Integrated Pest & Crop Management Newsletter University of Missouri-Columbia Vol. 15, No. 9 May 13, 2004 Stripe Rust is Showing Up in Missouri Wheat By Laura Sweets Southern states have been reporting unusually high levels of stripe rust in wheat for over a month. Over the last week, reports have been coming in from southeastern and southwestern Missouri that stripe rust is showing up in some wheat fields. There appears to be some variation in severity with some fields showing rather severe symptoms on the flag leaves. Stripe rust, caused by the fungus Puccinia striiformis, develops as yellow or yellowish red stripes or streaks that run lengthwise on wheat leaves. This disease is more commonly associated with lower temperatures (especially lower night temperatures) and intermittent rain or dew. Varieties vary greatly in their susceptibility to stripe rust. Some varieties have good resistance and may show little disease development. Other varieties are rather susceptible and may show severe symptom development and, in some cases, yellowing and premature death of leaves. On these varieties yield may be impacted significantly. Stripe rust is controlled primarily through the use of resistant varieties or the use of foliar fungicides. A table of foliar fungicides labeled for use on wheat was published in the April 15 issue of the Integrated Pest and Crop Management Newsletter. Most of these materials may be applied up to Feekes growth stage 10.5 which is full head emergence. Once flowering has started it is too late to apply most of these materials. If there is a question on whether or not to apply a foliar fungicide to manage stripe rust of wheat this season, it would be wise to scout fields very closely as quickly as possible for stage of growth and disease severity. If the crop is flowering it is too late for legal application. If a significant number of the flag leaves are showing high levels of infection and the forecast is for warm, dry weather, it is probably too late for the fungicides to be of much benefit. If most flag leaves have little to light infection and the forecast is for cool or cool, wet weather (or if there is a chance that weather conditions might favor an extended grain fill period), there might still be some benefit from a fungicide application. But the fungicide application would need to be done immediately. This would also be a good year to check out any wheat variety trials in your area and evaluate varieties for reaction to stripe rust or other diseases. Laura Sweets, Plant Pathologist 573-884-7307 Fusarium Head Blight or Scab of Wheat By Laura Sweets Fusarium head blight or scab of wheat develops on plants in the flowering to early grain fill stages of growth. Although winter wheat in southeastern Missouri began flowering a week or so ago, the winter wheat in much of the rest of the state is just beginning to flower. So the time for possible infection by the Fusarium head blight fungus is at hand. Infection is very dependent on environmental conditions while wheat is in susceptible stages of growth. Moderate temperatures in the range of 77-86 F, frequent rain, overcast days, high humidity and prolonged dews favor infection and development of scab. Weather conditions over the next week or so will determine the extent and severity of scab in this year’s wheat crop. Fusarium head blight or scab problems will be more severe if rains coincide with flowering of wheat fields. Many parts of the state have been dry but the forecast is for wet conditions several days this coming week which could be conducive to scab problems in many areas of the state. The characteristic symptom of scab on wheat is a premature bleaching of a portion of the head or the entire head. Superficial mold growth, usually pink or orange in color, may be evident at the base of the diseased spikelets. Bleached spikelets are usually sterile or contain shriveled and or discolored seed. Scab is caused by the fungus Fusarium graminearum. This fungus overwinters on host residues such as wheat stubble, corn stalks and grass residues. Spores are carried by wind currents from the residues on which they have survived to wheat heads. If environmental conditions are favorable, i.e. warm and moist, the spores germinate and invade flower parts, glumes and other portions of the spike. Scab infection occurs when favorable environmental conditions occur as the wheat crop is in the flowering to early grain fill stages. Unfortunately, the detrimental effects of scab are not limited to its adverse effects on yield. The fungi which cause scab may also produce mycotoxins. Vomitoxin (deoxynivalenol or DON) and zearalenone may occur in wheat grain infected by scab fungi. This is a primary concern where grain is fed to non-ruminant animals. Ruminants are fairly tolerant of these two mycotoxins. Also, the fungi which cause scab may survive on the seed and can cause seedling blight and root rot problems when scabby grain is used for seed. At this point in the season there are no management options available for controlling scab on wheat. Growers should be scouting