No. 11 July 23, Inside this Issue...

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1 No. 11 July 23, 2009 Inside this Issue... Time to Get Grain Bins Ready for Harvest... 1 Swath Grain with Heavy Infestations of Wheat Stem Sawfly... 2 Soybean Aphid Scouting Update... 3 Lodging in Small Grains... 3 Green Snap in Corn... 4 Field Pea Relay Cover Crop... 4 NDSU IPM Field Survey Update - July White-Tipped Awns in Wheat... 6 Soybean Leaf Blemishes... 6 Around the State... 7 Weather & Climate... 8 TIME TO GET GRAIN BINS READY FOR HARVEST If the weather stays warm this fall, insects may again pose a serious threat to stored grain. Confused flour beetle, Indian meal moth, rice weevil (Fig 1), lesser grain borer and red flour beetle are all potential threats. Damage caused by these insects includes reduced grain weight and nutritional value, contamination, odor, mold and heat damage, which lowers the grain quality. Figure 1. Adult rice weevil. (J. Berger, Bugwood.org) Take some time now to prepare your storage bins and prevent potential stored insect problems. The first step is to make sure that the bins are clean and free of insectinfested grain. Remove leftover grain from the bin and sweep and vacuum the walls. Clean all grain-handling equipment, including augers, combines, trucks and wagons, thoroughly. When cleaning the bins, remember to get under aeration floors and inside aeration tubes as these are great spots for insects to hang out while waiting for you to fill the bin. Apply a residual bin spray, such as Malathion, Tempo or Storcide II, to all interior bin surface areas two to three weeks before new grain is placed in the bin. The treatment will kill insects emerging from their hiding places (cracks, crevices, under floors and in aeration systems). Also, insects crawling or flying in from the outside will be killed. Check the label for rates. Remove any vegetation that may attract and harbor insect pests within 10 feet of a bin and preferably the whole storage area. Follow by spraying the cleaned area around the bin with a residual herbicide to remove all undesirable weedy plants. Repair and seal all damaged areas to the storage structure. This will help prevent insect infestation and reduce water leakage, which leads to mold growth. Whenever fans are not operated, they should be covered and sealed to reduce the opportunity for insects and vertebrates to enter the bin through the aeration system. If newly harvested grain and/or insect-free grain must be added to grain already in storage, the latter should be fumigated to prevent insect infestation. If grain will be in storage for one or more years, grain should be treated with an approved insecticide as it is augured into the bin. Grain protectants kill insects as they crawl about or feed on treated grain or grain fragments. Do not apply grain protectants before hightemperature drying because extreme heat will result in rapid volatilization and reduced residual qualities of the pesticides. Grain protectants applied to 13% moisture grain will have a greater residual life than grain at 15% or more moisture. Moist grain also is more attractive to insect infestations." Another important step in preventing insect infestations is immediate cooling of the grain after harvest. Grain insects that are flying in the general area will be attracted to harvested grain by smell. They can find and infest grain on the truck or through an open grain bin hatch. If the grain is warm (above 50 F), insects will start feeding and reproducing immediately. Bins should be inspected for insect activity every two weeks. Stored grain insect pests generally are inactive at temperatures below 1

2 50 F (Fig. 2). A grain probe can used to determine what species of insect pests are infesting the grain and the extent of infestation within the grain mass. Figure 2. Key Points Warm fall sets stage for insect threat to stored grain Above 50 F, insects will start reproducing Grain destined to be stored for a year or more should be treated A list of insecticides registered for stored grain insect control is available in the NDSU Extension publication North Dakota Field Crop Insect Management Guide 2009 at: SWATH GRAIN WITH HEAVY INFESTATIONS OF WHEAT STEM SAWFLY Wheat stem sawfly infestations were severe in southwestern North Dakota this year. Sawfly larvae tunnel inside the stem and interfere with water and nutrient flow as the wheat head develops. Losses from wheat stem sawfly injury are of two types: 1) Larval feeding inside stems reduces yield (5 to 15% decrease in total seed weight) and quality of grain (reduced protein and kernel weight). 2) Mature larvae cut stems and stems may lodge to the ground with wind and the weight of grain heads, and become unharvestable (Fig 3). Producers should sample wheat crops and determine the percent of plants infested by sawflies before harvest. The presence of wheat stem sawfly can be verified by splitting stems and looking for the S-shaped larvae about ½ to ¾ inch long and cream colored with dark head inside the stems (Fig. 4). Another symptom of sawfly feeding is the presence of sawdust-like frass inside the wheat stem. Infested wheat stems often have a darkened area on the stem just below the nodes as a result of the internal feeding from sawfly. This can be used to detect a sawfly infestation without splitting the stems. If more than 15% of stems are infested by sawflies, producers should swath the wheat crop. Producers should swath sawfly-infested wheat as soon as kernel moisture drops below 40% to save infested stems before they lodge. If producers decide to swath grain, use a high swathing height to conserve the parasitoids (Fig. 5) that attack wheat stem sawfly. 2

