Posts Tagged ‘19:16’

WCU Volume 19, Issue 16 – July 8, 2011

Friday, July 8th, 2011

PDF Version of WCU 19:16 – July 8, 2011

In this issue:

Vegetables
Vegetable Crop Insects
Boron Toxicity in Beans
Vegetable Disease Updates
Controlling Powdery Mildew in Cucurbits
Potato Disease Advisory #15 – July 7, 2011

Fruit
Spotted Wing Drosophila Confirmed in Virginia

Agronomic Crops
Agronomic Crop Insects
Agronomic Crop Diseases
Thinking of Renovating or Planting a New Pasture or Hay Field? Part 1: The Preplanning Process
Grain Marketing Highlights

Weather

 

Controlling Powdery Mildew in Cucurbits

Friday, July 8th, 2011

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

Powdery mildew is a problem on cucurbits each year. All cucurbits are susceptible, however host plant resistance in many cucumber and cantaloupe cultivars has successfully managed the problem. Susceptible varieties as well as other crops like pumpkin and squash are hit hard by powdery mildew. Disease builds up during July and becomes severe in August and September. Powdery mildew is a challenge to manage, especially in hot dry conditions. Also, there is resistance in the powdery mildew pathogen to many of our fungicides such as Quadris. Therefore, fungicides must be chosen carefully.

To manage powdery mildew, select cultivars (varieties) with resistance or tolerance. Even a moderate level of resistance will improve the efficacy of a fungicide spray (and help reduce the damage if you miss a spray). Scout the field and apply the first powdery mildew spray when you see one lesion on the underside of 45 old leaves.

Always follow good resistance management guidelines. 1) Keep on a good spray schedule (a 7-day interval for powdery mildew). 2) Apply fungicides at label rate (don’t cut the rate). 3) Be sure you are getting good fungicide coverage of your plants. 4) Be aware of products that are at risk for resistance development. 5) Materials with different modes of action (FRAC codes) should always be alternated. 6) Late in the season when powdery mildew has become well established, only apply protectant fungicides such as chlorothalonil or sulfur.

Below are the fungicide programs suggested for the various crops.

Summer Squash or Cucumber: Alternate a tank mix that contains chlorothalonil and either Procure, Rally, Folicur, or Inspire Super, with a tank mix containing Pristine plus chlorothalonil.

Muskmelon: Alternate Quintec plus chlorothalonil, with a tank mix containing chlorothalonil and either Procure, Rally, Folicur, or Inspire Super.

Extensive white sporulation of powdery mildew on pumpkin leaves.

Pumpkin: Alternate Quintec plus chlorothalonil with a tank mix containing chlorothalonil and either Pristine, Procure, Rally, Folicur, or Inspire Super. An alternative and less expensive option is to alternate Micronized Wettable Sulfur with one of the above options. Sulfur may injure plants, especially at high temperatures, which is why it is only recommended for pumpkin. Certain varieties can be more sensitive.

 

Grain Marketing Highlights – July 8, 2011

Friday, July 8th, 2011

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

Markets Expected to Trade Quietly While Awaiting July S&D Report
On next Tuesday, July 12, USDA will release their next round of monthly supply and demand estimates. The July report will be subject for debate until resurvey results are reported in August. The National Ag Statistics Service (NASS) will be resurveying Montana, North Dakota, South Dakota and Minnesota during July. The findings (revised acres) will be reported in the August supply-demand report. The revision isn’t expected to make any difference since most private analytical firms will have their own estimates before that time. Weather now takes the driver’s seat in terms of having the biggest potential impact upon price direction. The forthcoming production forecasts can make or break this market, even from current price levels. Currently, outside market forces are lending support with the Dow and crude oil prices are trading higher.

Weekly export sales were reported to be neutral corn, neutral wheat, and bearish for soybeans. Recent lower prices are expected to pick up the export pace for corn. The Southern Hemisphere production results for 2011 are reported to be slightly over 9% greater than last year. Therefore, soybean exports may not be bullish for U.S. supplies anytime soon. The value of the dollar will determine the pace of wheat exports in the weeks ahead. Currently, Dec ‘11 corn futures are trading at $6.19; Nov ‘11 soybeans at $13.41; July ‘11 SRW wheat at $6.13 per bushel; and Dec ‘11 SRW wheat at $6.66 per bushel.

