Posts Tagged ‘processing vegetables’

Early Peas Damaged by Freezing

Friday, March 30th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Early peas have suffered damage by the freezing winds on Monday night. Peas normally will stand cold temperatures down to the low 20s. However the combination of high winds (gusts up to 50 mph), freezing temperatures (25-30°F), and peas well ahead of schedule on growth (some as tall as 6 inches) set up conditions for plant damage. Areas protected by wood lines and hedgerows were not damaged. Peas planted later that were just cracking the ground were also not damaged.

Peas are interesting in that if the top is frosted to the ground level, they will develop new stems from dormant buds below ground. There will be 1-3 new stems that develop. This will be seen within a week after the frost. These stems will develop and flower later than undamaged plants. Generally, frost damaged peas will yield 5-20% less due to the differences in maturities in the field and having weaker plants.

Risk of Stewart’s Wilt in Sweet Corn is High in 2012

Thursday, March 29th, 2012

Bob Mulrooney, Extension Plant Pathologist;

The Stewart’s wilt prediction for 2012, as you can imagine with a very mild winter, is severe for all three counties in Delaware. We have not had such a mild December, January and February since the winter of 2001-2002 when the Index was 123.1 for Georgetown and 123.0 for Newark. The following table tells it all.

Winter Temperature Index For Predicting Stewart’s Wilt in Delaware Sweet Corn: 2002-2012

Average monthly temperatures in °F at Georgetown, DE, REC: 2002-2012

  2011-2012 2010-2011 2009-2010 2008-2009 2007-2008 2006-2007 2005-2006 2004-2005 2003-2004 2002-2003
December 43.2 31.3 37.9 41.8 39.7 43.5 36.2 38.9 38.6 36.7
January 39.5 31.0 32.7 31.0 36.8 39.7 43.0 34.9 29.5 28.9
February 40.4 39.6 31.1 39.2 39.9 30.1 37.4 36.7 35.2 33.8
INDEX 123.1 101.9 101 .7 112.0 116.4 113.3 116.6 110.5 103.3 99.4


Average monthly temperatures in °F at Newark, DE, Experiment Station: 2002-2012.

  2011-2012 2010-2011 2009-2010 2008-2009 2007-2008 2006-2007 2005-2006 2004-2005 2003-2004 2002-2003
December 41.3 30.8 34.9 37.1 37.5 42.5 34.0 35.5 34.0 33.5
January 37.0 28.7 31.6 28.0 35.5 37.3 39.5 31.0 26.4 27.1
February 39.5 35.2 31.0 35.8 36.5 27.8 34.5 34.2 33.1 29.5
INDEX 117.8 94.7 97. 5 100.9 109.5 107.6 108.0 100.7 93.5 90.1

Severity Index: < 90, usually absent; 90-100, intermediate; >100, usually severe.

The index is used to predict overwintering flea beetle populations that vector the Stewart’s wilt bacterium, Pantoea stewartii.

Prediction for 2012

      Average Temperature for Dec, Jan & Feb
Location Prediction   2011-2012 2010-2011
Georgetown 123.1=Severe   41.0°F 34.0°F
Dover 121.0=Severe   40.3°F 32.5°F
Newark 117.8=Severe   39.3°F 31.6°F


Control Strategies
For processing and fresh market growers the high risk of Swetart’s wilt means that if you are planting susceptible or moderately susceptible hybrids, flea beetle control is very important. A number of strategies are available including seed treatments, granular insecticides at planting and/or foliar applied insecticides after emergence. For foliar applied insecticides treat susceptible cultivars at spike stage when 5% of the plants are infested. See the 2012 Delaware Commercial Vegetable Production Recommendations for control suggestions.

Note: Weather records from University of Delaware Carvel REC, Georgetown, DE, DE State Fire School, Dover, DE and University of Delaware Ag Experiment Station Farm, Newark, DE. Data records found online at

Vegetable Crops are Off to an Early Start

Thursday, March 29th, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist; & Emmalea Ernest, Extension Associate-Vegetable Crops;

Asparagus harvest began last week which is four weeks early. Pea planting is ahead of schedule with heat units accumulating much more rapidly than the thirty year average making it likely that harvest will not extend past June. Peas have emerged rapidly and stands look very good. Average soil temperatures have already been in the mid 60s. Some fresh market sweet corn growers have their first and second plantings in already and sweet corn under plastic has emerged and is growing fast. Plastic mulch laying for summer crops is already underway. As we progress into April, a concern will be the potential for frosts and freezes with advanced crops.

