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| Field Crop Advisory Team Alert newsletter | ||||
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| Vol. 22, No. 14, July 26, 2007 |
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In this issue  Insect update Biology, scouting and control of spider mites Management of annual weeds following wheat harvest Four fundamental stages of corn grain yield determination Soybean rust update Soybean sudden death Asian soybean rust sentinel plot scouting report for July 12 to July 26 Two-day workshop on building healthy soils in vegetable and grain crops for organic and sustainable systems Regional reports WeatherNext issue August 8 |
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| Insect update
Spider mites Spider mites are being reported in southern Michigan on several crops. Hot or dry weather is favorable for mites, because the fungi that normally control mites need high humidity. Watch for mite damage to first show up on sandy knolls (drier) or on edges of fields, especially dusty edges along dirt roads. The best mite products are the older OPs such as dimethoate, Lorsban, and generic chlorpyrifos products. Be very careful spraying for mites. Treat only fields that have an economic mite infestation and avoid insurance applications. Mites reproduce even faster than aphids, they are difficult to kill and they become resistant quickly. During mite outbreaks, multiple sprays rarely help the situation, and in fact often make mite infestations worse. Detailed information about spider mite biology, scouting and control follows this article. Western corn rootworm The year has been kind to western corn rootworm beetles. Beetles emerged earlier and in larger numbers this year than I've ever seen. Leaf feeding may look dramatic, but ends when silks and tassels appear. There are no thresholds for leaf feeding. Do not waste spray applications targeting early leaf feeding. I have already seen aerial applications on corn for leaf feeding and these applications were a waste of time and money because they did not protect yield and killed mostly male beetles. Rootworm adults will still be emerging into August, and later emerging beetles are more often females (the real problem). Save your money and time to manage silk feeding which actually could impact yield, especially in seed corn. However, silks can still be pollinated even if they are just 0.5 inch long. Check percentage pollination before spraying. You may be surprised that the field is already pollinated. |
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| As far as damage from rootworm larvae, dig roots in early August to check for corn rootworm damage. I suspect we will see some dramatic lodging in some locations, even in treated or transgenic corn. Yield loss due to larval damage may be enhanced by dry conditions due to water stress and poor root regrowth. We haven't tended this year to get gentle, prolonged rains that alleviate water stress. Instead we've experienced storm fronts rolling quickly across the state bringing little rain and high winds. That increases the potential for lodging and goosenecking, followed by harvest problems in the fall. Bean leaf beetle The year has also been kind to bean leaf beetle. People are noticing more bean leaf beetle feeding this year than in previous seasons. To clarify, this is the first generation bean leaf beetle. The beetles that fed on soybeans in the spring were the overwintering generation (last year’s second generation). The eggs they laid in June gave rise to the first generation beetles feeding in soybeans now. Although first generation adults are nibbling on plants now, the threshold is quite high (25 to 30 percent defoliation) because soybeans can tolerate a lot of feeding. Most people vastly overestimate damage from defoliation. Twenty-five percent defoliation doesn’t mean the top few leaves are chewed; it means a quarter of the leaf material is gone across the entire field. Ron Hammond, the wise (I don’t want to say older) soybean entomologist at Ohio State has spent his career working on bean leaf beetle, and tells me he has seen only a couple fields damaged beyond this threshold in midseason. So, don’t treat for first generation bean leaf beetle! Even if there is a lot of chewing on top, there is plenty of lower leaf material left to carry on photosynthesis. I did get a question about the potential for pod-feeding by first generation beetles. While that could happen, it is more common to have second generation beetles feeding on pods later in the season when the pods are still green and succulent, and foliage is drying down. With a wide planting period for soybeans this year and spotty drought conditions, fields that senesce early or late may be more at risk for economic levels of pod feeding later this summer if they are an attractive feeding site for beetles. The threshold is 5 to 10 percent of pods with feeding damage. Soybean aphid As in previous outbreak years, soybean aphid came on early, with spraying in some locations. Then the hot weather at the end of June plus possibly poor soybean growth, seemed to knock them back. But aphids are still present in most fields, as if waiting for something to happen. Aphid outbreaks are reported in parts of Minnesota, Wisconsin and Ontario, and Quebec is hardest hit this season. We have had aphids go over threshold in June, July and even mid-August depending on aphid flights from other locations. So although things look good so far, we aren't safe yet. If numbers begin to increase, I will get the word out. Western bean cutworm Western bean cutworm is indeed in Michigan at low levels. Extension educators report western bean cutworm moths in traps in Cass, Van Buren, Allegan, Ingham, and Monroe counties. Cass County leads with over 30 moths captured so far. This year, moths are being trapped further north and east than in 2006. The western bean cutworm web site from Iowa State does not have 2007 maps up yet, but you can see a list of trap locations plus total catch: http://www.ent.iastate.edu/trap/westernbeancutworm/isite |
