Posts Tagged ‘19:4’

WCU Volume 19, Issue 4 – April 15, 2011

Thursday, April 14th, 2011

PDF Version of WCU 19:4 – April 15, 2011

In this issue:

Vegetables
Vegetable Crop Insects
Early Transplanting of Warm Season Vegetables
Pea Herbicides

Fruit
Primocane Blackberries
Blossom Damage in Strawberry Due to March Cold Snap
Thrips on Winter Annuals

Agronomic Crops
Agronomic Crop Insects
Manganese Deficiency Can Worsen with Spring N Applications on Small Grains – Part 2
Hay and Pasture Fertilization This Spring
Rates for Residual Herbicides in Corn
Grain Marketing Highlights

General
Penncap-M (methyl parathion) Cancellation
Managing Root Knot Nematode

Weather

 

Burning Down Cover Crops

Thursday, April 14th, 2011

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

When burning down cover crops this spring, be aware of a few things. Gramoxone Inteon or glyphosate are your two best options, Gramoxone Inteon can be inconsistent with many of the grass cover crops, particularly with annual ryegrass. The addition of atrazine, simazine, or metribuzin will improve the control of Gramoxone Inteon for burndown; furthermore, Gramoxone is not as effective on cloudy, overcast days. Glyphosate is more consistent for control of grass cover crops, however, annual ryegrass is difficult to control and may require higher glyphosate rates. Tankmixing glyphosate with atrazine (or atrazine containing herbicides) can reduce the activity of glyphosate and tankmixing should be avoided when treating annual ryegrass. Glyphosate can also be inconsistent with some of the broadleaf cover crops. The addition of 2,4-D will improve control of legumes, rape or canola.

 

Managing Root Knot Nematodes

Thursday, April 14th, 2011

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

Root knot nematodes are microscopic roundworms that are widely distributed in Delaware agricultural soils and can cause varying degrees of damage to susceptible crops. Most of the damage caused by root knot nematodes is evident as stunting on vegetables such as pickling cucumbers, cantaloupe, watermelon, squash, and lima beans. Root knot populations are favored by the sandy, low organic matter soils in Kent and Sussex counties. There are several species of root knot nematodes that could occur here but Southern root knot nematode, Meloidogyne incognita is the most commonly found root knot species here. Most of the field crops grown in Delaware; corn, small grains, sorghum, alfalfa, Sudan grass, and Sudex are not good hosts of root knot and can reduce populations of root knot, but not eliminate them.

Small grains are a good rotation crop because if planting is delayed until soil temperatures at planting depth are below 65°F, root penetration does not occur. Soil temperatures are generally too low during most of the small grain growing season for root knot to increase. Small grains are poor hosts to begin with and the crop basically avoids infection or penetration by root knot. In my long career here I have never seen root knot nematode affect small grains (wheat, barley, oats, triticale, etc.).

Unfortunately soybeans, unless they are a resistant cultivar, are susceptible to root knot nematode. Soybeans can tolerate low populations of root knot without producing visible symptoms but yield loss can occur depending on growing conditions, especially low rainfall. High populations and adverse growing conditions can cause stunting as severe as that produced by soybean cyst nematode. Root knot resistance has been available in soybean for a long time but it has been in group 5 or later maturity groups. Recently, advances have been made to incorporate resistance into group 4 varieties. There are a few resistant group 4s available that were posted on the VIPS website (http://www.vipsoybeans.org): Schillinger 479.RC, Southern States RT 4470N, HS HiSoy FS 41T80, FS HiSoy HS 4426, FS HiSoy HS 46T80. There should be an updated list on the VIPS site soon of soybean varieties rated in 2010. Another source of information is a soybean variety selector from North Carolina. There are no group 4, only group 5 resistant soybeans on this site http://www.soybean.ncsu.edu/soyvar/. Root knot resistant soybeans would be an excellent rotation crop for vegetable growers who plant susceptible fresh market or processing vegetables.