The earliest peas will start flowering at less than 675 heat units and will be at full flower at 775 heat units. Currently, peas planted on February 25 have accumulated 306 heat units. In 2011 during the same period only 181 heat units accumulated. If accumulations continue at an accelerated pace and peas flower early, there is increased risk for frost damage to flowers in early plantings, causing reduced yields, and split sets.

Early planted sweet corn can also be at higher risk this year of frost damage. If the sweet corn growing point is not out of the ground and a freeze occurs, the emerged leaves will be injured but the plants can continue to grow. The growing point of sweet corn is still below or at ground level until the 5-6 leaf stage and is therefore protected against frost injury. If a frost or freeze event does occur with sweet corn, wait 3-4 days to evaluate. If you seed signs of regrowth, the sweet corn can recover. If regrowth is not evident, start splitting the stems of a sample of plants and look at the growing point. If it is firm and white or cream colored it is still alive. If it is soft, water soaked, or gray in color, it has died and you will lose some stand.

Processing sweet corn planting will begin in the next 2 weeks. It is interesting to note that the industry is moving to supersweet varieties for processing. In the past, our recommendations were to avoid early planting of supersweets and wait until soil temperatures were above 65° F, because these varieties tended to have less seed vigor. In 2010 and 2011 we planted supersweet variety trials on April 12. Surprisingly, a number of the supersweet varieties we tested had emergence rates over 90%. This suggests that high quality seed of supersweet varieties with demonstrated cold tolerance can probably be planted earlier, before soil temperatures reach 65°F. Detailed reports on the 2010 and 2011 trials are available online at This year, early April supersweet plantings may be justified, given that soils have already warmed substantially.

Some rye windbreaks used for watermelon and other vegetable protection have already reached full height and are heading out. Growers may have to kill windbreaks much earlier than normal or realize that seed will likely set which is a problem if rotating into wheat or barley (seed mixing with rye next year). Forage radishes and spring oats did not fully winter kill this year.

As we go into next week, highs are forecast in the 60s and 70s. However the extended forecast for both 6-10 and 8-14 days from NOAA is for “enhanced odds for below average temperature along the Mid-Atlantic”

Pea Planting

Friday, March 2nd, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Pea planting has started across the region. A common problem with early pea plantings is compaction and resulting yield losses, particularly where field operations were performed when soils were too wet. Much of the loss is due to reduced germination or seedling death. In addition, early maturing (low heat unit) peas have a lower yield potential and cannot compensate for stand losses as well as later maturing varieties. Compacted soils also set up conditions favorable to the development of root rots which further limit yields. Research has shown that root rot severity can be increased by over 50% in peas where there is heavy compaction.

Another interesting note on peas is the potential to increase overall yields by planting longer maturing varieties, even for the early plantings. Long season varieties have greater genetic potential for producing high yields. While processors will want to plant early varieties to start the season to supply factories starting at the end of May, including later maturing varieties in early plantings will produce higher yields for the next round of harvests in early June and then onward.

Processing Acres Up This Year

Friday, March 2nd, 2012

Gordon Johnson, Extension Vegetable & Fruit Specialist;

Processing vegetable acres will be up this year in Delaware and on Delmarva including peas, lima beans, and sweet corn. Pickle acreage will remain steady. This increase in acres is largely due to reduction in stocks. For example, for lima beans, cold storage stocks in January 2011 were 58 million pounds and in January 2012 these stocks were down to 44 million pounds. Peas were down from 234 to 210 million pounds and sweet corn was down from 521 to 436 million pounds. This drop in sweet corn stocks is a major driver in picking up acres. It is interesting to note that in 2011, Delmarva lima bean acres were close to 19,000. This represented over 60% of the US acres and 40% of the production. California acres are down due to competition for land with more profitable crops.

Processing Vegetable Year in Review

Friday, September 23rd, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist;

2011 was a “mixed bag” for processing vegetable growers in Delaware. The pea planting season started out slow with a wet and cold March. April plantings went in on-time. There was a hot period in late May and early June that cause yield losses but the second half of June was more seasonable and yields were as expected.

Processing sweet corn yields were at or above average for earlier plantings. Later crops that were silking in the second half of July lost yield potential due to excessive heat.

