Soybean Information Package

So, you’ve decided to grow soybeans! Whether it’s your first time growing them, or you’ve tried it a time or two, hopefully the following pages will have something in them that you will find interesting and helpful.

Field selection

Soybeans can be grown on many different soil types, although the ideal soil type for soybeans is loam (Manitoba Agriculture, Food and Rural Initiatives 1). Although they do perform quite well on heavier clay soils, challenges experienced with these soils include difficulty planting and emergence problems. Drought conditions are often a concern when growing soybeans on sandy soils.

When selecting a field to grow soybeans on, it is important to leave three years between the same pulse crop, and two years between different pulse crops, as the same diseases can affect them (Guide to Field Crop Protection 2012).

Variety selection

The first choice to make when selecting a soybean variety to grow is if you are going to go the conventional or Roundup Ready route. Most soybeans grown are Roundup Ready varieties.

It is very important to select a soybean variety rated for your area. Each variety is assigned with a company crop heat unit (CHU) rating (Seed Manitoba 2012). These ratings help growers select varieties that have appropriate maturity dates for their areas. As CHU ratings are not always exact, it is a good idea to use the ‘relative days to maturity +/- check’ column in the Seed Manitoba guide as a second information source. The ‘relative days to maturity’ is determined by the number of days from seeding to maturity for a variety from four common sites. A third way to evaluate the maturity of a variety is to look at the season designation – long, mid or short season. The short season label is usually applied to areas on the outer edges of current soybean growing areas. Long season generally refers to the area of Manitoba south of highway 23, on the more central and eastern side of the province. The mid season reference applies to areas between the short and long season areas.

Soybean varieties have differences in the colour of their hilum (where the seed attaches to the pod) (Seed Manitoba 2012). The colours include yellow, imperfect yellow, grey, brown, buff and black. The hilum colour has no agronomic effects, but can affect some export markets.

Some soybean varieties can be affected by Iron Deficiency Chlorosis (IDC). IDC is a disease caused by a shortage of iron in the plant (Plant Health Initiative 2009). As iron is a necessary component of chlorophyll, leaves become pale green, yellow or white, inhibiting growth and reducing yields. IDC occurs in high pH soils where there is poor drainage and high levels of soluble salts and lime. Seed Manitoba 2012 gives two indicators for IDC – a rating score and a grouping. The rating score is a numerical value ranging from 1 to 5, with 1 being green leaves and 5 being severe chlorosis and a stunted growing point. A lower rating score means the variety will grow better on iron deficient soils. IDC groupings are split into three categories – tolerant, semi tolerant and susceptible. Varieties with close numerical ratings can be in different groupings, but still show similar symptoms. The same varieties can have different visual rating scores in different years.

There are several different varieties that are suitable to be grown in western Manitoba. An example of a few are Pekko (Brett Young), Libau (NorthStar Genetics), LS 003 (Legend Seeds) and Anola (NorthStar Genetics).

Field preparation

As with any crop, starting with a clean field is essential to maximize your yield potential. Soybeans are not strong competitors, therefore, it is important to get an effective burn-off done. Glyphosate can be sprayed alone, or mixed with Express SG (Dupont product), Heat (BASF product), or CleanStart (Nufarm product). In most situations, Heat looks to be the safest and most effective of the three options. If the field is going to be worked in the fall or spring before sowing soybeans, Edge (Dow AgroSciences product) is another early season weed control option.

If Express SG is used, the rate is 80 acre/bottle (standard rate for all registered crops). Express SG must be tank mixed with glyphosate (any glyphosate brand is okay). The Express SG is added first, followed by the glyphosate when tank mixing Express SG and glyphosate. Before using Express SG, it is important to know the soil characteristics of the field it is to be applied to. To avoid crop injury, the soil organic matter must be greater than 3%, and the sand content needs to be below 50%. Express SG should be applied a minimum of 24 hours before seeding. Although Express SG is registered for soybeans, Express PRO is not.

