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Agronomic Crop Insects – September 14, 2012

Friday, September 14th, 2012

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

Alfalfa
Continue to sample fields on a weekly basis for defoliators including earworm, webworms and all armyworm species. We continue to get reports of fields with economic levels of defoliators. Although we have limited experience at this time of year with damage to re-growth, it will be important to check for the presence of larvae to determine if they are still present and holding back the re-growth.

Soybeans
Where economic populations levels of corn earworm are still present, late planted soybean fields that still have susceptible pods will still be at risk from pod damage. If economic levels of defoliators (i.e. worm defoliators including soybean looper, beet armyworm and green cloverworm) are present, you will also need to consider the maturity of the crop as well as the health of the leaf canopy to make a treatment decision. In an article related to defoliation from soybean loopers, entomologists and agronomists in the south suggested that if economic levels are present:

“Fields will need to be protected as long as the pods are still green and until the lower leaves are just beginning to yellow. This should correspond, more or less, with the R6.5 stage (10 days after R6.0 = full green seed). If leaves are beginning to yellow up the stem, not from drought but from the maturity process, and there are any pods on the plant that are beginning to yellow, the field should be safe, that is no need to treat. Next you have to determine the health of the leaf canopy: is it robust, average, or thin. Each can tolerate different amounts of leaf loss before reducing yield potential. Robust fields (mid chest or higher) can tolerate a lot of feeding. Average fields (upper thigh to mid chest) can tolerate normal amounts of feeding. Thin canopy fields (mid thigh or below) cannot tolerate additional leaf loss. Also in this canopy assessment, you need to take a stab at estimating the current percent defoliation. This is not an exact measure, but your best estimate looking over the entire canopy top to bottom. The eyes tend to focus on those badly defoliated top leaves. Look beyond those and try to come up with an overall average.”

When it comes to stinkbugs, you should continue scouting until the latest planted fields reach the R7 growth stage (a few studies in the south even say through the R-7 stage) when beans should no longer be susceptible to stink bug feeding.

You will still need to consider the potential for grasshoppers and bean leaf beetles to feed on pods. Although bean leaf beetle populations have been generally low this past season, there are still some hot spots of activity, so you will need to examine pods for feeding damage. During the last wet fall, we did see significant pod scarring late in the season that resulted in moldy beans. Information from Ohio indicates that a “treatment is usually indicated when pod feeding reaches 10-15% and beetles are still present and actively feeding. In fields where the pods have started turning yellow and brown, the adults will be leaving in search of greener pastures”.

If you do need to treat, be sure to check the label for the pre-harvest interval (time needed between last application and harvest) as well as other restrictions, including rotational restrictions.

Don’t Mix PVC Pipe and Polyethylene Greenhouse Film

Friday, September 14th, 2012

Emmalea Ernest, Extension Associate-Vegetable Crops; emmalea@udel.edu

Here is another article you can file under “Learn from My Mistakes/Mishaps” (previous example here). When my inflated poly greenhouse at the Georgetown research farm went flat about a month ago I thought the blower had gone bad. It turned out that there were actually giant holes in my less-than-one-year-old five-year greenhouse film. The holes corresponded to areas of wear in places where the plastic touched the PVC electrical conduit. There was no sign of wear around the metal support structure. Could the conduit be reacting with the plastic film?

Greenhouse film around the PVC conduit with cloudy discoloration and signs of wear.

One of numerous large holes where the conduit touches the greenhouse film.

Yes, it turns out, that PVC electrical conduit can out-gas chlorine which destroys the UV light stabilizers in the polyethylene greenhouse film and causes the film to degrade. In talking with various greenhouse suppliers and plastic manufacturers I learned that there is a sizable list of materials that can react with greenhouse film and cause wear including any type of PVC pipe or PVC tape, oil based paints or wood preservatives, chlorine based disinfectants, and certain pesticides, especially those containing sulfur or copper.

To prevent premature wear to greenhouse film, manufacturers recommend that surfaces that the film touches should be covered with white acrylic latex paint (but not the mildew resistant kinds that contain fungicides) or non-PVC tape. The film should not be in direct contact with any of the materials listed above that can cause breakdown or wear. In fact failure to follow these recommendations can cause the warranty on the film to be void. There seem to be some differences between manufacturers in tolerance of films to chemical interactions and installation recommendations and requirements, so it is a good idea to check with your greenhouse film supplier and the film manufacturer if you have a concern.