Field corn varies in its susceptibility to southern root knot nematodes. There is no current data on corn hybrid screening for resistance to root knot nematodes. Earlier studies indicated that there was wide variation in susceptibility to root knot in corn. A test conducted at Auburn University in 2009 of hybrids grown in the South showed that none were resistant. Irrigated corn is not likely to be damaged by low to medium root knot populations, but can support damaging population levels if followed by a susceptible vegetable crop. It might be very difficult to even see symptoms of high root knot populations in field corn especially if it is irrigated. Nematode numbers in corn seem to be increasing but it is difficult to know for sure. It has been thought that the increase in Bt corn and the shift to pyrethroid insecticides has had an impact. Growers are not using the granular and liquid carbamate and organophosphate insecticides at planting which would suppress nematode populations as well as control the target insects.

Managing Root Knot Nematodes
Rotation is often a limited control strategy for root knot because it has such a wide host range. Alfalfa and oats are thought to be the safest crops to use in a rotation to reduce root knot nematodes. Increasing organic matter in fields with low organic matter and high levels of root knot or other plant parasitic nematodes can have a suppressing effect on root knot populations. Fall planted rape and other mustards may also be useful to suppress root knot populations as a biofumigant when they are plowed under before they go to seed in the spring prior to planting the crop. Rape can be infected with root knot if populations are high and soil temperatures are above 65°F at planting or the fall is warm. (See under small grains above). It is the decomposition of the plant parts when tilled into the soil that releases the chemicals that kill the nematodes, not root exudates from living plants. Soil sampling in the fall right after harvest is the best way to know if you have high root knot populations in your soil. Unfortunately spring is not the best time to sample because the nematode overwinters primarily as eggs which are not detected in the methods used for processing soil samples for nematode analysis. Soil sampling this time of year can underestimate the number present or not detect low populations.

Symptoms

Typical stunting from root knot nematode in an irregular area of a lima bean field

Heavily galled and stunted lima bean roots dug from an infected area. Soybeans can be this badly infected as well. Corn and other field crops produce much smaller and less evident galling

 

Penncap-M (methyl parathion) Cancellation

Thursday, April 14th, 2011

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

Penncap-M (methyl parathion) – It should be noted that the notice to cancel all uses of this product was posted in the Federal Register on Feb 25, 2011. Any distribution, sale, or use of the products subject to this cancellation order is permitted only in accordance with the terms of this order, including any existing stocks provisions. For information on the details of this cancellation as well as existing stocks provision please refer to the Federal Register posting: http://www.federalregister.gov/articles/2011/02/25/2011-4140/product-cancellation-order-for-certain-pesticide-registrations.

 

Grain Marketing Highlights – April 15, 2011

Thursday, April 14th, 2011

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

Outside Forces Impacting Commodity Prices
The sell-off in commodity prices on Tuesday this week was largely attributed to a report issued by Goldman Sachs that recommended liquidating a portion of investor held commodity baskets, commonly referred to as profit taking. Supply fears, stronger crude, and wet weather possibly causing a slow start to the 2011 U.S. planting season continue to support corn, which in turn is supportive to the soybean and wheat markets. The weekly export sales report, released this morning, was bullish for corn and soybeans, neutral for wheat.

USDA Export Sales Report 04/14
Pre-report estimates had weekly corn export sales at 21.7 to 35.4 million bushels. The weekly report showed export sales of 34.0 million bushels of old crop, well above the 19.0 million bushels needed to keep pace with USDA’s export demand projection of 1.95 billion bushels. Total shipments of 43.2 million bushels were also above the 43.1 million bushels needed this week to stay on pace with USDA’s projection.

Pre-report estimates for weekly export sales of soybeans ranged from 7.3 to 12.9 million bushels. The weekly report showed old-crop sales of 4.8 million bushels, above the 4.3 million bushels needed this week to stay on pace with USDA’s demand projection of 1.58 billion bushels. Shipments of 20.4 million bushels were also above the 13.6 million bushels needed this week.

Pre-report estimates for wheat ranged from 14.7 to 25.7 million bushels. The weekly report showed export sales of 16.3 million bushels, above the 4.0 million bushels needed this week to stay on pace with USDA’s export demand projection of 1.275 billion bushels. Shipments of 26.6 million bushels were below the 39.0 million bushels needed this week.

