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No. 8 June 23, 2005
Inside this Issue...Cottony Ash Psyllid in North Dakota . . . . . . . . . . . . . . . 1Sugarbeet Root Maggot: High Activity Continues . . . . . 1Aphids Infesting Area Small Grain Crops . . . . . . . . . . . . 2Armyworm Alert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Barley Thrips Populations Increasing in Barley . . . . . . . . 3Section 18 Exemption Approved - Mustang Max . . . . . . 3Adult Sunflower Beetle Emergence Underway! . . . . . . . 3Soybean: Stand Compensation and Yields . . . . . . . . . . . . 4Canola and Hail Damage . . . . . . . . . . . . . . . . . . . . . . . . . 4Corn Growth Staging . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Generic Tebuconazole Fungicide . . . . . . . . . . . . . . . . . . . 6Scab Spore Counts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6ND IPM Survey Results . . . . . . . . . . . . . . . . . . . . . . . . . . 6Disease Reports from Nebraska and South Dakota . . . . . 7NDSU Plant Diagnostic Lab-herbicide Injury . . . . . . . . . 7Soybean Rust Found in New Florida County . . . . . . . . . 7Fungicides for Sclerotinia Stem Rot of Canola . . . . . . . . 8Additional Topdressing Issues for Small Grains . . . . . . . 8Estimating the Need for Additional N for Corn . . . . . . . . 9Section 18 for Reflex on Dry Bean Approved . . . . . . . . 10Agdakota List Serve . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Rainfastness of Common Lambsquarters . . . . . . . . . . . . 10New Cereal Herbicide in Development . . . . . . . . . . . . . 10Select Use in Field Pea and Lentil . . . . . . . . . . . . . . . . . 11Moss Control in Stock Tanks and Standing Water . . . . 11Absinth Wormwood Control in Alfalfa . . . . . . . . . . . . . 11Around the State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
COTTONY ASH PSYLLID IN NORTH DAKOTA The Cottony Ash Psyllid, Psyllopsis discrepans (Flor),
is a European insect recently detected in Bismarck byAssistant City Forester Jeff Heintz, and subsequently foundin Fargo by Plant Protection Specialist Justin Knott. Thisaphid-like insect damages varieties of Black andManchurian Ash. Damage appears as leaflet curling fromthe edges and tips, or a more general leaflet and leafcrumpling and deformation known as ‘cauliflowering.’ Some trees in Bismarck show severe damage. The damageappears similar to that of certain herbicides.
Adults are small, 3 mm in length. Coloration is yellowwith black markings; the wings are clear, shading tosmoky-brown towards the apices. Nymphs extrude afilamentous whitish wax, hence the common name of theinsect. Because there are many native species of psyllids (also known as jumping plantlice), specimens should besubmitted to professional entomologists for final
determination.This insect, which usually can be found on the
undersurfaces of leaflets, imbibes phloem with itspiercing-sucking mouthparts. It inserts feeding stylets intothe leaf mid-rib or veins. The feeding injury and liquidremoval causes leaflet curling, the more generaldeformation may be due to high psyllid numbers, or, basedon evidence from other psyllid species, due to salivarysecretions. This species overwinters as eggs, in our areamay have as many as three generations annually.
Cottony ash psyllids are native to Central Europe andScandinavia and were first reported in North America froma single male specimen found in Nova Scotia in 1921. Recent reports from the year 2000 and continuing, are fromEdmonton and Calgary, Alberta. Populations in NorthDakota may be the result of natural wind dispersal or aninadvertent introduction on plant materials.
Cottony ash psyllids have been found on the variety ofBlack ash known as ‘fall gold’ and the Manchurian ashvariety ‘Mancana.’ This insect has also been found onhybrids of Black and Manchurian ash such as ‘NorthernTreasure’ and ‘Northern Gem.’ As yet, White ash, a rareornamental in ND, has not been examined and Green ash,one of our mainstay shade trees, appears to be unaffected. Currently, the winged adult stage is present and foliardamage is from insects of the first generation. This psyllidcan cause severe leaf deformation although with theexception of some trees in south Bismarck, much of thedamage observed thus far has not been severe. It is unclearwhat damage the second generation may cause now that theleaves are fully expanded. There is evidence that wellwatered trees are less susceptible to damage. We arecollaborating with Canadian entomologists to determinemanagement protocols for this insect.
Dr. Gerald Fauske, Research Collection Manager, NDSUJustin Knott, Plant Protection Specialist, ND Dept. of AgDavid Nelson, State Entomologist, ND Dept. of AgMichael Kangas, Forest Health Specialist, ND Forest Svc.
SUGARBEET ROOT MAGGOT UPDATESugarbeet root maggot fly counts at many monitoring
sites, including Pembina, north central Walsh and centralCass counties, have been higher this year than the pastseveral years, suggesting that populations are on the rise.Effective insecticide applications in highly infested areasmay not only be important for protecting this year’s crop,but could also reduce the intensity of infestations in the2006 production season.
Fly activity remains at fairly high levels, with the mostsevere infestations occurring between the cities of St.Thomas and Grafton, ND (especially in the townships ofSt. Thomas, Elora, Glenwood, and Martin). Activity isexpected to drop considerably by early next week.Therefore, growers planning to make a second liquidinsecticide in a split-treatment program (or those thatobserve an unexpected flare-up of activity) should applythe material as soon as possible.
North Dakota State University CROP & PEST REPORT June 23, 2005
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Fig 1. Economically important aphids of ND smallgrain crops.
Fig 2. Late-instar armyworm larva.