3 Research from Montana State University (source: Dr. David Weaver) has shown that taller residue (at least the lower a of the plant)is better for conserving the parasitoids (Fig. 6). If 10 to 15% of the crop was cut by sawfly in 2009, solid stem wheat is recommended for 2010 wheat plantings. The 2009 NDSU hard red spring wheat release, Mott, has the solid-stem characteristic that has high resistance to wheat stem sawfly. SOYBEAN APHID SCOUTING UPDATE With the cool weather, soybean aphid continues to be low and well below the economic threshold level of 250 aphids per plant. In fact, it is hard to find soybean aphids in fields! Only one of the 27 fields scouted by the NDSU IPM Scouts last week had soybean aphids in LaMoure County (Fig. 7). It averaged only 14 aphids per plant and 40% of the plants infested. Stay tuned for more scouting reports. LODGING IN SMALL GRAINS In many parts of the state, the small grain crop has good to excellent yield potential this year. With the growing weight of the spikes as the crop matures, lodging can become problematic especially as we get wind combined with rain. Lodging is the term used to describe a crop when its stems have partially or completely fallen over from their normal near vertical orientation. Root lodging, the most common type of lodging, occurs at the base of the plant when roots fail to anchor it properly. Stem lodging can occur at any location on the stem and tends to be most common later in the season as plants mature and stems become brittle. When root lodging occurs early it is possible for some stems to partially erect themselves. This is accomplished by the plant bending at one of its nodes. These nodes tend to enlarge and have the appearance of elbows. Yield losses resulting from lodging vary considerably. Data indicate that losses up to 40% can result from lodging during the 10 days following heading. Furthermore, lodged plants are more prone to losses from diseases and insects. Pesticide applications are largely ineffective on severely lodged plants as only part of the target tissue is exposed to the spray. Lodging that occurs later in the season results in much less yield loss. However, kernel damage and sprouting can occur in lodged fields that become wet. Figure 7. Janet Knodel Extension Entomologist janet.knodel@ndsu.edu The main factors that predispose a crop to lodging are: High levels of nitrogen - N causes lush growth and heavier plant tissue. Excessive N can cause stems to be weak. High seeding rates - With high plant densities there is less space for roots of individual plants, therefore, root systems are usually less extensive and poorly anchored. The trend towards heavier seeding rates in small grains exacerbates the lodging problem. Wet soil conditions - Excessive soil moisture limits root development. Furthermore, roots in these types of soils often suffer from root rot. Wet soils do not anchor the roots of a plant as effectively as a dry soil. Tall plant types or varieties with poor straw strength - Taller plant types are more prone to lodging as their center of gravity is higher than shorter plant types. Sort varieties (dwarf types) tend to be the most resistant to lodging. Within all plant height types, however, there is variability for lodging resistance and some varieties are more prone to lodging than 3

4 others. Although modern breeding programs screen their materials for lodging resistance, that does not mean that they all will have the same level of lodging resistance, nor does it mean you can manage them poorly and expect them to remain standing. GREEN SNAP IN CORN Corn development has been slow this year, and is just now approaching tasseling in many of the earlier planted fields. During this late vegetative stage corn is most sensitive to green snap. Green snap is the term used to describe the breaking of rapidly growing stalks of corn. Unlike stem lodging in small grains that occurs near maturity, green snap in corn occurs during the early development of the plant. During these stages if conditions are conducive to rapid growth (i.e. water and nutrients are not limiting and temperatures are high), cell division and elongation occurs so rapidly that there is no time for the cell wall to fully harden. There are a number of factors that affect green snap. The most important are the timing and velocity of the wind and the hybrid that is grown. High levels of nitrogen during the vegetative stage of crop development can also increase the likelihood of this problem as can the use of growth regulator type herbicides such as 2, 4-D, dicamba, and clopyralid. Reports on how much yield loss can be caused by green snap vary considerably. Nevertheless, plants that are damaged by green snap at an early stage of development will almost certainly have reduced yield potential. Given the difficulty of managing the environment and the likelihood of high winds during critical stages of development in North Dakota, the most effective way of managing green snap is by growing a hybrid with known resistance. Joel Ransom Extension Agronomist for Cereal Crops joel.ransom@ndsu.edu FIELD PEA RELAY COVER CROP Field peas are a leguminous crop, able to use atmospheric nitrogen and fix it into a plant usable form in a symbiotic relationship with bacteria in the root nodules. Dry peas are typically harvested in late summer and fields are tilled in the fall or a late chemical burn down will prepare the field for next season. However, there are opportunities to capture the sunlight after the harvest of the field pea and turn this energy into biomass and nitrogen. A field pea relay cover crop system can be used. This is a system where field pea seeds that dropped to the ground at harvest time are encouraged to germinate and start growing just after the harvest of the main crop. The new plant growth and fixation of nitrogen can be used as an additional source of organic matter and a biological nitrogen source for the next spring seeded crop. The living pea plants also provide a soil cover and protect the soil from erosive forces. This system can make use of the left over growing season since field peas are tolerant to minor freezing temperatures and the plant will continue to grow until late October or early November. The plants will winter kill. In order for the relay cropping to work the seed needs to be incorporated into the soil. The methods to get the seed into the ground include light disking, use of a coulter harrow, or rolling the field to press the seed into the soil. There needs to be enough seed left after combining (3 to 6 seeds per square foot equal to 1 to 2 bushel per acre). Field pea stubble left after harvest (Blaine Schatz). Relay crop of field peas after harvest of the main crop (Blaine Schatz). Height of pea re-growth on October 16, 2008 Carrington Research Extension Center (Blaine Schatz). 4