Market Strategy
Commodity prices are trading in an extremely volatile fashion, as traders seemingly await the next shoe to drop. After making new life of contract highs for old and new crop corn on Monday, commodity prices have bid up and down all week. The next item of interest will be crop progress, to be reported next Monday, that should give an indication of whether planting is delayed in the Corn Belt. Currently, Dec ‘11 corn futures are $6.42; Nov ‘11 soybeans $13.36; and July ‘11 SRW wheat futures are $7.77 per bushel.

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

 

Rates for Residual Herbicides in Corn

Thursday, April 14th, 2011

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

What rate of residual herbicide to use? In soybeans, use the full labeled rate because you need 4 to 6 weeks of residual control if spraying 3 to 4 weeks prior to planting, or you need the burndown activity at these rates because the weeds have gotten large. In my opinion, there is no clear cut answer for corn. A number of issues need to be considered:

Is this a no-till or conventionally tilled field?

· If it is no till you may need the higher rates because the amount of plant residue in the field;

· How far ahead of no-till planting are you spraying (so how long do you need to have residual control); and

· If spraying ahead of no-till planting, will you be coming back with additional preemergence herbicide at planting

Are you planning on a POST application? In our work, a preemergence followed by postemergence is the most effective and most consistent approach. A total preemergence approach can work if you have light weed pressure, have a dry year that limits a second flush of weeds, do not have large seeded species (morningglory, Texas panicum, cocklebur), do not have perennial weeds (horsenettle, yellow nutsedge, bermudagrass), are able to get your preemergence herbicides incorporated with timely rainfall or irrigation, or you are just plain lucky. Otherwise, most fields will need a postemergence spray.

My point of reference for a solid, one pass herbicide program is either Lexar or Lumax with additional atrazine; or a full-rate of a premix with atrazine and grass herbicide (Bicep, Harness Xtra, etc) PLUS pendimethalin (Prowl) or rimsulfuron (i.e. Basis). Any of these programs can include simazine. And I have seen all of these programs requiring postemergence treatments for acceptable weed control. None are consistently effective for full-season control.

If you need to spray postemergence then it makes sense to use a less intensive program at planting. But keep in mind, the less intensive soil-applied herbicide approach you use, the more likely you will need to spray earlier, may need to use more than one herbicide postemergence (particularly to provide residual control), and will need to be more timely with your postemergence treatment. If you can spray your postemergence herbicide before the weeds are 3 to 4 inches tall, and you are willing (able) to spray herbicide combinations (i.e. not rely solely on glyphosate), then reducing soil-applied herbicides by up to 20 to 30%, or not including all of the tankmixes, is a sound decision.

 

Hay and Pasture Fertilization This Spring

Thursday, April 14th, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

In many areas of the state, pastures and hay fields are either just beginning to green-up (northern sections) or while having started the process of greening-up several weeks ago are making slow growth with the cool, often cloudy and rainy weather. Now that calendar-wise, we are into mid-April, it’s time to apply nitrogen (N) fertilizer to hay and pasture grasses to boost production.

With fertilizer prices still high and the threat of frequent showers in the forecast, growers will want to limit their application rates of N to ensure maximum plant uptake and minimum loss to leaching or denitrification (wasted fertilizer dollars). The slow start to forage growth this year suggests that at least some N will be useful in encouraging forage (grass) production for grazing animals and reducing the need for supplemental hay or grain.

For pastures or hayfields that contain a significant proportion of legumes (clover, alfalfa, Birdsfoot trefoil, or lespedeza), N application rate should not exceed 30 lb N/acre/application. Otherwise, the N-fixing value of the legume will be lost to the grower.

On pure grass pastures not fertilized with N last fall, an application of 30 to 50 lb N/acre will be sufficient to boost grass productivity. On pastures fertilized with N last fall, the N stored in the plants should be adequate for much of the early grazing season but watch the pastures carefully for the first sign of slowing growth and then apply additional N at that time, probably in mid- to late-May.

For hay fields, research from The Pennsylvania State University and Dr. Marvin Hall suggests that an application of 40 to 60 lb N/ton of expected yield will maximize production of most forage grasses while minimizing the risk of nitrate toxicity. I would suggest going with the lower rate this year because of the growing conditions we’ve experienced so far this season.

