Integrated Pest & Crop Management Newsletter University of Missouri-Columbia Vol. 15, No. 14 July 15, 2005 Second Season Sprayer Shuffle By Bill Casady As herbicide applications taper off to nothing, it is usually appropriate to start thinking about putting sprayers away for the season. That usually means that we perform a thorough cleaning procedure and do some preventive maintenance to keep the sprayer in optimum operating condition and to prevent crop injury from left over residues the next time we take the sprayer to the field. The potential need for a second spraying season is still high in our minds in our first year of "certain uncertainty" about how Asian Rust will affect Missouri now that it has moved to the southern U.S. coast and is knocking on the doorsteps of our southern neighbors. As the weed offensive dies down and we have the opportunity to take the sprayer apart for a thorough cleaning and maintenance, take this opportunity, also, to equip and calibrate the sprayer for fungicide applications for Asian Rust. Cleaning field sprayers to avoid crop injury should be a season-long practice, but thorough cleaning also provides an excellent opportunity for upgrading and updating spraying equipment for the changing demands brought about by the potential for Asian Rust. A clean and well-maintained sprayer provides a better environment for calibration and ensures that we will, indeed, achieve optimum performance when we may need it most - for fungicide applications. Take a moment to review some "Simple Tips to Combat Asian Rust" at http://agebb.missouri.edu/mgt/soyrust/spraytips.htm as well as MU publication G4852, Cleaning Field Sprayers to Avoid Crop Injury at http://muextension.missouri.edu/explore/agguides/crops/g04852.htm. Always take precautions for personal safety by reducing exposure to crop protection materials with "Personal Protective Equipment for Working with Pesticides" available as MU publication G1917 and online at http://muextension.missouri.edu/explore/agguides/agengin/g01917.htm. For basic information on cleaning herbicide residues from sprayers see the "Condensed Guide for Cleaning and Storing Field Sprayers" in this issue. Be professional, be prepared, and be safe. Bill Casady 573- 882-4370 Spider Mites Problems in Dry Areas of State By Wayne Bailey Prior to rainfall from tropical storm Dennis, two-spotted spider mite populations were rapidly increasing in the drought areas of the state and had reached or exceed economic levels in some locations. The potential for this organism to continue as a pest of soybean remains high in those areas of the state where recent rainfall was limited or lacking. Spider mites are small organisms most closely related to chiggers and spiders than to insects. The two-spotted spider mite, Tetranychus urticae, is often an economic pest of soybean and to a much lesser extent of corn in Missouri during periods of drought conditions. This pest gets its name from two dark spots on the sides of the abdomen which are visible through the mite’s translucent, greenish-yellow, white, orange, or red colored body. Spider mites feed on the underside of soybean leaves and are difficult to detect due to their small size of about 1/60 of an inch. Damage to soybean is thought to be cause by the mites piercing individual plant cells with their mouthparts and then feeding on cell contents. Spider mite injury to soybean initially appears as yellow stipples or spots on soybean plants growing along field margins (where mites often overwinter). As mite populations increase, damage moves across the field as mites infest additional soybean plants. In heavy infestations the yellow stipples are generally followed by the injured foliage turning yellow, then brown/bronze and finally dropping from the plant as leaves senesce or dry. Identification of this pest is best accomplished using at least a 10X magnification lens or by shaking infested leaves over a white paper and watching for the small yellow mites to crawl about the paper after being dislodged from the soybean plant. Although good thresholds for this pest are not available, treatment of infested fields is recommended if drought conditions exist, stipples are present of soybean leaves, and live mites are present. Generally infestations of this pest move downwind, so it is necessary to scout the entire field to determine if mites are present in spots or throughout the entire field. If hot and