APHIDS INFESTING AREA SMALL GRAIN CROPSCereal aphids are beginning to show up in ND small
grain fields. Most reports are coming in from thesouthwest part of the state. Activity is also surfacingacross the much of the southern tier of ND counties, aswell as in southern and western MN. Aphids can usuallybe found in area field crops each growing season, but donot always reach economically damaging levels.
Description. Aphids are tiny, soft-bodied,pear-shaped insects with tapered, thread-like antennae.Most have two tailpipe-like structures called “cornicles”that protrude from the posterior end of their abdomen.Most aphids of concern are lime or yellowish-green toblue-green in color, and are about 1/3 to 3/16-inch long.The most common aphid pests of small grain crops inNorth Dakota are the greenbug, English grain aphid, andbird cherry oat aphid (Fig. 1). None of these species areknown to overwinter in the state. They migrate into theregion from southern areas in late spring.
Damage. Aphids injure small grain by usingpiercing/sucking mouthparts to feed on plant sap. Theyreproduce quickly under favorable conditions fordevelopment, and the resulting infestations are capable ofcausing major yield reductions. An added concern is thepotential of aphids to transmit barley yellow dwarf virus.High aphid populations are capable of quickly spreadingthis disease throughout entire fields. Small grain fields arequite variable in growth stage this year because somewere planted very early while others were planted late dueto excess soil moisture. Impacts of aphid infestations aremost severe in late-seeded grain fields because youngplants are less capable of withstanding feeding injury.Such fields should be monitored closely. Aphids are alsomore problematic when cool and wet periods occur duringspring and early summer, which further justifies carefulmonitoring of grain fields this year.
Treatment threshold. North Dakota producers andcrop scouts should be vigilant about monitoring grainfields during the next few weeks. Economic yield loss ismost likely when significant aphid damage occurs duringvegetative to boot stages. Field monitoring should begin atstem elongation and continue until the heading stage ofwheat. Treatment with an insecticide is probably justifiedif at least 85% of stems have at least one aphid presentbefore heading. Economic return from an insecticideapplication will be reduced if it is made after flag stage.
ARMYWORM ALERTPockets of armyworm activity have been observed in
small grain fields in southwestern North Dakota duringthe past ten days, although insecticide applications havenot been reported. Armyworm infestations occasionallydevelop in our area following migrations of moths fromsouthern states in late spring and early summer.
Moths typically lay their tiny white eggs at the basesof plants in moist, shady areas, and prefer sites withlodged and/or hail-damaged grassy weed or crop plants.Eggs hatch and larvae (Fig. 2) quickly begin feeding onnearby plants. Moth flights can occur over a few weekstime, so it is not unusual to find a wide size range oflarvae present. Early detection of armyworm infestationsis difficult because they feed at night and hide undervegetation or in loose soil during the day. Damage issometimes obscured by wind injury or the dense smallgrain plant canopy itself. Armyworms are a favorite foodof birds, so significant bird activity in a grain field can bean indicator of an armyworm infestation.
Scouting for armyworms in small grain fieldsinvolves parting the plant canopy back and searching forfeeding injury or fecal pellets. If either is evident, look forlarvae under plant trash, soil clods or in soil cracks. Fieldcan also be checked during evening hours (when larvaeare most active) by shaking plants and using a flashlightto count dislodged larvae on the ground. Whethersampling during the day or in the evening, it is importantto sample as many locations in a field as practical (at least5 sites per field). To avoid economic loss fromarmyworms, treat with a registered foliar insecticidewhen an infestation reaches 4 to 5 larvae per squarefoot. As the name implies, armyworms will assume the“army” habit and move in large numbers to neighboringfields when the food supply becomes depleted in theoriginal feeding site. Applying a foliar insecticide as abarrier treatment to a strip of plant material ahead of theinfestation in the direction of movement can provide goodprotection of neighboring fields if timed correctly.
Options for aphid and armyworm control in smallgrains can be found in the 2005 Field Crop InsectManagement Recommendations guide. It is online at:http://www.ext.nodak.edu/extpubs/plantsci/pests/e1143w1.htm
Always read, understand, and follow all pesticide labelinginstructions and precautions - it’s the law.
Mark BoetelResearch & Extension Entomologist
North Dakota State University CROP & PEST REPORT June 23, 2005
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Barley Thrips
Adult Sunflower Beetle
BARLEY THRIPS POPULATIONS INCREASINGIN BARLEY
It is somewhat surprising to see high populations ofbarley thrips with the cool, wet spring weather andvigorously growing crop conditions. Typically, hot dryweather conditions increase populations of barley thrips tolevels that may result in crop losses.
Barley thrips are small dark brown to black insectsabout 1.1 to 1.8 mm long. Females have feathery wingswhile males are wingless. Immatures (larvae) arewingless pale yellow, white or green with red eyespots. Larvae are difficult to see due to their light, almosttransparent color and extremely small size. Adult andimmature thrips have a long, narrow body shapes.
Female thrips overwinter as adults in debris in fieldsand shelterbelts. Thrips emerge in late May and earlyJune and move into winter wheat/rye and eventually intoearly seeded barley (preferred host). Occasionally, barleythrips will feed on hard red spring wheat and durum aswell.
Adult and immature thrips cause damage by feedingon succulent plant tissues (puncturing plant cells andsucking out the contents). Feeding injury symptoms are awhitened or bleached appearance in plants and this oftenresults in gooseneck-shaped stems and heads under severepressure. Pollen feeding by barley thrips may result inpoor head filling and reduced seed germination. Intensivefeeding at the beginning of head formation producessmall, shriveled grains. Often there is no seeddevelopment at the top and bottom of head andintermediate grains are shriveled.