If using Heat, only the 80 acre/bottle rate is safe. At rates higher than this, the soybeans may experience tolerance issues. Similar to Express SG, Heat must be tank mixed with glyphosate (any brand okay). Two jugs of Merge must be added to the spray tank for every 80 acre bottle of Heat used. The tank mixing order is Heat, glyphosate, Merge. The ideal timing for Heat application is just before crop emergence. This ensures that the maximum residual activity of the Heat can be taken advantage of. When Heat is applied before seeding, the soil disturbance

in the seed row will move the residual Heat into the row spaces, resulting in weeds growing in the seed row. At the 80 acre/bottle rate of Heat, 4 – 7 days of residual activity can be expected, depending on conditions. At higher moisture/rainfall levels, the residual is less than when lower rainfall amounts are received. Also, the length of residual activity is dependent on soil texture, with shorter residual on sandier soil than on heavy clay soils.

Clean Start is a pre-packaged product of a ½ litre of glyphosate and Aim. The registered rate is 40 acre/case. The rate can be increased to 20 acre/case if the grower is targeting weeds that more glyphosate alone would not help with, such as extreme pressures of or larger than labelled Roundup Ready canola. If only a higher glyphosate rate is desired, Clean Start can be topped up with an addition of glyphosate. It is recommended to not go over 1 litre REL/acre of glyphosate (Nufarm). If using the 20 acre/case rate, no additional glyphosate can be added, and at the 40 acre/case rate, only ½ litre REL can be added. If the 40 acre/case option is used, the following glyphosates are compatible for tank mixing: all except for Touchdown and the cheap Chinese glyphosates. It is important to use a minimum of 10 gal/ac of water to ensure that the Aim component performs effectively. Clean Start must be applied before seeding, with no waiting period between spraying and seeding.

Table 1 – Pre-seed/Pre-emergence glyphosate additives – options for use before a soybean crop (Guide to Field Crop Protection 2012)

Product Express SG Heat CleanStartRate 80 ac / bottle 80 ac / bottle 20 - 40 ac/caseWater Volume 5 – 10 gal/ac 5 - 10 gal/ac Min. 10 gal/acTank mix glyphosate Any glyphosate okay Any glyphosate okay All except

Touchdown and the cheap Chinese glyphosates

Surfactant required None 2 jugs Merge per bottle of Heat

None

Application timing Minimum 24 hours before seeding

Just before emergence Before seeding

Soil restrictions OM > 3%Sand content < 50%

none none

Re-cropping restrictions

No restrictions one year after. Canola, flax, lentils, alfalfa may be planted 2 months after application.

Canola, dry beans, flax, mustard, all registered crops may be seeded year after use. Canola may be planted the spring following a fall application.

All crops may be planted 12 months after application

Mixing order Express SG, glyphosate Heat, glyphosate, Merge

Aim, glyphosate

Edge is a granular grassy and broadleaf chemical that must be incorporated into the soil within 24 hours of application (Guide to Field Crop Protection 2012). A second incorporation, at a right angle to the first, must be done at least three days after. If Edge is fall applied, both incorporations should be done in the fall, however, the second incorporation can be left until spring to conserve trash if it is done to the same depth as the first. The rate of Edge used is dependent upon timing of application (fall or spring) and the soil texture and organic matter of the field (details on page 135 of the Guide to Field Crop Protection 2012). There are several re-cropping restrictions with the use of Edge. The ones most relevant to our area are: i) oats and small-seeded grasses (timothy, canary seed) cannot be grown after a crop treated with Edge and ii) wheat cannot be seeded as a rotational crop onto land treated with Edge at the oilseed/special crop/barley rates for two consecutive years.

Seed treatments and inoculants

Before soybeans can be planted, they need to be treated with double inoculant and a seed treatment to help ward off disease and insects. It is recommended that soybeans in our area receive double inoculant because the rhizobia needed to colonize soybean roots are a different strain from peas, and is not found naturally in our soils (Brett Young Seeds). There are three different forms of inoculants – peat, liquid and granular. Peat and liquid are both applied directly to the seed, whereas granular inoculant goes down into the seed row (separately from the seed) through an attachment to the air drill. It is also recommended to use two different types of inoculant, a granular with either a liquid or peat, in order to maximize the number of nodules present on the roots (Manitoba Agriculture, Food and Rural Initiatives 2). Because the liquid and peat inoculants are placed on the seed, once the main root tip has grown away from the seed, the rhizobia can no longer colonize that root, and the number of nodules cannot be increased. The use of granular inoculant gives the opportunity for nodules to form on lateral roots, as well as the main roots. Because granular inoculants are in the seed row, the lateral roots can come into contact with rhizobia, and be colonized, giving a greater number of nodules than if liquid or peat were the only inoculant types used. There are several different choices when it comes to inoculants. The Isis soybeans this year will come treated with Cruiser Maxx seed treatment and Optimizer, a liquid inoculant that has an extender in it to prolong the life of the bacteria. It is also recommended to add TagTeam granular to the seed row. You may observe that the leaves on the soybeans are a light green or pale yellow colour (Ontario Ministry of Agriculture, Food and Rural Affairs 1). This often happens before the nodules are fully functional, and is a normal phase of development that lasts about 7 – 10 days. Once the nodules begin producing nitrogen, the leaves will become a dark green colour.