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

 

Thinking of Renovating or Planting a New Pasture or Hay Field? Part 1: The Pre-Planning Process

Friday, July 8th, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

I have received several requests over the past several weeks concerning overseeding or renovating pasture and hay fields and feel it’s a good time to begin a discussion on the process. All too often, we find ourselves moving into mid to late fall without having taken the time to really consider all decisions that have to go into improving the odds that the planting will be successful. You need to keep in mind that seed costs alone can equate to a hundred dollar an acre investment; and, if we really take into account all the variable costs, that new pasture or hay field can easily represent an investment of hundreds of dollars per acre.

So in the pre-planning process, what’s first? I know many get tired of hearing the phrase but testing the fertility of your soil far ahead of time is still the number one issue. If the field will not be tilled and you have not been applying significant quantities of commercial nitrogen (N) fertilizer to the field, sample at 0 to 4 inches deep in each field or management zone (an area of the field treated in a similar fashion and not much different from other areas of the field in soil type).

If you have used large quantities of commercial N fertilizer in the past, you really should take both a 0-2 inch depth sample for determining the soil acidity in the upper soil layer as well as a 0 to 4 inch depth sample for nutrient content (phosphorus, potassium, calcium, magnesium and other essential elements).

The reason for this distinction is that the ammonium or urea N forms that we apply as fertilizer are converted by soil bacteria into nitrate and in the process acidity is released into the soil. Since the N is all surface applied, the release of acidity near the soil surface can create a condition known as ‘acid roof’ where the top inch or two of soil is much more acidic than the deeper layers of soil. A second reason involves the very slow movement of limestone down through the soil. Studies on pastures in Connecticut many decades ago showed that lime moves at a rate of about 1 inch per year so it takes a very long time to have an impact on the entire rooting zone of forage grass and legume plants.

For fields that will be tilled and a new planting established, the traditional plow layer sample (0 to 8 inches) for both soil pH (acidity) and essential nutrient status will be the correct choice. If the soil sample indicates that the soil must be limed, apply the recommended amount of limestone and work it into the soil as soon as possible to allow time for the limestone to neutralize soil acidity before planting time. Although, if it remains dry, lime may not completely react, and a second soil test still would be useful to determine if any additional lime will be needed. Additional agricultural lime and the recommended phosphorus (P) and potassium (K) and any other needed nutrients can be applied and worked into the soil shortly before planting the field.

Everyone asks the question of whether to apply N at the time you plant a new field or seed a field you are renovating. My preference is that you should wait until the new grass is several inches tall and has enough biomass and roots to compete for the applied N and to store any extra N for future growth. Until forage plants have enough leaf area to rapidly capture the sun’s energy and convert it into more plant tissue or into sugars for storage, weeds in new plantings or the current vegetation in renovations are likely to outcompete the new seedlings for N and then for light, water, and other nutrients. When waiting to apply N although weeds and current vegetation will still be present, the new seedlings will at least be in a better competitive position when the N is finally available to stimulate growth.

Now that you’ve taken care of any soil fertility issues that can reduce the chance for a successful stand, the next decision involves choosing the right seed to plant. I’ve had the opportunity over the years to read many seed labels on various pasture mixes offered for sale. I understand the convenience of buying a prepared pasture mix and the allure of these mixes. The buyer often assumes that the seller has spent the time and energy studying the issue and has come up with a mixture that in their opinion and experience has the best chance of success. I certainly can’t speak to motivation of the seller but keep in mind that from a business point of view, seed that is mixed and offered for sale need to be sold over as large an area as possible to justify the expense of wholesaling large quantities of seed, blending, packaging, and labeling the seed. In my opinion, this nullifies the expectation that the seller has designed the mix for your particular field or location.

After looking at the species of forages used in the prepared pasture mixes, I find that these mixes are more like a shotgun approach to seeding where you plant a little of everything in hopes that something will establish in all areas of the field. Usually they contain a quick establishing grass such as ryegrass that can germinate in as little as 5 to 7 days so the buyer can feel comfortable with the new seeding. The mixes also usually contain the feel-good or highly recognized grasses such as timothy and Kentucky bluegrass in horse pasture mixes and at least some orchardgrass and probably an endophyte-free tall fescue to provide more permanent cover. Finally, a legume such as white or ladino clover, red clover, or alsike clover will be in a pasture mix to provide the N-fixing legume everyone would like in a pasture.