I have been told that some growers wrap PVC pipe that contacts the greenhouse film with old poly film. That would be an inexpensive means of dealing with the problem, but in my greenhouse I was concerned about that creating habitat for pests and diseases. After talking with the plastic manufacturer of the new film I am purchasing, I have decided to try covering the conduit with pipe insulation made out of polyethylene, which is readily available and inexpensive.

Some of the problematic conduit, soon to be covered with pipe insulation.

Excess Nitrogen and Vegetables and Fruits

Friday, September 14th, 2012

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

Vegetable crops vary considerably in their needs for nitrogen with crops such as sweet potatoes falling on the low end and tomatoes on the high end. While a lack of nitrogen will definitely limit vegetable productivity, excess nitrogen can also cause production problems.

Excess nitrogen will often delay maturity in crops. This is a particular problem in fruiting vegetables and vegetables with harvested roots and tubers. Too much nitrogen will favor the growth of foliage over flowering and fruiting or formation of storage organs such as tubers and roots. In a crop such as pumpkins, this can result in delaying fruit set so long that the crop will not mature in time for sales. Excess nitrogen can also reduce yields by limiting storage organ formation. Sweet potatoes would be a good example of a crop that will have reduced yields with excess nitrogen.

Excess nitrogen can also cause reductions in the quality of fruits and storage organs both in flavor and physical characteristics. High nitrogen applications can result in lower sugar content, lower acidity, and reduced firmness in fruits and storage organs. It can cause reduction in nutritional content. In leafy green vegetables, it can result in the accumulation of nitrates in the plant tissue to unhealthy levels. High nitrogen can cause reduced volatile production and negatively impact flavor and aroma in vegetables and fruits. Excess nitrogen can increase disorders such as hollow stems of broccoli and reduce storage and keeping qualities of fruits and vegetables.

Excessive production of foliage from high nitrogen applications can also lead to an increase in disease pressure from having a higher proportion of young tissue that is more susceptible to infections, by creating a more humid microclimate favorable for disease development, and by making it more difficult to get good coverage with fungicides.

Excess nitrogen can cause reductions in the levels of other mineral nutrients in plants such as potassium, calcium, and magnesium, often resulting in the development of deficiencies and associated disorders.

Recommended nitrogen rates and timings for most vegetable crops grown in our region can be found in the Commercial Vegetable Production Recommendations (online at http://ag.udel.edu/extension/vegprogram/publications.htm). These recommended rates have been developed over many years of research by our universities. Applications in excess of these recommended rates is justified only under special circumstances (excess rainfall and leaching for example).

Low Plant Tissue Potassium and Calcium

Friday, September 14th, 2012

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

Growers, consultants, and soils laboratories have noted that plant tissue tests on several vegetables (such as watermelon) have been showing lower than expected levels of potassium (K) and calcium (Ca) in plant tissues this year, even though soil levels are high.

There are a number of possible causes for these lower than expected tissue test results. High rates of nitrogen applied to vegetable crops can often reduce the levels of K and Ca in plant tissue. High nitrogen promotes foliage growth and more leaf area. This can have a dilution effect on K and Ca as there is less available proportionally to supply the new leaves.

The use of fertilizers high in ammonium and/or urea (which quickly released ammonium) can cause a temporary suppression of K and Ca uptake because ammonium is a competing cation. This suppression lasts until the ammonium is converted into nitrate in the soil by nitrifying bacteria. In drip irrigated vegetables where Urea Ammonium Nitrate (UAN) solutions are used as the nitrogen source during regular fertigation, this suppression can last throughout much of the season. The use of fertilizers with calcium nitrate and potassium nitrate as the nitrogen source can eliminate this competitive effect.

Very high levels of K fertilization can also reduce Ca uptake and excess magnesium can interfere with both K and Ca uptake.

In addition to dilution effects and cation competition, use of acidifying nitrogen fertilizers such as UAN or ammonium sulfate will drop the soil pH. When soil pH drops below 5.3, root function can be negatively affected, which will further limit K and Ca uptake. This can occur if soil pH is marginal to begin the season. It is common practice to lime fields on a 3 year rotation throughout the region. In the third year before the next liming, many fields fall into this marginal pH category.

Lower than normal K and Ca in leaf tissues can also be related to high temperatures and plant stress. In periods with extreme high temperatures, plant stomates close earlier in the day, transpiration is reduced, and K and Ca uptake are reduced because less water is being taken up by the plant.

Managing plant tissue K and Ca requires balancing fertilization. Where high nitrogen rates are being used to push high production, additional K should also be added in equal or higher amounts than nitrogen (1:1 to 1:2 ratio). This is particularly true for fruiting crops such as tomatoes, peppers, watermelons, and cantaloupes. Additional fertilizer calcium will also be needed for crops susceptible to blossom end rot.