Soybean seeds are susceptible to seed and seedling rots (Manitoba Agriculture, Food and Rural Initiatives 1). There are options when choosing a soybean seed treatment, but Cruiser Maxx seed treatment has both a fungicide and an insecticide (Guide to Field Crop Protection 2012). It has also been used extensively in eastern Manitoba, where it consistently shows a 5 bushel/acre yield increase (Brett Young Seeds).

Seeding

The recommended seeding rate for soybeans is 200,000 – 230,000 seeds/acre (Brett Young Seeds). It is important to keep the seeding rate high when seeding soybeans with an air seeder so that the plants compete somewhat with each other and grow taller, reducing harvest losses from pods too low to the ground being left in the field. For the first few times growing soybeans, growers should not alter the row spacing on their air seeders (Brett Young Seeds). Once the grower becomes comfortable growing soybeans, some air seeder runs can be blocked to increase row spacing and decrease seeding rates.

Under moist conditions and in a loamy or heavy soil, soybeans should be seeded ¾ to 1 inch deep (Manitoba Agriculture, Food and Rural Initiatives 1; Grow Community of Independents). If conditions are drier, or the soil is sandier, seed up to 1.5 inches deep to make sure the seeds are into moisture.

Soybeans should be sown between May 15 and May 25, when the average soil temperature is at least 10°C, although the ideal soil temperature for soybeans is 18 – 22°C (Manitoba Agriculture, Food and Rural Initiatives 1).

Fertilizer

Soybeans do not require any nitrogen fertilizer, as long as effective nodulation occurs (Manitoba Agriculture, Food and Rural Initiatives 1). Application of nitrogen fertilizer to soybean can delay nodulation. If nodulation does not occur, and the leaves are yellowing at early flower, nitrogen can be broadcast onto the crop.

The common phosphorus recommendation for soybeans is 30 to 40 lbs/acre (Manitoba Agriculture, Food and Rural Initiatives 1). Sideband or 1 inch below the seed are common placements for phosphorus. The maximum safe rate of phosphate applied with the seed is 10 lbs P2O5/acre for seed rows with a width of 15 inches or less (Soil Fertility Guide). If seed row widths are greater than 15 inches, the safe rate of P2O5/acre is 0 lbs/acre. Phosphorus deficiency symptoms are varied, and include stunted growth, dark green leaf colour, necrotic leaf spots, purpling of the leaves and leaf cupping, as well as delayed blooming and maturity (Kansas State Agronomy Update 2008).

Potash requirements for soybeans usually range from 30 to 60 lbs/acre (Manitoba Agriculture, Food and Rural Initiatives 1). Due to seed sensitivity to potassium, the potash should be applied away from the seed. Yellowing or browning on the leaf margins of the older leaves indicates a potassium deficiency (Ontario Ministry of Agriculture, Food and Rural Affairs 2).

A common sulphur recommendation for soybeans is 20 lbs/acre of sulphate (Soil Fertility Guide). Similar to potash, it should be placed away from the seed. Sulphur deficiencies in soybean show up as stunted, pale green plants (Kansas State Agronomy Update 2008).

Rolling

The soybean field needs to be rolled after planting and before crop emergence. The purpose of rolling is to conserve moisture and to level the field by pushing rocks into the soil, making it easier to harvest the soybean crop. If rolling is done after the soybeans emerge, damage can be done to the plants.

In – crop weed control

The type of in-crop weed control that is used depends on the variety selected. If conventional soybeans were chosen, then there are several different options available to growers (Guide to Field Crop Protection 2012). The choice of chemical in a conventional system will depend on several factors, including the stage of the crop, weed spectrum of the field, tank-mix options, re-cropping restrictions of the chemicals and the plans for next year’s crop, and the pre-harvest interval of the chemical.

