Posts Tagged ‘17:12’

Increase in Soil Rots May Be in Store for Area Cucurbits

Friday, June 5th, 2009

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

Last week Gordon Johnson wrote an excellent article, “Tough Year for Early Peas,” about problems with peas due to the wet soil conditions we have had in our area resulting in “soil rots”. We have had anywhere from 2-5 inches above average rainfall for the month of May throughout the Delmarva area, which has resulted in the second wettest May over the last 50 years for many areas. Last year we also had a very wet May; it was the third wettest May in many areas of Maryland, which resulted in many more root rot problems in cucurbits, i.e., watermelons, cucumbers, cantaloupes, pumpkins, etc. We can probably count on similar problems this year in the field as the June forecast calls for wetter than normal conditions.

The symptoms in watermelon fields usually begin with leaves flagging on a few plants down a row and then a few days later a total collapse of those same plants. Sometimes the wilting occurs within certain rows while in adjacent rows the watermelon plants look fine (Fig 1a). If wilted plants are dug up you can see reddish-brown discoloration of the crown of the plant (Fig 1b). The roots will be decayed as well. There are several fungi that can cause crown and root rot diseases, including Fusarium, Pythium and Phytophthora. To identify the specific fungi involved, samples should be sent to a diagnostic laboratory for testing. The disease often starts with a few plants in one row then moves down that row. Water, either through irrigation or heavy rains is usually responsible for the movement of the disease down a row. High plant loss can occur in the lower areas of fields where water stands after heavy rains. In the last month we have had several days of heavy rains with water sitting in fields, which will stress young plants and allow root rot diseases to get started.

 watermelon rows with and without fusarium crown rot

Fig 1a. Watermelon rows with and without Fusarium crown rot

plant with crown rot 

Fig 1b. Watermelon plant with crown rot

One thing growers can do for root and crown rot diseases is to be sure to not over water the plants or apply excess nitrogen. Rotation helps somewhat, especially for Fusarium wilt, but the root and crown rot pathogens can infect many hosts, making crop rotation less effective in reducing disease. Environmental conditions are probably the most important component for the development of root and crown rot diseases. Well drained fields will have less of a problem than poorly drained fields.

Besides seed treatments containing fungicides which will protect the seed from rots, there is a biological control that can be seed applied (preferred application method) or drenched onto the transplant that will help protect the plant from soil rots. The product is T-22 a naturally occurring fungus, Trichoderma harzianum, strain T-22. Trichoderma grows on the surface of roots, where it provides disease control and enhances root growth. Its spores survive in the soil, but the food it exists on is secreted from the root surface. The fungus multiplies on its own, protecting the roots over the growing season. The fungus, however, does not work very well if fields have standing water in them over a period of days, so it is important to keep your fields well drained.

Vegetable Crop Insects – June 5, 2009

Friday, June 5th, 2009

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

Cucumbers
Cucumber beetle activity increased significantly this past week, so be sure to scout for beetles as well as aphids. Fresh market cucumbers are susceptible to bacterial wilt, so treatments should be applied before beetles feed extensively on cotyledons and the first true leaves. Although pickling cucumbers have a tolerance to wilt, a treatment may still be needed for machine-harvested pickling cucumbers when 5% of plants are infested with beetles and/or plants are showing fresh feeding injury. A treatment should be applied for aphids if 10-20% of the plants are infested with aphids with 5 or more aphids per leaf.

Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. The treatment threshold for aphids is 20% infested plants with at least 5 aphids per leaf. Although not wide-spread at this point, we continue to find fields with spider mites at economic levels. The threshold for mites is 20-30% infested crowns with 1-2 mites per leaf. Cucumber beetles increased significantly in cantaloupes and watermelons. Since beetles can continue to re-infest fields as well as hide under the plastic, be sure to check carefully for beetles as well as their feeding damage. Multiple applications are often needed to achieve effective control. Now that most fields are blooming, it is important to consider pollinators when making an insecticide application. See this publication for information on protecting pollinators: (http://extension.oregonstate.edu/catalog/pdf/pnw/pnw591.pdf).

