Posts Tagged ‘18:12’

WCU Volume 18, Issue 12 – June 4, 2010

Friday, June 4th, 2010

PDF Version of WCU 18:12 – June 4, 2010

In this issue:

Vegetables
Vegetable Crop Insects
Calcium Disorders
Potato Disease Advisory #6 – June 3, 2010
Late Blight Update
MELCAST Forecasting for Gummy Stem Blight on Watermelon and Alternaria Leaf Blight on Cantaloupe

Agronomic Crops
Agronomic Crop Insects
Soybean Rust Update
Consider Temporary Annual Forage Crops for Fields to be Planted Later this Year
Those Pesky Interveinally Cholorotic Corn Leaves
Grain Marketing Highlights

Announcements
Livestock Pasture Walk – June 9
Pea Twilight Meeting – June 10
Delaware Organic Food and Farming Association Workshop and Business Meeting – June 10

Weather

Grain Marketing Highlights – June 4, 2010

Friday, June 4th, 2010

Carl German, Extension Crops Marketing Specialist; clgerman@udel.edu

Commodity Markets Grow More Bearish
New crop Dec ‘10 corn and July ‘10 SRW wheat closed below support levels at the close in yesterday’s trading. Dec corn broke $3.74, closing at $3.69 and July SRW wheat broke $4.47, closing at $4.42 per bushel. New crop Nov ‘10 soybean futures were only slightly higher on the day closing at $9.03 per bushel. Old crop ‘10 soybean futures are inverted to the new crop ‘11 futures contracts, indicating a longer term bearishness to the soybean market. The primary reasons being given for the lull in prices are: (1) planting progress/crop conditions ; (2) ample supplies in the U.S. and world for the remainder of ‘09/‘10 and building into the ‘10/‘11 marketing year; and (3) strength in the U.S. dollar. The U.S. corn crop is now 97% planted and 85% emerged with 76% reported to be in good to excellent condition. The soybean crop was reported as 74% planted and 46% emerged, for the week ending May 30. USDA’s next supply and demand projections will be released on Thursday, June 10.

Market Strategy
Soybean futures tend to make their seasonal high between now and the first of July. The time has expired when corn futures typically make their season high, ending around the first week of June. This is not to say that a summer rally isn’t possible. It is to say that the likelihood of a rally occurring isn’t very great absent a weather problem developing that hinders crop development and yield potential. Thus far, crop conditions for both crops are in line or better than the 5-year average. There is some possibility that the corn market is becoming oversold that could result in a short term rally. Weekly export inspections for corn were reported as bullish. Soybean inspections were reported to be neutral to bearish, as evidence builds of U.S. exports slowing down with the availability of a very large Southern Hemisphere crop. U.S. wheat export inspections were reported to be bearish in their final reporting week for the ‘09/‘10 marketing year. U.S. wheat exports for the ‘09/‘10 marketing year are likely to fall short of USDA’s 865 million bushel projection.

Rumors of China buying U.S. corn were true. However, Chinese corn purchases were more directed at controlling their internal corn price than need for corn. Recently, a source indicated that while China was purchasing 1 million bushels from the U.S. they were exporting 6 million (+) bushels. Currently, Dec ‘10 corn futures are trading at $3.69; Nov ‘10 soybeans at $9.07; and July SRW wheat at $4.44 per bushel. Nearby crude is trading at $72.88 per barrel; the U.S. Dollar Index at 87.00; and the Dow at 10,270.

For technical assistance on making grain marketing decisions contact Carl L. German, Extension Crops Marketing Specialist.

Those Pesky Interveinally Chlorotic Corn Leaves

Friday, June 4th, 2010

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

During the past two growing season, I’ve tried a number of remedies for a common early season problem on field corn. It seems that more and more corn has been showing distinctive interveinal chlorosis (yellowing between the veins) on the upper leaves. A number of theories have been bantered about as to what these symptoms represent and if they are even meaningful from a final yield point of view. Farmers who have kept track of the problem areas and who have yield monitors have not reported that lower yields are necessarily associated with these symptoms. It may be that small yield effects do occur but so far the yield effects mostly have been very subtle. Up to now, I’ve tried foliar applications of manganese, zinc, copper, iron, boron, magnesium, and sulfur (usually as a component with one of the previous cations). None of these foliar-applied nutrients have lessened the symptoms. The corn does tend to grow out of the symptom when it reaches the rapid growth phase around side-dress time.