In Roundup Ready soybeans, glyphosate applications must be made after the plant has its first trifoliate leaf through flowering (Guide to Field Crop Protection 2012). A single application of 1 litre REL may be applied for regular weed pressures, followed by a second 1 litre REL application if late flushes of weeds are present. Alternatively, a single application of 2 litres REL can be made if very heavy weed pressures are present at the timing of the first application. It is important to check the label of the glyphosate product before applying it to Roundup Ready soybeans, as not all glyphosates are registered for use. Recommended water volumes for spraying glyphosate are 5 to 10 gal/acre. There are no re-cropping restrictions after spraying glyphosate alone.

Disease

Manitoba soybean crops can be affected by three diseases – root rot (damping off), powdery mildew and sclerotinia (Manitoba Agriculture, Food and Rural Initiatives 1). Root rot is caused by soil-borne fungi that can attack any part of the root system and the portion of the stem at the soil line (Manitoba Agriculture, Food and Rural Initiatives 3). Root rot usually leads to the death of young seedlings. Symptoms of root rot are yellow colouration, stunted growth, with

brown-black lesions on stems and roots. In severely infected plants, the underground parts are constricted, rotted and dark brown, leading to the loss of lower leaves and death of the plant. In addition to the above symptoms, indications of a root rot infection in a field are patchy stands, with missing plants in the rows. Prevention options include using seed treatments to protect the seedlings. Use of seed treatments is especially recommended during cool, wet springs. A second method of prevention is following a 5 year crop rotation to reduce the build up of root rot fungi in the soil.

Figure 1 – Root rot. Picture on left caused by Fusarium species, picture on the right caused by Phytophthora (Ontario Ministry of Agriculture, Food and Rural Affairs 4).

Powdery mildew is a disease caused by fungi that produce brown, pitted spots on the pods, and the premature ripening may cause shrunken seed (Manitoba Agriculture, Food and Rural Initiatives 4). A light, greyish powdery growth on the leaves, pods and sometimes on the stems are symptoms of powdery mildew. This powdery growth can be rubbed off, and over time, fruiting bodies develop in the powdery growth. The fungi overwinter on plant debris, and the inoculum is spread by wind. Powdery mildew develops in lush crop stands, with dew formation and temperatures between 20 -25°C. Rain can help to disrupt the disease cycle. If crops are planted early, they usually escape the effects of this disease.

Sclerotinia is another fungal disease (Manitoba Agriculture, Food and Rural Initiatives 5), and can cause large yield losses. In addition to reduced yields, affected seed can be discoloured and light weight. The disease overwinters as sclerotia (hard black bodies) in debris from the previous crop and in the soil. When temperatures reach 20 – 25°C, and there is adequate

Figure 2 – Powdery mildew on soybeans. (Manitoba Agriculture, Food and Rural Initiatives 4)

moisture, the sclerotia germinate and produce tiny mushroom shaped structures. The mushrooms mature, and produce spores. These new spores germinate and infect the growing crop, using the plant’s own dropped flower blossoms as a source of nutrients. Within 2 –3 days, the fungus can spread from the dead blossoms of one plant to the adjacent flowers, stems, leaves and pods. The sclerotia formed during the growing season may stay in the harvested crop or fall to the crop residue or soil. Symptoms are present on the stems, leaves, pods and even the seeds of soybeans. The first visible symptoms are brown, water-soaked lesions, which grow under cool, moist conditions, into watery, rotted areas of plant tissue. The lesions then become covered with white, cottony growth. Black sclerotia are formed within the infected tissues, usually in about a week. In the final stages, the lesions become dry, bleached and shredded. The branches and main stems of the infected plants may wilt and die when the fungus circles the stem. Increasing row spacing can improve the air flow between plants, which may help to reduce the occurrence of Sclerotinia. Crop rotation is an important tool in managing sclerotinia, leaving 3-4 years between bean crops, as well as avoiding other sclerotinia-susceptible crops in rotation will help reduce the number of sclerotia present in the soil.

There are no registered in-crop fungicides for control/suppression of sclerotinia in soybeans. However, there is Contans WG, a biological fungicide (Guide to Crop Protection 2011). It is a relatively new product available on the market, and it is

sprayed onto the soil approximately 3 months before the onset of the disease. It can be either spring or fall applied, and needs to be incorporated into the top 2 inches of the soil after application. The rate of application is 0.4 to 0.8 kg/acre, with a water volume sufficient to give thorough coverage of the soil or remaining crop residue. Contans WG infects the sclerotia in the soil, preventing production of spores to infect the growing crop with. This product cannot protect the crop from spores that blow into the field.