So far the lima bean season has been disappointing. Early planted limas had very low yields due to the record breaking heat in July. Limas planted in the first half of June have had their harvests delayed several weeks and are suffering split sets. On top of that, the excess rainfall in later August has caused yield losses due to diseases and brown beans. There is better promise for limas planted later in June and in July.

Snap beans yielded well up to July. As with last year, summer yields were low due to split sets. Summer planted snap beans for fall harvest were hurt badly by storm damage and excess rain from the hurricane and tropical storms and will have lower than expected yields.

Pickling cucumber yields for the first 2/3 of the season were excellent. Plantings for later August and September harvest were hurt by storm damage and excess rain. Late plantings also had higher levels of fruit diseases.

Wet Weather Woes

Friday, June 26th, 2009

Gordon Johnson, Extension Ag Agent, Kent Co.;

Vegetable and fruit growers would rather have a dry year than a wet one. Keeping irrigation going might be a problem in the dry year, but vegetable and fruit crops have better quality and disease control is much less challenging. The following are some observations from this season.

● Disease pressure is very high with wet weather diseases being a major problem. Pythium rots in seeded and transplanted crops, Aphanomyces root rot in peas, late blight in potatoes and tomatoes, downy mildew of cucurbits, downy mildew of grapes, Phytophthora blight in cucurbits, gummy stem blight in melons, blossom blights and Botrytis on fruits, and numerous other diseases favored by wet weather are active in the region this year.

● Scheduling processing crops has been a challenge in 2009 and plantings have had to be juggled and moved around to account for fields too wet to plant.

● Peas have been hurt badly by the wet weather. Root rot is a major problem along with drowned out areas, extra weed pressure, and rutted up fields at harvest.

● Early plantings of snap beans and sweet corn have variable and reduced stands due to seedling blights, crusting over with heavy rains, and standing water in fields.

● Hail and severe winds have affected several vegetable fields with significant damage.

● Quality of vegetable transplants this year has often be substandard due to having to hold plants too long in greenhouses, overcast and cloudy weather causing stretch, and diseases such as gummy stem blight attacking plants in humid greenhouses.

● Not only are plants in the field being subjected to extra disease pressure, but wet soils will have low levels of oxygen, causing deleterious physiological changes to vegetable and fruit plants. The following are excerpts from an article we posted in the WCU during the last wet season we had in 2003:

“When soils are water-saturated, plants roots can be in an oxygen-deficient condition and thus respiration and metabolic activities can be markedly impacted due to low oxygen and high levels of carbon dioxide and other chemicals. Therefore, most of the functions normally performed by the root system are in potential jeopardy of performing poorly or in altered manners. The temperature at the time of the saturation and the duration of the events greatly impact the severity and symptom pattern.

“Saturated soils result in loss or reduction in normal root functions. Nutrient and water adsorption and their translocation are often impacted; consequently, wilting, yellowing, stunting, and nutrient deficiencies are the most common symptoms associated with flooded soils with most vegetables.

“During periods of high evaporation or high temperatures, the aboveground symptoms of saturated soils usually involve wilting and severe stunting, but the cool temperatures have limited such development this year. As temperatures start to increase, expect to see much more of the sudden wilting and yellowing of plants.

“Hormonal imbalances often occur when roots are in saturated soils, especially at cool temperatures, as production declines in the root-made hormones while stress/aging hormone production increases in other parts of the plant. These shifts create serious imbalances in the levels, ratios, and timing of hormones which results in abnormal plant development. Some plants are showing strong leaf epinasty (bending and twisting of the leaf petioles) resulting from increased ethylene production, while adventitious roots proliferate from the stem due to auxin imbalance. Timing of flower production and development can also be greatly impacted, which can significantly impact timing of fruit for critical market windows.”

(Taken from “Wet Soils Impacting Vegetable Crops” Written by William Nesmith, University of Kentucky and edited for Delaware)

● Extra watermelon acreage was planted this year (more watermelons are often planted the year after a good season such as 2008). Unfortunately, some of this acreage has gone into marginal ground that has remained overly wet. This sets up problems with water damage and increased disease risk.

● We are seeing heavy gummy stem blight pressure this year. In particular, one of the pollenizer varieties is being heavy hit. Plants have come out of greenhouses with gummy stem blight setting up the problem. Once in the field, the disease has spread to other plants with the wet weather.

● Crown sets in early plantings of melons are reduced due to poor weather (rain and cold) during pollination, affecting bee flights.

● Many vegetable crops are behind and harvest will start later than normal. Watermelons and cantaloupes are 10-20 days behind. Tomatoes and peppers are also behind by 10 days or more. Sweet corn will see smaller delays in harvest.