 

Manganese Deficiency Can Worsen with Spring N Applications on Small Grains – Part 2

Thursday, April 14th, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu and Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

Last week, we discussed the possibility that either the starter fertilizer or knifed in nitrogen solution from the previous year’s corn crop might be responsible for the row-like pattern to manganese (Mn) deficiency that we had observed in barley recently fertilized with broadcast nitrogen (N). We took soil tests within the rows where barley was alive and vigorously growing (good area) and between the rows where barley plants were dead or growing very poorly (Photo 1). The soil samples have been analyzed and support our original conclusion (Table 1).

 

 

Table 1. Soil test analyses of good and bad barley areas in field showing barley surviving on 30-inch row spacing.

Barley Area Sampled

Sample Depth (inches)
0 to 4 4 to 8 8 to 12
Water pH Mn lb/A Zinc lb/A Water pH Mn lb/A Zinc lb/A Water pH Mn lb/A Zinc lb/A
Bad barley 6.1 15.1 8.5 6.6 9.0* 2.9 6.6 5.0* 1.0*
Good barley 6.2 16.3 8.7 6.3 10.8 3.2 6.5 6.3* 1.3*

*Deficient soil test level

Photo 1. Barley rows generated following renewed spring growth and nitrogen application showing effect of last year’s fertilizer (either starter band or knifed in nitrogen solution). Barley between corn rows was either severely Mn deficient or had died while barley on rows 30 inches apart grew vigorously.

Another interesting factor showed up on the soil test results. While the visual symptoms resembled traditional Mn deficiency on barley, the soil test indicated that at the deepest (8 to 12 inch) sampled layer zinc was also deficient. For any crop planted after barley (soybeans by tradition), the grower should conduct a tissue analysis mid-season before the crop begins to bloom to determine if tissue zinc levels indicate the possibility of a hidden zinc deficiency that could reduce yield potential. In addition, the grower should scout the crop for obvious zinc and Mn deficiency symptoms so that foliar zinc or Mn can be applied as early as possible.

Zinc deficiency symptoms on soybean include the following:
· Soybean yields are considerably decreased in zinc deficient soils.

  • · Deficient plants have stunted stems and leaves with chlorotic interveinal areas.
  • · Later on the entire leaves turns yellow or light green.
  • · Lower leaves may turn brown or grey and may drop early.
  • · Few flowers are formed and the pods that are formed are abnormal and slow in maturity.

Manganese deficiency symptoms on soybean include the following:
· Manganese deficiency commonly occurs in plants in well drained, neutral and alkaline soils.

  • · Interveinal areas become light green to white and the veins remain green.
  • · Necrotic brown spots develop as the deficiency becomes more severe.
  • · The leaves drop prematurely.
  • · Soybean yields can be significantly reduced by Mn deficiency.

Both micronutrient deficiencies can be reduced or eliminated by either a soil application of the sulfate or oxide compound of the micronutrient at 15 to 25 lbs per acre or by a foliar application of either the chelated form of the micronutrient or the sulfate form of the micronutrient at 1 to 2 lb of the nutrient per acre.

 

Agronomic Crop Insects – April 15, 2011

Thursday, April 14th, 2011

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

Alfalfa
Continue to scout fields for both alfalfa weevil and pea aphids. As a general guideline, you should consider a treatment in alfalfa less than 10 inches tall if you find 40-50 aphids per stem. The treatment threshold for alfalfa 10 inches or taller in height is 75- 100 per stem. Although beneficial insects can help to crash aphid populations, the cooler temperatures have slowed their activity. As a general rule, you need one beneficial insect per every 50-100 aphids to help crash populations. For alfalfa weevil, the following thresholds, based on the height of the alfalfa, should be used as a guideline when making a treatment decision: up to 11 inches tall – 0.7 per stem; 12 inches tall – 1.0 per stem; 13 – 15 inches tall – 1.5 per stem; 16 inches tall – 2.0 per stem and 17 – 18 inches tall – 2.5 per stem.

Small Grains
Aphids and cereal leaf beetles can still be found in fields throughout the state. With the cool rainy weather this past week, be sure to watch for increases in aphid populations, especially if we get a brief warm up. In general, small grains can tolerate a fair amount of feeding in the spring, especially lower in the canopy. As a general guideline, the treatment threshold for aphids in wheat and barley over a foot tall is 150 aphids per foot of row with low beneficial insect activity. Since we are past the time of barley yellow dwarf transmission (fall transmission is the most important), the next important time to consider aphid management in small grains is at grain head emergence. Cereal leaf beetle adults and eggs can be found in fields throughout the state; however, cooler temperatures have slowed development. There are reports of larvae being found in fields in Virginia and we can expect to see larvae as soon as temperatures increase.

