Vol. 17, No. 14 July 13, 2007 White Grubs in Corn, Soybean and Wheat By Wayne Bailey This spring many problems with white grubs have occurred in several different crops. The mature stage of white grubs may be any one of several May and June beetle species. Some are considered annual grubs with a one year life cycle beginning in early summer when eggs are laid and larvae emerge to feed and eventually overwinter in the soil. The life cycle is completed the following spring and summer when the grubs mature, pupate in the soil, and emerge as beetles to feed, mate, and lay eggs for the next generation. Many additional white grub species exhibit a perennial life cycle in which the larval stage or grubs remain in the soil for 3 or 4 years before emerging as beetles. Many white grub species do not have common names, but are identified only by scientific Latin names. Some common annual grub species include northern and southern masked chafers, Japanese beetles and green June beetles. White grubs have always been present in field crops with most damage reported from corn and soybean fields. In recent years white grub problems also have been observed in wheat and grass pastures during spring. In all cases damage is often seen as large circles of dead, dying, or stunted (sometimes yellow) plants. In wheat, severe grub damage can be seen as large circles of weeds in fields during late spring although feeding by the grubs occurred either the previous fall or during early spring when the wheat plants were destroyed and replaced by weeds. Traditionally, effective management of white grub infestations has been accomplished through pre-plant or planting-time insecticide applications which were often applied for control of other insect species. With the recent adoption of Bt corn varieties and insecticide seed treatments, the amount of insecticides used during early spring has been reduced in Missouri. White grub is listed on the label of most insecticide seed treatments which research shows provide protection from insect pests for about 45 to 60 days following plant emergence. It has also been observed in Missouri that white grub populations can be reduced by the use of insecticide treated seed. Data gathered from submitted grub samples and field visits suggest that a majority of white grub problems in Missouri originate from grubs with annual life cycles. Perennial grub problems do occur, but account for about half as many infestations in most years as annual grubs. So why are steadily increasing number of May and June beetles being captures in our light traps and higher numbers of white grub larvae being observed in Missouri crop fields? No one knows for sure, but several factors can influence numbers of white grub beetles and larvae. There is a normal cycle for most insect populations which fluctuates over a several year period. Weather, soil conditions, insecticide use, crop rotations, crop residue management, tillage practices, beneficial insects, pest life cycles, soil type, organic matter content and many other factors may also influence pest numbers in any one year. Rescue of corn or soybean crops from white grub infestations is difficult after the crop has been planted. Few insecticides are available for rescue applications for white grubs in field crops. In fields with frequent white grub problems soil insecticides, broadcast insecticide applications at planting, and seed treatments all offer some control. At this time in the season, white grub problems in field crops are difficult to control unless the crop is replanted. Two factors are often present at the location of white grub infestations in field crops. They include the presence in field borders of willow, cottonwood, or other trees often associated with river bottom areas and drainage ditches. The beetles congregate on these trees, especially willows, to feed and mate. The female beetles will then return to surrounding fields to lay eggs. The second factor often associated with white grub infestations is the presence of cattle and/or previous feeding of hay bales in the crop field experiencing white grub problems. Wayne Bailey BaileyW@missouri.edu ********************************************************************* Corn Foliage Diseases By Laura Sweets After a slow start many corn fields have really “taken-off” and plants have increased substantially in size. Foliage diseases are showing up in scattered, isolated fields. So far low levels of Stewart’s bacterial wilt, common rust and gray leaf spot have been reported. In most cases these diseases are showing up on the lower leaves to mid-canopy but are not yet on the ear leaves. Generally speaking with the corn foliage diseases, the later in the season (especially the longer after pollination) that the foliage disease becomes established, the lower direct yield losses will be. Highest yield losses occur if diseases such as rust or gray leaf spot develop prior to pollination. Also, most of the corn foliage diseases are favored by extended periods of free moisture on the leaf surfaces. This moisture can be from rain, overhead irrigation or heavy dews that stay late in the day. Fields with poor air movement, river bottom fields