Integrated Pest and Crop Management Newsletter Vol. 17, No. 8 May 1, 2007 ********************************************************************** Seed Decay and Seedling Blights of Corn By Laura Sweets Some years, early season stand establishment problems are widespread and, in some cases, severe- especially in early planted field corn. The weather pattern during and immediately after planting is a major factor contributing to those problems. Corn planted before extended periods of cold, wet weather in April or early May tends to show damage from saturated soils, cold soil temperatures, frost injury, herbicide injury, nitrogen deficiencies, seed decay and seedling blights. In some fields the seed decay and seedling blight may progress into crown decay resulting in even more severe stunting and yellowing of plants. If weather patterns are favorable for germination and emergence of corn and not as favorable for development of corn seed and seedling diseases, there will be a substantial reduction in seed decay and seedling blight problems in corn. Corn planting has been behind normal because of the cold, wet weather. There were some windows for planting in mid-April and a number of corn acres were planted in a short period of time just prior to the last period of almost state wide rain. There have been a few reports of fields in which corn has emerged or can be rowed but not as many as would normal for this time of year. Although there were some reports of very early planted fields that were damaged by the cold temperatures in late March-the first of April, there have not been any reports of seedling blights or seed decay caused by soil fungi so far this season. Certainly weather conditions over the next several weeks will be a key factor in which early season corn diseases develop and how serious these diseases are. Seed decay and seedling blights of corn are generally caused by soilinhabiting fungi such as Pythium, Fusarium, Diplodia, Rhizoctonia and Penicillium. These fungi may rot the seed prior to germination or cause preemergence or postemergence seedling blight. Affected seeds are usually discolored and soft and may be overgrown with fungi. Rotted seed may be diffi cult to find because they decompose very rapidly and because soil adheres fairly tightly to the decomposing seed. With preemergence seedling blights, the seed germinates but the seedlings are killed before they emerge from the soil. The coleoptile and primary roots are usually discolored and have a wet, rotted appearance. With postemergence seedling blights, the seedlings emerge through the soil surface before developing symptoms. Seedlings tend to yellow, wilt and die. Discolored, sunken lesions are usually evident on the mesocotyl. Eventually the mesocotyl becomes soft and water soaked. The root system is usually poorly developed, and roots are discolored, water soaked and slough off. If the primary root system and mesocotyl are severely affected before the nodal or permanent root system has developed, the plants have little chance of surviving. The Pythium, Fusarium, Diplodia, Rhizoctonia and Penicillium species which cause seed decay, seedling blight and crown decay are common in soils throughout the state. If conditions are favorable for germination and emergence, these fungi may not have the opportunity to invade seed, germinating seed or young seedlings so seed decay, seedling blights and crown rot will not be significant problems. On the other hand, conditions that are not favorable for germination and emergence, give these soil fungi more time to attack the seed and developing plants. Numerous other factors also contribute to early season corn establishment problems. Insect damage, nutrient imbalances, herbicide injury, soil conditions and environmental factors, especially saturated soil conditions and oxygen depravation, may also cause or contribute to early season corn establishment problems. Corn seedling blights are more severe in wet soils, in low lying areas in a field or in soils that have been compacted or remain wet for an extended period of time. Low soil temperatures (50- 55 degrees) and wet soil conditions especially favor Pythium seed decay and seedling blight. Disease severity is also affected by planting depth, soil type, seed quality, mechanical injury to seed, soil crusting, herbicide injury or other factors which delay germination and emergence of corn. Planting high quality seed into a good seedbed when soil temperatures are above 50 degrees will help minimize these early season problems. Virtually all field corn seed comes with a fungicide seed treatment. Hopper box treatments can be used to supplement the existing seed treatment. Laura Sweets SweetsL@missouri.edu ********************************************************************** Wheat Diseases By Laura Sweets Cold temperature or frost damage continues to be the major concern on winter wheat in Missouri. We have had a few more reports of virus-like symptoms in wheat, particularly