Scout for barley thrips from flag leaf to heading. Barley thrips can be found by unrolling the flag leaf awayfrom the stem. Remember, populations will probably behigher at the field edges. The economic threshold is 7-8barley thrips per plant before the crops is fully headed. One thrips per stem results in a 1.25 bushel per acre loss! Once the barley crop heads the insect damage is done andno insecticide treatment is advised. The only registeredinsecticide for barley thrips control in North Dakota ismethyl parathion 4 EC at 4-6 fl oz. per acre (do not entertreated fields within 48 hours after application).
SECTION 18 EXEMPTION APPROVED -MUSTANG MAX FOR GRASSHOPPER CONTROLIN FLAX IN ND
This exemption allows ground or aerial application ofMustang Max (FMC) at a rate of 2.8 to 4 fluid ounces ofproduct per acre from June 10 to September 20, 2005. Amaximum of 8 fluid ounces per acre may be applied perseason. Although early grasshopper levels have been lowwith the cool, wet spring, we will need to continue towatch the later adult populations. Adult grasshoppersmigrate from maturing small grain fields, drying grasses,canola and other crops to flax fields in late summer intofall. Flax is a preferred host crop later in the season, sinceplants will be green and attractive to grasshoppers asadults. Large groups of adult grasshoppers can migrateand move long distances, 30 miles or more, to find flaxfields, and cause crop losses quickly.
The exemption use directions have been posted onthe North Dakota Department of Agriculture Section - 18pagehttp://www.agdepartment.com/Programs/Plant/Section18Exemptions.html and the NDSU Pesticide Program pagehttp://www.ag.ndsu.nodak.edu/aginfo/pesticid/LabelPage.htm#nd
ADULT SUNFLOWER BEETLE EMERGENCEUNDERWAY!
Adults sunflower beetles can be found in sunflowerfields now. The head of the adult is reddish-brown andthe thorax (area between head and abdomen) is palecream-colored with a reddish-brown patch at the base. Each wing cover is cream-colored and has three darkstripes that extend its length. A shorter lateral stripe endsat the middle of the wing in a small dot that resembles anexclamation point. The beetle is about ½ inch long whenmature.
North Dakota State University CROP & PEST REPORT June 23, 2005
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Sunflower Beetle Larvae
Damage due to adult feeding begins soon afterbeetles emerge from hibernation. They seldom feed onthe cotyledons, but the first true leaves may be severelydamaged or completely consumed. If beetles areabundant, fields may be severely defoliated. Adults feedpredominately on leaf margins during the day. Damagemay be most noticeable in field margins. In the seedlingstage, one-two adults per seedling plant is therecommended economic threshold.
Eggs will hatch into larvae in about a week. Sunflower beetle larvae are yellowish-green with a brownhead capsule and humpbacked in appearance. Newlyhatched larvae are about 1/16 inch, and will reach a lengthof about 3/8 inch when fully developed. Larvae feed overthe entire leaf surface for about six weeks during thenight. When larvae are numerous, damaged leaves takeon a lacy appearance. During the daytime, larvaetypically rest in the terminal growth area where they areeasily found in leaf axils and flower buds. If larvalfeeding is severe, defoliation can reduce yield by poorseed set or fill. When foliar defoliation reaches 25-30%in late vegetative stages of sunflower and larvae are lessthan ¼ inch, a treatment may be warranted.
Janet KnodelArea Extension Specialist
North Central Research Extension [email protected]
SOYBEAN: STAND COMPENSATION ANDYIELDS
Soybean have the remarkable ability to compensatefor reduced stands through aggressive branching.University of Minnesota research suggests that evensubstantial reductions in plant stands has negligibleimpact on yield. The data below from the National HailInsurance Services handbook supports this research.
Soybean Stand Reduction Loss
- ROW WIDTH -
Plants/AYield %
Optimum
30" 15" 7.5"
Plant Count
103 52 26 180,000 100
92 46 23 160,000 100
80 40 20 140,000 100
69 34 17 120,000 99
63 32 16 110,000 97
57 29 14 100,000 94
52 26 13 90,000 90
46 23 11 80,000 86
40 20 10 70,000 82
NOTE: All plant counts are made on the basis of“number of plant in 10 feet of row.”
As the above table indicates, reduced soybean standscan produce acceptable yields. However, weed controlmanagement may need to be closely watched. Incompletecanopy closure can create additional weed pressures.
CANOLA AND HAIL DAMAGECanola in North Dakota is now near the bolting stage
or is just starting into the bloom stage of development. Hail has been reported in some of the canola productionareas of the state. Plantings in seedling stages can havestands reduced by 50% and still produce acceptableyields. An average stand of 11-12 plants/ft2 can bereduced to 4/ft2 before yield losses exceed 10 percent.Prior to bolting and flower development, canola canwithstand hail without much economic loss. Canola withleaves that are torn and shredded suffer only partial loss,while leaves bruised on the main vein or torn and brokenwill be lost. Leaf area destroyed will result in seed yieldloss. Seed yield losses in canola is approximately 25percent of leaf area lost. If leaf defoliation is 50 percent,then yield loss would be approximately 12.5 percent.
