Integrated Pest & Crop Management Newsletter University of Missouri-Columbia Vol. 16, No. 9 May 27, 2006 Article 1 of 9 Missouri Sunflower and Rice Nitrogen Recommendations Updated By John A. Lory Updated June 7, 2006 University of Missouri nitrogen recommendation for sunflower was changed to the following: Fertilizer N/acre = yield goal (lbs/acre) X 0.06 - warm season organic matter adjustment The warms season organic matter adjustment is an estimate of nitrogen released by the soil during the growing season and ranges from approximately 20 to 80 lbs nitrogen/acre depending on soil type and the amount of organic matter in the soil. The new recommendation increases our estimate of sunflower nitrogen need based on research and recommendations in neighboring states. Rice recommendations are variety specific so they need to be updated regularly as new varieties are introduced. The rice varieties covered by the current MU recommendations include Bengal, Cheneire, CL161, Cocodrie, Francis, and Wells. All these varieties have a recommended rate of nitrogen application of 150 lbs N/acre. MU also recommends all nitrogen be applied preflood except on slow flooding fields, fields with water management problems or on varieties prone to lodging. In these situations apply N in a three-way split application with 90 lbs N/A pre-flood, 30 lbs N/A at 1/2-inch internode elongation and again 10 to 14 days later. The MU recommendations assume rice follows soybean in rotation. These changes are based on research by Gene Stevens and David Dunn at the Delta Center and recommendations in neighboring states. These changes have been approved but it will take some time before they are implemented in the soil test reporting software. You can track changes MU fertilizer recommendations at http://www.nmplanner.missouri.edu/recommends.asp. Expect to see 53significant changes to other aspects of the MU fertilizer recommendation system for agronomic crops over the next year. John Lory, 573-884-7815 ********************************************************************* Article 2 of 9 Corn Disease Update By Laura Sweets There have been very few calls or questions related to seed decay and/or seedling blights in corn. After the recent period of below normal air and soil temperatures this may change. When scouting corn fields be sure to carefully dig up stunted or yellowed plants to check roots for symptoms of seedling blights (see the April 28, 2006 issue of Integrated Pest and Crop Management Newsletter) for descriptions of the various corn seed decay and seedling blights. Based on mild winter temperatures during December, January and February, the potential for corn flea beetle in most regions of Missouri was high for this season. The cooler than normal temperatures over the last few weeks may have slowed their activity. However, with the return to warmer temperatures there may be more flea beetle activity and more evidence of Stewart’s bacterial wilt. On young corn plants the symptoms of Stewart’s bacterial wilt include linear, pale green to yellow streaks that tend to follow the veins of leaves and originate from feeding marks of the corn flea beetle. Lesions may extend the length of the leaf. Plants may appear stunted or somewhat distorted. If the bacteria become systemic within the plant, the entire plant wilts and may die prematurely. Cavities of a brown, soft rot can develop in the stalk pith. On field corn the disease tends to be limited to the leaf blight phase of the disease in which foliage symptoms develop but the pathogen does not become systemic within the plant. With the leaf blight phase of Stewart’s bacterial wilt, the linear, pale green to yellow lesions develop on the leaves. These lesions tend to parallel the leaf veins and to have wavy, irregular margins. These streaks soon become dry and brown. The bacterium which causes Stewart’s bacterial wilt overwinters in the guts of some species of adult corn flea beetles. Adult beetles feeding on corn seedlings in late spring and early summer can contaminate the feeding wounds with the causal bacterium. Flea beetles can continue to spread the bacterium throughout the season by feeding on infected plants and then healthy plants. The potential for Stewart’s bacterial wilt to develop on young corn plants is greater after mild winters when higher levels of the corn flea beetle may be present. Most field corn hybrids have enough resistance to Stewart’s bacterial wilt that additional management is not necessary. Anthracnose is the other foliage disease that may be evident on young corn plants early in the season. Anthracnose lesions tend to be brown, spindle-shaped lesions with yellow to reddish-brown borders. Concentric circles or zones are sometimes apparent within the diseased