Posts Tagged ‘19:9’

Potato Disease Advisory #2 – May 19, 2011

Friday, May 20th, 2011

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

Late blight Advisory
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. Our location this year is:

Location: Art and Keith Wicks Farm, Rt 9, Little Creek, Kent County
Greenrow: May 3

Date DSV Total DSV Spray Recommendation
5/3–5/12 0 0 none
5/13-5/15 11 11 none
5/15-5/16 3 14 none
5/16–5/18 16 30 5-days

The threat of late blight from seed infection is low, but there was some in Wisconsin last season. Maine was reported to be late blight free in 2010. Be vigilant anyway, given this recent weather pattern, which is supposed to continue for several more days. The first late blight fungicide application is recommended once 18 Disease Severity Values (DSVs) accumulate from green row. Green row occurred on approximately May 3, 2011 at this location. 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) or cholorthalonil (Bravo) is still a very effective early season protective fungicide to use. A recent addition to the list of late blight fungicides available for use in DE is Presidio from Valent. This registration came out after the 2011 Commercial Vegetable Production Recommendations was printed so it is not in the current book.

The threshold of 18 DSVs has been exceeded as of today. Thirty (30) DSVs have accumulated so far for any potatoes that established green row (approximately 50% emergence) prior to and since May 3. Spraying as soon as possible with a protectant fungicide would be advised.

 

Vegetable Crop Insects – May 20, 2011

Friday, May 20th, 2011

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

Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. In many fields, lady beetle populations are high and have helped to keep aphid populations in check. We are starting to find cucumber beetles, especially in cantaloupe fields. As soon as we get a day of warm, sunny weather, populations can explode 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, and endosulfan (Thionex). As a reminder, the Phase Out Labels are in effect for endosulfan so be sure to check the most recent labels for rates as well as new REIs and PHIs (http://www.cdms.net/LDat/ld9P4000.pdf). 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. 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. You can call the Crop Pest Hotline for the most recent trap catches (in state: 1-800-345-7544; out of state: 302-831-8851) or check our website at http://ag.udel.edu/extension/IPM/traps/latestblt.html