or shaded portions of fields may also have higher levels of corn foliage diseases. Most of the control recommendations for minimizing losses due to corn foliage diseases are preventative measures such as planting resistant hybrids, rotating crops so the corn doesn’t follow corn in the same field or tillage to reduce the amount of infected residue left on the soil surface. Several fungicides are labeled for use on corn to control foliage diseases. Please see the accompanying table of foliar fungicides labeled for use on corn. Fields with high levels of various foliage diseases may also show higher levels of stalk rot this fall. As harvest approaches, check fields which have had foliage disease problems for stalk rot and try to harvest problem fields promptly. Symptoms of Common Corn Foliage Diseases Anthracnose (Colletotrichum graminicola) Infection is most common on lower leaves of young plants but may occur on upper leaves of maturing plants too. Anthracnose lesions tend to be brown, spindle-shaped lesions with yellow to reddish-brown borders. Concentric rings or zones are sometimes apparent within the diseased areas. Stalk symptoms appear as black linear streaks on the surface of lower internodes late in the season. Holcus Leaf Spot (Bacterial leaf spot) Lesions usually are oval to rectangular in shape. Initially, they are dark-green and water soaked. Later they become dry and turn light brown with a reddish margin. The lesion resembles parchment paper. Holcus leaf spot may occur a few days after a rain storm but does not usually cause serious losses. Common Rust (Puccinia sorghi) Circular to elongate, golden-brown to reddish-brown pustules develop on both upper and lower leaf surfaces. As plants mature, the pustules become brownish-black. The pustules rupture, revealing powdery brown spores. Southern Rust (Puccinia polysora) Light, reddish-brown, circular to oval pustules develop primarily on the upper leaf surface. Eventually pustules rupture to reveal powdery spores. Later a brownish-black spore stage often forms in rings around the initial pustules. Gray Leaf Spot (Cercospora zeae-maydis) Lesions on maturing corn are pale brown to reddish-brown and blocky to rectangular in shape when compared to other corn leaf blights. The lesions typically are restricted by leaf veins giving the lesions parallel edges. Older lesions have a gray cast. Lesions may merge, resulting in large areas of dead leaf tissue. Lesions usually develop first on lower leaves but under favorable weather conditions, extensive leaf blighting over the entire plant may occur. Northern Corn Leaf Blight (Exserohilum turcicum) Long, elliptical, grayish-green or tan lesions ranging from 1.0-6.0 inches in length develop on the lower leaves. As the season progresses, nearly all leaves of a susceptible plant may be covered with lesions, giving this plant the appearance of having been injured by frost. During damp weather, dark olive-green to black spores may be produced across surface of lesions. Southern Corn Leaf blight ( Bipolaris maydis) Lesions are small, tan with buff to brown borders and somewhat elliptical in shape. Lesion appearance may vary greatly with genetic background of hybrids. Lesions may merge, blighting or killing large areas of leaf tissue. Northern Corn Leaf Spot (Bipolaris zeicola) Lesions are small, tan to reddish-brown and oval to circular in shape. Over time the lesions may become more tan to grayish-tan in color and be surrounded by a light to darkly pigmented border. Eyespot (Kabatiella zeae) Initial symptoms are small, translucent, circular to oval lesions with yellowish haloes. Later lesions develop tan to cream centers surrounded by a brown or purple ring with a narrow, yellow halo. Lesions may coalesce to from large areas of dead leaf tissue. Laura Sweets SweetsL@missouri.edu ********************************************************************* Foliar Fungicides Labeled for Use on Field Corn By Laura Sweets In addition to crop rotation, residue management and resistant hybrids, foliar fungicides can be used to control corn foliage diseases. Products labeled for use on field corn are listed in the following table. Fungicide labels do differentiate among field corn, seed corn, sweet corn and processing sweet corn. Other products not listed in this table may be labeled for use on other types of corn. The following table was prepared using current company product labels and manufacturers’ Web sites. However, label registrations can change at any time. Before using any agricultural pesticide, read and follow directions accompanying that product. Product names have been used for clarity. Reference to specific trade names does not imply endorsement by the University of Missouri; discrimination is not intended against similar products not listed. Trade Name Company Common Chemical Name % of Active Ingredients Rate Additional Label Information Bumper 41.8 EC Makhteshim-Agan propiconazole 41.80% 2.0 to 4.0 fl oz per acre For control of Helminthosporium leaf blights (Helminthosporium maydis, H. turcicum, and H. carbonum), rusts, gray leaf spot, and eye spot, apply Bumper 41.8 degrees Celsius by ground or aerial application or through