symptoms of wheat spindle streak mosaic and/or wheat soil-borne mosaic (see issue 4 of Integrated Pest and Crop Management Newsletter, 2007 for descriptions of wheat virus diseases). Powdery mildew has been reported in some fields, especially fields showing lodging as a result of low temperature damage. Other foliage diseases do not appear to be widespread or severe at this time. Wheat in the southern part of the state, especially in the Boot Heel is beginning to flower. Wet conditions, frequent light rains, heavy dews as the crop is flowering or immediately after flowering can be conducive for the development of scab or Fusarium head blight. Laura Sweets SweetsL@missouri.edu ********************************************************************** Soybean Rust Update- April 30, 2007 By Laura Sweets January 2007 started off with more reports of soybean rust on kudzu in southern states than in 2005 or 2006. This caused speculation that soybean rust could be a more serious problem in 2007 because of the earlier development of inoculum in the southern states. But the record low temperatures that occurred throughout the Midwest the last of March and first of April also struck in the South. Previously infected kudzu patches were killed back. There have not been any new reports of soybean rust since late March. Since the disease can no longer be found in many of the previously infected kudzu patches in Florida, Georgia and Alabama, those sites on the national IPM PIPE Website (www.sbrusa.net) have been turned from red (soybean rust confirmed) to red cross hatch (soybean rust confirmed but not longer found). Recent dry weather conditions in southern states except for Texas have been unfavorable for the development of soybean rust. Soybean sentinel plots have been planted and are still being planted in the southern states and scouting for soybean rust on both kudzu and soybean in underway in earnest for the 2007. The IPM PIPE Web at www.sbrusa.net is a good site for information on the current status of soybean rust in the United States. Missouri will be participating in the sentinel plot program for both soybean rust and soybean aphid during the 2007 season. We will have approximately 20 sentinel plots and are in process of identifying those sites right now. It will likely be mid-May before plots reach a stage of growth suitable for scouting. Laura Sweets SweetsL@missouri.edu ********************************************************************** Use of Plant Analysis as a Diagnostic Tool By Manjula Nathan Plant analysis has been used as a diagnostic tool for many years. Plant analysis and soil testing go hand in hand. To determine nutrient deficiencies, most agriculturists rely primarily on visual symptoms, plant tissue analysis and soil analysis. Plant analysis can be used to diagnose or confirm diagnoses of visible symptoms or to identify "hidden hunger" where a plant may be suffering from a nutrient deficiency but show no symptoms, and to suggest additional tests or studies to identify problems in a field. Use of plant analysis in today’s agriculture * Tool for diagnosing nutrient deficiency. * Use as a monitoring tool to assess the nutrient status of plants in relation to the fertilizer program used. Used in evaluation of crops in a given soil, many times farmers and their crop consultants will develop fertility program and want to know whether there is a need for future adjustments. * End of season corn stalk NO3- N test at one to three weeks after black layer stage is used at Iowa State to evaluate the previous season N management practices. If NO3-N test in the stalk (cut at 6” above ground level to obtain an 8” long stalk sample) is less than 250 ppm N it is considered as low, and 250 to 700 ppm N is marginal, 700 to 2,000 ppm N as optimum and greater than 2,000 ppm as excess. * Measuring NO3-N content on corn, wheat or forages after drought or freeze damage if used for feeding livestock to check for nitrate toxicity. * For perennials and trees that have a tap root system (blueberries, apples, grapes, peach, etc.,) tissue testing is the only way by which you can monitor the plant's nutrient needs. * For turf nutrient management evaluation. How to take samples The normal tendency of individuals is to collect the stunted plants and conduct an analysis of the plant tissue to diagnose a nutrient related problem. Plant sampling, however, is more complicated if we expect tissue analysis to be an effective diagnostic tool. Technologies and procedures used in the collection of plant samples vary with the intended purpose. Instructions for sampling and submitting samples as specified by the lab should be followed to get meaningful results. If specific sampling instructions are not found for the crops, the general rule of thumb is to sample upper, recently matured leaves. The recommended time to sample is just prior to the beginning of the reproductive stage for many plants. Paired samples Where a deficiency is suspected, take