I will continue to look at this situation and try some soil-applications since some work Dr. Greg Binford did last year seemed to indicate that soil applied sulfate may help. Another possibility since we’ve had two very unusual springs is that on early-planted corn that received substantial amounts of cold rain, root system restrictions from some production factor may be limiting nutrient uptake leading to smaller, yellowed (interveinal yellowing) corn. For the most part, warm temperatures and corn reaching the rapid growth phase of development seems to be initiating the recovery of the crop.

If you’ve seen this type of problem in some of your corn fields, please take time to pass along to me or your Extension ag agent as much information on your production practices and weather for these areas as possible so we can try to understand more about this problem. If you have a yield monitor on your combine and can yield check problem areas versus nearby good areas, we would appreciate learning if your yields have been affected.

Consider Temporary Annual Forage Crops for Fields to be Planted Later this Year

Friday, June 4th, 2010

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

If you were one of those producers whose pasture or hay field replanting was prevented by this past spring’s cold rainy weather, now is the time to consider a method of preparing the field for late-summer/early-fall (LS/EF) reseeding. The beginning of June’s hot weather (warm soil conditions) is ideal for seeding warm-season annual, weed-suppressing grasses such as hybrid pearl millet, sudangrass, the sorghum-sudangrass hybrids, or even teff. These grasses, if seeded when soil temperatures are >75° F and adequate soil moisture is present, can germinate and establish very rapidly. They have the ability to suppress many weed species and can add organic matter to the soil via the root mass left at the end of the season or the root mass plus final top growth of the season.

Another advantage of the warm-season annual grasses comes from the need for land preparation prior to the permanent LS/EF seeding. This soil preparation provides the producer with the opportunity to check the pasture or hay field’s soil fertility status and to make early adjustments that can be rechecked prior to planting the more expensive perennial grass seed. As an agronomist, I typically recommend checking six months to a year ahead of reseeding a field so that pH adjustment (liming) and nutrient amendments (phosphorus, potassium, or manures) can be applied and will have time to correct any problems in the field. Although the timing here may be tight, it still will allow a producer to recheck the field before establishing the permanent cover.

Another obvious benefit is the increased tonnage the summer annuals offer forage producers. However, care must be taken in selecting not only the annual grass species but the animal species that the forage will feed. Summer annual grasses can have a number of limitations/problems that can be successfully managed by the knowledgeable producer.

Common to all the species (even the cool-season grasses) is the potential for nitrate accumulation and nitrate toxicity during drought or cloudy weather when nitrates are not metabolized rapidly enough by the plant into proteins and amino acids. Nitrates taken up from the soil then accumulate, especially in the lower stems, and can reach toxic levels and are not reduced during hay harvest. Cyanide toxicity issues exist for sudangrass and the sorghum-sudangrass hybrids but this can be managed with grazing or cutting height. Sorghum species and species such as foxtail millet (Setaria spp.) can be harmful to horses (cystitis problems to name one concern). Hybrid pearl millet and pearl millet do not cause these problems and are generally considered safe for horses. Most of the species also have thick stems and large leaves that make hay making a bit more challenging. With careful management, the benefits from weed suppression, forage production, soil tilth, and early soil fertility adjustment out-weigh other concerns.

Soybean Rust Update – June 4, 2010

Friday, June 4th, 2010

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

It is the first week of June and there is no active soybean rust in the US. This is very unusual compared to past seasons. The cold winter in the South killed back kudzu and reduced most of the overwintered spores in that region. Dry weather again in the South is not providing the conditions needed for infection. Only time will tell what this season’s rust scenario will be. The southern states continue to monitor for rust using the established sentinel plot system that is in place.