Figure 3 – Top: Mushroom-like structures (Manitoba Agriculture, Food and Rural Initiatives 5); Middle: cottony-white, bleached stem lesion; Botton: black sclerotia bodies produced on/in stems and pods (Ontario Ministry of Agriculture, Food and Rural Affairs 5).

Insects

Soybeans are affected by several insects, including soybean aphid, grasshoppers, wireworms and cutworms. Soybean aphids are pale yellow, and adults may or may not have wings (Ontario Ministry of Agriculture, Food and Rural Affairs 3). The eggs are laid on twigs of the buckthorn species, nymphs hatch in the spring, and the aphids go through two, wingless adult generations on the buckthorn plants. It is the third generation that causes problems in soybeans, as these winged adults move onto soybean plants. Once on the soybeans, the aphids produce wingless after wingless generation, until overcrowding occurs, and resources become too limited. At this point, a winged generation is produced, which moves to less crowded soybean plants. The aphids are all female, until the fall when males are born to mate with females and produce the eggs on the buckthorn plants. Over the spring and summer, all female aphids are born pregnant, and give birth to live nymphs. As many as 18 generations can be produced per year on soybeans. Aphids damage soybeans when they suck juices and nutrients from the plant using their piercing-sucking mouthparts. Symptoms of threshold levels of aphids include aborted flowers, stunted plants, reduced pod and seed quality. If the aphid infestation occurs when soybeans are beginning to bloom, flowers are aborted. Infestation at this time causes the greatest yield loss. Infestations during pod fill and later usually result in smaller seed size and lower seed quality. Early in the growing season, aphids are found on emerging leaves and the upper trifoliates. As the season progresses, the aphids move down the plant to avoid heat and predators. Fields should be checked every 7 – 10 days (every 3-4 days when aphid numbers approach threshold), and counts done on 20 -30 plants across the field, avoiding the field edges. Scouting should continue until the crop has filled the upper pods, leaves begin to yellow and lower canopy leaves begin to fall off. Once aphid counts reach 250 – 300 aphids/plant, scout frequently to see if numbers increase (Guide to Crop Protection 2011). At 250 – 300 aphids/plants, they do not cause economic yield loss. If aphid numbers remain steady, there are enough natural predators to keep the aphid population from reaching the economical threshold. If aphid numbers are increasing during the time soybeans are beginning to bloom and starting to set seed, treatment is economical. Treatment options include Cruiser Maxx seed treatment (Syngenta product), Concept (Bayer product), Matador (Syngenta product)/Silencer (MANA Canada product) or Lagon (UAP product)/Cygon 480 EC (IPCO product).

Figure 4 – Soybean aphids (Ontario Ministry of Agriculture, Food and Rural Affairs 3).

Table 2 – Available insecticides for treatment of soybean aphids in soybean crops (Guide to Field Crop Protection 2012)

Product Concept Matador/Silencer Lagon/Cygon 480 ECRate 132 – 263 ml/ac 34 ml/ac 0.28-0.4 L/acWater volume 10 – 20 gal/ac Not specified, but

need good coverage (10 gal/ac min)

Sufficient water for good coverage (10 gal/ac min)

Application timing When pest has reached economic threshold levels

When pest has reached economic threshold levels

When pest has reached economic threshold levels

Application method Ground Ground, aerial Ground, aerialContact/systemic Contact and systemic Contact and stomach Systemic and contactToxicity to bees Very toxic Very toxic Very toxicPre-harvest interval 20 days 21 days 30 daysRestrictions Do not use after

group 4 seed treatment (ex. Cruiser Maxx bean)Min 5 day interval between applications