North Dakota State University CROP & PEST REPORT June 23, 2005
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Canola plants injured in late bolting or earlyflowering stages seldom die. The well developed rootsystems and ability to rebranch and develop secondaryflower clusters help the plants recover. When buds orflowers are destroyed, the canola recovers rapidly bydevelopment of flowers which normally would haveaborted. New branches also develop from growth budslower down on the plant. Seed yield loss will depend onboth percent leaves and branches lost. For example, ifcanola has 60 percent lost branches 7 days into flowering,seed yield loss is estimated at 18 percent, whereas 21 daysinto flowering, yield loss would be an estimated 60percent. If hail strikes late, such as during pod filling orripening, plant recovery is not possible. The time neededto develop new growth, flowers and mature is limitedbefore a killing frost. Canola seed yield loss if injuryoccurs at the ripening stage depends directly on the loss ofbranches, individual pods and seed knocked out of pods.Severe hail losses have occurred in canola swaths in pastyears.
Duane R. BerglundExtension Agronomist
CORN GROWTH STAGINGCorn growth is now starting to accelerate with the
arrival of more summer-like weather. Early planted cornin the southeastern region of the state is approaching the6th leaf stage. At the five leaf stage, the corn plantswitches from vegetative growth to reproductive growthas the growing point stops initiating leaves and beginsinitiating the tassel. At the 6 leaf stage, ear shoots beginto form. The number of kernel rows on the developingear is determined relatively soon after it beginsdevelopment and is largely determined by genetics, andless so by the environment. The length of the kernel rowand therefore the total number of potential kernels,however, is determined during a longer period of time (6leaf stage through one to two weeks before tasseling). Severe stress during this stage can shorten the length ofthe cob and reduce yield potential. Nevertheless, stressduring ear development is far less damaging to yieldpotential than stress during and shortly after pollination,as the potential number of kernels developed typicallyexceeds the number that can be pollinated filled.
Certain management practices are growth stagedependent; therefore, properly identifying the growthstage of your corn crop will be important to ensuring thatmanagement practices are applied at the appropriate time. This is particularly true of the application of herbicides.
When growth staging a crop you should begin byobtaining a representative sample of plants from the fieldor part of the field of interest. Remove any soil attachedto the plants so that you are able to observe the roots andcrown. Vegetative growth stages of corn are defined bythe number of leaves. Counting leaves in corn is fairlystraight forward as the process is not encumbered with
tillers and leaves on tillers as is the case in small grains.However, care must be taken to ensure that the earliestleaves are included when counting leaf numbers. The firstleaf is small and often dies and is torn from the plant earlyin the growth of the plant. The first leaf has a blunt tip. Look for sheath remnants at the crown of the plant if yoususpect that the first leaf (or second for that matter) ismissing. Include only those leaves that have a collar. Include all leaves, even those that have been damaged byhail or frost. The total number of leaves that a plant willdeveloped is more or less fixed for a given hybrid; leavesthat are stripped from the plant will not be replaced byadditional new leaves.
In order to determine the growth stage of older plantsthat have lost their lower leaves, uproot the plant and splitthe stem with a knife through the root ball. At the verybase of the stem, identify the first visible internode. Internodes are the white area between the more yellowbands of the nodes. The first obviously visible internodeshould about ½ to 3/4 inch in length. The node directlyabove this internode will be the fifth node, and the leafarising from this node will be the 5th leaf. Find that leafand continuing counting leaves from that point.
In corn, management recommendations can also referto the height of the plant, rather than leaf stage. Forexample, certain herbicides can only be applied to cornless than 12 inches tall. The plant height in this case ismeasure from the base of the plant to where the uppermost leaf reaches without stretching it out.
Joel RansomNDSU Extension Agronomist
Cereal [email protected]
North Dakota State University CROP & PEST REPORT June 23, 2005
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GENERIC TEBUCONAZOLE FUNGICIDESeveral weeks ago, Folicur fungicide (tebuconazole)
received a Section 18 emergency exemption for use onwheat and barley in ND. Although Folicur has not yetreceived a full federal label for wheat and barley, it isalready off patent, and generic tebuconazoles are beingproduced. Orius, a generic tebuconazole produced byMakhteshim AGAN, is labeled for soybean rust in ND,under a Sec. 18 quarantine exemption. However, the NDDept. of Agriculture has NOT approved a Sec. 18 forOrius on wheat and barley, so at this time, there is nogeneric tebuconazole registered for use on wheat andbarley in ND. I am testing three generic tebuconazolesthis summer in research plots at Fargo to get informationon how the generics perform in relationship to Folicur.
SCAB SPORE COUNTSThe NDSU small grain disease forecasting web site is
predicting high risk for scab infection in much of the state,based on temperature, rainfall, and relative humidityfavorable for spore production. However, the modeldoesn’t tell you IF spores have developed and arepresent in the atmosphere. With winter wheat floweringor have already flowered and some spring grains soon atthe growth stage for fungicide decisions, the question is,are scab spores now in the environment? The answer is,we don’t know. NDSU researchers will have a spore trapin Fargo, to tell us if any spores are in the atmospherehere, but this trap will not provide information for otherlocations.
ND IPM SURVEY RESULTS, 6-13 through 6-17NDSU IPM field scouts surveyed 136 wheat fields
and 23 barley fields the week of June 13-17. KelseySteenblock, scout for the SE and EC region had a devil ofa time getting into fields in her scouting territory becauseof heavy rains during the week and the heavy soils of theregion, but the other scouts were generally successful inscouting their territory.
Tan spot was commonly found throughout the state,but highest severities were reported in counties insouthwest ND (see figure of tan spot severity).
