recommendations for managing powdery mildew and fungicide resistance include using a diversity of fungicides. Fortunately, three new fungicides have been registered for use in the U.S. since March 1999 and two more are being reviewed by EPA. These three new fungicides are the strobilurin fungicides Quadris (azoxystrobin, Zeneca) and Flint (trifloxystrobin, Novartis) and the DMI fungicide Nova (myclobutanil, Rohm & Haas). Unfortunately, these new fungicides have a high risk for resistance development; thus it is imperative to use them in a fungicide program designed to manage resistance. A high level of resistance to strobilurin fungicides developed within two years in other countries where these fungicides were used exclusively. Although Nova is much more effective than Bayleton, these fungicides are in the same fungicide class. As a result, strains of the powdery mildew fungus that are fully resistant to Bayleton (e.g. cannot be controlled by Bayleton) are less sensitive to Nova than strains that are sensitive to Bayleton.
The fungicide program recommended for cucurbits (powdery mildew) in 2000 is a strobilurin fungicide (Quadris or Flint) applied in alternation with Nova tank mixed with a contact fungicide on a 7-day schedule. …The first spray should be applied at the IPM threshold (1 of 50 leaves with symptoms) or before symptoms when fruit are starting to enlarge. One major change from the program recommended in 1999 is to begin with a strobilurin fungicide.
Several
multi-site contact fungicides are
registered for use on cucurbits.
Chlorothalonil (Bravo, Echo, etc.) fungicides and copper fungicides
(Basicop, Champ, Kocide, etc.) are also effective for diseases other than
powdery mildew. Sulfur (Microthiol
special, Micro Sulf, etc.), potassium bicarbonate (Armicarb 100), monopotassium
phosphate (Nutrol), mineral oil (JMS Stylet-oil, SunSpray Ultra-Fine, etc.),
and biofungicides (AQ10) are only effective for powdery mildew.