irrigation equipment according to the following schedule: Helminthosporium leaf blights: apply 2.0 to 4.0 fl oz of Bumper 41.8 degrees Celsius per acre when disease first appears and continue on a 7 to 14 day schedule. Rusts: apply 4.0 fl oz of Bumper 41.8 degrees Celsius per acre when rust pustules first appear and continue on a 7 to 14 day schedule. Gray leaf spot and eye spot: apply 4.0 fl oz of Bumper 41.8 EC per acre when disease first appears. If conditions favorable for disease persist, continue to apply on a 14 day schedule. Do not apply Bumper 41.8 degrees Celsius to field corn and field corn grown for seed after silking. Do not apply more than 16 fl oz of Bumper 41.8 degrees Celsius per acre per season. Do not harvest field corn, field corn grown for seed or popcorn for forage within 30 days of last application. Dithane DF Rainshield Dow AgroSciences mancozeb 75.00% 1.5 lb per acre For control of common corn rust and Helminthosporium leaf blight on field corn and hybrid seed corn. Start applications when disease symptoms first appear and, depending on severity of infection, continue on a 4 to 14 day schedule. The addition of Latron CS-7 will improve performance. Amount of product that can be applied over course of season will vary with formulation- see label. Do not apply within 40 days of harvest. Dithane F-45 Rainshield Dow AgroSciences mancozeb 37.00% 1.2 qt per acre Dithane M45 Dow AgroSciences mancozeb 80.00% 1.5 lb per acre Headline BASF pyraclostrobin 23.60% 6.0 to 9.0 fl oz per acre or 9.0 to 12.0 fl oz per acre The 6.0 to 9.0 fl oz per acre rate targets common rust, southern rust and gray leaf spot. The 9.0 to 12.0 fl oz per acre rate targets anthracnose, northern corn leaf blight, northern corn leaf spot, Physoderma brown spot, southern corn leaf blight and yellow leaf blight. For optimal disease control, begin applications of Headline prior to disease development and continue on a 7- to 14- day interval if conditions are conducive for disease development. Use the higher rate and shorter interval when disease pressure is high. Headline may be used with adjuvants. Headline may be applied by ground sprayer, aerial equipment or through sprinkler irrigation systems. See label for information on resistance management. Minimum time from last application to harvest (PHI) is 7 days. Manzate Pro-Stick DuPont mancozeb 75.00% 1.5 lb per acre For control of common rust, Helminthosporium leaf blight and gray leaf spot on field corn and field corn for hybrid seed production. Use sufficient water for thorough coverage. Start applications when disease first appears and repeat at 4 to 7 day intervals. Do not apply more than 15 lb or 12 qt/ acre/ season. Do not feed treated forage to livestock. Do not apply within 40 days of harvest. Manzate Flowable Griffin L.L.C. mancozeb 37.00% 1.2 qt per acre Penncozeb 4FL Cerexagri mancozeb 37.00% 0.8 to 1.2 fl oz per acre For control of common rust, gray leaf spot and Helminthosporium leaf blight on field corn and corn grown for seed. Start application at the onset of disease and repeat as needed. Amount of product that can be applied over course of season will vary with formulation- see label. Do not apply within 40 days of harvest. Penncozeb 75DF Cerexagri mancozeb 75.00% 1.0 to 1.5 lb per acre Penncozeb 80WP Cerexagri mancozeb 80.00% 1.0 to 1.5 lb per acre PropiMax EC Dow AgroSciences propiconazole 41.80% 2.0 to 4.0 fl oz per acre For control of Helminthosporium leaf blights (Helminthosporium maydis, H. turcicum and H. carbonum), rusts (Puccinia spp.), gray leaf spot (Cercospora zeae maydis), and eye spot (Kabatiella zeae), apply PropiMax EC by ground or aerial application or through irrigation equipment according to the following schedule: Helminthosporium leaf blights: apply PropiMax EC at the rate of 2-4 fl oz per acre when disease first appears and make repeat applications on a 7 to 14-day schedule. Rusts: apply PropiMax EC at the rate of 4 fl oz per acre when rust pustules first appear and continue on a 7 to 14-day schedule. Gray leaf spot and eye spot: apply PropiMax EC at the rate of 4 fl oz per acre when disease first appears. If conditions favorable for disease persist, continue to apply on a 14-day schedule. Do not apply PropiMax EC to field and field corn grown for seed after silking. Do not apply more than 16 fl oz of PropiMax EC per acre per season. Do not harvest field corn, field corn grown for seed, or popcorn for forage within 30 days of application. Quadris Syngenta azoxystrobin 22.90% 6.0 to 9.0 fl oz per acre for rust (Puccinia sorghi) 9.0 to 15.5 fl oz per acre for anthracnose leaf blight, gray leaf spot, northern corn leaf blight, northern corn leaf spot, southern corn leaf blight or eyespot For control of rust, gray leaf spot, northern corn leaf blight and northern corn leaf spot on field, pop and sweet corn (includes seed production). For gray leaf spot, apply Quadris at the onset of disease. A second application may be required 14 days later if disease pressure persists. For all other diseases, Quadris applications should begin prior to disease development and may continue throughout the season every 7 to 14 days following resistance management guidelines (see