Ending Vegetable and Fruit Notes for the 2008 Season

Friday, September 19th, 2008

Gordon Johnson, Extension Ag Agent, Kent Co.;

Some observations from the 2008 vegetable and fruit season for this last Weekly Crop Update for 2008:

● Strawberry season was extended this year due to the cooler May weather. We did not get our first 90 degree weather until June 7. Both matted row and plasticulture systems got a later start on harvest but were extended into June. The nor’easter in mid-May did affect fruit quality for a week period.

● Asparagus also did well in 2008 with constant, quality harvest with the cooler weather.

● Early peas had very good yields due to the cooler weather. Several days of 90 degree weather the second week in June caused some mid season and later plantings to mature together but, in general, growers were pleased with pea yields.

● Potato growers had the perfect storm of a good growing season and exceptional prices. This was the most profitable season in recent history. The heat in mid-June did reduce tuber bulking and caused premature decline in some early varieties, resulting in a higher percentage of small tubers, but the prices more than compensated. There were more acres of non-irrigated potatoes planted this year and digging was delayed due to dry soil conditions in August.

● Processing sweet corn growers reported excellent yields this year with many fields in the 8 and 9 ton/A range. With normal hot temperatures in July, and a cooler than normal August, June and early July plantings had good growing conditions. With increased prices being paid, processing sweet corn was very profitable this year. 2008 was a good year for fresh market sweet corn as long as there was adequate irrigation. Wholesale prices in July were $18-25 per crate, August prices ranged from $10-14 per crate. Prices in general were higher in 2008 than in 2006 or 2007.

● Pickle growers report having a good year. A larger portion of the acreage is being harvested with self propelled harvesters and significant acreage is being custom harvested. This is a shift away from the farmer-owned tractor mounted harvesters. Downy mildew was a factor again in 2008 and fungicide timing was an issue in some fields.

● Lima beans in 2008 have been a mixed bag. Dryland lima beans suffered greatly with the August drought and many fields have yielded under 1000 lbs/A. Irrigated lima beans are giving excellent yields. August temperatures in 2008 were considerably lower than in 2006 or 2007 leading to improved pod set and pod retention in irrigated fields. White mold is being reported as a current issue due to the good vine growth in irrigated lima beans. Herbicide resistant pigweed has been a major challenge in lima bean fields in 2008 and I have seen more wick bars and wipers being used in fields than in past years.

● Watermelons and cantaloupes suffered a poor start due to the cold May and nor’easter. Harvest was delayed and early yields were reduced in 2008. Dry weather did reduce disease pressure and later plantings have done well. Prices were very good (significantly higher than 2007) and held throughout the season.

● This has been an average pumpkin season. Dryland plantings were hurt by the August drought. Powdery mildew pressure has been heavy in all pumpkins and we are seeing reduced fungicide efficacy in some fields. Viruses are also present at significant levels in many fields.

● Early snap beans had reduced growth due to the cold spring and yields were reduced. Late spring and summer prices were excellent for fresh market. The cooler August helped to improve set in mid-summer plantings. Processing snap bean yields have been variable and improved as the season progressed.

● Squash and other vine crops had significant issues with squash bugs and cucumber beetles. Squash bug numbers were higher than in recent years and had higher early populations. Fungal wilts were a major problem in a number of plantings, especially summer squash.

● 2008 was an excellent year for peaches. Late freezes were not an issue and dry summer weather reduced disease pressure. Irrigation was necessary to maintain fruit size.

● Grape quality is good in 2008 with the dry weather during the ripening period. There were periods in 2008 where downy mildew and powdery mildew pressure was high.

● We had one of the worst years for fire blight in recent memory with apples and pears. The wet weather in mid-May set up perfect conditions for the disease. Orchards that missed bactericide application timings were hard hit.

● This has been an average year for tomatoes and peppers. Stinkbug pressure was high for a period of time leading to fruit issues in tomatoes. Disease pressure in tomatoes was much reduced due to the dry weather.

● Weather was conducive to good spring cabbage production. Prices were $14 per crate, well up from the $8 per crate in 2007.

● Prices are up in general for vegetables in 2008, but so are production, harvest, packing, and shipping costs. Adjustments to processing crop prices paid to growers helped to maintain acreage on Delmarva. Higher field crop prices have helped to take pressure off of shipping markets for fresh market vegetables by reducing vegetable acreage in parts of the country.