Min 7 day interval between applications

Wait 10 days before putting leafcutter bees in treated field

Maximum # of applications/year

3 2 @ 33.2 ml/ac Check label

Grasshoppers feed on the leaves and pods of soybeans (Manitoba Agriculture, Food and Rural Initiatives 1). Grasshoppers lay eggs from late July into the fall (Manitoba Agriculture, Food and Rural Initiatives 6). The eggs overwinter in the soil, and hatch from late April, early May until mid-late June. Grasshopper eggs cannot start to hatch until the soil temperature has been 15 – 16°C for approximately 200 hours. It takes grasshopper nymphs 35 – 55 days to reach maturity, and the adults live for 4 – 6 weeks. There is usually very little effect observed on yield if moderate feeding occurs before flowering, as at this point, defoliation of 50% results in a yield loss of only 3% (Manitoba Agriculture, Food and Rural Initiatives 1). However, if populations reach 8 – 12 grasshoppers per square metre before flowering, control is often economical (Manitoba Agriculture, Food and Rural Initiatives 6). Once the soybeans have begun to flower and pod, the economic threshold for control is 2 grasshoppers per square metre. There are several options that can be used to try to control grasshoppers. Hopper baits, which are an insecticide on bran, are a low cost option that is not harmful to pollinators and other beneficial insects. Hopper baits are usually applied with equipment that is used to spread granular herbicides or seed. A common grasshopper control strategy is to spray the grasshopper nymphs in the ditches and field headlands to keep them from moving into the rest of the field.

In severe cases, it may be necessary to treat the entire field. Matador (Syngenta product)/Silencer (MANA Canada product) are the only insecticides registered for grasshopper control in soybeans. The product and use information is the same as that in Table 2 for soybean aphids.

Wireworms feed on germinating seeds and young seedlings, causing damage by shredding the stems (Manitoba Agriculture, Food and Rural Initiatives 7). Adult wireworms are known as ‘click beetles’ because they are able to flip themselves upright when on their backs, and the flipping action causes a click sound (Ontario Ministry of Agriculture, Food and Rural Affairs 6). Wireworms spend most of their 6 year life cycle as larvae. They over winter in the soil, and come to the surface in the spring when soil temperatures rise (Manitoba Agriculture, Food and Rural Initiatives 7). Female beetles lay 200 – 1400 eggs from May to June, after emerging from the soil. The larvae (wireworms) hatch, and start feeding on the roots, seeds and germinating seedlings of plants. Larvae that are fully grown pupate in the soil during July, and do not re-emerge from the soil as adults until the following spring. Indications of wireworm feeding are non-uniform or gaps in the stand (Ontario Ministry of Agriculture, Food and Rural Affairs 6). Injured plants are stunted and wilted. Wireworms are most prevalent on fields with low soil disturbances and sandier soils. Scouting for wireworms needs to take place before planting. Bait balls are buried 2 – 3 inches below the soil surface, and the bait ball should be checked for wireworms a few days before sowing the crop. If there is 1 wireworm per bait ball (Ontario Ministry of Agriculture, Food and Rural Affairs 6), the economic threshold has been reached. Soil can also be sieved to a depth of 6 inches over a 20 x 20 inch area. Using this method, the economic threshold is reached when 32 wireworms per square metre are found (Manitoba Agriculture, Food and Rural Initiatives 7). The only practical suppression method is to use a seed treatment with an insecticide in it, such as Cruiser Maxx. There are no control/suppression methods that can be used if a wireworm infestation is discovered after the seed has been planted.

There are cutworms in most fields most years, but usually at populations too low to cause significant damage to crops (Manitoba Agriculture, Food and Rural Initiatives 8). The redbacked cutworm is the species that most often causes economic losses in Manitoba. Other species that contribute to losses are the darksided cutworm and the dingy cutworm. The species of

Figure 5 - Wireworm larvae (Ontario Ministry of Agriculture, Food and Rural Affairs 6)

cutworm present in the field is important, as some complete larval stages sooner than others and some are more likely to clip to stems or just chew on leaves.

Table 3 – Characteristics of common species of cutworm of economic importance in Manitoba

Cutworm species Redbacked Darksided DingyAppearance - Two broad, dull-red

stripes down length of back- yellowish-brown head

-similar to redbacked cutworm, except grey coloured instead of red

-thin light line down middle of back-broader diagonal marks that look like tire tracks or ‘V’s on both sides of thin line-4 equal sized black dots on back surface of each abdominal segment

Feeding activity -young larvae: small holes and notches in leaves-older larvae: eat stems, often severing them