label). An adjuvant may be added at recommended rates. Resistance management: Follow the resistance management guidelines in the general use precaution section of the Quadris label. Do not apply more than 3.75 qt of product per crop per acre per season. Do not apply within 7 days of harvest. Quilt Syngenta azoxystrobin 7.00% 7.0 to 14.0 fl oz per acre for northern corn leaf blight, northern corn leaf spot and southern corn leaf blight 10.5 to 14.0 fl oz per acre for rusts, gray leafspot and eye spot For leaf blights apply Quilt when disease first appears. Continue on a 7 to 14 day schedule. Use the low rate when disease pressure is low. Under heavy disease pressure or if conditions are favorable for disease apply the high rate. Apply no more than 2 applications of Quilt or any other Group 11 fungicide per year. Quilt may be applied by ground, air or chemigation. Do not apply to field corn and field corn grown for seed after brown silk. Do not apply within 30 days of harvest for forage. Do not apply more than 56 fl oz per acre per season of Quilt. propiconazole 11.70% Stratego Bayer CropScience propiconazole 11.40% 7.0-10.0 fl oz per acre for rust (Puccinia sorghi) 10.0-12.0 fl oz per acre for eye spot, gray leaf spot or Helminthosporium leaf blights Applications may be made to corn between the V4 (4-leaf) to after silking growth stages. Apply when disease first appears and continue on a 7 to 14 day interval if favorable conditions for disease development persist. Use the higher rates and shorter intervals when disease pressure is severe. Do not apply Stratego to field corn and field corn grown for seed after silking. Do not apply more than 24 fl oz of Stratego per acre per crop. Do not apply more than 2 sequential applications of Stratego. Limit the number of Stratego or other (Group 11) -containing fungicide application to no more than 2 per acre per crop. Do not graze or harvest for forage within 30 days of application. trifloxystrobin 11.40% Tilt Syngenta propiconazole 41.80% 2.0 to 4.0 fl oz per acre For control of Helminthosporium leaf blights (Helminthosporium maydis, H. turcicum, and H. carbonum), rusts, gray leaf spot, and eye spot, apply Tilt according to the following schedule: Helminthosporium leaf blights: apply 2.0 to 4.0 fl oz of Tilt per acre when disease first appears and continue on a 7 to 14 day schedule. Rusts: apply 4.0 fl oz of Tilt per acre when rust pustules first appear and continue on a 7 to 14 day schedule. Gray leaf spot and eye spot: apply 4.0 fl oz of Tilt per acre when disease first appears. If conditions favorable for disease persist, continue to apply on a 14 day schedule. Do not apply Tilt to field corn and field corn grown for seed after silking. Do not apply more than 16 fl oz of Tilt per acre per season. Do not harvest field corn, field corn grown for seed or popcorn for forage within 30 days of last application. Laura Sweets SweetsL@missouri.edu ********************************************************************** Summer Cleaning and Maintenance of Field Sprayers By Bill Casady I can say with much certainty that many of the ideas we promote are not just necessity, but matters of convenience and efficiency. For example, a sprayer that is cleaned up immediately after spraying is a lot easier to clean than one that is left to sit and dry out for some time before we finally decide to make time to rinse it and clean it up. Those repairs that we know are needed are also just so much easier and safer to accomplish with a clean sprayer too. Not only are they easier, but they prevent you from wasted time and questions about why the thing just isn’t working properly the next time you go to the field. For example… foam marker solution that has been drained from the tank doesn’t have the same properties as the original concentrate, so if you intend to keep the already diluted solution, it may be a good idea to mark the original container as ‘Already Diluted.’ Consider just pitching (meaning proper disposal of) that last half gallon of foam marker mixture. We spent an hour or two trying to make twice diluted foam marker solution make foam at the ends of the boom. We could hear the pump pumping and we could tell we were getting pressure. We were even getting some liquid to come out of the marker, but there was no way we were going to make any foam. By the time we figured out what had happened, I’d already stepped off the first field with flags and missed the prime spraying weather the first day out. Anyway, whenever you reach the point that you’re fairly certain you won’t be going back to the field for any kind of re-spray, take some time to make those repairs, but start with a good thorough cleanup procedure. The following cleaning procedure is recommended for all herbicides unless more specific instructions are listed on the label. 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 will improve the thorough cleaning of tops and sides of the tanks. At the very least, I’ve learned a pressure washer with a straight handle and a straight tip just won’t cut it. Don’t attempt this - as if it were even possible - but short of crawling inside the tank to clean it, you are going to miss some hard to reach areas. The right tools for the job make the job so much easier and so much safer. Make sure you wear the proper personal protective equipment especially when cleaning the tank where splash-back is certain to occur. 