dry conditions persist, the entire field may require treatment even if mite numbers are low in some areas of the field. Both soybean maturity and shattering of grain will be increased by the presence of economic levels of spider mites. Fields which received rainfall should continue to be scouted as damaging levels of spider mite may redevelop if drought conditions return. Two insecticides are labeled for spider mite control in soybean. They include dimethoate, sold under several labels, and chlorpyrifos, marketed as either Lorsban 4E or Nufos 4E. The use rate for dimethoate varies depending on the formulation, whereas, Lorsan 4E and Nufos 4E are labeled for use at ½ to 1 pt per acre. Wayne Bailey Entomology 573-882-2838 Update on Soybean Diseases By Laura Sweets We are getting an increasing number of calls related to yellow soybean plants, yellow leaves on soybean plants, wilting plants and dying or dead soybean plants. In some cases these symptoms may be occurring on scattered plants in fields and in other cases the symptoms are in patterns related to soil type and soil moisture conditions in the field. The yellowing may be a marginal yellowing of lower leaves suggestive of a potassium deficiency, it may be a marginal yellowing followed by browning of those tissues more suggestive of scorch or it may be a general yellowing followed by wilting and death of leaves or entire plant. When troubleshooting in these fields it is important to dig up a range of plants and check the root systems carefully. Although potassium deficiencies certainly can occur and can cause symptoms on soybean plants, similar symptoms may also occur if the plants have poorly developed or rotted root systems and can not absorb and translocate nutrients that may be available in the soil. This season both Fusarium root rot and Rhizoctonia root rot have been widespread and in some fields quite severe. Fusarium root rot tends to cause a rotting of the main taproot. The taproot may be discolored and beginning to shrivel or it may be completely rotted so that it breaks off when the plant is pulled from the ground. Rhizoctonia root rot tends to cause a brick red to bright red discoloration of the stem tissue near the soil line. Plants in one field in Union County, Missouri showed red discoloration of almost the entire lower stem. Stems may be somewhat constricted or shrunken and stem tissues may show more cracking than normal. With both Fusarium root rot and Rhizoctonia root rot the plants may send out adventitious or secondary roots near the soil surface trying to compensate for loss of primary root tissue. If weather patterns were to change so that conditions were favorable for soybean growth and development, in particular more frequent rain and moderate temperatures, plants with low to moderate levels of these root rot diseases might recover. However, if hot, dry conditions continue, these plants are more likely to show severe scorch symptoms or simply wilt and die. There are no management strategies that can be implemented at this point in the growing season. When checking affected plants, take time to observe overall root development and health. In addition to root rot symptoms, some plants have very shallow root systems or root systems that are bent or J-shaped suggesting compaction, a hard pan layer, or other site related problems. Damage from soybean cyst nematode can be more severe under periods of moisture stress or drought conditions. If plants are carefully dug up and soil gently removed from the root system, it may be possible to see the bodies of female soybean cyst nematode on the roots. This time of the year SCN females might be more readily found on new roots formed deeper in the soil profile or on lateral roots. Submitting soil samples for SCN analysis would be another means of determining if SCN is contributing to yellowing, stunting or premature death of plants. See information on submitting samples for SCN analysis in this issue of the newsletter. Septoria Brown Spot Samples with Septoria brown spot and questions related to Septoria brown spot continue to come in from all parts of the state. Much of the state did receive rain over a several day period early in June. This rain apparently triggered a flush of Septoria brown spot. The dry conditions over most of the state for the last 3-4 weeks have slowed or stopped the development of this disease in most fields. At this time Septoria brown spot