Continue to watch for winter grain mite activity in no-till wheat fields, especially in fields planted into corn stubble. The recent cool weather has been favorable for increases in mite populations. Remember that these mites do not cause the yellowing characteristic of spider mite feeding. Heavily infested fields appear grayish or silvery, a result of the removal of plant chlorophyll by mite feeding. When high infestations feed on the plants for several days, the tips of the leaves exhibit a scorched appearance and then turn brown. Many of the infested plants do not die, but become stunted and produce little forage or grain; damage on young plants, however, is more severe than on large, healthy ones. Damage may also be greater in plants stressed by nutrient deficiencies or drought conditions. Heavy spring infestation can result in reduced yields so be sure to check for mites if fields appear off color.

Timothy
Another cool weather mite species that feeds on timothy is the cereal rust mite. If you have not checked fields for this pest, be sure to sample fields since they are easily found in timothy fields at this time. Symptoms can appear as retarded growth, leaf curling, stunting, and plant discoloration. Injured plants appear to be drought stressed even when adequate moisture is available for plant growth. There are no established economic thresholds for the pest; however, treatment is recommended in fields with a previous history of cereal rust mites and/or when 25% of the plant tillers exhibit curled tips of the new leaf blades within several weeks following green-up. If you are familiar with this microscopic mite species, the use of a 20x-magnifying lens is often necessary to find mites on leaves. The only effective and labeled material on timothy is Sevin XLR Plus. Be sure to read the label for information on the number of applications per season as well as the days to harvest. For effective rust mite control, the use of the higher labeled rate and at least 25 gal/acre of carrier to get good coverage of leaf surfaces generally results in better control.

 

Thrips on Winter Annuals

Thursday, April 14th, 2011

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

Vegetable and bramble growers in Maryland have called me often over the last couple of years about fruit problems in their fields possibly caused by thrips. As an overall study of the possible impact thrips may be having on vegetable and fruit quality I have been conducting surveys for their numbers and species. I have taken weed samples throughout the winter and early spring from vegetable fields and high tunnels looking to see if any thrips were overwintering and if so what species they were. Below is a 9-point summary of the sampling program.

1.  For most samples very few thrips were found.

2.  In 14 of the 20 sample sites thrips were found in December through January on winter annuals.

3.  At 9 sample sites thrips were found in March.

4.  The worse sample sites were high tunnels that had chickweed and/or henbit winter annuals growing along the outer or inner edge of the base of the high tunnel (Fig 1). 87% of the sampled winter annual weeds at these sites over the last two years had at least 3 female thrips (one sample had 23 female thrips).

5.  Of the total thrips found 76% were female adults, 19% were males and 5% were immatures or pupae.

6.  Western flower thrips were found to overwinter in Maryland, Delaware, SE Pennsylvania and NE Virginia, although only in low numbers (Fig 2).

7.  Chickweed was found to harbor 66% of all thrips with wild mustards and henbit being the next best winter hosts.

8.  Sampling-sites near high tunnels or woods had a greater probability of containing thrips than sites out in a field.

9.  Farms where thrips were found to overwinter had greater probabilities of infestations during the season.

Even though several thrips species, including Western flower thrips, were found to overwinter in the mid-Atlantic area it does not mean we have a thrips problem. However, growers do need to watch for any early season infestations in their field and high tunnel brambles and not overreact by spraying an insecticide unless really needed. Most brambles can have at least 5 thrips or more per fruit/flower before there is any possibility of damage. The species of thrips you have should be determined only if you think thrips are causing fruit quality problems at low densities. I would be glad to look at your thrips if you send them to me: 2005 Largo Rd, Upper Marlboro, MD 20774 or you can call 301-627-8440 or email me: jbrust@umd.edu.

Figure 1. Winter annual weeds along outside (under snow) and inside border of high tunnel

Figure 2. The proportion of thrips species found to overwinter at the 20 sample sites