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, finish the needed maintenance, perform a calibration, and then 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. For a complete guide to cleaning field sprayers refer to publication MU publication G4852 available online at http://extension.missouri.edu/explore/agguides/crops/g04852.htm. Bill Casady 573-882-4370 CasadyW@missouri.edu ********************************************************************** Wilting Soybeans By Laura Sweets Since the first of July we have seen a significant increase in calls concerning wilting or yellowing and wilting soybean plants. So far, Phytophthora root rot appears to be the cause of the problem in many fields. However, Fusarium root and taproot rot and Rhizoctonia root rot are the main pathogens in some fields. Rapid wilting may also have been triggered by heavy rainfalls and saturated soils in some areas of the state. Heavy rains and moderate temperatures followed by the switch to higher temperatures, higher relative humidity and reduced rainfall may help explain the rapid wilting of affected plants. In the field it may be possible to distinguish between Phytophthora root rot, Fusarium root and tap rot and Rhizoctonia root rot if plants are carefully dug up and the soil gently removed from the root system. These diseases may occur alone but can also occur in combination which makes field diagnosis more difficult. At this point in the season there are no management options for these root rot diseases. Foliar fungicides will not control Phytophthora root rot, Fusarium root rot or Rhizoctonia root rot. Moderate and consistent weather conditions might help alleviate the stress on plants and keep some plants from dying but continued high temperatures or fluctuations in weather conditions may lead to more wilting and death of plants. Phytophthora can cause seed rot, preemergence damping-off and early postemergence damping-off as well as late-season Phytophthora. Phytophthora seedling blight causes established seedlings to turn yellow, wilt and die. Generally the entire seedling is affected and roots may be poorly developed and rotted. As plants begin to flower and set pods, symptoms of late-season Phytophthora root and stem rot may develop. Infected older plants may show reduced vigor through the growing season, die gradually over the season or, as this year, die quite rapidly. Lower leaves may show a yellowing between the veins and along the margins. Upper leaves may yellow. Or the entire plant may have a yellow, off-color cast. The stems typically show a characteristic brown discoloration that extends from below the soil line upward. Eventually the brown discoloration may extend out several inches on the lower side branches of the plant. Entire plants may wilt and die. Withered leaves tend to remain attached even after the plant dies. 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. 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. Rhizoctonia can also cause a root rot of older plants. On older plants the lower leaves may begin to yellow. The yellowing may be from the margin in resembling symptoms of potassium deficiency or may be a more general yellowing. Plants may be stunted and appear less vigorous than adjacent plants. When plants are removed from the soil, the root system may be poorly developed, lateral roots may be discolored or rotted and the stem may have a brick red discoloration beginning at the soil line and extending in either direction from the soil line. If plants are stressed by hot, dry conditions, severely infected plants may die. If cool, wet conditions occur after plants are infected with Rhizoctonia root rot, a flush of secondary roots may develop above the diseased portion of the stem. These plants may survive but are likely to remain stunted for the rest of the season. 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. Older plants may be stunted, have an off-color or yellow cast and appear less vigorous than adjacent plants. When plants are removed from the soil, the taproot will show varying degrees of discoloration and deterioration. Discoloration may range from brown to purple-brown to almost black. The taproot and lower stem may show distinct lesions or may be rotted completely through. If the taproot is rotted through, it may break if the plant is pulled from the ground. If plants are stressed by hot, dry conditions, severely infected plants may die. Once the crop has been planted, there is little that can be done to reduce incidence or severity of soybean root rot diseases. Additional stress from poor growing conditions, herbicide injury or other factors may compound problems with soybean root rot 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 SweetsL@missouri.edu ********************************************************************** Stink bugs in Corn and Soybean By Wayne Bailey Stink bugs are a group of insects which often overwinter as adults and feed using their