is most evident low in the canopy on the first one to two sets of trifoliolate leaves. These leaves may be heavily spotted with individual spots ranging from very small reddish brown to brown spots to larger, more irregularly shaped lesions. Leaves may exhibit a general yellowing and may drop prematurely. In many fields the plants have not been growing vigorously and rows still haven’t canopied over. This makes the leaf yellowing or leaf drop from Septoria brown spot much more obvious. If the rows were closed, symptoms on those lower leaves wouldn’t be as evident from a distance. A change in weather to periods of frequent rains, heavy dews and moisture that stays in the canopy could lead to the buildup of Septoria brown spot and another outbreak of symptoms on newer growth. But continued periods of hot, dry weather with little or no dew formation will not be favorable for Septoria brown spot. Quadris and Headline as well as chlorothalonil products such as Brave WeatherStik and Echo, do have full federal registration for use on soybean against a number of diseases including Septoria brown spot. Benefit from an application of these materials under the current weather pattern seems questionable. Update on Soybean Rust Soybean rust has not been detected in any of the Missouri sentinel plots thus far this season. There have been a few changes in the status of soybean rust since the article in the last issue of the Integrated Pest and Crop Management Newsletter. As of July 12, 2005, soybean rust has been confirmed on soybeans in sentinel plots in Baldwin County, Alabama and in Marion County, Florida. Soybean rust had been reported earlier in the season on volunteer soybeans in Seminole County, Georgia and these volunteer soybeans have since been destroyed. Soybean rust has also been reported on kudzu in seven counties in Florida, i.e. Dade, Hernando, Pasco, Marion, Jefferson, Leon and Gadsen Counties. Over the last week there have also been reports that spores suspected of being spores of the soybean rust pathogen were identified from spore traps in Kentucky and Tennessee. The spore trapping is part of a multi-state project established by Syngenta Crop Protection, Inc. Syngenta located approximately 100 spore traps containing vaseline coated microscope slides throughout the southern United States (none of the original locations were in Missouri). The slides are replaced at regular intervals and the collected slides sent to a central location for examination. Spores resembling the Phakopsora pachyrhizi have been detected on slides from about ten sites including one in western Tennessee and one in Woodburn, Warren County, Kentucky. Follow-up surveying in areas close to the spore traps has not detected soybean rust in sentinel plots or production areas close to the spore traps. Surveying of sentinel plots has intensified in these areas with most being scouted on a 3-4 day interval. Certainly Hurricane Dennis has also lead to increased concern about the movement of soybean rust. Hurricane Dennis touched ground in the western panhandle of Florida and the eastern portion of Alabama. Rains from this storm system reached portions of Missouri on Monday, July 11th. But there are several points that are important to keep in mind. First the inoculum level in the southern United States has remained very low so far in the 2005 season. Although there have been detections of soybean rust in two soybean sentinel plots, one area of volunteer soybeans and seven areas of kudzu, the disease has not built up to high levels in those areas and has not spread significantly beyond those initial detection areas. So there don’t seem to be high levels of spore inoculum for Hurricane Dennis to bring north. In addition to having weather patterns, such as Hurricane Dennis, which might spread inoculum through large geographic areas, the weather conditions in the areas to which inoculum is carried must be favorable for infection to occur and the disease to develop. On July 7, as Hurricane Dennis was approaching the Florida Keys, 23 Missouri counties were put under drought alert. If Hurricane Dennis brings 1or 2 days of rain and the weather pattern reverts back to the dry conditions which preceded it, an immediate epidemic of soybean rust in much of Missouri is very unlikely. If weather conditions after the remnants of Hurricane Dennis pass through change, so that there are periods of more extended rainfall, heavy