● Vegetable crops for fall harvest look good in general. Pumpkins are being shipped. Sweet potatoes are being dug. Cabbage harvest will start soon. Broccoli, cauliflower, greens, and turnips are growing well. Later snap bean and lima bean plantings have good sets. August planted spinach crops have good growth.

Late Summer Vegetable Notes

Thursday, August 28th, 2008

Gordon Johnson, Extension Ag Agent, Kent Co.;

Early processing baby lima beans have been harvested over the last two weeks. Dry-land lima yields are ranging in the 900-1100 lbs/acre range. Cooler weather in August has contributed to decent pod set but drought conditions have reduced seed fill and increased pod abortion in later planted dry-land baby limas. In August there were only 3 days in the high 80s or low 90s and nighttime temperatures have dropped to the 50s or 60s. As a result, irrigated mid to late season lima beans should have excellent yields. Pigweed escapes continue to be a major issue in lima beans and wiper bars were used in many fields this year for control once pigweeds were over top of the beans.

Nematodes can be an issue in heavy vegetable rotations. It would be wise to take soil and root samples while there are still live roots in fields if you are seeing reduction in growth, extra stress, or reduced yields in vegetable fields. Sampling instructions and sample bags can be obtained at any Delaware Extension Office.

It is common to find low pH to be a problem in vegetable fields where there is poor growth. Mark any areas that are showing poor vegetable performance and once summer vegetables are finished, plan to take soil samples in these areas and field wide. Low pH spots will need additional lime this fall.

I encourage more vegetable growers to try some acreage using cover crops that can be no-tilled into next spring. In particular, hairy vetch has proven to be an excellent cover crop for late spring, direct-seeded and transplanted vegetables. The key is to plant as early in September as practical and make sure there is irrigation to get the hairy vetch out of the ground and growing this fall if there is no rain. Pumpkins no-tilled into hairy vetch are becoming the standard in much of the region, but we have limited acreage in Delaware.

A common question is when to stop spraying pumpkins for disease and insect control. Unless pumpkins will be harvested in the next two weeks, plan on additional sprays. The best place for a pumpkin is on a healthy vine. Late season powdery mildew will greatly reduce handle (stem) quality and reduce marketability. We have several growers that plant pumpkins into rye cover crops. The rye mulch has greatly improved quality by eliminating fruit rots and greatly reducing dirt where the pumpkin sits on the ground.

Vegetable Double Cropping

Friday, June 20th, 2008

Gordon Johnson, Extension Ag Agent, Kent Co.;

Double cropping season is here and many vegetables will be planted as a second crop behind barley, wheat, peas, early sweet corn, early snap beans, other spring vegetables, and even strawberries. The following are some considerations when double cropping vegetables.

● Crop residue management is critical in order to get a good seed bed for the double crop vegetable. Make efforts to spread and incorporate residue evenly. Heavy areas of incorporated straw or vine will lead to crop variability. Incorporation of high carbon materials such as small grain straw can lead totemporary nitrogen deficiencies. Therefore, extra nitrogen fertilizer will be needed to speed decomposition of these materials (green materials such as pea vines will not cause this problem and will rapidly decompose). It is advised to allow some time (minimum 5-7 days) for residue decomposition before planting the next crop. Allelopathic responses (toxic reactions) in the double crop planting have been found in certain cases when planting has occurred immediately after incorporation of residues.

● Pay close attention to herbicide plant back restrictions. Low rates (0.5-0.75 lbs) of atrazine are often used in sweet corn and this normally does not affect subsequent plantings. However, higher rates can damage the double crop planting. Mesotrione (Callisto), which is used in sweet corn, has significant replant restrictions to many vegetables as does Impact, a related herbicide. Command, Reflex, and Pursuit are examples of other common herbicides with significant plant back restrictions. Check the Delaware Commercial Vegetable Production Recommendation book and the specific herbicide labels for appropriate waiting periods and crops rotational restrictions.

● Some pest problems can be an issue in double crop plantings. Once a crop is harvested, some insects will be seeking a new food source and the newly emerging double crop planting can be at risk. Insects and mites may also move from field margins into the double crop planting. Grasshoppers and two-spotted spider mites would be examples.

● Herbicide programs should be designed to deal with any regrowth issues from the previous crop. Examples would be effectively killing plasticulture strawberries so that vine crops can be double cropped on the beds or dealing with spring brassica crops that went to seed as volunteer weeds.