piercing-sucking mouthparts to suck up plant juices. Although many species of stink bugs are present in Missouri, the brown stink bug is the most common species causing damage to field corn and the green stink bug predominately damages soybean. Several problems with brown stink bugs in corn have been reported during the past several weeks. The economic threshold for this insect on corn is to treat when stinkbug damage occurs on 3 to 5 percent or more of seedling plants. Mortality of plants may occur or those that survive may be twisted and disfigured similar to 2-4-D damage. Seedling corn which survives stink bug attack often produces tillers and greatly reduced yield. Damage is often restricted to border rows in the field as stink bug overwinter in woody border areas and move into the field gradually causing an “edge effect” of damage. Severe infestations may require an insecticide application prior to replanting or a spot treatment of insecticide applied along the edge of the field. Most damage from stink bugs to corn occurs during the seedling stage of growth. High numbers of stink bug may cause a distorted, twisted ear if feeding occurs at the time of silking, although this type of damage is not often found at economic levels in Missouri. The green stink bug generally causes most damage to soybean where adults and nymphs feed from June until frost. Similar to the brown stink bug, several generations may occur during the season with both adults and various nymph stages present. Green stink bugs feed by sucking plant juices from soybean, but does not cause the twisting and plant distortion observed in seedling corn. However, heavy feeding by green stink bug can result in “delayed senescence” of the soybean plant. The stems, leaves, and pods of damaged plants will remain green long after non-damaged plants in the field mature and dry. In Missouri research plots as few as 5 stink bugs caged on a square yard of soybean plants for a period of 10 days beginning at plant growth stage R-3 resulted in “delayed senescence” later in the season. The economic threshold for stink bug in soybean is to treat when 1 or more adult or large nymphs are present per foot during pod fill. Insecticides Recommended for Rescue Treatment of Brown Stink Bug in Field Corn Economic Threshold: Rescue may be necessary if unacceptable numbers of plants are killed or produce tillers. Insecticide Chemical Name Insecticide Trade Name Rate of formulated Material/Acre cyfluthrin *Baythroid 2 1.6 to 2.8 fl oz bifenthrin *Capture 2 EC 2.1 to 6.4 fl oz bifenthrin *Fanfare 2.1 to 6.4 fl oz zeta-cypermethrin *Mustang Max 2.72 to 4 fl oz Microencapsulated methyl parathion *Penncap-M 1 to 3 pts gamma-cyhalothrin *Proaxis 2.56 to 3.84 fl oz lambda-cyhalothrin *Warrior 2.56 to 3.84 fl oz *designates a restricted use product note: Capture 2EC being replaced by Brigade insecticide Insecticide Recommendation for Rescue Treatment of Green and Brown Stink Bug in Soybean Economic Threshold: Treatment is justified if 15 or more nymphs per square yard are present in non-cropland areas. Treatment is justified when adult stinkbugs or large numphs reach one or more per foot of row. Delayed senescence has been linked to heavy feeding by green stink bug nymphs and adults during late flowering and pod fill stages. Insecticide Chemical Name Insecticide Trade Name Rate of formulated Material/Acre esfenvalerate *Asana XL 5.8 to 9.6 fl oz cyfluthrinv *Baythroid 1.6 to 2.8 fl oz chlorpyrifos *Lorsban 4E 2 pts zeta-cypermethrin *Mustang Max 3.2 to 4 fl oz chlorpyrifos *Nufos 4E 2 pts Microencasulated methyl parathion *Penncap-M 1 to 3 pts *Proaxis 2.56 to 3.84 fl oz gamma-cyhalothrin *Proaxis 3.2 to 3.84 fl oz lambda-cyhalothrin *Warrior 3.2 to 3.84 fl oz *designates a restricted use product Wayne Bailey BaileyW@missouri.edu ********************************************************************** Potato Leafhoppers Numbers Remain High in Alfalfa By Wayne Bailey Potato leafhopper adults and nymphs continue to infest alfalfa throughout the state. Many alfalfa fields in the state have required insecticide applications this year. Many other fields are exhibiting the wedge shaped yellowing of leaflets referred to as “hopper burn.” Potato leafhoppers are about 1/8-inch in length, wedge shaped, and greenish-yellow in color. They are very mobile and quickly move sideways, jump, or fly when disturbed. This is a native insect which migrates into Missouri each spring from more southern states and Mexico. The potato leafhopper is often transported into the state by early spring storms which move in a northeast direction. The leafhoppers are thought to actively fly into the storms and be carried great distances by low level winds which approach 100 mph in speed. Leafhoppers are usually associated with strong thunderstorms containing hail. After a storm passes, high numbers of leafhoppers can often be found in the trail of the storms. In Missouri, the potato leafhopper adults generally arrive about 5 May of each year. The arriving adults may feed initially on several tree species before moving to alfalfa to feed and reproduce. Two to three generations of potato leafhopper are often produced with economic