dews and moisture that stays in the canopy, soybean rust infections would be more of a possibility. So for right now it is important to continue to monitor events in the southern United States. (There are a number of web sites which post information on soybean rust including the USDA/APHIS site at www.sbrusa.net) and to monitor weather conditions in the southern United States as well as locally. Rainfall events in Missouri have been scattered and localized this season. And it is important to continue to scout or monitor fields. Once spores are deposited on susceptible leaf tissue, lesions may form in 5-10 days but spores may not be evident until 10-14 days after infection. Laura Sweets Plant Pathologist 573-884-7307 Condensed Guide for Cleaning and Storing Field Sprayers By Bill Casady The following cleaning procedure is recommended for all herbicides unless more specific instructions are listed for a particular product. Cleaning Add one-half tank of fresh water; flush tanks, lines, booms and nozzles for at least five minutes using a combination of agitation and spraying. Rinsate sprayed through the booms is best sprayed onto cropland to avoid the accumulation of pesticide-contaminated rinsate. Thoroughly rinse the inside surfaces of the tank, paying particular attention to the surfaces around the tank fill access, baffles and tank plumbing fixtures. The use of a 360-degree nozzle, such as the TeeJet Model 27500E-TEF rinsing nozzle, permanently installed to the spray system can automate the thorough cleaning of tops and sides of the tanks. Several nozzles may need to be positioned carefully to clean tanks with baffles. Pressure sprayers are useful for removing caked on internal and external residues. Hot water can increase penetration of dried residues, but the addition of hot water rinsing may cause unacceptable health hazards due to the vapors produced. Carefully review label safety precautions for the agrichemicals and cleaning products used. See MU publication G1917, Personal Protective Equipment for Working With Pesticides. Fill the tank with fresh water and add one of the following cleaning solutions or a commercially available tank cleaner and agitate the solution for 15 minutes. Add one of the following to each 50 gallons of water to make a cleaning solution: two quarts of household ammonia or four pounds of trisodium phosphate detergent. Operate the spray booms long enough to ensure that all nozzles and boom lines are filled with the cleaning solution. Let the solution stand in the system for several hours or overnight. Agitate and spray the solution onto an area suitable for the rinsate solution. Add more water and rinse the system again by using a combination of agitation and spraying. Remove nozzles, screens and strainers, and clean separately in a bucket of cleaning agent and water. Finally, rinse and flush the system once again with clean water. Storing After thorough cleaning, remove nozzles and pumps and allow all parts of the sprayer to dry thoroughly. Seal all openings with tape or rubber stoppers to prevent insects, rodents and pests from nesting in the equipment. Then store the sprayer in a clean and dry location, especially when it will sit through the freezing weather of winter months. Remember, maintenance is also a much more appealing job while the sprayer is clean. Before you back the sprayer into its final resting spot, perform a thorough inspection of all systems and make a list of needed repairs. While the sprayer is still clean, perform a thorough calibration and any maintenance needed to make it spray like a new one. Bill Casady Agricultural Engineering 573-882-4370 Consider Sampling for Soybean Cyst Nematode By Laura Sweets and Bob Heinz We usually think of fall or after soybean harvest as good times to sample for soybean cyst nematode (SCN). But samples can be taken at any time of the year. SCN damage can be more severe when plants are suffering from moisture stress. When making field calls related to yellow soybean plants, stunted soybean plants or dying and dead soybean plants right now, consider collecting a soil sample for SCN analysis. SCN could be contributing to the symptoms occurring in many fields throughout the state and having an SCN egg count done now would verify that and would give information to use in making decisions on crop rotation, variety selection, etc. for next season. The SCN egg count test is what most soybean growers need. If you haven’t had a test run in 5 to 10 years, an investment of $15 and a bit of time is little for the peace of mind" or the knowledge that a problem is making a comeback. Sample a field that you notice is slipping in yield, or the one that had high egg counts years ago. If the egg count is medium or high, you may want to sample your other fields. Because SCN egg counts are only as good as the sample taken, here are some hints to improve sampling for SCN: 1. Limit the size of the area being sampled: 10 acres is a good target. 