areas. The fungus which causes anthracnose leaf blight early in the season also causes anthracnose stalk rot late in the season. Stalk symptoms appear as black linear streaks on the surface of lower internodes on corn plants late in the season. Laura Sweets 573-884-7307 ********************************************************************* Article 3 of 9 Early Season Soybean Diseases By Laura Sweets This could be an interesting year for early season soybean diseases in Missouri. Approximately 15 percent of the crop had been planted during the warm, dry spell in April. Colder than normal air and soil temperatures the end of April and the first of May slowed planting and could increase the potential for Pythium seed decay and seedling blight as well as Phytophthora in beans that were planted prior to this cool, wet weather. With the return to more normal temperatures and drier conditions, soybean planting is preceding at a strong pace. The early season soybean diseases include those that cause seed decay, seedling blights and root rots of soybean. Most of these early season soybean diseases are caused by fungi in the soil that are found wherever soybeans are grown. Pythium, Phytophthora, Rhizoctonia and Fusarium are the most common of these early season pathogens, although Macrophomina (charcoal rot fungus) may also cause early season seedling problems. Soybean seedling blights have the potential to cause losses in Missouri soybean fields every year. The specific seedling blights that occur and their severity vary with the environmental conditions each season. With the changes in weather patterns this spring and soybean planting delayed in much of the state because of wet soil conditions, it is difficult predict which, if any, seedling blights may occur or may cause significant problems this season. Pythium and Phytophthora are favored by wet conditions and are more likely to be serious problems when wet conditions exist at or just after planting. Rhizoctonia and Fusarium are not as restricted by soil moistures and soil temperatures but still need some moisture to initiate infection. Macrophomina phaseolina grows best at temperatures between 82-95 degrees. Infection of seedlings with Macrophomina is most likely to occur if conditions of high soil temperatures and low soil moisture exist during the first two to three weeks after planting. Symptoms of Pythium damping-off range from seed rot or preemergence damping-off to early postemergence damping-off. Affected tissue develops a soft, watery brown rot. Pythium damping-off is most likely to occur in cool (50-550F), wet soils. Phytophthora can cause seed rot, preemergence damping-off and early postemergence damping-off. Initially affected tissue develops a soft, watery brown rot. Within several days the affected plant parts may dry out and shrivel up becoming dark, dry and brittle. This early stage Phytophthora is difficult to distinguish from Pythium damping-off; it may be necessary to submit a sample to the Plant Disease Clinic for an accurate diagnosis Phytophthora can also cause a seedling blight in which established seedlings turn yellow, wilt and die. Generally the entire seedling is affected and roots may be poorly developed and rotted. Phytophthora root rot is more likely to occur in heavy, wet soils, low areas or compacted areas, but it may occur in light soils or better drained areas if heavy rains occur after planting. Rhizoctonia can cause seedling blight and root rot of soybean. Affected stands may have an uneven appearance and seedlings appear pale green in color and stunted in growth. The identifying feature of this disease is a small, reddish lesion on one side of the stem at or just below the soil line. This lesion develops into a sunken, cankered area a the point of infection. Sometimes the lesion will expand to completely girdle the stem. On severely infected seedlings, the entire hypocotyl may be discolored and shriveled into a dry, stringy or wiry stem. Fusarium can also cause root rot of soybean. Infection is usually confined to roots and lower stems. The lower part of the taproot and the lateral root system may be discolored, deteriorated or completely destroyed. General roots show a nondescript brown discoloration and a dry, shrunken rot. Above ground portions of plants may appear off-color and stunted. Plants with severe Fusarium root rot may die prematurely. Charcoal rot, caused by Macrophomina phaseolina, may be more commonly recognized as a mid to late season disease on maturing soybean plants, but it can also occur early in the season on seedlings. Infected seedlings tend to show a reddish brown discoloration from the soil line up the stem. The discolored area changes from reddish brown to dark brown to black. Foliage may appear