damage generally occurring on alfalfa following removal of first harvest. Damage is caused when both adult and nymphal (immature) leafhoppers use their piercing-sucking mouthparts to penetrate alfalfa leaflets and stems. They remove plant juices and often cause yellowing of established plants, stunted plant growth, and mortality of seedling alfalfa. Both forage quality and quantity are reduced by this alfalfa pest. This year potato leafhopper adults were found in alfalfa very early this year with adults arriving sometime during mid-April. Scouting is best accomplished using a 15-inch diameter sweep net. Take 10 pendulum sweeps at five random locations in the field. If the average number of potato leafhopper adult and nymphs per sweep reach or exceed the threshold numbers listed below, treatment is justified. The economic threshold for potato leafhopper in alfalfa depends on the height of the alfalfa and whether the alfalfa is a potato leafhopper resistant variety or a traditional alfalfa variety. Economic Threshold for Potato Leafhopper in Alfalfa Alfalfa Stem Length – inches Ave # PLH/Sweep (traditional variety) Ave # PLH/Sweep (PLH Resistant Variety) <3 0.2 0.6 6 0.5 1.5 8-10 1.0 3.0 12-14 2.0 6.0 Recommended Insecticides for Management for Potato Leafhopper Adult and Nymphs in Alfalfa Chemical name Common name Rate of Formulated Material Rate of Active Ingredient (a.i.) Preharvest Interval Beta-cyfluthrin *Baythroid XL 0.8 to 1.6 fl oz/acre 0.0065 to 0.0125 a.i./acre 7 days Dimethoate Dimethoate see specific label 0.25 to 0.5 lb a.i./acre 10 days Carbofuran *Furadan 4F 1 to 2 pts/acre 0.5 to 1 lb a.i./acre 14 - 28 days Chlorpyrifos 4E *Lorsban 4E 1 to 2 pts/acre 0.5 to 1 lb a.i./acre 7 - 14 days *numerous products see specific labels see specific labels 7 - 14 days Malathion numerous products see specific labels 1 to 1.25 lbs a.i./acre 0 - 7 days Methyl Parathion *numerous products see specific lables 0.5 to 1 lb a.i./acre 15 days Zeta-cypermethrin *Mustang Max 2.24 to 4.0 fl oz/acre 0.014 to 0.025 lb a.i./acre 3 days Permethrin *numerous products see specific label 0.1 to 0.2 lbs a.i./acre 7 - 14 days Gamma-cyhalothrin *Proaxis 1.92 to 3.2 fl oz/acre 0.0075 to 0.0125 lb a.i./acre 1 day forage 7 day hay Carbaryl Sevin 4F 1 qt/acre 1.0 lb a.i./acre 7 days Carbaryl Sevin XLR Plus 1 qt/acre 1. lb a.i./acre 7 days Lambda-cyhalothrin *Warrior 1.92 to 3.2 fl oz/acre 0.015 to 0.025 lb a.i./acre 1 day forage 7 days hay Lambda-cyhalothrin *Numerous products see speciic labels see specific labels 1 day forage 7 days hay Read and follow all label direction, precautions, and restrictions. * Designated a restricted use product. Wayne Bailey 573 864-9905 BaileyW@missouri.edu ********************************************************************** Japanese Beetles Expand Their Distribution Across Missouri By Wayne Bailey During the past two weeks Japanese beetles have been collected from many corn fields in northern Missouri and from pheromone traps throughout the state. Adult Japanese beetles can be collected from tassels and silks of corn plants in many fields and on many different flowering plants and weeds in field borders and waterways. Many of these fields are those that we visit regularly, but have not found Japanese beetle adults in past years. Although low numbers of beetles are present in most of these fields, other fields have received economic levels of damage to corn tassels, silks, or soybean foliage. These fields have required insecticide applications for control of adult beetles. This beetle was first found in the United States in 1916, following its accidental introduction from its native country of Japan. Japanese beetles are approximately 1/2–inch in length, metallic green in color with bronze or copper colored wing covers. A diagnostic characteristic is the presence of several white tufts of hair or bristles located around the edge of the shell. Without magnification, these structures are seen as white dots. Japanese beetles can be confused with adult green June beetle, but are smaller in size. Adult beetles emerge from the soil in May and June to feed for approximately 60 days. During this time the beetles mate and females deposit eggs in the soil. Each female may lay 40 to 60 eggs with larvae emerging in about 2 weeks. Larvae will feed on plant roots and decaying material before overwintering in the soil as 3rd instars. The following spring larvae quickly finish development, pupate, and emerge as adult beetles beginning in May. Japanese beetle adults often congregate in large numbers to feed on foliage and fruit of 300 to 400 different hosts, including ornamental, tree and small fruit, and corn and soybean plants. Typical feeding damage by the beetles is often seen as a lace-like pattern on host plant foliages as beetles avoid leaf veins when feeding. Beetles often begin feeding on the top of plants and move downward. Tassels and silks of corn can be severely damaged by adult feeding, whereas foliage feeding is common on soybean. Feeding on corn silks can disrupt pollination and result in substantial yield losses. Foliage feeding on soybean is less damaging, although small double-crop soybean may sustain economic