2. With your bucket and probe or shovel in tow, walk the area in a W or Z pattern, sampling about 8 inches deep between the rows. Take about 20 cores with a shovel (take 1/4 cup of soil from near the shovel tip). Mix the core well into a composite sample, and place about a pint of it in a plastic bag for submission. 3. Label the plastic bag, avoid storing it in the sun, and ship it as soon as possible. 4. Fill out a submission form (available from our Web site or your local extension agent) or on a piece of paper indicate: * Name, address, phone, and email address (if you have e-mail, results can be sent quickly.) * County and cropping history * Type of test: SCN egg count ($15), HG type race test ($50 instate, $100 out-of-state), or complete nematode analysis ($20) * The mailing address for the lab is: Extension Nematology Lab 46 Agriculture Building University of Missouri Columbia, MO 65211 The HG type race test is a good choice for the grower who has high egg counts after growing resistant lines for years. This test indicates the HG type (or race) of SCN in the field, and what sources of resistance would be good to choose when buying seed. The Web site below gives a comprehensive listing of the "sources of resistance" for commercial soybean lines: http://www.ag.uiuc.edu/~wardt/cover.htm. The complete nematode analysis is a count of the worm stages of all the plant parasitic nematodes in the sample. (It does not give an SCN egg count.) This test is important for southeast Missouri growers who may have the root knot nematode as well as SCN. The Extension Nematology Lab Web site gives more information about how to sample, the tests provide available, and how samples are actually run in the lab. A submission form can also be downloaded from the following Web site: http://soilplantlab.missouri.edu. Laura Sweets Plant Pathologist 573-884-7307 and Bob Heinz Research specialist, Extension Nematology Lab Coordinator 573-882-0816 Weather Data for the Week Ending July 13, 2005 By Pat Guinan -------------------------------------------------------------------------------- | Monthly | Growing Weekly Temperature (deg. F) |Precip (in.)|Degree Days* -----------------------------|------------|------------ Ext- Ext- Depart| Depart|Accum Depart Avg.Avg. reme reme from |Jul 1 from |Since from Station County Max.Min. High Low Mean avg. |Jul 13 avg. |Apr 1 avg. ------------------------------------------------------|------------|------------ Corning Atchison 91 68 92 66 80 +3 | 0.06 -2.33|1832 +363 St. Joseph Buchanan 88 67 89 64 78 +1 | 0.09 -2.07|1703 +191 Brunswick Chariton 90 65 92 62 77 -1 | 0.44 -1.46|1764 +208 Albany Gentry 90 63 91 58 78 0 | 0.09 -2.48|1667 +147 Auxvasse Audrain 89 64 94 58 77 -1 | 0.27 -1.64|1733 +178 Columbia Boone 89 67 93 63 78 0 | 0.15 -1.84|1757 +138 Sanborn Field Boone 90 68 93 63 79 0 | 0.09 -1.93|1865 +212 Novelty Knox 87 65 90 61 76 -1 | 0.31 -1.48|1623 +98 Linneus Linn 89 65 91 60 77 0 | 0.28 -1.91|1630 +153 Monroe City Monroe 88 64 92 59 76 -1 | 0.30 -1.45|1680 +106 Versailles Morgan 92 66 96 62 79 +1 | 0.00 -1.72|1880 +229 Green Ridge Pettis 90 66 93 63 78 0 | 0.24 -1.80|1806 +289 Lamar Barton 89 66 93 62 77 -2 | 0.68 -1.83|1846 +115 Cook Station Crawford 86 61 94 53 73 -5 | 3.05 +1.55|1629 -80 Delta Cape | | Girardeau 85 67 92 63 75 -5 | 4.36 +2.96|1845 -88 Cardwell Dunklin 86 68 91 64 77 -5 | 4.13 +2.77|2104 -10 Clarkton Dunklin 87 69 94 65 77 -5 | 4.22 +2.96|2045 -34 Glennonville Dunklin 85 68 91 66 76 -6 | 4.96 +3.64|2028 -44 Charleston Mississippi 86 68 92 65 76 -4 | 4.93 +3.17|1947 +57 Portageville- | | Delta Center Pemiscot 86 69 92 65 77 -4 | 4.41 +3.14|2115 +52 Portageville- | | Lee Farm Pemiscot 86 69 92 65 77 -4 | 4.28 +2.92|2114 +69 Steele Pemiscot 87 69 93 61 78 -3 | 3.15 +1.60|2185 +123 -------------------------------------------------------------------------------- *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