samples from normal plants in an adjacent area as well as from the affected area. You will be charged the price of one and a half sample when an abnormal sample is accompanied by a normal sample. It is important to take a soil sample from each area. Comparing soil and plant analysis results can greatly assist in the interpretations. Handling Procedures Collected plant tissue is very perishable and requires special handling to avoid decomposition. Therefore, fresh plant tissue should be placed in clean paper bags left open; partially air dried if possible or kept in a cool environment during shipment to the laboratory. Wash dusty plants before airdrying. Fresh plant samples should not be placed in closed plastic bags unless the tissue is either air-dried or bag and contents are kept cool (40 degrees). Airdrying of fresh plant tissue can be done by placing the plant tissue in an open, dry environment for 12 to 24 hours. Air died samples can be place in a clean brown bag or envelop and take mailed to the lab. What Not To Sample * Tissue covered with soil or dust * Plants damaged by insects, mechanically injured, or diseased * Tissue from dead plants or tissues * Plants under moisture or temperature stress * Plants markedly effected by nutritional stress * Border-row plants or end-row plants * Plants in weed infested areas * Whole plants unless seedlings How, when and what part to sample? Since the results of the plant analysis will be compared to known standards, it is important that parts of plants are sampled at a certain stage of development. Some examples of field crops sampling guides are given below: Corn When to sample? Some time between emergence and silking/pollination. Do not sample after silks have dried. Nutrient concentrations decline substantially after this point in the life cycle and recognized standards cannot be used for comparison. Plant part to sample: Seedling stage- all above ground portion (10-15 plants). Prior to tasseling- the entire leaf fully developed below the whorl (10-12 plants). Tasseling and shooting to silkingthe entire leaf at the ear node (10-12 plants) Soybean When to sample? The ideal time is when the first bloom appears. However, if problems appear prior to bloom, a sample can be taken. Do not sample after the first pods begin to fill. Plant part to sample: Seedling stage- all the above ground portion (10-15 plants). Prior to or during flowering- Two or three fully developed trifoliate leaves at the top of the plant. (10-15 plants). Small Grain When to sample? Any time before head emerges. Plant part to sample: Seedling stage- all the above ground portion. (15-30 plants). Prior to heading- select tissue from upper one third of plant. (15-30 plants). Alfalfa and Clovers When to sample? Just prior to bloom (1/10 bloom) or at harvest stage. Plant part to sample: Take top 6 inches of plant or top 1/3 of plant. (20-25 plants). Sorghum When to sample? Ideal time is when head is fully emerged but before pollination. Samples may be taken at earlier stage if problem develops. Plant part to sample: Fully expanded and mature leaves. (10-12 plants). Cotton When to sample? Before bolls start to set. Plant part to sample: The most recently matured leaves. (15-20 plants). When specific information is not available use general rule of thumb If specific sampling instructions are not found in the selected crops, the general rule of thumb is to sample upper, recently matured leaves. The recommended time to sample is just prior to the beginning of the reproductive stage for many plants. Submitting Plant Samples Samples can be submitted to the County Extension Centers or to the lab directly. Plant Analysis Information forms can be picked up at the County Extension Centers or at the University of Missouri-Columbia Soil Test Lab free of charge or can be printed from the lab’s Website at http://soilplantlab.missouri.edu/soil. Each sample submitted to the lab should be accompanied by a Plant Analysis Information form. When submitting a sample to the lab the sample information form should be filled out accurately for the lab to properly interpret the plant analysis. Send the original form with the plant sample(s) to the following address and retain a copy for your records. MU Soil and Plant Testing Lab University of Missouri Columbia 23 Mumford Hall Columbia, MO 65211 Tel: 573-882-0623 Fax: 573-884-4288 E-mai l :SoilTestingServices@missouri.edu. Web: http://soilplantlab.missouri.edu/soil. Manjula V. Nathan, Director, MU Soil Testing and Plant Diagnostic Service Laboratory NathanM@missouri.edu ********************************************************************** Potential for Economic Infestations of Black Cutworm Larvae By Wayne Bailey Intensive captures of BCW moths continue to be recorded for several locations in Missouri. Intensive captures of moths indicate heavy moth activity which may result in problems with black cutworm larvae in field corn. At present, the Missouri Black Cutworm Predictive Model is predicting