Agronomic Crop Insects – June 4, 2010

Friday, June 4th, 2010

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

Alfalfa
Continue to sample for potato leafhoppers on a weekly basis. Although adults are the main life stage present, we are starting to see the first nymphs. Although both life stages can damage alfalfa, the nymphs can cause damage very quickly. Once plants are yellow, yield loss has already occurred. The treatment thresholds are 20 per 100 sweeps on alfalfa 3 inches or less in height, 50 per 100 sweeps in 4-6 inch tall alfalfa and 100 per 100 sweeps in 7-11 inch tall alfalfa.

Although we do not have any local research on potato leafhopper thresholds for fields planted with the glandular haired varieties, here is some information from Ron Hammond from Ohio regarding treatment thresholds on these varieties:

“If the alfalfa is one of the glandular-haired, leafhopper-resistant varieties of alfalfa, the economic threshold is three leafhoppers per inch of growth (24 leafhoppers for 8” tall alfalfa, for example). However, if the resistant alfalfa is a new planting this spring, growers might want to use thresholds meant for regular alfalfa during the very first growth from seeding. Because its resistance improves as the seedling stand develops, research suggests that the threshold for a resistant variety can be increased to 3 times the normal level after its first cutting.

“More information on potato leafhopper, including how alfalfa growing conditions might affect the threshold, is available at http://ohioline.osu.edu/ent-fact/pdf/0033.pdf.”

Field Corn
We continue to receive reports of larger cutworms feeding below the ground and causing plant lodging and wilting. It can be difficult to achieve control when cutworms are feeding below the soil surface and in some fields worms are large (greater than one inch long). This below ground feeding is generally done by cutworms that range in size from ½ inch to 2 inches in length (4th instars and later instars). If you can find 3% of plants damaged (cut or tunneled), larvae are one inch or less in length, and corn growth stage is between plant emergence and the 6th leaf stage, controls may still be needed. However, when damage is occurring below the soil surface ( plants appear tunneled) it is important to treat as late in the day as possible, direct sprays to the base of the plants and use at least 30 gallons of water per acre. For information on cutworm biology and management, please refer to the following fact sheet from Ohio
http://ohioline.osu.edu/ent-fact/pdf/0035.pdf

Small Grains
We continue to see economic levels of armyworms in both wheat and barley that did not receive an earlier insecticide treatment. As indicated in past newsletters, damage can quickly occur in barley. In many cases there is a mixture of worm sizes so the potential for head clipping is high, especially in barley. Be sure to read the label before applying any insecticide for the rate, days between last application and harvest and other restrictions. Control options are limited at this late date due to pre-harvest intervals.

Soybeans
Continue to sample for bean leaf beetles and grasshoppers. In the earliest planted and emerged fields, we have started to see an increase in activity for both insects. As barley is harvested and soybeans are planted, these fields will be especially susceptible to attack and grasshopper feeding can often cause stand loss. If stand reductions are occurring from plant emergence to the second trifoliate, a treatment should be applied. Although no precise thresholds are available, a treatment may be needed if you find one grasshopper per sweep and 30% defoliation from plant emergence through the pre-bloom stage. As a general guideline, a treatment may be needed for bean leaf beetle if you observe a 20 – 25% stand reduction and/or 2 beetles per plant from cotyledon to the second trifoliate stages.

MELCAST Forecasting for Bummy Stem Blight on Watermelon and Alternaria Leaf Blight on Cantaloupe

Friday, June 4th, 2010

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

Forecasts for fungicide applications in watermelon and cantaloupes for the 2010 season are set to begin on Friday, June 4. If you have not received forecasts in the past and would like to receive them, please call Mrs. Jeri Cook (410-742-8788) and give her your email address. Locations will remain the same as last year. Maryland forecasts are for Woodbine, Waldorf, Galestown and Hebron. Delaware forecasts are for Coverdale Crossroads, and both northeast and southwest of Laurel. To use MELCAST, select weather data for the site closest to your farm.