The convenience of these mixtures comes from not having to mix them yourself before you fill the seed drill and the allure comes from not having to make a decision other than how much seed per acre to plant and not having to choose individual species to plant. For most buyers, the convenience and allure end up costing them many, many dollars per acre in seed costs for seed of grasses that won’t survive in grazing situations or won’t survive more than a season or two at best or will be unproductive for much of the grazing season.

So what should you do? I prefer going with a simpler mixture using forage species that are adapted to our region. In most cases, the only species that will survive for many years in our transitional zone climate is tall fescue. Because of endophyte (an fungus growing in some tall fescue plants) issues, many growers have tried the endophyte-free tall fescue varieties and some have had success with keeping a stand for many years while others have seed stands decline or disappear quickly. The newest chapter in this issue has been the development of novel or friendly endophyte tall fescue varieties. The novel endophyte tall fescue varieties do not produce the chemical compound (alkaloids) that interfere with animal performance but still provide benefits to the tall fescue plants helping them survive in many stressful environments. A limitation still in evidence with these new tall fescue varieties is that horse owners who breed horses do not all accept tall fescue as a feed source for their animals. This limits tall fescue’s acceptance.

What other species can you include in your simple mixture? Orchardgrass is another grass that many producers like to include in a pasture mixture but you should be aware that many orchardgrass fields are failing due to a disease/insect/environment/management complex interaction we’ve been calling orchardgrass decline. If you choose to include orchardgrass, keep it as a small proportion of your mixture. The other grass to include at least on the heavier soils is Kentucky bluegrass. Be sure to include several varieties of the Kentucky bluegrass to help with disease resistance. It will be most productive early in the year (early spring to early summer) and mid- to late-fall. Finally, add in a legume to help with providing N for the grass to use as well as to improve the protein and forage digestibility of the pasture. For grazing, most people prefer a ladino-type of white clover. Although slobbers (the animal produces excessive amounts of saliva) is a potential concern with all clovers, it seems to be mostly associated with red clover. Often included in commercially sold horse pasture mixtures, alsike clover is known to cause photosensitivity (sunburn) especially in horses and should not be included in your pasture mix.

You will find it useful to talk to your seed dealer about the various varieties of each species that are available. Once you decide on the varieties to use and you purchase seed, you can mix your own pasture mix by either purchasing or renting a cement mixer and combining the seed in the proportions you decide are best for your purpose and field. Since many legumes now come pre-inoculated with the N-fixing bacteria and often are coated with a fine limestone, do not over mix the seed and when you re-bag it store it where it is protected from high temperatures and humidity. Stored properly, the seed can be held over the winter if something prevents you from seeding this fall but you should plan to plant as soon as possible after purchasing seed. Not only are the N-fixing bacteria alive; but, if you use a novel endophyte tall fescue variety, the endophyte has a limited storage time (around a year under good conditions) before it should be planted. Although the tall fescue seed will germinate after longer storage times, the endophyte fungus may no longer be alive. The fungus only lives in the plant and is not soil-borne.

Next time, I’ll cover some of the other management issues to consider, such as planting date.

The other articles in this series are:

Thinking of Renovating or Planting a New Pasture or Hay Field? Part 3: Pasture and Hay Planting Time Has Arrived

Thinking of Renovating or Planting a New Pasture or Hay Field? Part 2: Planning to Planting

 

Agronomic Crop Disease Update – July 8, 2011

Friday, July 8th, 2011

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

Soybeans
Now is the time to start checking soybeans for soybean cyst nematode. Once soybeans have reached the 3rd trifoliate leave stage (roughly about 28-32 days from planting) the white or yellow female cysts can be seen on the roots. If you see irregular patches of stunted soybeans don’t presume the stunting is from drought. Digging the plants carefully may reveal SCN is present and could be the cause of the stunting. If you are seeing many cysts and stunting on resistant soybeans it is time to rotate out of that field to reduce SCN egg numbers.

White and yellow female soybean cyst nematodes on roots, 34 days after planting

Corn
Three corn samples arrived in the plant clinic this week with bacterial stalk rot. If you are irrigating from surface water sources, such as ponds or ditches, there is a risk of bacterial stalk rot. The bacterial can be in the irrigation water and get trapped in the whorl, the ear leaf sheath, and the ear shank. These places provide a place for water to sit and the bacteria can enter the stalks and cause a soft decay of leaf sheath, stalk, and ear shanks. It is foul smelling as well. It appears as random infected plants in the field and as a result it does not cause major losses. Corn is thought to be susceptible for a short period of time and the older the corn the less likely infection will occur. There is no chemical control for bacterial stalk rot. Treating irrigation water in the system with hypochlorite is an alternative solution.