off color or begin to dry out and turn brown. If the growing point is killed, a twin stem plant may develop. Under hot, dry conditions, infected seedlings may die. Under cooler, wetter conditions, infected seedlings may survive but carry a latent infection. Then symptoms may reappear later in the season with hot, dry weather. Once the crop has been planted, there is little that can be done to reduce incidence or severity of soybean seedling diseases. Additional stress from poor growing conditions, herbicide injury or other factors may compound problems with soybean seedling diseases. Prior to planting it is important to consider variety selection (especially in fields with a history of Phytophthora), fungicide seed treatment, crop rotation, seedbed preparation and conditions at planting. Laura Sweets, 573-884-7307 ********************************************************************* Article 4 of 9 Prime Grain Storage Weather Past By Bill Casady If you’re still holding grain and have decided to continue to hold it through the summer, then it needs to be checked very often now that warmer temperatures are here. I will never recommend that grain be held for periods of up to one year, but it can be done safely if you are willing to over-dry by at least a couple points of moisture. Ideally, over-drying is performed way before May and the natural cooling available in the winter months is maintained in the grain mass. Warming is discouraged because the cool grain mass minimizes the activity of both storage fungi and insect pests. However, if telltale signs of spoiled grain such as a musty smell are recognized, fans should be run to help break up heating in those isolated areas where spoilage has started and that grain should be moved and probably sold. Do not mess around with a questionable bin! Get that grain out of there immediately and use marketing tools to continue hedging your bet on a better price for that commodity. Watch out for your health and your life too. A layer of carbon dioxide can form at the surface of the grain and since carbon dioxide does not have an odor of its own, victims can lose consciousness within moments. Loss of life is nearly inevitable if this happens. Your rescuer may also give his or her life in an attempt to save you, so if you are unprepared, that’s not fair to them either. Do not enter a suspicious bin or ANY bin alone. Use fire rescue approved harnesses and other gear to prepare for unsafe conditions. Also, remember that you can not see a bridge of grain at the surface. Never enter a bin unless you know the history of the bin. If grain has been removed, do not enter that bin unless you can clearly see the cone that always forms from drawing grain through the center well of the bin. Be Safe. Bill Casady 573-882-4370 ********************************************************************* Article 5 of 9 Plan Now to Attend the MU Weed and Pest Management Field Day on July 12th By Kevin Bradley The annual Weed and Pest Management Field Day will be held this July 12th at the Bradford Research and Extension Center near Columbia, Missouri. As in recent years, we have expanded the focus of this field day to include a variety of pest management topics that are of interest to agricultural industry representatives, agrichemical dealers, Extension specialists and producers. Some of the research topics and trials that will be on display at this year’s field day include corn rootworm transgenics, black cutworm thresholds and control tactics, fungicides for soybean rust, seed treatments for soybean, glyphosate-resistant weed research in Missouri, invasive weeds and their management, pasture weed management considerations, fall herbicide implications, and much more. As usual, you will also have the opportunity to view plots that showcase a wide variety of herbicide treatments and weed management systems for use in either corn or soybean. The program will begin at 8:30 a.m. and will include guided wagon tours with stops that feature presentation of results and talks by university weed scientists, entomologists, plant pathologists, and agronomists. There will be a $20 registration fee collected at the time of check-in. This will cover costs associated with lunch and will provide each attendee with a tour booklet that describes the layout and location of each experiment. After lunch, you are welcome to spend the afternoon browsing the plots on your own. For certified crop advisors, 2 CEU credits for the field day are pending. If you plan on attending the field day, you must pre-register before July 8 by calling 573-884-7945 or by sending an e-mail to chismt@missouri.edu. The Bradford Research and Extension Center is located 7 miles east of Columbia, off of highway WW. For more complete