Leaf rust was observed in 28% of the wheat fieldssurveyed, with severities in the 1-5% range most common(see figure of wheat leaf rust severity).
Field scouts also observed stripe rust in 18 wheat fieldssurveyed, primarily in the southwest region (see figure ofstripe rust incidence).
North Dakota State University CROP & PEST REPORT June 23, 2005
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Grain aphids were found in 15.4% of the wheat and13.0% of the barley fields surveyed, and barley yellowdwarf (BYDV) symptoms are also being observed. Thehighest percent of tillers with aphids was 22%, in onewheat field in Morton county.
In barley, approximately half the fields exhibitedeither spot blotch or net blotch symptoms. During theweek of June 20-24, the NDSU field scouts will also startlooking for soybean aphid in soybeans and the extent ofsunflower beetle and downy mildew damage in youngsunflower fields.
Weekly maps of disease occurrences in cropssurveyed this year can be found at the following web site:http://www.ag.ndsu.nodak.edu/aginfo/ndipm/.Darla Verbitsky, Extension Administrative Secretary inPlant Pathology, and Justin Knott, Pest Survey specialistwith the ND Dept. of Agriculture, have worked togetherto provide these weekly map updates on the ND IPM website.
DISEASE REPORTS FROM NEBRASKA ANDSOUTH DAKOTA
Plant pathologists from Nebraska report that striperust is common in their winter wheat and many farmersare spraying fungicides to control this disease. In SouthDakota, Jeff Stein and Marty Draper report that stripe rustis most severe in the winter wheat variety Nekota. Hightemperatures of this week may halt spore production ofstripe rust.
A low level of Fusarium head blight (scab) wasobserved in several winter wheat fields in South Dakota,from the far southeast corner of the state. Black chaffbacterial infection on glumes of wheat heads was alsoobserved in some winter wheat fields.
Marcia McMullenNDSU Extension Plant Pathologist
NDSU PLANT DIAGNOSTIC LAB-HERBICIDEINJURY
As previous crop and pest report articles haveindicated, our recent cool, wet weather has beenparticularly favorable for many diseases that affect cropsand ornamental plants. The Plant Diagnostic Lab hasreceived over 650 samples so far for fiscal year 2005.This is about a 30% increase over the number of samplesreceived last year through June. Diseases that have beenseen in the lab recently include downy mildew onsunflower, tan spot on wheat, wheat streak mosaic virus,barley yellow dwarf virus, Rhizoctonia crown rot (alfalfa),Rhizoctonia brown patch (on turfgrass), Pythium root rot(sugarbeet, soybean), and Aphanomyces root rot onsugarbeet. With the excess moisture that many NorthDakota soils have experienced recently, root rot diseasesand other soil-borne diseases are expected to flourish.Several crop samples that have been submitted during this
growing season have showed symptoms consistent withherbicide or other chemical injury, from misapplications,uncooperative weather, or drift events.
Samples that exhibit symptoms that are consistentwith herbicide injury (or injury from other chemicals)comprise a significant proportion of samples that areevaluated by the lab. The NDSU Plant Diagnostic Labevaluates such samples visually (not chemically), for a$15 fee for North Dakota residents and a $25 fee for non-residents. A visual assessment of plants suspected toexhibit symptoms of herbicide or other chemical injurycan be valuable for at least two reasons. It can determineif the symptoms are consistent with herbicide injury, andif so, the injury can usually be associated with a specificgroup of herbicides. Often, a visual assessment by a thirdparty, such as the NDSU Plant Diagnostic Lab, may besufficient for neighbors, applicators, or others involved toresolve potential conflicts. Furthermore, by narrowing thepossibilities with a visual assessment, the expense ofchemical analysis, if warranted, can be reduced, becausethe possibilities can typically be significantly narrowed. Ifchemical analysis is needed, several laboratories arecapable of testing for herbicide or other chemical residuein plant tissue or soil, and a partial list of such laboratoriescan be found at the NDSU Plant Diagnostic Lab website:
http://www.ag.ndsu.nodak.edu/diaglab
If you have any questions regarding herbicide injury,visual assessments, or laboratories that can providechemical analysis services, feel free to call the NDSUPlant Diagnostic Lab (701-231-7854) or e-mail the lab([email protected]).
Kasia KinzerPlant Diagnostician
SOYBEAN RUST FOUND IN NEW FLORIDACOUNTY
Soybean rust was recently found in Jefferson County,Florida on kudzu. This is the fifth county in Florida toreport having soybean rust in 2005. All findings ofsoybean rust in Florida has been on kudzu, which is analternative weed host. Georgia is the only other state toreport having soybean rust thus far in 2005. The Georgiafind was in only one county on volunteer soybean.
Because soybean rust has not yet become widespreadin the southern U.S., it is becoming more likely that NorthDakota growers will not have to deal with this disease thisseason. Soybean fields and soybean rust sentinel plots arestill being scouted for soybean rust in North Dakota andother soybean-producing states. For more informationabout the presence of soybean rust in the United States,visit the USDA Soybean Rust Monitoring Maps at:http://www.usda.gov/soybeanrust/.
North Dakota State University CROP & PEST REPORT June 23, 2005
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Apothecia of the Sclerotinia fungus (J. Venette, NDSU)
FUNGICIDES FOR SCLEROTINIA STEM ROT OFCANOLA
With canola near to or beginning to bloom in parts ofthe state, its susceptibility to Sclerotinia stem rotincreases. The airborne spores of the Sclerotinia fungususe dead flower petals as an energy source which allowsthem to cause infections on the canola plant. Before anyof these airborne spores can be produced, mushroom-likestructures of the Sclerotinia fungus known as apotheciamust be present in the soil. These apothecia arise fromsclerotia in the soil when the environment is favorable. Soil moisture is a key component to this favorableenvironment, as the soil must be at or above field capacityfor 10 to 14 consecutive days for apothecia emergence tooccur.