Instructions on use of MELCAST are available at http://mdvegdisease.umd.edu/forecasting/index.cfm.

Late Blight Update

Friday, June 4th, 2010

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

Unfortunately late blight has continued to appear in tomatoes over the past week. Locally, a second high tunnel outbreak in St. Mary’s County, MD was confirmed last week. This is the second confirmation in Maryland and is about one mile from the first outbreak. So far no other outbreaks in Maryland and none in Delaware have been reported. In other states, an outbreak in a Pennsylvania greenhouse was confirmed on May 17 (that crop was destroyed).

In northern Kentucky on May 27, infected transplants were found in one home garden and several box stores. These transplants had been grown outside of Kentucky and shipped to the box stores for sale. The stores involved are national chains. The transplants, which are destined for home gardens, pose a huge threat because they would provide widespread dispersal of inoculum. We hope to avoid a recurrence of this scenario, which caused widespread commercial losses in 2009. Everyone is encouraged to be vigilant. If late blight is suspected – please contact your extension educator.

Again I am recommending that commercial tomato growers apply a protectant fungicide such as chlorothalonil (Bravo), Gavel, or mancozeb. Scout aggressively for symptoms and switch to more targeted translaminar products when late blight is found.

Potato Disease Advisory #6 – June 3, 2010

Friday, June 4th, 2010

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

Disease Severity Value (DSV) Accumulation as of June 2, 2010 is as follows:
Location: Art and Keith Wicks Farm, Rt 9, Little Creek, Kent County.
Green row: May 6

  LATE BLIGHT EARLY BLIGHT
Date Daily DSV Total DSV Spray Recs Accumulated P- days*
5/20 0 11 none -
5/21-5/23 0 11 none -
5/23-5/25 18 29 5-7 days -
5/26 0 29 7-days -
5/27-5/28 1 30 10-days -
5/29-5/30 1 31 10- days -
5/31 0 31 10-days 199
6/1 1 32 10-days 206
6/2 0 32 10-days 214

Maintain the recommended spray interval. At 300 P-days fungicide sprays will be needed to control early blight. Growers who do not want to rely only on the DSV calculations for scheduling fungicide applications should apply at least 1-2 sprays of mancozeb (Dithane, Manzate, Pencozeb, Manex II) or Bravo (chlorothalonil) before plants canopy down the row. At this point weekly fungicide applications would be suggested. There have been no reports of late blight on potatoes in the region.

* 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, 214 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.

The Spray Recs column in the table is also generated by the WISDOM software program. This recommendation combines the DSV accumulation for late blight as well as the P-day accumulations for early blight and computes a spray recommendation. This is presented as a guide only. Spray decisions should be made with local conditions in mind and this information can help to determine if disease conditions are favorable.

For specific fungicide recommendations, see the 2010 Delaware Commercial Vegetable Production Recommendations Book.

Calcium Disorders

Friday, June 4th, 2010

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

I have recently looked at both cabbage and spinach fields showing signs of calcium deficiency. With that in mind, the following is information taken from a 2008 article that I wrote on calcium deficiencies.

Calcium disorders in field crops are not common because calcium dominates exchange sites in soils and is therefore rarely deficient in corn, soybeans, and small grains if they have been properly limed. However, a number of calcium disorders can occur in vegetable and fruit crops, even in well limed soils. Some of these disorders include:

● Blossom end rot in tomatoes, peppers, and eggplants
● Blossom end rot in watermelons
● Watercore and glassiness in melons
● Internal leaf tipburn in cabbage
● Leaf tipburn and curd defects in cauliflower
● Internal browning of Brussels sprouts
● Leaf tipburn in spinach
● Leaf tipburn in lettuce
● Leaf tipburn and deformity in strawberry
● Internal browning, hollowheart, storage disorders, and poor skin set in potatoes
● Cavity spot in carrots
● Bitter pit, cork spot, cracking, internal brownspot, and water core in apples
● Hypocotyl necrosis in beans and other legumes
● Meristem death or distortion of new growth from meristems in many plants (cupped leaves)