5 The amount of biomass produced and total amount of nitrogen accumulated in the plant tissue depends upon the pea plant density, the timing of initiation of re-growth, soil moisture, rainfall, and the date of a killing frost event. Relay cropping can work well as the growing conditions in the fall are cool and favorable for nitrogen fixation by the pea which is a cool season plant. As the stimulated volunteer plants are following the main crop of field peas there will be high numbers of Rhizobium leguminosarum bacteria (inoculum) in the soil. Table 1 provides data on the above ground dry matter of the pea at the end of the season and the amount of nitrogen in the plant tissue. It should be noted that the pea plants, while they grow, will take up nitrogen from the soil as well as fix atmospheric nitrogen. The stimulated volunteer crop can be used as a plough down, winter soil cover, or can be grazed. However, do not expect to harvest a second dry pea crop for seed as there is not enough time for the crop to mature. Table 1. Biomass, percent N in the plant tissue, and total nitrogen in the above ground plant tissue, Carrington, Field Number Total above ground plant dry matter at the end of the season Percent Nitrogen in the plant tissue Nitrogen in the plant tissue (lb/a) (%) (lb/a) 14B A Blaine Schatz Agronomist Carrington Research Extension Center Hans Kandel Extension Agronomist hans.kandel@ndsu.edu NDSU IPM FIELD SURVEY UPDATE - JULY 22 NDSU IPM field scouts surveyed 119 wheat fields and 22 barley fields across the state for the week ending July 17th. Average growth stage over all wheat fields surveyed was head half emerged and for barley, full head emergence. Wheat: Tan spot was observed in 83% of the surveyed fields, and average severity was 16.2% of the leaf area covered by tan spot. The previous week, tan spot severity averaged about 12%. Only trace levels of leaf rust were observed, in two winter wheat fields, one in Bowman county in the southwest and one in Nelson county, in the northeast. Head scab was observed in only five fields, with an average field severity of 1.7%. Loose smut was observed in 10% of the surveyed wheat fields this past week, similar to last week. Wheat streak mosaic virus (WSMV) symptoms were observed in 10% of the wheat fields surveyed, similar to the previous week. Barley yellow dwarf virus symptoms were easily observed along field edges in some areas. A golden yellow flag leaf, with the yellowing beginning at the leaf tip, is characteristic of barley yellow dwarf virus infection. This virus is transmitted by grain aphids. Our survey scouts found grain aphids in 36% of the wheat fields surveyed, with an average of 13% of the tillers in these fields having at least one grain aphid. Barley: As in wheat, along with fungal leaf spot infections, symptoms of barley yellow dwarf virus were observed in some barley fields. (See picture). In barley, 41% of the surveyed fields this past week had grain aphids observed, with an average of 35% of the tillers in these fields having at least one grain aphid. Head scab has not been reported yet from barley. Barley yellow dwarf virus symptoms in barley 5