Fungicides registered for management of Sclerotiniastem rot in canola include Ronilan, Topsin M (andgenerics), Endura, and Quadris. From studies conductedat NDSU and the University of Minnesota, Ronilan,Topsin M, and Endura have provided the most consistentcontrol. These products should be applied when canola isbetween 30 to 50% flowering.
To help with spraying decisions, a Sclerotinia riskmap is available (see Crop & Pest Report No. 7) at twowebsites: http://www.northerncanola.com/ and http://www.ag.ndsu.nodak.edu/aginfo/sclerotinia/sclerotinia.htm. The most recent map (June 20) shows that the majority ofNorth Dakota is under moderate risk. A fungicide application may be most beneficial if:
• Yield potential is above normal (at least 2,000lb/A) if canola prices are minimal
• Weather leading to early bloom has been wet (atleast 1-2 inches of rain in the 2 weeks prior toearly bloom)
• More rain or high humidity is expected• Sclerotinia has been a problem in recent years• If canola is on tight rotations (3 years or less) or
if other susceptible crops were in the rotation
Carl A. BradleyExtension Plant Pathologist
ADDITIONAL TOPDRESSING ISSUES FORSMALL GRAINS Topdressing for Protein
For protein enhancement, extra N applied beforeheading using stream technology not incorporated intoincreased yield will be used for protein. Also, aerialapplication of urea might also be attempted. Thesestrategies, although there is little burn risk (make sure notto apply streamer N in a high wind which breaks up sprayparticle stream into a broadcast application. This willresult in a high leaf burn risk!) need rainfall to work. A ½inch rain is needed to move the fertilizer into the soil.With the wet leaves and heavy dew we have experienced,high levels of urea can convert within a week afterapplication using this method. 28% will be better able tohang in there due to its ammonium nitrate component. Dryurea will not.
An approach not dependent on rainfall is a foliarapplication of 10 gal/a (30 lb N) as 28%, mixed with 10gal/a water, and applied just after pollination at thewatery-ripe stage of kernel development This applicationrisks leaf burn, which is why I do not recommend itbefore pollination at flag leaf emergence or at pollination.The need to protect the flag leaf is crucial, and pollinationis also a critical time to protect sensitive anthers.Although some leaf burn with a foliar application isexpected, it will be minimized when the fertilizer isapplied during the cool of the day. In years with nighttemperatures in the 40's and daytime temperatures in the60's and low 70's, low levels of burn have been reported.Lately, with daytime temperatures in the high 80's and90's, the best times would be early in the morning from4AM until perhaps 9 or 10 AM, then again in the eveningafter 7-8 PM. This is an art, not a science, and there is noguarantee against leaf burn. Leaves that are burned do notrecover, however, bushels lost due to burn are usually lowfollowing pollination, and if the protein premiums remainhigh this fall, the protein increase will probably be worthmore than any lost bushels due to superficial burning.Topdressing distressed wheat fields for yield?
In most years, the possibility of increasing yield withapplications of N later than jointing will not be successful.However, in areas with extreme rainfall, the plants may beso deficient that there is not enough N in the plants toadequately fill kernels. In this situation, application ofsupplemental N may increase yield through better kernelfill and increase in test weight. This increase would beaccomplished with about 30 lb N, applied with stream-bars, or aerial urea, both with rainfall helpers, or a foliarapplication as described previously for proteinenhancement. The best to expect would be about a 10%yield increase.
North Dakota State University CROP & PEST REPORT June 23, 2005
9
Side-dressing corn With saturated soils, it might appear that time is
slipping by to apply side-dressed N on row crops.However, the weather has cooperated so far in bringingcool conditions along with the deluge. Corn growth hasbeen slow, so it is possible that the soil will dry up enoughto allow a side-dress application before it becomes too tall.
Corn yield decisions are made later in growth than insmall grains. Corn can be 8-10 leaves and still have closeto full yield potential if N application is delayed untilthen. Corn yields can be increased with N applications allthe way to tasseling if conditions completely fall apart,although I wouldn’t wait that long on purpose. It is best totry to get the N on before 10 leaves show.
If the corn becomes too tall for injecting withanhydrous or liquid, set up a boom on a high-clearancesprayer with drop nozzles placed between the rows. Thenozzles should be weighted or braced so they don’t rideabove the canopy. Don’t broadcast N either dry or liquid.Remember that corn isn’t like wheat. Wheat sheds dry andliquid fertilizers to some extent, while corn gathers mostof what lands on it into the whorl, which concentrates thefertilizer, resulting in significant and often serious burnand yield reduction potential.
Successful post-N applications with drop nozzles arepossible until the corn is taller than the high-clearancesprayer platform. The taller the corn, the more damagewill be done turning on the field ends and corn breakagefrom crowding rows (especially in 22 inch rows).Soybean/Flax chlorosis
It is probably no surprise that after the heavy rainssoybeans in the first trifoliate stage or older are showingchlorosis. Saturated soil, with high pH, carbonates andespecially higher soluble salts are ideal conditions forchlorosis to develop. The adoption by growers of morechlorosis/salt tolerant varieties has resulted in moresoybean fields withstanding this stress. However, work byDr. Goos as NDSU suggests that even fields that recoverquickly probably have had 5 bu/a taken off the top due tothe condition. To date, iron sprays have not been effectivein increasing yields from this condition. The best thing tohave happen is for dry weather to move back into theregion.