possible damage resulting from this pest during the 2nd to 3rd week of May. Some locations will record multiple intensive captures which indicate the possibility of multiple infestation dates of larvae. Predicted dates of first cutting are updated daily as local weather conditions are incorporated into the model. Intensive trap captures and predicted dates of first cutting by 4th instar black cutworm are listed by locations reporting moth intensive captures: Ray County (Richmond): Intensive capture date, 4/11/2007. Predicted first cutting, 5/15/2007. Barton County (Lamar): Intensive capture date, 4/13/2007. Predicted first cutting, 5/13/2007. Callaway County (Fulton): Intensive capture date, 4/18/2007. Predicted first cutting, 5/20/2007. Audrain County (Mexico): Intensive capture date, 4/2/2007. Predicted first cutting, 5/17/2007. Knox County (Edina): Intensive capture date, 4/25/2007. Predicted first cutting, 5/23/2007. Franklin County (Union): Intensive capture date, 4/20/2007. Predicted first cutting, 5/23/2007. Intensive moth captures do not always result in economic infestations of black cutworm, but do predict a date of first cutting. Scouting activities should occur from first emergence of corn plants and continue through the 5th leaf stage of plant development. If this is not possible, then scouting of fields should begin a minimum of one week prior to the predicted date of cutting. Early damage by black cutworm larvae smaller than 4th instars may be visible as leaf feeding on corn plants. For more information on the black cutworm predictive model and the counties currently monitoring for black cutworm, please visit our Website at: http://ipm.missouri.edu/pestmonitoring/blackcutworm/index.htm. Although the economic threshold for black cutworm varies from state to state, under normal conditions in Missouri treatment is recommended when cutting of corn seedlings reach or exceed 4-6 percent cutting above ground and 2-3 percent cutting below ground. These thresholds are based on the location of the plant growing point at the time of cutting by black cutworm. Rescue Insecticides for Control of Black Curworm in Field Corn |-------------------------------------------------------------------------------------------------------| |Chemical name | Trade name | Rate of Formulated | Placement/Comments | | | | Material/Acre | | |-------------------|---------------------|-------------------------------|-----------------------------| |esfenvalerate | *Asana XL | 5.9 to 9.6 fl oz/acre | foliar broadcast - rescue | |-------------------|---------------------|-------------------------------|-----------------------------| |beta-cyfluthrin | *Baythroid XL | 0.8 to 1.6 fl oz/acre | foliar broadcast - rescue | |-------------------|---------------------|-------------------------------|-----------------------------| |bifenthrin | *Capture 2EC | 1.47 to 2.2 fl oz/acre | foliar broadcast - rescue | | | *Capture LFR | (2ee MO label) | | |-------------------|---------------------|-------------------------------|-----------------------------| |bifenthrin | *several products | 3.4 fl oz/acre | foliar broadcast - rescue | |-------------------|---------------------|-------------------------------|-----------------------------| |bifenthrin | *Lorsban 4E | see specific labels | foliar broadcast - rescue | |-------------------|---------------------|-------------------------------|-----------------------------| |chlorpyrifos | *numerous products | 1 to 4 pts/acre | foliar broadcast - rescue | |-------------------|---------------------|-------------------------------|-----------------------------| |chlorpyrifos | *Mustang Max | see specific labels | foliar broadcast - rescue | |-------------------|---------------------|-------------------------------|-----------------------------| |zeta-cypermethrin | Pounce 3.2EC | 1.28 to 2.8 fl oz/acre | foliar broadcast - rescue | |-------------------|---------------------|-------------------------------|-----------------------------| |permethrin | Pounce 3.2EC | 4.0 to 8.0 fl oz/acre | foliar broadcast - rescue | | | | 0.3 to 0.6 fl oz/1000 ft row | foliar broadcast - rescue | |-------------------|---------------------|-------------------------------|-----------------------------| |permethrin | *numerous products | see specific labels | foliar broadcast - rescue | |-------------------|---------------------|-------------------------------|-----------------------------| |gamma-cyhalothrin | *Proaxis | 1.92 to 3.20 fl oz/acre | foliar broadcast - rescue | |-------------------|---------------------|-------------------------------|-----------------------------| |Lambda-cyhalothrin | *Warrior | 1.92 to 3.20 fl oz/acre | foliar broadcast - rescue | |-------------------------------------------------------------------------------------------------------- ********************************************************************** Increasing Aphid Populations in Wheat By Wayne Bailey Bird cherry-oat aphids and greenbugs can be