Bacterial stalk rot

 

Agronomic Crop Insects – July 8, 2011

Friday, July 8th, 2011

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

Alfalfa
If you have not been scouting fields, be sure to keep a close watch for leafhoppers. Remember, the nymphs can quickly cause damage and once yellowing is present significant damage has already occurred both in season as well as to the long term health of the stand. With the hot, dry weather, you should consider reducing treatment thresholds by at least one third.

Field Corn
We are starting to see an increase in beetles feeding on corn silks. Although beetles feeding on silks can potentially interfere with pollination, research from the Midwest indicates that silk feeding does not reduce pollination if they cut the corn silks after pollination has already taken place. As a general guideline, an insecticide treatment may be needed if two or more Japanese beetles or corn rootworm beetles are present per ear and silks are clipped to less than 1/2 inch prior to pollen shed.

Soybeans
We continue to see a wide variety of defoliators present in full season soybeans. The best way to make a treatment decision in full season soybeans is to estimate defoliation. Before bloom, the defoliation threshold is 30%. As full season beans enter the reproductive stages, the threshold drops to 15% defoliation. Remember that double crop soybeans can not tolerate as much defoliation as full season beans so be sure to watch newly emerged fields carefully.

Continue to scout for spider mites in full season and double crop soybeans. With the current hot, dry weather, economic populations are being found field wide so be sure to scout the entire field because edge treatments may not be effective.

As full season beans enter the flowering stage, we are starting to see low levels of stink bugs (mostly green). The first brown marmorated stink bugs have also been detected by consultants on field edges. Economic damage from stink bugs is most likely to occur during the pod development and pod fill stages. You will need to sample for both adults and nymphs when making a treatment decision. Available thresholds are based on beans that are in the pod development and fill stages. This year we will again use the same thresholds for stink bugs that are being used in Virginia and were developed in states to our south. As a general guideline, current thresholds are set at 1 large nymph/adult (either brown or green stink bug) per row foot if using a beat sheet, or, 2.5 per 15 sweeps in narrow-row beans, or 3.5 per 15 sweeps in wide-row beans.

This year we are participating in a regional project to identify the distribution of another new potential pest of soybeans in the U.S., the Trochanter Mealybug. This insect feeds on the roots of soybean plants. In the few states where it has been found, the fields looked like they had potassium deficiency-like symptoms (e.g., yellowed leaf margins and stunted plants). See attached photos 1 and 2 of damage symptoms and mealybugs on roots from Ron Hammond, OSU.

Photo 1. Leaf symptoms associated with Trochanter mealybug

Photo 2. Trochanter mealybug on roots

If you see plants with these symptoms, you should carefully dig up the roots and look for the presence of mealybugs. If you find a suspect field, please contact Joanne Whalen (jwhalen@udel.edu) since we would like to verify presence and distribution in the state.

 

Spotted Wing Drosophila Confirmed in Virginia

Friday, July 8th, 2011

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

The first reports of the presence of spotted wing drosophila (SWD) were confirmed last week in Virginia. Although we have not found any yet in our limited survey (only one location), it is very likely that it could make it to our area this season. The following link from Virginia provides more information about this important potential new pest. http://www.virginiafruit.ento.vt.edu/SWD.html

 

Potato Disease Advisory #15 – July 7, 2011

Friday, July 8th, 2011

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

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

Date Late Blight Early Blight Spray Interval Recommendation
DSV Total DSV Accumulated P-days*
6/16 1 67 328 7-days
6/17 0 67 336 7-days
6/18-6/19 0 67 352 10-days
6/20-6/22 1 68 377 10-days
6/23 1 69 383 10-days
6/24-6/26 0 69 407 10-days
6/27 1 70 416 10-days
6/28 1 71 424 10-days
6/29 0 71 432 10-days
6/29-7/2 0 71 456 10-days
7/3 1 72 462 10-days
7/4 0 72 468 10-days
7/5 1 73 474 10- days
7/6 0 73 481 10-days

Continue to scout fields for symptoms of late blight. Conditions will continue to favor early blight. Continued dry weather will not favor the spread of late blight.