directions call 573-884-7945 or visit http://aes.missouri.edu/bradford/index.stm. Kevin Bradley 573-882-4039 ********************************************************************* Article 6 of 9 Wheat Drying and Storage By Bill Casady Wheat can be dried by a few points with natural air to hurry up the harvest. Early harvested wheat can help avoid continued drying and re-wetting from wet weather after maturity and help preserve test weight and other quality factors of wheat. Before harvest, the bin should be thoroughly cleaned and treated for insect pests. Ask your pest management advisor for approved insecticides and consider hiring a professional to do the job right. Natural air should be used to dry shallow layers of wheat when moisture content is 18 percent or less. A very small amount of heat resulting in a temperature rise of just 3 to 5 degrees Fahrenheit is typically necessary when moisture contents are as high as 20 percent. The key to success is to dry shallow layers only 2 to 3 feet deep so that airflow rates are on the order of 2 to 5 cfm per bushel. Drying to 14 percent moisture content should be completed within one day. For more information on wheat production including a chapter on Wheat Harvest Drying and Storage, get a copy of MU publication IPM1022 "Management of Soft Red Winter Wheat" by calling Extension Publications at (573) 882-7216. The entire manual is also available to the people of Missouri at our Web site at http://extension.missouri.edu/explore/agguides/pests/ipm1022.htm. Bill Casady 573-882-4370 ********************************************************************* Article 7 of 9 Few Insect Problems Found During Past Two Weeks By Wayne Bailey Predicted problems with black cutworm were minor with economic infestations found in a few scattered fields across the state. The black cutworm predictive model suggested heavy cutting by black cutworm to begin on May 9 in central Missouri. Good news concerning the model is that the May 9 prediction was accurate for those few fields that had economic infestations of black cutworm. The good news for producers is that numbers of economic infestations were limited and found mostly from Columbia to the east and north. This prediction was based on the high numbers of moths captured in central Missouri pheromone traps. However, this did not occur suggesting that data from an increased number of traps are needed to better reflect actual moth activity in an area. Damage from this pest was heavy in some fields where the 2-4 percent underground cutting threshold was greatly exceeded. Knowing why black cutworm moths select one field over another as a preferred egg laying site would be valuable information, but at this time no pattern is apparent for those fields supporting heavy larval infestations. It is possible that eggs were laid in many fields, but larvae were successful in only a few due to tillage, insect pathogens, environmental factors, or some unknown factor. Similarly, high numbers of true armyworm moths reported from Missouri and neighboring states during early spring did not result in high numbers of first generation larvae. In most years 3 to 4 generations of true armyworm are produced in Missouri. Migrating moths often select grass pastures, wheat, fescue seed fields or occasionally field corn as their preferred egg laying sites during early spring. First generation larvae typically damage field crops with later generations attacking grass lawns. At present, low numbers of true armyworm larvae still can be found in grass pastures throughout the state, although damage is non-economic in most fields. Some feeding on seedling corn by southern corn rootworm beetles (also call the spotted cucumber beetle) has occurred during the past two weeks. Infestations have been reported from most regions of Missouri with a few fields requiring insecticide applications to prevent further loss of seedling foliage. Although foliage feeding by Southern corn rootworm beetles occasionally occurs, reports this year are more numerous than in most years. Wayne Bailey 573 864-9905 (cell) ********************************************************************* Article 8 of 9 Bean Leaf Beetle in Soybean By Wayne Bailey The bean leaf beetle adult is a beetle similar in size to rootworm beetles or ladybird beetles. It can range in color from green to dark red and always has a dark triangle on its back directly behind the head. It may or may not have four dark spots on the back and a dark line running the length of the body on each side. There are two generation produced annually in Missouri with beetles feeding on soybean foliage and larvae feeding on roots and stem below the soil surface. Economic thresholds are based on soybean growth stage, beetle numbers and