found in increasing numbers in most wheat fields in the state. These aphids can cause direct feeding damage by sucking plant juices, but may also transmit barley yellow dwarf virus (BYD) in wheat. Greenbugs are light or pale green in color with a predominant dark green line running down the back. They may damage wheat plants in both fall and spring, but generally migrate into the state each spring. At present very low numbers of greenbug are present, but these populations can change rapidly depending on weather conditions and the number of beneficial insects present. Thresholds for this aphid are based on the average number of aphids present per foot of row depending on plant height and stage of growth. In general, traditional economic thresholds would be as follows: treatment is justified if 50 or more aphids are present per linear foot of row in the seedling stage; 100 or more present during the three- to sixinch stage of growth, and 300 or more aphids when the plants reach six- to ten-inches in height. Recent research in Missouri and other states suggest that these thresholds may be too high and allow for more damage and subsequent yield loss than necessary. Much of this variability is due to plant size, stand density when infestations occur, the variety of wheat under production, the number of aphids and amount of BYD virus present, and spring growing conditions. Another factor to consider is whether biological control agents such as ladybugs and parasitic wasps are active in the field. Based on the preceding information, the recommendation for management of the greenbug is as follows: Scout several locations in the field to determine number of aphids present per linear foot of row or number of aphids per tiller. If the average number of greenbug per linear foot of row equal or exceed 50 to 100 on wheat less than six-inches in height, then treatment may be needed. Producers should consider the number of beneficial insects present (examples: adults and larvae of pink ladybugs and other species of ladybird beetles, parasitic wasps) and whether the wheat is under other stressors such as drought. The presence of high numbers of beneficial insects will increase the threshold and reduce the need for insecticides, whereas, the greater the stress on the plants, the lower the thresholds as stressed plants are less able to withstand aphid infestations. The bird cherry-oat aphid is typically dark olive in color with a rosy patch of color found on the back of the abdomen. This is a relatively large aphid which can look black in color at times. This insect is present in wheat in most years, but is often control by beneficial insects. The bird cherry-oat aphid can transmit BYD, but because this aphid often attacks the wheat at boot to heading stages of growth, thresholds are based on numbers of aphids present per tiller. In general, if an average of 25- 50 or more bird cherry-oat aphids are present per tiller when the wheat is in the boot to heading stages of growth, then treatment is justified. The lower threshold is appropriate if plants are under additional stressors such as severe drought. Feeding by this aphid may result in damage to the flag leaf with the head taking on a hooked appearance as it emerges. We will continue to monitor this pest over the next couple of weeks. Recommended Insecticides for Control of Aphids in Wheat |----------------------------------------------------------------------------------------| |Chemical name | Trade name | Rate of Formulated | Placement/Comments| | | | Material/Acre | | |-------------------|--------------------|--------------------------|--------------------| |diamethoate | *Dimethoate | see specific labels | foliar broadcast | |-------------------|--------------------|--------------------------|--------------------| |chlorpyrifos | *Lorsban 4E | 0.5 to 1 pts/acre | foliar broadcast | |-------------------|--------------------|--------------------------|--------------------| |chlorpyrifos | *numerous products| see specific labels | foliar broadcast | | | Malathion | see specific labels | foliar broadcast | |-------------------|--------------------|--------------------------|--------------------| |zeta-cypermethrin | *Mustang Max | 3.2 to 4.0 fl oz/acre | foliar broadcast | |-------------------|--------------------|--------------------------|--------------------| |microencapsulated | *Penncap-M | 2 to 3 pts/acre | | |methyl parathion | | | | |-------------------|--------------------|--------------------------|--------------------| |gamma-cyhalothrin | *Proaxis | 3.84 fl oz/acre | foliar broadcast | |-------------------|--------------------|--------------------------|--------------------| |lambda-cyhalothrin | *Warrior | 3.84 fl oz/acre | foliar broadcast | |-------------------|--------------------|--------------------------|--------------------| |lambda-cyhalothrin | *Several products | see specific labels | foliar broadcast | -----------------------------------------------------------------------------------------| Read