Peppers
Continue to sample for thrips. We continue to hear reports of high thrips activity on crops in Virginia. You should also continue to sample for corn borers and watch carefully for egg masses. Before fruit is present, these young corn borer larvae can infest stems and petioles. As soon as the first flowers can be found, be sure to consider a corn borer treatment. Depending on local corn borer trap catches, sprays should be applied on a 7 to 10-day schedule once pepper fruit is ¼ – ½ inch in diameter. Be sure to check local moth catches in your area by calling the Crop Pest Hotline (instate: 800-345-7544; out of state: 302-831-8851) or visiting our website at (http://ag.udel.edu/extension/IPM/traps/latestblt.html). You should also watch for an increase in aphid populations. A treatment may be needed prior to fruit set if you find 1-2 aphids per leaf for at least 2 consecutive weeks and beneficial activity is low.

Potatoes
Continue to scout fields for Colorado potato beetle (CPB), corn borers (ECB) and leafhoppers. Adult CPB as well as the small and large larvae can now be found. A treatment should be considered for adults when you find 25 beetles per 50 plants and defoliation has reached the 10% level. Once larvae are detected, the threshold is 4 small larvae per plant or 1.5 large larvae per plant. As a general guideline, controls should be applied for leafhoppers if you find ½ to one adult per sweep and/or one nymph per every 10 leaves.

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, continue 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. As a general guideline, once corn borer catches reach 2 per night, fresh market and processing snap beans in the bud to pin stages should be sprayed for corn borer. Sprays will be needed at the bud and pin stages on processing beans. Once pins are present on fresh market snap beans and corn borer trap catches are above 2 per night, a 7 to 10-day schedule should be maintained for corn borer control. (http://ag.udel.edu/extension/IPM/traps/latestblt.html) and http://ag.udel.edu/extension/IPM/thresh/snapbeanecbthresh.html).

Sweet Corn
Continue to sample seedling stage fields for cutworms and flea beetles. You should also sample whorl through pre-tassel stage corn for corn borers and corn earworms. A treatment should be applied if 15% of the plants are infested with larvae. We have also seen an increase in corn earworm catches so be sure to watch carefully for small larvae being found in tassels. The first silk sprays will be needed for corn earworm as soon as ear shanks are visible. Be sure to check both blacklight and pheromone trap catches since the spray schedules can quickly change. Trap catches are generally updated on Tuesday and Friday mornings (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/silkspraythresh.html). You can also call the Crop Pest Hotline for the most recent trap catches (instate: 800-345-7544; out of state: 302-831-8851).

MEETING CANCELED: On Farm Delaware Food Safety Training – Level I Certification

Friday, May 22nd, 2009

Tuesday, June 30, 2009    

Due to lack of registrations, we are going to cancel the On-Farm Food Safety Workshop (Level 1 certification) and the Level 2 Food Safety Workshop scheduled on June 30 and July 7, respectively.

We plan to reschedule for sometime in the fall/winter. We hope the weather stays dry and this will allow you all to get out in the field and do some work!

If you have any questions or would like to schedule a mock food safety audit on your farm, please feel free to call me. My contact information is below.

Best regards,
Anna Stoops
New Castle County Agriculture Extension Agent

University of Delaware Cooperative Extension New Castle County Extension Office
461 Wyoming Rd, Rm 139
Newark, DE 19716

Phone: 302-831-8860
E-Mail: stoops@udel.edu
Fax: 302-831-8934

Agronomic Crops Twilight Tailgate Session

Friday, May 22nd, 2009

Wednesday, June 10, 2009     6:00 p.m.
UD Cooperative Extension Research and Demonstration Area
(3/4 mile east of Armstrong Corner, on Marl Pit Rd. – Road 429, Middletown)

Join your fellow producers and the UD Extension team for an overview of UD’s Weed Science Program-Fall Soybean Herbicide Applications research trial; updates on the latest disease and insect outbreaks and a grain market update. We will wrap things up with the traditional ice cream treat!

Bring a tailgate or a lawn chair.

We will apply for DE Pesticide and Nutrient Management re-certification credits and Certified Crop Advisor credits.

This meeting is free and everyone interested in attending is welcome. Please register by June 5. To register, request more information or if you require special needs assistance for this meeting, please call our office in advance at (302) 831-2506.

See you there!
Anna Stoops, New Castle County Agricultural Extension Agent