-young larvae: feed on leaves-older larvae: cut plants at ground level

-leaf feeders-rarely cut plants off

Over-wintering stage Eggs Eggs Partly grown larvae

Cutworm moths lay eggs in or on the soil. After hatching, the larvae feed on the host plants. Cutworm larvae moult (shed their skin) between each of their six instar stages (the darksided cutworm has seven instars). During moulting, larvae are a few centimetres below the soil surface, and are inactive. If larvae are moulting, they will not have a greenish appearance to their mid-gut. When they are ready to pupate, the larvae move deeper into the soil. The moths exit the soil through the tunnel the larvae made. Evidence of cutworm feeding is notched, wilted or cut-off plants. The rows will have missing plants, and bare patches in the field may even be present. Cutworms can be found by looking in the soil (from just under the surface to 3-4 inches deep) around the cut-off or injured plants. Small larvae have the greatest potential for damage as they have the most growing and eating to do. If the larvae are close to being fully grown, it may not be economic to use control methods. The length of time it takes larvae to move into the pupae stage depends on the temperature and the cutworm species, with cooler temperatures extending the larvae stage. There is no specific economic threshold for cutworms in soybeans given for Manitoba, but the economic threshold in dry beans is 1 or more cutworms per metre of row when the cutworms are still less than 2 centimetres long. Insecticide applications made in the evening when cutworms are feeding are most effective. In situations where the cutworms are restricted to a few patches of the field, it may be more cost

effective to treat only the infected areas rather than the whole field. Matador (Syngenta product)/Silencer (MANA Canada product) are the only insecticides registered for control of cutworm in soybeans (Guide to Crop Protection 2011). The product and use information is the same as that given in Table 2.

Harvest

The best way to harvest soybeans is by straight cutting using a flex-head header. They need to be cut quite low to the ground to get the lowest pods, as the best beans are often in the pods lower down on the plant (Manitoba Agriculture, Food and Rural Initiatives 9). Careful setting of the combine is also important to minimize seed cracking and splitting and harvest losses. Keeping knives sharp and the reel speed at approximately 25% faster than the ground speed will help to minimize the harvest losses (North Dakota State University Extension Service). The ideal moisture content for soybeans to be harvested at is 14%, although it can be done at 17-18% if air drying is available. The moisture content needs to be below 14% before they can be stored safely. Soybeans are prone to seed damage and harvest losses due to pod shattering if they are combined at moistures below 12%. If moisture contents get to 12% or lower, combining during the morning and evenings can reduce losses and seed damage.

Conventional soybean varieties can be desiccated using glyphosate at a rate of 1 litre REL when the crop has 30% moisture or less (Preharvest Staging Guide). At this moisture level, the stems are green – brown, the pods are brown and dry, and 80-90% of leaf drop has occurred. If the crop is going to be used for seed, it is not recommended to desiccate it, as the glyphosate can damage the germination of the seeds.

Storage

As soybeans need to be at a moisture content of 13% or below, it may be necessary to use aeration or even a grain dryer to bring the moisture content down to a level safe for long term

Figure 6 – Top: Redbacked cutworm, Middle: Darksided cutworm, Bottom: Dingy cutworm (Manitoba Agriculture, Food and Rural Initiatives 8)

storage (Manitoba Agriculture, Food and Rural Initiatives 9). Aeration works best when the air temperature is still warm. If soybean harvest occurs later in the fall, aeration may not be able to dry the soybeans very much as the cooler fall air does not have much drying ability. Soybeans at 18% moisture will keep over the winter, after freeze up. If this is necessary, the aeration fan should be run every couple of weeks to cool any ‘hot spots’ that may exist. The high moisture soybeans will still have to be dealt with in the spring. Grain dryers can be used to reduce the moisture content of soybeans, but the process has to be monitored closely. The temperatures can easily become too hot, and the air too dry, causing cracked seed coats and split seeds. For soybeans that will be used for seed, the maximum temperature of the dryer should be 38-49°C to prevent harming the germination of the seeds, whereas safe temperatures for crush soybeans are 54-66°C as the seed integrity is less important.

Conclusion

Although the above paragraphs contain only a brief discussion of the soybean growing process, we hope that they will serve as a guideline for your farm. We are always available to answer any questions and to help you deal with any concerns that you may have.

References

Brett Young Seeds, Jeremy Jones. Regional Account Manager for SE Saskatchewan and SW Manitoba.

Guide to Field Crop Protection 2012. Manitoba Agriculture, Food and Rural Initiatives.

Grow Community of Independents. Grow Academy Business Agronomy Manual.