Late Blight was reported last week in DE, on the eastern shore VA, and Long Island, New York. There have been no further reports of late blight in DE or VA but late blight has been reported on the North Fork on Long Island, NY in addition to the earlier find on the South Fork.

For specific fungicide recommendations, see the 2011 Delaware Commercial Vegetable Production Recommendations Book.

 

Vegetable Disease Updates – July 8, 2011

Friday, July 8th, 2011

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

Late Blight
There have been no new late blight detections in DE or VA on potatoes. The disease apparently is under control and the weather has not been very favorable, especially where the temperatures have been over 90°F. Besides the two finds in DE and VA the only active late blight at present appears to be on Long Island, NY on both potato and tomato.

Downy Mildew on Cucurbits
As most of you know by now downy mildew was found in Sussex County on Tuesday and Dorchester County, MD. Both finds were on pickling cucumber. Since then downy mildew was found in an additional field near Bridgeton, NJ, Talbot County, MD, Wyoming County, PA, and several more cucumber fields in NC. Now is the time to be spraying specific fungicides for downy mildew on cucumbers. Continue to check the IPM pipe website for more information on the spread of downy mildew: http://cdm.ipmpipe.org.

Root Knot Nematode
Root knot nematode can be a very yield limiting pathogen on very susceptible crops like cucumbers and other vine crops, lima beans, snap beans and tomatoes to name a few. They are often worse in very sandy soils or sandy knolls in fields. With the temperatures that we have seen here in DE you can begin to see the swellings or galls on the roots in about 21 days from seeding or transplanting. Plants in infested areas of the field will be stunted and if the plants are dug carefully, if root knot is present, you will see galls of varying sizes on the roots. We have no chemical controls except for vine crops once the nematodes are seen. Vydate should be applied preventatively in fields with known root knot infestations at seeding and/or later when plants are still small. See label for details. Treating early is always better than waiting until galls can be seen.

Root knot galls on baby lima bean roots, 23 days from planting

Pepper Anthracnose
Be on the lookout for anthracnose on peppers. It has been reported in southern NJ. Anthracnose fruit rot can be a very difficult disease to control if it gets established in a field. Fields should be scouted frequently especially if peppers or tomatoes have been planted in the past. It is best controlled by preventative fungicide sprays beginning at flowering. Apply Bravo or another chlorothalonil product every 7 days and alternate with a stroblilurin fungicide (FRAC code 11) like Cabrio or Quadris plus Bravo. If anthracnose fruit rot appears, removing infected fruit from heavily infected areas will help to reduce spore loads and reduce spread if done early and often enough. Fruit will need to be removed from the field and not just thrown on the ground.

Anthracnose on pepper fruit

 

Boron Toxicity in Beans

Friday, July 8th, 2011

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

We recently had a suspected case of boron toxicity in snap beans. Boron toxicity is common in western states where boron levels in soils or irrigation water are high. In the east, we do not have high boron soils or high levels in irrigation water. In addition, boron leaches readily from soils. Boron toxicities therefore occur only when excess boron is applied in fertilizers.

Boron is a micronutrient needed by plants. It is closely associated with calcium and calcium transport, cell wall production, cell division in plant growing points, sugar transport in plants, flower and fruit development, and plant hormone regulation. Vegetables vary in their boron requirements. Cole crops, turnips, and beets have the highest demands. Even so, recommended rates of application in low boron soils for these high demand crops is only 3 lbs/acre. More commonly, 1-2 lbs of boron per acre is applied to vegetables as a broadcast. Margin of safety for boron application is small and excess application or improper blending in fertilizers may lead to toxicities – deficiencies show up at 1 ppm and toxicities appear at 5 ppm of available boron in the soil.

The vegetable crops most sensitive to excess boron are beans, particularly snap beans. Boron is generally not recommended for snap bean production and boron should never be included in starter fertilizer for snap beans. Boron toxicity often occurs where starter fertilizer containing boron for other crops, such as corn, is applied to snap beans.

Boron toxicity in beans commonly appears as yellowing in unifoliate leaves with burning of leaf edges and yellowing of leaf edges of the older trifoliate leaves that can progress to edge burn. In severe cases, plants will develop a scorched appearance and leaves may prematurely drop off.