visible plant damage. Typical defoliation damage by beetles is characterized by oval holes chewed in plant leaflets which do not go through leaf veins and by holes chewed into soybean pods later in the season. This soybean pest overwinters as adults in leaf litter and plant debris in border areas of crop fields. In spring, beetles move from overwintering sites to soybean fields where they feed on foliage, mate, and lay eggs in the soil. Adult beetles will feed on seedling soybean foliage for several weeks and eventually die. These beetles can damage to seedling soybean if they reach or exceed the seedling economic threshold of five or more beetles per foot of row and defoliation exceeds 30% or if an average of 1 or more plants are killed per foot of row. Although not common, beetles from the overwintering generation occasionally require management with an insecticide application. Problems with early season soybean defoliation or plant death is most common in years when springs are cool and dry, resulting in slowed seedling growth. Fields most at risk this spring are those planted earliest in an area. Bean leaf beetle adults are good fliers and will fly relatively long distances to infest early season soybean fields. If treatment is necessary, use one of the recommended insecticides. ********************************************************************* Chemical Name Product Name Rates: Amount of Product /acre (unless otherwise noted permethrin *Ambush 3.2 to 6.4 fl oz esfenvalerate *Asana XL 5.8 to 9.6 fl oz cyfluthrin *Baythroid 2 0.8 to 1.6 fl oz dimethoate Dimethoate; Dimatesee specific label methomyl *Lannate LV 0.75 to 1.5 pts methomyl *Lannate SP 0.25 to 0.5 lb thiodicarb *Larvin 3.2EC 18 to 30 fl oz chlorpyrifos *Lorsban 4E 1 to 2 pts zeta-cypermethrin *Mustang Max 2.8 to 4.0 fl oz chlorpyrifos *Nufos 4E 1 to 2 pts methyl parathion *Penncap-M 2 to 3 pts permethrin *Pounce 3.2EC 2 to 4 fl oz gamma-cyhalothrin *Proaxis 1.92 to 3.2 fl oz carbaryl Sevin XLR Plus 1 to 2 pts lambda-cyhalothrin *Warrior 1.92 to 3.2 fl oz * indicates Restricted Use ********************************************************************* Wayne Bailey, 573 864-9905 (cell) ********************************************************************* Article 9 of 9 May 27, 2006 Weather data for the Week Ending May 22, 2006 By Pat Guinan Weather Data for the Weekly Period May 16, 2006 - May 22, 2006 -------------------------------------------------------------------------------- | Monthly | Growing Weekly Temperature (deg. F) |Precip (in.)|Degree Days^ -----------------------------|------------|------------ Ext- Ext- Depart| Depart|Accum Depart Avg.Avg. reme reme from |May 1 from |since from Station County Max.Min. High Low Mean avg. |May 22 avg. |Apr 1 avg. ------------------------------------------------------|------------|------------ Corning Atchison 83 52 95 47 68 +3 | 0.58 -2.58 | 539 +200 St. Joseph Buchanan 80 55 92 50 67 +2 | 0.76 -2.70 | 509 +127 Brunswick Chariton 79 52 90 47 65 0 | 1.33 -2.34 | 544 +152 Albany Gentry 78 48 93 43 64 -1 | 0.31 -2.98 | 444 +89 Auxvasse Audrain 76 52 85 49 64 -1 | 1.35 -2.49 | 529 +138 Columbia Boone 76 52 86 48 64 -1 | 0.91 -2.93 | 546 +116 Sanborn Field Boone 77 54 87 50 66 0 | 1.18 -2.68 | 613 +167 Novelty Knox 75 49 87 46 62 -3 | 1.80 -1.71 | 438 +65 Linneus Linn 77 50 91 47 63 -1 | 1.50 -2.13 | 453 +97 Monroe City Monroe 75 50 86 47 62 -3 | 0.60 -2.91 | 473 +71 Versailles Morgon 77 55 89 50 66 0 | 2.32 -1.63 | 607 +123 Green Ridge Pettis 78 54 90 48 66 +2 | 0.21 -3.86 | 568 +201 Lamar Barton 81 57 88 50 69 +3 | 4.05 -0.20 | 659 +168 Cook Station Crawford 75 51 88 46 63 -3 | 3.99 +0.42 | 555 +48 Alley Spring Shannon 76 50 89 40 63 -2 | 6.06 +2.37 | 569 +112 Round Spring Shannon 77 51 86 41 63 -2 | 5.00 +1.31 | 566 +110 Delta Cape | | Girardeau 75 54 83 49 65 -4 | 4.74 +1.12 | 631 +41 Cardwell Dunklin 83 60 91 51 71 0 | 2.32 -1.24 | 834 +145 Clarkton Dunklin 79 58 89 50 68 -2 | 3.59 +0.88 | 755 +86 Glennonville Dunklin 79 57 88 50 67 -3 | 3.33 +0.77 | 762 +92 Charleston Mississippi 76 56 84 50 66 -2 | 4.38 +1.05 | 700 +129 Portageville- | | Delta Center Pemiscot 79 58 90 52 69 -1 | 3.61 +0.43 | 802 +136 Portageville- | | Lee Farm Pemiscot 79 58 90 51 68 -2 | 3.51 +0.27 | 807 +150 Steele Pemiscot 84 60 92 53 71 +1 | 2.31 -1.40 | 867 +200 -------------------------------------------------------------------------------- ^Growing degree days are calculated by subtracting a 50 degree (Fahrenheit) base temperature from the average daily temperature. Thus, if the average temperature for the day is 75 degrees, then 25 growing degree days will have been accumulated. -------------------------------------------------------------------------------- Pat Guinan, Commercial Agriculture Program (573) 882-5908