Posts Tagged ‘19:11’

High Temperature Effects on Peas

Friday, June 3rd, 2011

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

Recently, we have had reports of pea fields with reduced seed set. Peas are best adapted to areas with warm days and cool nights. Extended high temperatures in excess of 85º F will cause yield declines in pea by reducing the number of seeds that are carried to harvest.

Experiments have shown that yields can be reduced by as much as 20% with a 5º increase in temperature from 85-90ºF. It has been shown that when peas are exposed to extended periods with high temperatures above 85º F that yields will decline greatly, especially in sensitive varieties. High temperatures in the last 10 days have been >85º F in much of the region.

The critical period where seed set will be reduced is late bloom. If the plant cannot support the full number of seeds due to high respiration and premature stomatal closure, seeds will abort or will not fill.

 

E. coli O104:H4 Outbreak in Germany

Friday, June 3rd, 2011

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

The produce industry in Europe has been affected by an outbreak of food-borne illness from a new strain of E. coli (O104:H4) which has sickened over 400 adults and killed 19. Recommendations have been for German consumers to stop eating produce or to cook produce. Particularly hard hit are growers of produce consumed fresh. Produce sales have been so hard hit in countries such as Spain that the EU is considering an aid program to compensate farmers for losses.

Originally, German officials blamed cucumbers from Spain because they found toxic E. coli on cucumbers imported from that country. However, the strain found in those who were sickened did not match the strain found on Spanish cucumbers. Currently, no other potential source has been identified, but salad items are suspected.

New toxic strains of E. coli have been emerging throughout the world. Bacteria are well adapted to exchange genetic material and a previously non-toxic organism can become toxic by picking up genes for toxin production from another bacteria. Some of these toxic strains are particularly dangerous because they can shut down the kidneys of persons infected.

Produce growers in the US and locally, especially direct marketers, may be asked by customers about this outbreak and the potential for it being found in US grown produce. This new strain in Europe has not been found in the US food supply and consumers should not be concerned.

However, growers should be aware that toxic strains of E. coli (O157:H7) do exist in this region. The major source is fecal matter from animals (domestic and wild such as cattle and deer) and irrigation water contaminated with fecal matter. Growers should take all precautions to avoid or eliminate contamination of produce from these sources.

 

Potato Disease Advisory #5 – June 2, 2011

Friday, June 3rd, 2011

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

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

Date DSV Total DSV Accumulated P-days* Spray Interval Recommendation
5/19-5/21 5 38 5-days
5/21-5/23 12 50 5-days
5/23-5/24 2 52 5-days
5/24-5/25 0 52 5-days
5/27-5/28 2 54 175 5-days
5/28-5/29 2 56 183 7-days
5/29-5/30 1 57 191 5-days
5/30 0 57 197 7-days
5/31-6/1 0 57 207 10-days

The dry weather and the recent high temperatures will reduce the risk and slow any development of late blight. Continue to scout fields for symptoms of late blight.

P days: We use the predictive model WISDOM to determine the first fungicide application for prevention of early blight as well. The model predicts the first seasonal rise in the number of spores of the early blight fungus based on the accumulation of 300 physiological days (a type of degree-day unit, referred to as P-days) from green row. To date, 207 P-days have accumulated at the site. Once 300 P-days have accumulated, the first fungicide for early blight control should be applied. This usually occurs when rows are touching.

 

Vegetable Disease Updates – June 3, 2011

Friday, June 3rd, 2011

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

Late Blight Update
There has been no late blight observed in the region.

Cucurbit Downy Mildew Update
Downy mildew movement has been very limited so far. The most recent find was in Hidalgo County in very southwest Texas. You can keep current on the progress of downy mildew by visiting the website http://cdm.ipmpipe.org.

 

Vegetable Crop Insects – June 3, 2011

Friday, June 3rd, 2011

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 to 20 percent 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. We are finding fields with economic levels of cucumber beetles and spider mites. The threshold for mites is 20-30% infested crowns with 1-2 mites per leaf. 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 (http://extension.oregonstate.edu/catalog/pdf/pnw/pnw591.pdf).

Peppers
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 — in state: 800-345-7544; out of state: 302-831-8851.