damage. The grub stage of this pest will feed on plant roots of both corn and soybean with most feeding occurring in late June, July and August. Damage to plant root hairs may result in poor uptake of water and nutrients or be more severe and cause reduced stands through plant mortality. In field corn, an insecticidal treatment is justified if during the silking period there are an average of 3 or more beetles present per ear, silks have been clipped to ½ inch or less in length, and pollination is less than 50 percent complete. For soybean treatment is justified if foliage feeding exceeds 30 percent prior to bloom and 20 percent from bloom through pod fill. The following insecticides are recommended for control of Japanese Beetle in field corn and soybean in Missouri. -----------------------------------------------------------| | Insecticides Recommended for Control of Japanese | | Beetle Adults in Field Corn | |----------------------------------------------------------| | Economic Threshold: Treat when 3 or more beetles per ear | | are present during silking period and pollination is | | not complete. | |----------------------------------------------------------| | Insecticide | Insecticide | Rate of formulated | | Chemical Name | Trade Name | Material/Acre | |--------------------|----------------|--------------------| | cyfluthrin |*Baythroid 2 | 1.6 to 2.8 fl oz | | bifenthrin |*Capture 2 EC | 2.1 to 6.4 fl oz | | bifenthrin |*Fanfare | 2.1 to 6.4 fl oz | | zeta-cypermethrin |*Mustang Max | 2.72 to 4 fl oz | | Microencapsulated | *Penncap-M | 2 to 4 pts | | methyl parathion | | | | permethrin | *Pounce 3.2 EC | | | gamma-cyhalothrin | *Proaxis | 2.56 to 3.84 fl oz | | carbaryl | Sevin XLR Plus | 2 to 4 pts | | lambda-cyhalothrin | *Warrior | 2.56 to 3.84 fl oz | |----------------------------------------------------------| | *designates a restricted use product | | | | note: Capture 2EC being replaced by Brigade | | insecticide | ------------------------------------------------------------ ---------------------------------------------------------| | Insecticides Recommended for Control of Japanese | | Beetle Adults in Soybean | |--------------------------------------------------------| | Economic Threshold: Treatment is justified if 15 or | | more nymphs per square yard are present in non- | | cropland areas. Treat when defoliation reaches 30% | | before bloom and 20% between bloom to pod fill. | |--------------------------------------------------------| | Insecticide | Insecticide | Rate of formulated| | Chemical Name | Trade Name | Material/Acre | |--------------------|---------------|-------------------| | permethrin | *Ambush | 2.9 to 5.8 fl oz | | esfenvalerate | *Asana XL | 5.8 to 9.6 fl oz | | cyfluthrin | *Baythroid | 1.6 to 2.8 fl oz | | zeta-cypermethrin | *Mustang Max | 2.8 to 4 fl oz | | Microencasulated | *Penncap-M | 2 to 3 pts | | methyl parathion | | | | permethrin | *Pounce 3.2EC | 2 to 4 fl oz | | gamma-cyhalothrin | *Proaxis | 3.2 to 3.84 fl oz | | carbaryl | Sevin XLR | 1 to 2 pts | | lambda-cyhalothrin | *Warrior | 3.2 to 3.84 fl oz | |--------------------------------------------------------| | *designates a restricted use product | ---------------------------------------------------------| Wayne Bailey 573 864-9905 ********************************************************************** Weather Data for the Week Ending July 8, 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 |Jul 1 from |since from Station County Max.Min. High Low Mean avg. |Jul 8 avg |Apr 1 avg. ------------------------------------------------------|------------|------------ Corning Atchison 91 69 94 64 80 4 | 0 -1.45 | 1732 367 St. Joseph Buchanan 89 68 91 63 79 2 | 0 -1.47 | 1629 231 Brunswick Chariton 88 66 90 63 77 0 | 0.85 -0.35 | 1670 238 Albany Gentry 91 66 94 61 79 2 | 0.27 -1.25 | 1608 227 Auxvasse Audrain 88 65 90 59 76 -1 | 0.09 -0.90 | 1671 240 Columbia Boone 88 66 90 61 77 -1 | 0 -1.17 | 1695 198 Sanborn Field Boone 89 68 91 62 79 1 | 0 -1.24 | 1800 262 Williamsburg Callaway 89 65 92 59 77 1 | 0.04 -1.36 | 1713 322 Novelty Knox 87 65 89 58 77 0 | 0 -1.13 | 1543 146 Linneus Linn 88 65 92 59 77 1 | 0.09 -1.25 | 1585 236 Monroe City Monroe 88 65 90 59 77 0 | 0.38 -0.55 | 1620 178 Versailles Morgan 89 67 91 63 78 1 | 0.12 -0.91 | 1769 236 Green Ridge Pettis 88 66 90 63 77 0 | 0.28 -0.95 | 1678 283 Lamar Barton 87 68 89 67 77 -1 | 0.832-0.73 | 1686 85 Cook Station Crawford 89 63 91 55 75 -3 | 0.29 -0.51 | 1629 61 Alley Spring Shannon 89 64 92 59 76 -1 | 0.23 -0.80 | 1598 120 Round Spring Shannon 90 64 92 58 76 -1 | 0.7 -0.33 | 1632 153 Delta Cape 89 63 91 57 76 -4 | 0.46 -0.37 | 1847 59 Girardeau | | Cardwell Dunklin 88 69 91 66 78 -3 | 2.34 1.69 | 2039 72 Clarkton Dunklin 88 68 92 63 78 -3 | 2.30 1.77 | 2003 67 Glennonville Dunklin 88 68 90 63 78 -3 | 2.03 1.44 | 1989 61 Charleston Mississipp 87 67 90 62 77 -2 | 2.57 1.38 | 1939 184 Portageville- 89 69 93 64 79 -2 | 1.95 1.25 | 2094 164 Delta Center Pemiscot | | Portageville- 89 69 93 64 79 -2 | 1.96 1.25 | 2092 179 Lee Farm Pemiscot | | Steele Pemiscot 90 70 93 65 80 -1 | 0.91 0.24 | 2177 246 ‡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. Wayne Bailey 573 864-9905