fields to get a feel for incidence and severity of scab in this year’s wheat crop. Because of possible mycotoxin concerns and seed quality concerns, grain from fields with scab may require special handling. Wheat planted on corn, sorghum or wheat residue (even wheat double cropped with soybeans) has a greater risk for scab. Laura Sweets, Plant Pathologist 573-884-7307 Managing Endophyte Infected Tall Fescue Pastures During Mid- to Late-Spring By David K. Davis Over the past several months I have determined that we have done a poor job of educating you on how to manage your endophyte infected (E+) tall fescue pastures during the spring. All too often, I hear complaints about how poorly cattle are performing during the summer months, even though you are following a managed grazing system. After pinpointing exactly when cattle were moved off of E+ pastures, it becomes apparent that the cattle were moved off the E+ pastures too late. Typically, cattle are left on E+ pastures to graze through the month of June because "there is a ton of grass out there". In reality, E+ grass produced during the last half of May through June is the most toxic grass produced during the year. These toxins accumulate in cattle during May and June and with the onset of hot and humid weather (stress) the cattle just cannot perform. Toxin concentration within the plant varies with the plant part and time of year. Highest concentrations are found in the seedhead, followed by the stem, and the lowest concentrations are found in leaf material. Seedheads can contain about a four times greater concentration of the toxin (ergovaline) than leaf blades, and about a twice as much toxin as stems. During late May tall fescue plants begin reproductive growth and stem elongation begins. Cattle will continue to readily graze the fescue at this time, but are ingesting a greater concentration of toxin. The problem only becomes worse with advances in plant maturity. So what are you to do? Several options are available but all of them require you to start managing the toxin load your cattle are consuming. The first step is to test pastures for endophyte infection levels. Pastures recently tested at the Forage Systems Research Center have ranged from less than 5% infection up to greater than 95% infection. And it is not unusual to find a wide variation in endophyte infection level on commercial farms either. As a rule of thumb, for every 10% increase in infection level you can expect steer average daily gain to decrease by approximately 0.1 lb/hd/day. For example, a pasture found to be 75% infected tall fescue will decrease ADG by 0.75 pounds when compared to an endophyte free pasture, and over a short 100 day period (valuing steers at $1.00/lb) this translates to a $75 loss/head. To avoid this loss cattle must be moved off of infected pastures as soon as the tall fescue begins reproductive growth (in Missouri this happens sometime in May). The best solution for highly infected fescue pastures, over the long run, is renovating pastures to endophyte free or novel endophyte cultivars. This is expensive and can take land out of season-long production for a year or more. When renovating pastures, we recommend using the spray-smother-spray technique. Briefly, this involves spraying the infected field with an effective herbicide, seeding an annual smother crop, and respraying prior to replanting the new forage. For spring seedings of the new perennial forage, the smother crop should be a winter annual small grain. For fall seedings of the new perennial forage, the preceding smother crop should be a summer annual (pearl millet, sudan...). Other management options exist but implementing them every year is a necessity. These options include: rotating livestock to non-infected pastures beginning in late May, interseeding infected pastures with legumes and other grasses to "dilute" the infected fescue pasture, avoiding heavy applications of nitrogen fertilizer in spring, controlling seedheads and stems with clipping in mid- to late spring to reduce consumption of these plant parts by livestock, and feeding supplements to dilute the livestock diet. Although all of these management options work, it will probably take implementing several of them at the same time in order to attain livestock performance equal to what could have been attained by renovating pastures. Most livestock farmers know that fescue toxicosis exists and have implemented corrective measures to help alleviate the problem. However, I would like to stress that many times we rotate cattle too late in spring to optimize the benefits of rotation. By rotating too late in the spring, livestock performance will suffer during the summer even though the livestock will not be eating highly toxic fescue during the summer months. This is because the toxin that is ingested in the spring accumulates in livestock and it takes time for the livestock to detoxify themselves. The best solution is to manage in such a manner as to not allow the livestock to consume the toxin in the first place. David K. Davis, Superintendent Forage