ESTIMATING THE NEED FOR ADDITIONAL NFOR CORN, OTHER CROPS
During the last few weeks, much of the state hasexperienced substantial, and often excessive rainfall.Rainfall is good to a point. However, these rains haveresulted in losses of N from leaching in center and westparts of the state and both leaching and denitrification inthe east. As a result, we have good growth conditions insome fields, but lower available N than is needed toachieve good yields.
It is difficult even with soil testing and plant analysisto determine rates of N needed to supplement N loss.These losses are often very small scale in variability, sosample numbers need to be large to have a good chance topredict N status based on numbers alone.
The following decision chart was developed by Dr.
George Rehm at the University of Minnesota. It appearedin last week’s Minnesota Crop News. With hispermission, I reproduce it here for your use, with mycomments.
Decision Table for the Need for Supplemental NQuestion #1 When and how was the N applied?
A. In the fall, less the 4 inches deep and soiltemperatures were above 50oF
6
B. In the fall, 4 or more inches deep and soiltemperatures were above 50oF
5
C. In the fall, less than 4 inches deep and soiltemperatures were below 50oF
4
D. In the fall, 4 or more inches deep and soiltemperatures were below 50oF
3
E. In early spring (March/April) 3
F. Broadcast on the soil surface in the fall,unincorporated
4
G. Broadcast on the soil surface in the fall,incorporated, below 50oF
3
H. N applied in May, incorporated. 2
Question #2- What was the predominant spring(May/June) soil condition?
A. Normal or drier than normal 1
B. Wetter than normal 3
C. Standing water in low areas 4
Question #3- What does the crop look like?
A. Crop is tall and moving on in maturity,showing N deficiency*
5
B. Crop is short and early in maturity,showing N deficiency*
3
C. Crop is short and early in maturity,showing no N deficiency*
2
D. Crop is tall, moving on in maturity, green 1
TOTAL SCORE
* N deficiency symptoms vary for each crop. Generally,crops are yellow, more so in lower leaves, with upperleaves greener. Lower leaves on corn will become yellowfrom leaf tip in a V pattern following the mid-vein withthe V-tip aimed towards the stalk.
Add the points for each of the three questions. Total is 7 or less- Supplemental N for yield not
necessary Total 8-9 Supplemental N may or may
not be necessary Total of 10 or more- Supplemental N is suggested
North Dakota State University CROP & PEST REPORT June 23, 2005
10
Rates from 30-50 lb N/acre are suggested for most crops.High rates for crops with high yield potential and lowdown-size quality risk from application of N (any cropsexcept flax, barley, sugarbeet, safflower).Also, for canola, if N appears lost, assume that sulfur wasalso lost and include some in the supplement.
Sulfur supplementationAlthough less common than N deficiency, if
yellowing is seen, particularly in younger leaves onhilltops and eroded areas, S may have leached from theroot zone and the crop may require supplementation if nottoo far advanced. Plant analysis may confirm a Sdeficiency. Ammonium sulfate or another availablesulfate fertilizer would be suggested to correct a problem.Do not broadcast liquid ammonium thiosulfate on mostcrops, except through irrigation water or on canola.Canola has a heavy wax leaf layer after 5 leaves thatprevents serious burning.
Dr. Dave FranzenExtension Soil Specialist
SECTION 18 FOR REFLEX ON DRY BEANAPPROVED
The long awaited ND Section 18 application forReflex on dry bean HAS BEEN approved by the EPA.The NDDOA has issued a press release. The label can befound on the NDDOA web site or the NDSU PesticideCertification Web site. Both web sites are listed on theback cover of the 2005 ND Weed Control Guide. Asummary of use information can be found on page 29 ofthe 2005 ND Weed Control Guide.
AGDAKOTA LIST SERVEMany of you subscribe to <agdakota> list serve
which has become one of the most used and preferredavenues to quickly get critical information to consultants,agronomists, and ag professionals. Area and StateExtension Ag specialists, and ND Dept of Ag staff sendnew pesticide registration announcements, label updates,Section 18 approvals, new pest epidemics, and a widevariety of other timely agriculture information throughthis list serve. If any of you are not subscribed or if youknow of new hires or others that would appreciate thistimely information updates, please send the persons emailaddress to [email protected] to request a FREEsubscription.
RAINFASTNESS OF COMMONLAMBSQUARTERS
Dr. Chris Boerboom, U. of WI Weed Scientist wrotean interesting article in his Pest Report last week aboutdifferential rainfastness on weeds. He noted from his fieldresearch and farm visits that foxtails and several broadleafweeds were controlled by glyphosate after a rain eventshortly after application. However, commonlambsquarters was only stunted. It appears thatlambsquarters might need more time to fully absorbglyphosate than other weeds. If you have a situationwhere lambsquarters was not controlled and other weedswere, rain could be considered as a potential cause.Different glyphosate formulations have differentrainfastness periods. Page 69 of the ND Weed ControlGuide gives a summary but in general:
Most Monsanto Roundup brands have a 0.5 hour, New Syngenta Touchdown brands have a 1 hour, Generic full adjuvant load formulations have 1 to 2 hour,Generic partial adjuvant load formulations have a 4 hour,and Generic no adjuvant load formulations have a 4 to 6hour rainfastness interval.