Calcium is taken up in quantity from the by plants from the undifferentiated area right behind the root tip. Once in the root, it moves in the xylem (water conducting vessels) and is distributed in the plant. Much of this movement in the xylem occurs by exchange. Calcium is attracted to the xylem wall and must be displaced by another ion (another calcium or other cation). This process is driven by transpiration and subsequent water movement through the xylem. Therefore, calcium movement is relatively slow compared to other nutrients that move easily in the transpiration flow. Calcium is not translocated in the phloem (plant food transport system) so it cannot move from one area of the plant to another.

Calcium has many roles in the plant from root growth control, to cell membrane function, to stomatal regulation. The main function that leads to the disorders listed above is in the formation of plant structure. Calcium is component of cell walls and the middle lamella that cements plant cells together. Calcium provides cross linkages in the pectin-polysaccharide matrix and adds to the structural strength of plant tissues. When insufficient calcium is present, plant tissues do not form properly and they may appear deformed and in severe cases may become necrotic – tissues may die or collapse.

There are a number of reasons why vegetables and fruits are more susceptible to calcium disorders. Because calcium moves slowly through exchange in the xylem and is dependent upon water flow, disruptions in that flow can lead to localized deficiencies in calcium. Plant organs with low transpiration rates or that are rapidly expanding such as fruits and storage roots often do not receive enough calcium to support that growth. Growing tips and meristematic areas that are rapidly laying down new cells are also at risk for calcium deficiencies when water flow is interrupted. High humidity, drought, flooding (leading to roots shutting down), root injury, compaction, and root diseases can therefore lead to calcium disorders by the reduction of water flow and calcium exchange and movement in the xylem.

Competition from other cations such as magnesium (Mg2+), ammonium (NH4+), and potassium (K+) can also affect calcium (Ca2+) uptake and movement. In low pH soils, aluminum can interfere with calcium uptake and lead to deficiencies.

Control of calcium disorders starts with proper liming. This provides soil calcium and raises the pH to eliminate the effect of aluminum. The most important factors to control calcium disorders are to supply a steady rate of water (through a good irrigation program), limit root damage (such as root pruning by cultivation), provide a rooting area for plant that is free from compaction and waterlogging, and create a healthy soil environment that limits root disease potential. Above ground, planting at spacings that allow for good air movement around the plant will also help. Control fertilizer programs to limit competition between calcium and other ions (use nitrate forms of nitrogen instead of ammonium forms for example). In addition, choose varieties that are less susceptible to these calcium disorders (varieties with very large or very long fruit are more susceptible to calcium deficiencies).

In cases where calcium is low but where you do not want to increase the pH (as is the case with scab susceptible potatoes or with blueberries), gypsum (calcium sulfate) can be applied to supply additional calcium to the crop. Rates of gypsum application are from 500 to 1000 lbs/acre commonly.

If a calcium deficiency is evident or suspected, calcium nitrate applications often will help. For crops grown with drip irrigation, the calcium nitrate can be put on through the drip system. For other crops, calcium nitrate can be spun on, watered in, sidedressed, or applied through fertigation with overhead irrigation. Calcium nitrate is very water soluble so uncoated forms are used for fertigation and coated forms are used when it is being spun on. Calcium nitrate is 15.5% nitrogen so application rates will largely depend on how much nitrogen can be applied to the crop at any time. Generally 200-400 lbs/acre of calcium nitrate are used.

Sidedressed calcium has been shown to have positive effects on root crops such as potatoes, particularly in sandy soils. Forms that have been used include calcium sulfate (gypsum) and calcium nitrate.

There have been mixed results with foliar application of calcium and these applications should be considered a supplement to help limit these disorders and not a correction for calcium deficiencies and good soil and water management. As stated before, calcium movement is limited so it will be difficult to get calcium to where it is needed by foliar sprays except when applied to active meristematic tissue. However, calcium sprays have been effective in improving quality and eliminating calcium disorders in apples.