Volume
10, Issue 17
July 19, 2002
Vegetables
Vegetable Insects
-
Lima Beans
With the recent increase in corn earworm catches, be sure to watch for earworms in fields with pin pods. You should also sample for lygus and stinkbugs. 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, Mustang or Capture can be used to control all 3 insects on lima beans.
Melons
Spider mite populations continue to increase in many fields. In our field trials this season, Agri-Mek and Capture have provided 3-4 weeks of control with 2 applications. A few growers have tried dimethoate this season with varying degrees of success. If you have not used dimethoate in a few years and you are having limited success with other products, you may want to consider one application of dimethoate. You should not use it more than once, especially if you experienced poor control or resistance in past years. If you have not used it for 3 or more years and you had reduced efficacy when you stopped using it, we often find you can make one application and get good control. However, multiple applications usually result in a quick reversion to resistance and an explosion in populations. The maximum rate for dimethoate 4EC on melons is 1 pt/acre.
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. With the recent increase in corn earworm catches, chemical selection will be important. Remember Orthene or Address will not provide satisfactory earworm control. A pyrethroid or Lannate will be needed for earworm control. Also, a continuous pyrethroid program should not be used to avoid aphid explosions.

R. Bessin,
Snap Beans
Processing snap beans in all areas of the state should be treated at the bud and pin stages for corn borer control. Orthene or Address should be used at the bud and/or pin stages for corn borer control. Once corn earworm trap catches reach 20 per night in your area, a pyrethroid should be added to the pin spray. After the pin stage, Lannate, Capture or Mustang should be used. After the pin spray, sprays will be needed on a 7-day schedule from the pin spray until harvest except in the Bridgeville and Laurel areas where sprays are needed on a 5-6 day schedule. Since this can change quickly, be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decisions in processing snap beans (http://www.udel.edu/IPM/traps/latestblt.html and our link to http://www.udel.edu/IPM/thresh/snapbeanecbthresh.html). You should treat fresh market snap beans for corn borers on a 7-day schedule from the pin stage until harvest. Lannate, Capture or Mustang should be used.
Sweet Corn
Fresh market silking sweet corn should be sprayed on a 3-day schedule in all areas of the state. Be sure to also sample late-planted fields for fall armyworm larvae. No controls will be needed until 15% of the plants are infested. Sap beetles are also starting to show up silking sweet corn. Warrior, Penncap-M and diazinon have provided the best control.
![]()
Scorch on Sweet
Corn -
Several fields of processing sweet corn have exhibited small
percentages of scorched tissue and tassles.
High temperatures (99 degrees and above) can cause scalding of corn leaf
tissue. Hybrids differ in their
tolerance, and the stage of development of the tassel also influences the
plant’s reaction to those temperatures.
The emerging or recently emerged tassles may appear “blasted or
bleached.”
Usually, the percentage of affected plants is small and the effect on total yield is neglible.

Scorch on Sweet Corn
![]()
Vegetable Diseases
-
Cucurbits
Cucurbit powdery mildew is now present in
From the
Latest EFI values from local weather stations
Any
questions please call (410) 742-8788
EFI Values (Environmental Favorability Index)
Do
not use MELCAST if there is a disease outbreak in your field, it is a preventative program.
Location
Charles Co. 0 0 9 2 0 0 0
Collins Farms 1 2 4 4 0 0 0
Vincent Farms 1 2 5 5 1 0 0
White Marsh 0 0 10 3 0 0 0
The first fungicide
spray should be applied when the watermelon vines meet within the row. Additional sprays
should be applied using
MELCAST. Accumulate EFI (environmental
favorability index) values beginning the
day after your first
fungicide spray. Apply a fungicide spray
when 30 EFI values have accumulated by the
weather station nearest
your fields. Add 2 points for every
overhead irrigation. After a fungicide
spray, reset
your counter to 0 and
start over. If a spray has not been
applied in 14 days, apply a fungicide and reset the
counter to 0 and start
over. The first and last day listed
above can be partial days so use the larger EFI value
of this report and other
reports for any specific day.
If,
for some reason, a serious disease outbreak occurs in your field, return to a
weekly spray schedule.
More
detailed information concerning MELCAST and sample data sheets are available on
the web at http://www.agnr.umd.edu/users/vegdisease/vegdisease.htm.
![]()
Vegetable Diseases
-
Potato Disease Advisory.
Late Blight Advisory
Disease Severity
Value (DSV) Accumulations as of
|
Date |
Total DSV |
Spray
Recommendation |
|
5/1 |
12 |
None |
|
5/11 |
19 |
5 days, low rate |
|
5/19 |
23 |
10 days, low rate |
|
5/22 |
23 |
10 days low rate |
|
5/27 |
27 |
10 days low rate |
|
5/29 |
30 |
7 days, low rate |
|
6/3 |
33 |
7 days, mid-rate |
|
6/5 |
33 |