Systems Research Center 660-895-5121 Integrated Machinery and Soil Management With Autosteer - Ultimate Control By Bill Casady Autosteer is rapidly becoming a popular accessory on field equipment, touting benefits such as eliminating skip rows, running day and night, and minimizing skips and overlaps when applying crop protection materials. Autosteer can even reduce other capital costs by eliminating the need for foam markers on sprayers and disk markers on wide planters. Throughout the last century, steering equipment through the field has been a primary operator task. Some operators have an uncanny ability to steer their way through the field with precision, but the task of steering is sometimes at the expense of controlling the performance of the implement behind the tractor or the operating characteristics of the combine, sprayer or planter. At the very least, autosteer reduces operator fatigue and increases operator productivity. Already, high-end autosteer units are available that can guide implements through the field achieving accuracies within an inch. The opportunities are limited only by imagination. Avoid traveling over wet areas of a field while planting or spraying the rest of the field when it is ready. Return later when the ground is ready and finish up without damaging the soil. Automatically start and stop spraying or planting precisely at the beginning and the end of the field to reduce overlap and waste and with confidence that no area of the field has been missed. Precision agriculture over the last decade or so has meant that the soil could be planted, fertilized, sprayed and generally cared for by using prescriptions based on location and previously collected data. Advanced autosteer with subinch accuracy truly provides precision in placement of the equipment within an inch of the intended rows or soil area not only in parallel passes, but consistently from spring to fall and from year to year. When paired with equipment that has been set up on the same wheelbase and swath width, precision guidance provides another dimension of accuracy that offers an opportunity of its own - namely, controlled traffic. Controlled traffic eliminates random traffic patterns in a field that cause widespread compaction. Without some visual or electronic means of controlling exactly where a tractor will travel within a field, the spacing of successive passes becomes random. Over a period of several years, nearly all of the soil will have been exposed to wheel traffic that can cause productivity-limiting compaction. Controlled traffic can be accomplished without precision steering, especially when permanent soil beds or furrows are prepared for irrigation or to help warm the soil. The system of beds and furrows become the ‘white lines’ marking the permanent pathways through the field. Controlled traffic provides unsurpassed control over compaction. Combined with continuous conservation practices that allow the soil to reach a long-term no-till condition, the increases in productivity and energy efficiency are very likely to become a new standard for competing in a tight agricultural industry. Bill Casady 573-882-4370 Weather Data for the Week Ending May 9, 2005 By Pat Guinan -------------------------------------------------------------------------------- | Monthly | Growing Weekly Temperature (deg. F) |Precip (in.)|Degree Days^ -----------------------------|------------|------------ Ext- Ext- Depart| Depart|Accum Deprt Avg.Avg. reme reme from |May 1- from |since from Station County Max.Min. High Low Mean avg. |May 9 avg. |Apr 1 avg ------------------------------------------------------|------------|------------ Corning Atchison 77 50 84 33 63 +3 | 0.23 -1.18| 336 +172 St. Joseph Buchanan 73 50 80 35 62 +2 | 0.14 -1.05| 295 +93 Brunswick Chariton 75 48 82 31 62 +1 | 0.22 -1.20| 321 +110 Albany Gentry 74 47 82 30 61 +1 | 0 -1.44| 291 +107 Auxvasse Audrain 74 49 81 35 62 +1 | 0.15 -1.50| 307 +98 Columbia Boone 73 49 80 34 62 +1 | 0.10 -1.42| 310 +67 Sanborn Field Boone 74 50 81 34 63 +1 | 0.22 -1.33| 342 +89 Novelty Knox 72 47 80 32 60 0 | 0.21 -1.35| 273 +74 Linneus Linn 74 45 81 28 61 +1 | 0.40 -1.19| 284 +96 Monroe City Monroe 74 47 82 31 61 0 | 0.19 -1.44| 286 +61 Versailles Morgan 74 49 82 36 62 0 | 1.11 -1.60| 334 +45 Green Ridge Pettis 74 49 80 33 62 +2 | 0.12 -1.60| 318 +123 Lamar Barton 73 49 81 35 61 -1 | 0.03 -1.68| 309 +16 Cook Station Crawford 76 43 82 30 60 -3 | 0.01 -1.51| 283 -30 Delta Cape | | Girardeau 75 47 85 37 62 -2 | 0.22 -1.30| 325 -36 Cardwell Dunklin 77 50 86 42 64 -2 | 0.26 -1.44| 411 -25 Clarkton Dunklin 77 49 87 40 64 -2 | 0.40 -0.75| 380 -43 Glennonville Dunklin 76 50 85 39 64 -2 | 0.14 -1.02| 388 -38 Charleston Mississippi 75 50 84 43 63 0 | 0.20 -1.27| 369 +23 Portageville- | | Delta Center Pemiscot 75 52 83 44 65 -1 | 0.32 -1.12| 417 0 Portageville- | | Lee Farm Pemiscot 76 51 85 43 65 0 | 0.27 -1.16| 420 +11 Steele Pemiscot 77 52 85 41 65 -1 | 0.36 -1.23| 428 +11 -------------------------------------------------------------------------------- ^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