Vegetable Crop Insects – September 14, 2012

Friday, September 14th, 2012

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

Cabbage
Continue to scout all fields for harlequin bugs, beet armyworm, fall armyworm, diamondback and cabbage looper larvae.

Lima Beans
Continue to scout all fields for lygus bugs, stinkbugs, corn earworm, soybean loopers and beet armyworm.

Peppers
Be sure to maintain a 5 to 7-day spray schedule for corn borer, corn earworm, beet armyworm and fall armyworm control. You should also watch for flares in aphid populations.

Snap Beans
All fresh market and processing snap beans will need to be sprayed from the bud stage through harvest for corn borer and corn earworm control.

Spinach
Continue to sample for webworm and beet armyworm larvae. Controls should be applied when worms are small and before webbing occurs.

Sweet Corn
Our last trap catches for the season will be September 13. If you have questions about spray intervals, please call Joanne Whalen at 302-831-1303 for more information.

Weekly Crop Update User Survey

Friday, September 14th, 2012

It has been several years since we surveyed you, the Weekly Crop Update’s readers and subscribers, to see what you find useful about this publication and to try to get some ideas on how it could be improved. We hope that you will take some time to complete the survey and let us know what you think. The online survey is at:  https://delaware.qualtrics.com/SE/?SID=SV_bmypKOsFJVVnkKp

WCU Volume 20, Issue 25 – September 7, 2012

Friday, September 7th, 2012

PDF Version of WCU 20:25 – September 7, 2012

Vegetable Crops

Vegetable Crop Insects
Stip Disorder in Peppers
Boron Deficiencies in Cole Crops

Agronomic Crops
Agronomic Crop Insects
Considerations for Small Grains Weed Control
Mid-Atlantic Crop Management School Program Available
Grain Marketing Highlights

Announcements
UD Extension Tour and Discussion: Improving Soil Health/Cover Crops for Agronomic and Commercial Vegetables – September 13
Workshops for Farmers with Drought-Plagued Fields – September 17
University of Delaware Irrigation Field Day – September 19
2012 Delmarva Poultry Conference – September 26
Delaware Ag Week – January 14-18, 2013

Weather

Grain Marketing Highlights – September 7, 2012

Friday, September 7th, 2012

Short Term Downtrend in Commodity Prices Expected
Even though the long term outlook for corn, soybeans, and wheat remains bullish a short term price break appears to be developing. There are several reasons to believe this scenario. First, the early 2012 harvest has begun in the U.S. Short crop or not the harvest period has a tendency to pull commodity prices down in the near term. Second, corn and soybean futures contracts (nearby contract months compared to the distant months) remain inverted albeit at a reduced difference compared to a couple of weeks ago. Second, the highs appear to be getting lower. Dec ‘12 corn futures topped at $8.49 per bushel on August 10, hit a high of $8.06 per bushel in Wednesday’s trade and are currently posted at $7.94 per bushel. Nov ‘12 soybean futures topped at $17.89 on September 4, hit a high of $17.69 on Wednesday and are currently posted at $17.42 per bushel. The weakening of the inverted spreads may well be a signal that the markets are due for a correction. Third, a record large long-futures position held by noncommercial traders in soybean futures is expected to result in profit taking, while stepping to the sidelines with the intention of coming back at a lower price. In other words, Dec ‘12 corn futures could be working toward a test of support in the vicinity of $7.86 per bushel. Nov ’12 soybean futures could be looking to test support in the $15.70 to $15.65 area. (Source: DTN)

Fundamentally, these markets remain long term bullish. The futures market is expected to remain in a sideways to down trend for the remainder of this week going into the September 12th USDA Supply and Demand report. The impact of the September report may turn out to be significant in so far as we have seen a reduction in U.S. corn exports falling about 54 million bushels shy of reaching USDA’s 1.55 billion bushel projection. However, yield reports on the first 10% of the U.S. corn harvest have been disappointing with the idea forming that 2012 U.S. corn production may be hard pressed to achieve USDA’s August forecast of 123.4 bushels per acre.

U.S. soybeans managed to top USDA’s ‘11/‘12 marketing year export market projection of 1.35 billion bushels by 15.5 million bushels. Rumors are circulating that dry weather in the Southern Hemisphere may hamper South America’s crop development beginning with delayed plantings.

U.S. wheat exports are on pace with USDA’s projection of 1.2 billion bushels, although inspections for shipment are running roughly 15% behind schedule. On August 10 July ‘13 SRW wheat futures hit a high of $8.68 per bushel and are currently posted at $8.60 per bushel. Continued dry weather in the Southern Plains with the date for fall wheat plantings rapidly approaching is having an impact on 2013 wheat futures prices. Hopefully, we will be able to get a better handle on world wheat production projections in USDA’s September report.