Kansas State Agronomy Update. 2008. Kansas State Extension Agronomy e-Updates. E-Update 070808.pdf, from www.agronomy.ksu.edu Accessed March 29, 2011.

Manitoba Agriculture, Food and Rural Initiatives 1. Soybean – Production and Management. http://www.gov.mb.ca/agriculture/crops/specialcrops/bih01s01.html Accessed March 28, 2011.

Manitoba Agriculture, Food and Rural Initiatives 2. Factors affecting plant survival from flooded soil. http://www.gov.mb.ca/agriculture/crops/cropproduction/gaa01d51.html Accessed March 28, 2011.

Manitoba Agriculture, Food and Rural Initiatives 3. Root Rot (Damping Off). http://www.gov.mb.ca/agriculture/crops/diseases/fac24s00.html Accessed March 29, 2011.

Manitoba Agriculture, Food and Rural Initiatives 4. Powdery Mildew. http://www.gov.mb.ca/agriculture/crops/diseases/fac23s00.html Accessed March 29, 2011.

Manitoba Agriculture, Food and Rural Initiatives 5. White Mould (Sclerotinia). http://www.gov.mb.ca/agriculture/crops/diseases/fac04s00.html Accessed March 29, 2011.

Manitoba Agriculture, Food and Rural Initiatives 6. Grasshoppers. http://www.gov.mb.ca/agriculture/crops/insects/fad10s00.html Accessed March 30, 2011.

Manitoba Agriculture, Food and Rural Initiatives 7. Wireworms. http://www.gov.mb.ca/agriculture/crops/insects/fad28s00.html Accessed March 30, 2011.

Manitoba Agriculture, Food and Rural Initiatives 8. Cutworms in Field Crops. http://www.gov.mb.ca/agriculture/crops/insects/fad06s00.html Accessed March 30, 2011.

Manitoba Agriculture, Food and Rural Initiatives 9. Harvesting Soybeans in Late Fall. http://www.gov.mb.ca/agriculture/crops/cropproduction/faa25s04.html Accessed March 31, 2011.

North Dakota State University Extension Service. Harvest. http://www.ag.ndsu.edu/procrop/syb/soyhar09.htm Accessed March 31, 2011.

Nufarm Agriculture Inc. Myles Robinson. Manitoba Provincial Sales Manager.

Ontario Ministry of Agriculture, Food and Rural Affairs 1. 2009. Soybeans: Planting and Crop Development. http://www.omafra.gov.on.ca/english/crops/pub811/2planting.htm Accessed March 29, 2011.

Ontario Ministry of Agriculture, Food and Rural Affairs 2. 2009. Soybeans: Fertility Management. http://www.omafra.gov.on.ca/english/crops/pub811/2fertility.htm#table2-16 Accessed March 29, 2011.

Ontario Ministry of Agriculture, Food and Rural Affairs 3. 2009. Insects and Pests of Field Crops: Soybean Insects and Pests. http://www.omafra.gov.on.ca/english/crops/pub811/13soybean.htm#soybean Accessed March 30, 2011.

Ontario Ministry of Agriculture, Food and Rural Affairs 4. 2009. Diseases of Field Crops: Soybean Diseases. http://www.omafra.gov.on.ca/english/crops/pub811/14soybean.htm Accessed March 30, 2011.

Ontario Ministry of Agriculture, Food and Rural Affairs 5. 2009. Diseases of Field Crops: Edible Bean Diseases. http://www.omafra.gov.on.ca/english/crops/pub811/14edible.htm#plate161 Accessed March 30, 2011.

Ontario Ministry of Agriculture, Food and Rural Affairs 6. 2009. Insects and Pests of Field Crops: General Insects and Pests. http://www.omafra.gov.on.ca/english/crops/pub811/13general.htm#wireworm Accessed March 30, 2011.

Plant Health Initiative 2009. Iron Deficiency Chlorosis. http://www.planthealth.info/idc_basics.htm Accessed March 28, 2011

Preharvest Staging Guide. Monsanto.

Seed Manitoba 2012. Variety Selection & Growers Source Guide. Manitoba Agriculture, Food and Rural Initiatives, Manitoba Seed Growers’ Association, Manitoba Co-operator.

Soil Fertility Guide. Manitoba Agriculture, Food and Rural Initiatives. Online version http://www.gov.mb.ca/agriculture/soilwater/nutrient/fbd02s00.html Accessed March 29, 2011.