NEW CEREAL HERBICIDE IN DEVELOPMENTAxial (pinoxaden), a new cereal herbicide was
introduced at the Syngenta research facilities in Stein,Switzerland, last week. Axial is a post-emergencegraminicide (not a “dim” or “fop”) developed forworldwide use in cereals. Axial will control a broad-spectrum of annual grasses. Pinaxaden will be formulatedwith cloquintocet-mexyl safener to impart excellent cropsafety in both wheat and barley. Studies are beingconducted to determine of this compound will controlACC-ase resistant grass biotypes.
Pinoxaden is effective on wild oat, green and yellowfoxtail, barnyardgrass, and Persian darnel but does notcontrol brome species. The application window in wheatand barley will be from 2-leaf up to pre-boot and grassweeds from 1-leaf to 6-leaf + 3 tillers. One rate will beregistered for use. A specific adjuvant was developed andwill be marketed with Axial.
Axial is not yet registered for sale or use in theUnited States or Canada. It is under joint review by theEnvironmental Protection Agency and Canadianregulatory authorities as a reduced-risk product. Axial willbe featured as a research product in grower, retailer anddistributor demonstration tours in the northern UnitedStates and in western Canada beginning June 22. Dr. KirkHowatt has been testing pinoxaden in his state-wide grassweed control studies in wheat. Control information will beavailable this winter in extension meetings and updates.
North Dakota State University CROP & PEST REPORT June 23, 2005
11
SELECT USE IN FIELD PEA AND LENTILThere has been some discussion on whether or not
clethodim products are labeled for use in dry pea andlentil. Select, Arrow, and Prism are NOT labeled for usein these crops yet. However, they can be used in chickpeaand dry bean. It will be at least 2006 before they areapproved for use in dry pea and lentil. Assure II andPoast can be used in dry pea and lentil.
MOSS CONTROL IN STOCK TANKS ANDSTANDING WATER
Algae in stock and nurse tanks can be a nuisance forboth animals and for chemical application especially withhard water. Adding copper sulfate to the water will takecare of the problem until the tank is refilled with freshwater. The process must then be repeated.
Dissolve 1 ounce of copper sulfate in 1 pint of waterin a glass jar. Add 0.25 pt/1000 gallons of water. Thecopper sulfate will not affect herbicide and weed control.
An alternative for nurse tanks is to paint the entiretank black. This eliminates the sunlight requirementwhich prevents algae growth.
ABSINTH WORMWOOD CONTROL IN ALFALFA- THE REST OF THE STORY
In an earlier pest report article I reported that anunusual number of inquiries were made this spring foreffective postemergence absinth wormwood controloptions in alfalfa. I mentioned that 2,4-DB (example,Butyrac 200) could possibly be effective because someplants convert 2,4-DB to 2,4-D in the plant. Alfalfa doesnot make the conversion, which gives it some immunity. Idiscussed this with Dr. Rod Lym, who was conductingabsinth wormwood control trials this year. He applied 2,4-DB to absinth wormwood over 2 weeks ago at 2 to 4 qt/A(1 and 2 lb ai/A). Th maximum use rate allowed in alfalfais 2 qt/A. He evaluated the 2,4-DB plots for absinthwormwood control on Tuesday, June 21. There was nosign of control from either treatment. A few leaves mayhave been stunted in the 4 qt/A (2 lb ai/A) plot, butnothing more. Treatments that included Tordon, Banvel,Stinger/Transline. had near 100% "burn down". The restof the story is that, with exception of Roundup Readyalfalfa, there appears to be no postemergence controloption of absinth wormwood in alfalfa. Registered soil-applied herbicides ( Velpar, Sencor, Sinbar, Kerb - seepage 45 in the 2005 ND Weed Control Guide) for late fallor early spring application to dormant alfalfa do not haveabsinth wormwood on their labels. Thus, there is nothingknown to control absinth in alfalfa.
Richard ZollingerNDSU Extension Weed Specialist
South-Central ND
During the past 30 days (May 23 to June 21), thesouth-central region’s rainfall ranged from 3.5 inches atRobinson to 9.6 inches at Edgeley as recorded atNDAWN (North Dakota Agricultural Weather Network)sites. Hail and strong winds injured crop in Ransom andSargent counties on June 20. Areas north of I94 and westof Hwy 281, and south of I94 and west of Hwy 3generally have less challenges with excessive soilmoisture compared to other areas in eastern ND. Growerscontinue to struggle with completion of crop planting inthe southeast ‘wet’ counties. Timely herbicide applicationin warm-season crops, fungicide application in wheat, andhay harvest are challenging most farmers.
The region’s cool-season crops generally continue to haveexcellent plant stands and yield potential. The region’sspring wheat crop is in the flag-leaf to flowering stages ofgrowth. Wheat growers should be applying a fungicideduring early-flowering for scab suppression andprotection from leafspot disease. Aggressive farmmanagers are applying foliar N for increasing wheatprotein content. Small grain lodging will be an increasingconcern as the crop enters the grain-fill stages. Smallgrain aphids and barley thrips are present in the region.The region’s abundant moisture is increasing thepossibility of white mold infections in flowering canola.Corn growth is rapidly accelerating with the currentlyadequate moisture and warm temperatures, and shouldeasily be at or beyond ‘knee-high height’ by July 4.Soybean aphids have been reported in the Valley Cityarea. Soybean are in the mid-vegetative stages and willbegin flowering during the week of July 4.
Greg EndresArea Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center [email protected]
North Dakota State UniversityCROP & PEST REPORTExtension EntomologyHultz Hall 202Fargo, ND 58105-5346
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