Market Strategy
Fundamentally the markets remain long term bullish. However, we can expect a short term downtrend in Dec ‘12 corn and Nov ‘12 soybean futures due to the need for the bull to be fed with new news. U.S. and world supplies for corn and soybeans will be tight going into the 2013 cropping season. Making sales for next year’s intended production of corn and soybeans should be considered on a very limited basis. Taking an initial forward cash sale for 2013 SRW wheat based upon the July ‘13 futures contract recently making a new life-of- contract high should be considered. It might not be a bad idea to cover the downside price risk of any new crop (2012) corn or soybeans held in storage for sale at a later date.

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

Considerations for Small Grains Weed Control

Friday, September 7th, 2012

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

For no-till fields, a non-selective herbicide needs to be used prior to planting. If grasses are present glyphosate is a better choice than paraquat. Fields worked with a vertical tillage implement for residue management still need a non-selective herbicide. These implements are not weed control tools.

There are few effective herbicides labeled for preemergence applications. Sharpen is labeled but we have limited data in the region to recommend it for either residual weed control or crop safety. Valor can be used at 1 to 2 oz with the burndown application, but there must be a 30 day period between application and planting wheat due to concerns with crop safety.

A few products can be used shortly after the crop has emerged. Axiom and Prowl H2O can be used at crop emergence (Axiom at the spike stage and Prowl H2O at 1 leaf stage); however they need to be tankmixed with other herbicides or followed by postemergence herbicides to provide a broad spectrum of control.

Products that provide postemergence control include: Harmony, Harmony Extra, Starane Ultra, Osprey, PowerFlex, Axial XL, 2,4-D, or dicamba. Others labeled with a limited fit include metribuzin, Finesse, and Maverick.

Agronomic Crop Insects – September 7, 2012

Friday, September 7th, 2012

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

Soybeans
We continue to find corn earworms in soybeans. If you have not checked your fields, be sure to sample fields so you do not miss a late hatch of larvae. Although trap catches appeared to be declining on September 3, we will need to watch trap catches at the end of this week to see if this trend continues. In addition, we need to watch what happens in states to our south.

A number of defoliators are still present in double crop beans. The threshold for defoliation will need to be reduced if a mixed population is present. Although soybean looper populations remain low, there are reports from the southern states of building populations.

In New Castle and Kent Counties, we are a finding a few more fields with high levels of Brown Marmorated Stink Bugs on field edges of full season soybeans. Although we do not have a threshold for BMSB, we are also finding levels that we use as a threshold for native stinkbugs (2.5 per 15 sweeps) along the edges of double crop fields in New Castle County. Native stink bugs populations continue to be at threshold levels in fields throughout the state.

Small Grains
As you make plans to plant small grains, you need to remember that Hessian fly can still be a problem. Since the fly survives as puparia (“flax seeds”) in wheat stubble through the summer, you should still consider this pest as you make plans to plant small grains. In our area, damage has generally been the result of spring infestations. Plants attacked in the spring have shortened and weakened stems that may eventually break just above the first or second node, causing plants to lodge near harvest. Warm fall weather conditions can extend fly emergence and egg-laying beyond the fly-free dates, but these dates should still be used as a guideline for planting. Plants attacked in the fall at the one-leaf stage may be killed outright. Wheat attacked later in the fall will be severely stunted, with the first tillers killed and plant growth delayed. Plants infested in the fall can easily be recognized by their darker than normal bluish coloration and leaves with unusually broad blades. Combinations of strategies are needed to reduce problems from Hessian fly:

● Be sure to completely plow under infested wheat stubble to prevent flies from emerging.

● Avoid planting wheat into last season’s wheat stubble, especially if it was infested with Hessian fly.

● Avoid planting wheat next to last season’s wheat fields – the most serious infestations can occur when wheat is early planted into wheat stubble or into fields next to wheat stubble.

● Eliminate volunteer wheat before planting to prevent early egg-laying.

● Do not use wheat as a fall cover crop near fields with infestations.

● Plant after the fly-free date. (Oct 3 – New Castle County; Oct 8 – Kent County; Oct 10 – Sussex County).

● Plant resistant varieties. You should look for varieties that have resistance to Biotype L. You will need to check with your seed dealers to identify varieties that our adapted our area.

The following link from Alabama provides additional information on Hessian Fly Management (http://www.aces.edu/dept/grain/HessianFly.php