and follow all label direction, precautions, and restrictions. * Designated a restricted use product. Wayne Bailey 573-864-9905 (cell) BaileyW@missouri.edu ********************************************************************** True Armyworm Moths Numerous in Some Areas of Western Missouri By Wayne Bailey Elevated numbers of true armyworm moths are being captured in traps along the western side of the state. Highest numbers have been reported by MU extension agronomist Jay Chism in Barton county. It is unknown whether this population of moths will result in economic infestations of larvae, but the potential does exist. Migrating adults from more southern states or moths produced in Missouri from overwintering pupae often select grass pastures, wheat, fescue seed fields or occasionally field corn as their preferred egg laying sites during early spring. In most years three to four generations of true armyworm are produced in Missouri. First generation larvae typically damage field crops with later generations attacking grass lawns. In some years this insect will feed only on plant foliage, whereas in other years armyworms may feed on foliage plus cut seed heads from both tall fescue plants and wheat. Tall fescue seed fields are generally first attacked followed by wheat fields when armyworm populations reach outbreak levels. Rank or dense fields of grasses or wheat are common infestation sites for this pest. True armyworm moths have grayishbrown to tan forewings each with a white spot in the center and grayishwhite hind wings. Eggs are greenishwhite in color, but darken just prior to hatch. Young larvae are pale green in color but change to dull greenishyellow to brown as they grow. Larvae have smooth bodies with three dark lines running the length of the worm (one on top and one down each side). The main identifying characteristic for true armyworm larvae is the presence of a dark triangle or spot located on the outside of each of the four pair of prolegs (legs found near the center of the caterpillar’s body). The head capsule is greenish-tan and mottled with darker brown coloration. Producers should scout tall fescue forage, tall fescue seed, and wheat fields to determine if armyworm larvae are present in economically damaging numbers. Scouting for armyworm is best done at night or during early morning. Armyworm larvae are nocturnal (night) feeders and generally remain hidden during bright, sunny days. Larvae typically feed on foliage from the soil surface upward. This often results in the canopy of an infested fescue field looking normal on one day and disappear the next as larvae complete their feeding on the host plant by consuming the remaining upper foliage. Larvae grow to about 1.5 inches in length, and often move from field to field as each food source is exhausted. Treatment is warranted when an average of four or more nonparasitized, half-grown or larger worms per square foot are present during late spring and before more than two-three percent of the heads are cut from fescue stems or wheat. In some years it may be necessary to control armyworm in grass pastures not used for fescue seed production. If defoliation of grass pastures by armyworm reach levels where control is needed, insecticides labeled for use against armyworm in grass pastures are the same as those for fescue Insecticides Recommended for Control of True Armyworm in Wheat |--------------------------------------------------------------------------------------| |Chemical name | Trade name | Rate of Formulated | Placement/Comments| | | | Material/Acre | | |-------------------|------------------|--------------------------|--------------------| |zeta-cypermethrin |*Mustang Max | 1.76 to 4.0 fl oz/acre | foliar broadcast | |-------------------|------------------|--------------------------|--------------------| |gamma-cyhalothrin |*Proaxis | 1.92 to 3.20 fl oz/acre | foliar broadcast | |-------------------|------------------|--------------------------|--------------------| |spinosad |Success | 3 to 6 fl oz./acre | foliar broadcast | |-------------------|------------------|--------------------------|--------------------| |spinosad |Tracer 4SC | 1.o to 3.0 fl oz/acre | foliar broadcast | |-------------------|------------------|--------------------------|--------------------| |lambda-cyhalothrin |*Warrior | 1.92 to 3.20 fl oz/acre | foliar broadcast | |-------------------|------------------|--------------------------|--------------------| |lambda-cyhalothrin |*several products | see specific label | foliar broadcast | |--------------------------------------------------------------------------------------- Read and follow all label direction, precautions, and restrictions. * Designated a restricted use product. Insecticides Recommended for Control of True Armyworm in Tall Fescue. |----------------------------------------------------------------------------------| |Chemical name | Trade name | Rate of Formulated | Placement/Comments| | | | Material/Acre | | |------------------|---------------|--------------------------|- ------------------| |zeta-cypermethrin | *Mustang Max | 1.76 to 4.0 fl oz/acre | foliar broadcast | |------------------|---------------|--------------------------|- ------------------| |spinosad | Success | 3 to 6 fl oz./acre | foliar broadcast | |------------------|---------------|--------------------------|- ------------------| |spinosad | Tracer 4SC | 1.o to 3.0 fl oz/acre | foliar broadcast | -----------------------------------------------------------------------------------| ********************************************************************** Alfalfa Weevil Larvae Still Present in Many Fields By Wayne Bailey Alfalfa weevil larvae have survived the cold weather and are still feeding in many central and northern and some southern Missouri alfalfa fields. Larvae continue to feed on foliage in fields which were not harvested following the freezing conditions. In fields that were harvested, larvae are present on the soil surface where they are feeding on developing plant tillers. Both types of feeding by larvae can result in economic damage to the alfalfa crop. In fields where adult weevil numbers are high, an insecticide application may be needed to prevent the adult weevils from girdling the new stems and limiting tiller growth. Fields in which alfalfa weevil larvae and adults are allowed to feed on developing tillers often exhibit heavy weed growth due to the lack of an alfalfa canopy. Producers are encouraged to scout alfalfa fields and determine numbers of alfalfa weevil larvae and adults. The threshold of an average one or more larvae present per alfalfa stem is still valid, but difficult to determine if plants are no longer standing. Treatment thresholds for larvae and adults feeding on tillers have not been determined, but treatment is recommended if either feeding by larvae or adult alfalfa weevils is preventing alfalfa tiller regrowth. Recommended Insecticides for Adult Alfalfa Weevil Control - 2007. Insect Pest |-----------------------------------------------------------------------------------------------------| | | Chemical name | Common name | Rate of Formulated | Rate of Active | | | | | Material | Ingredient (a.i.) | | |-------------------------------------------------------------------------------------| | | Carbofuran | *Furadan 4F | 1 to 2 pts/acre | 0.5 to 1 lb/acre | | |-------------------------------------------------------------------------------------| |Alfalfa weevil | Chlorpyrifos 4E | *Lorsban 4E | 1 to 2 pts/acre | 0.5 to 1 lb/acre | | Adults: | | *numerous products | see specific labels | see specific labels| | |-------------------------------------------------------------------------------------| | | Methyl Parathion | *Chemnova Methyl 4EC | 1 pt/acre | 0.5 lb a.i./acre | | |-------------------------------------------------------------------------------------| | | Phosmet | Imidan | see specific label | see specific label | |-----------------------------------------------------------------------------------------------------| Read and follow all label direction, precautions, and restrictions. Be aware of preharvest restrictions following insecticide application to alfalfa crop. * Designated a restricted use product. Recommended Insecticides for Larval Alfalfa Weevil Management - 2007 Insect Pest |--------------------------------------------------------------------------------------------------------------------| | | Chemical name | Common name | Rate of Formulated | Rate of Active | | | | | Material | Ingredient (a.i.) | | |----------------------------------------------------------------------------------------------------| | | Beta-cyfluthrin | *Baythroid XL | 1.6 to 2.8 fl oz/acre | 0.0125 to 0.022 lb a.i./acre | | |----------------------------------------------------------------------------------------------------| | | Carbofuran | *Furadan 4F | 1/2 to 2 pts/acre | 0.25 to 1 lb/acre | | |----------------------------------------------------------------------------------------------------| | | Chlorpyrifos 4E | *Lorsban 4E | 1 to 2 pts/acre | 0.5 to 1 lb/acre | | | | *numerous products | see specific labels | see specific labels | | |----------------------------------------------------------------------------------------------------| |Alfalfa weevil | Methyl Parathion | *Chemnova Methyl 4EC| 1 pt/acre | 0.5 lb a.i./acre | | Larvae: |----------------------------------------------------------------------------------------------------| | | Gamma-cyhalothrin | *Proaxis | 2.56 to 3.84 fl oz/acre| 0.02 to 0.03 lb a.i./acre | | |----------------------------------------------------------------------------------------------------| | | Phosmet | Imidan | see specific label | see specific label | | |----------------------------------------------------------------------------------------------------| | | Zeta-cypermethrin | *Mustang Max | 2.24 to 4.0 fl oz/acre | 0.014 to 0.025 lb a.i./acre | | |----------------------------------------------------------------------------------------------------| | | Carbaryl | Sevin 4F | 1.5 qts/acre | 1.5 lb a.i./acre | | |----------------------------------------------------------------------------------------------------| | | Carbaryl | Sevin XLR Plus | 1.5 qts/acre | 1.5 lb a.i./acre | | |----------------------------------------------------------------------------------------------------| | | Lambda-cyhalothrin | *Warrior | 2.56 to 3.84 fl oz/acre| 0.02 to 0.03 lb a.i./acre | | | | *Numerous products | see speciic labels | see specific labels | |--------------------------------------------------------------------------------------------------------------------| Wayne Bailey 573-864-9905 (cell) BaileyW@missouri.edu ********************************************************************** Spraying Windows on Horizon Point Prevent Drift By Bill Casady How many times have we said something like "If I just had a crystal ball, I could tell you about tomorrow’s weather." It’s still true that we never know until after the fact just exactly what the records will say, but scientists have made a lot of progress in weather forecasting since the first almanacs and observations. There are a lot of things you can do in a stiff wind, but spraying crop protection materials is not one of them. Of course there will always be some wind, but selecting a less windy window will maximize effi cacy and help prevent spray drift. The wind report on Horizon Point e-mails is a great tool for watching, learning and planning when to spray. The e-mails are is available as a service to Missourians through http://agebb.missouri.edu/horizonpoint/. Horizon Point provides much more than a simple weather forecast, but for spraying purposes, you may be interested primarily in the wind forecast for the next couple of days. As you study the wind, patterns often emerge, but there are always exceptions. The most common pattern is for winds to calm through the night and to pick up during the advent of daily heating, decreasing again into the early evening hours. Weather systems with dramatic frontal boundaries change all of the rules, but that’s where Horizon Point e-mails help to frame up your spraying plans. One day might bring a fairly constant or even gusty strong wind, but the next day may provide a couple of nice windows of relative calm. The three-hour Horizon Point wind forecast can help identify those windows of opportunity so that the sprayer is ready when the wind subsides. For more information and to sign up for the free e-mails, visit the Horizon Point website or for specific questions about how to get started call 573- 884-6311 or e-mail HorizonPoint@ missouri.edu. Bill Casady 573 882-4370 CasadyW@missouri.edu ********************************************************************** Weather Data for the Week Ending April 30, 2007 By Pat Guinan -------------------------------------------------------------------------------- | Monthly | Growing Weekly Temperature (deg. F) |Precip (in.)|Degree Days^ -----------------------------|------------|------------ Ext- Ext- Depart| Depart|Accum Depart Avg.Avg. reme reme from |Apr 1 from |since from Station County Max.Min. High Low Mean avg. |Apr 30 avg |Apr 1 avg. ------------------------------------------------------|------------|------------ Corning Atchison 72 50 90 43 61 +5 | 2.94 -0.22 | 207 +118 St. Joseph Buchanan 71 52 86 43 61 +4 | 2.07 -1.55 | 196 +77 Brunswick Chariton 74 51 88 44 62 +4 | 2.70 -0.61 | 201 +74 Albany Gentry 70 48 88 39 60 +3 | 2.14 -1.68 | 167 +70 Auxvasse Audrain 75 53 85 46 63 +5 | 3.88 +0.18 | 207 +80 Columbia Boone 74 52 84 46 63 +5 | 3.92 -0.30 | 209 +52 Sanborn Field Boone 76 53 86 47 64 +5 | 3.53 -0.70 | 234 +67 Williamsburg Callaway 76 52 87 45 64 +7 | 4.45 -0.03 | 217 +90 Novelty Knox 70 50 83 46 60 +2 | 4.17 +0.84 | 161 +44 Linneus Linn 72 49 85 45 61 +4 | 2.67 -0.74 | 180 +74 Monroe City Monroe 73 50 84 45 61 +3 | 3.28 -0.06 | 176 +41 Versailles Morgon 75 53 85 46 64 +5 | 4.03 -0.28 | 233 +41 Green Ridge Pettis 73 51 82 42 62 +5 | 3.80 -0.26 | 202 +86 Lamar Barton 73 51 83 44 62 +3 | 3.88 -0.54 | 213 +20 Cook Station Crawford 77 48 87 43 63 +3 | 4.13 -0.08 | 213 +9 Alley Spring Shannon 78 48 89 41 63 +4 | 2.97 -1.27 | 202 +22 Round Spring Shannon 79 49 91 42 64 +5 | 3.44 -0.81 | 206 +25 Delta Cape 80 55 89 51 67 +6 | 3.09 -0.95 | 250 +7 Girardeau | | Cardwell Dunklin 78 57 89 53 67 +4 | 3.64 -1.06 | 282 -22 Clarkton Dunklin 79 56 89 52 67 +4 | 2.40 -1.95 | 264 -30 Glennonville Dunklin 79 56 88 53 67 +4 | 2.56 -1.65 | 272 -24 Charleston Mississippi 78 56 87 52 68 +7 | 2.80 -1.76 | 268 +30 Portageville- 79 58 89 54 68 +5 | 3.03 -1.65 | 294 +1 Delta Center Pemiscot | | Portageville- 79 58 90 54 68 +6 | 2.94 -1.76 | 294 +7 Lee Farm Pemiscot | | Steele Pemiscot 79 57 91 54 68 +5 | 3.42 -1.37 | 299 +9 -------------------------------------------------------------------------------- ^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 GuinanP@missouri.edu