6 WHITE-TIPPED AWNS IN WHEAT I ve observed some white tipped awns of wheat this week, in plots that were planted on May 13 th (see picture). I ve also heard of similar observations in commercial wheat fields. White tipped awns may be more visible in certain varieties or be associated with specific planting dates. These white awn tips are NOT due to a disease, but are most likely associated with the sunny days and high winds that have recently occurred - the plants couldn t translocate moisture fast enough to the White-tipped awns in wheat. awns, and the tips dried out. Sun scald. Photo courtesy of L. Wyum. Septoria Brown Spot. Caused by a fungal pathogen. Often occurs on the lower leaves, and symptoms are small brown spots with a general yellowing of leaf tissue. Septoria brown spot is favored by warm and wet conditions and very unlikely to be economic in North Dakota. Marcia McMullen NDSU Extension Plant Pathologist marcia.mcmullen@ndsu.edu SOYBEAN LEAF BLEMISHES In the last week, I have received numerous calls about soybean leaf blemishes. Many have been related to sunscald, but some due to low levels of disease. This article is intended to provide a few photos and brief information about some common ailments people are starting to see on their soybeans. I would encourage anyone interested in additional information and photographs of regionally important soybean diseases to visit the website of University of MN Extension Plant Pathologist Dr. Dean Malvick at Sun Scald. Often observed on leaves after sunny days, and more frequent on the undersides when leaves are turned upwards. Septoria Brown Spot. Photo courtesy of D. Malvick. Bacterial Blight. Caused by a bacterial pathogen. Bacterial blight is the most common disease on soybean leaves in North Dakota, and favored by cool and wet weather. A yellow-green halo will be present around small necrotic lesions. It most commonly appears after rain, high winds, or hail. In some fields, minor economic losses may be possible, but in most situations it is unlikely. Fungicides will not control bacteria. 6

7 South-Central ND Bacterial Blight. Photo courtesy of D. Malvick. Physiological / Unknown. Last year we saw tremendous amounts of this symptom. After numerous discussions last year, we are still unclear. Ozone, physiological spoting, hot winds, etc. were considered. The disease Cercospora leaf blight resembles sunscald or this unknown ailment. However, this disease is rarely found outside of the southern U.S., and is favored by hot humid conditions, something we have definitely not had in North Dakota. In over 25 years of research in the state, soybean pathologist Dr. Berlin Nelson has never identified Cercospora leaf blight in North Dakota. During the past two weeks (July 8-21), rainfall at NDAWN sites in the region ranged from 0.4 inch at Dazey and Jamestown, to 2.5 inches at Wishek. Growing degree day (GDD) units for corn continue to be behind this season compared to the long-term average. For example, corn planted May 1 has a range of -130 to -285 GDD units for the period ending July 21, compared to the long-term average. Winter wheat and barley are nearing maturity, while spring wheat is in various stages of seed development. Early-planted soybean is in the first flower (R1) to initial pod-forming (R3) stages of growth. Also, early-planted dry bean is flowering and sunflower is in the reproductive stage (R1). Scab currently is at very low levels in winter and spring wheat. Low levels of sunscald can be found on the underside of soybean leaves on scattered plants in the region. Soybean aphids are present in the region, currently at low levels. Farmers should be scouting soybean for the aphids until the full seed stage (R6), requiring weekly (or more often) field checks during the next 45 days. Other crop insects to be aware being found in the region include bean leaf and blister beetles in soybean, pea aphids in field peas, and banded sunflower moth in sunflower. Greg Endres Area Extension Specialist/Cropping Systems NDSU Carrington Research Extension Center gregory.endres@ndsu.edu Photo courtesy of Hans Kandel. Sam Markell Extension Plant Pathologist samuel.markell@ndsu.edu 7

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9 F. Adnan Akyüz, Ph.D. Assistant Professor of Climatology North Dakota State Climatologist 9

10 North Dakota State University CROP & PEST REPORT Extension Entomology NDSU Dept 7650; PO Box 6050 Fargo, ND Non-Profit Org. U.S. Postage Paid Permit No. 818 Fargo, N.D. Sam Markell, Co-Editor Plant Pathology phone fax Janet Knodel, Co-Editor Entomology phone fax Plant Sciences phone fax Soils phone fax Weeds phone fax Ag Engineering phone fax Helping You Put Knowledge To Work The information given herein is for educational purposes only. References to a commercial product or trade name is made with the understanding that no discrimination is intended and no endorsement by the North Dakota Extension Service is implied. NDSU Extension Service, North Dakota State University of Agriculture and Applied Science, and the U.S. Department of Agriculture cooperating. Duane Hauck, Director, Fargo, North Dakota. Distributed in furtherance of the Acts of Congress of May 8 and June 30, We offer our programs and facilities to all persons regardless of race, color, national origin, sex, handicap, age, Vietnam era veterans status, or sexual orientation; and are an equal opportunity employer. This publication will be made available in alternative formats for people with disabilities upon request (701) NDSU Crop and Pest Report