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| Biology, scouting and control of spider mites Spider mite infestations are now being reported in southern Michigan. Be careful about spraying too early or too many times for mites, as they easily flare and become resistant. Life cycle Spider mites overwinter as adults. In spring, they move to new plant growth and lay eggs on the undersides of leaves. Mites can be blown by wind, so initial colonization of a field will often occur in the direction of prevailing winds, or along landscape features that disrupt air flow, such as tree lines, houses or even telephone poles. Infestations usually start on dusty edges of fields. It is thought that dust dries the leaf surface, protecting mites from disease, or perhaps that the dust provides a surface for the mites to anchor their webs. With a hand lens or microscope, you can see that webbing acts like an interstate highway, with mites moving back and forth above the leaf surface. Eggs hatch in a few days, and small mites begin to feed. Immature mites resemble the adults, except that they are smaller in size. They grow by molting, and if you look closely at a mite-infested leaf, you sometimes see the shed skins of immature mites. A leaf heavily colonized by mites will have eggs, immatures, adults, shed skins and webbing. Damage Spider mites feed on numerous crops and under certain conditions will increase to the point where they affect yield. This is especially true under dry conditions or on sandy soils where water stress is an issue. Mites pierce individual plant cells and suck out the contents, initially causing tiny yellow spots (called stippling) on leaves. This feeding also increases water loss from the plant. As populations increase, symptoms include yellowing of leaves and in more severe cases browning, bronzing or death of foliage. As leaves become yellow and die from mite damage, the photosynthetic ability of the plant is reduced. With the additional water loss, leaf drop and reduced photosynthesis, yield and quality of crops is reduced by severe mite feeding. Scouting If an infestation is identified early, spot treatments of the affected area plus a border strip may be enough to take care of mites. Otherwise, if mites spread across a field, estimate the percentage of leaf surface damaged by mites. Thresholds for beans Treatment thresholds for soybeans (based on percentage yellowing) vary with plant stage: pre-bloom = 40 percent; bloom R1 to pod fill R5 = 15 percent; R5 to early maturity R7 = 25 percent; after R7 = do not spray as damage at this point has little impact on yield. A handy evaluation scheme (originally from Ohio State) for mites in soybean is listed in this article. Ohio State evaluation for mites in soybean
Control Mite control is difficult, and more than one application may be needed. Unfortunately, multiple applications can lead to resistance. Later in the season, spraying obviously becomes more difficult due to closing of the canopy, but spraying is also less effective as plants mature (yield is no longer affected).
Mites and aphids
What about natural controls? A heavy rain may reduce the population a little, but don't depend on rain alone. The real key is high humidity, since the fungal pathogens that kill mites require high, sustained humidity to grow and spread through the population. A brief rain, followed by quick drying, does not provide a long enough period for diseases to spread and kill a significant portion of the mite population. Instead, you need a sustained rainy pattern, or repeated dewy wet mornings. |
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| Management of annual weeds following wheat harvest David Hillger and Jim Kells Crop and Soil Sciences Typically, management of annual weeds in wheat stubble is not difficult, however timeliness is critical. These weeds must be managed soon in order to prevent seed production. Several effective options are available for management of annual weeds in wheat stubble. However, these practices must be implemented before seed production to avoid significant additions of seeds to the weed seed bank. After wheat harvest, weeds take advantage of available resources, especially newfound sunlight, and will grow rapidly with adequate soil moisture. These weeds are capable of producing large amounts of seed prior to a killing frost. Common ragweed, velvetleaf, common lambsquarters, redroot pigweed and foxtail species are examples of summer annual weeds commonly found in wheat stubble. At this time of the year, these weeds are completing their life cycles by flowering and producing seed. The main goal following wheat harvest is to prevent or reduce weed seed production. Post-harvest weed control options include tillage, mowing and herbicides. Tillage is a viable option for control of both broadleaf and grass weeds. Mowing will reduce seed production of most grass and broadleaf weeds; however mowing is often less effective on grasses since seeds can be produced on tillers low on the plant. Glyphosate (for grasses and broadleaves) and 2,4-D (for broadleaves only) are common herbicides that can used for post-harvest weed management in wheat stubble. It is important to refer to the herbicide labels for appropriate rates, adjuvants and acceptable tank mixes. |
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| Four fundamental stages of corn grain yield determination Kurt Thelen Crop & Soil Sciences Although recent rains brought relief to some areas of the state, areas of droughty conditions still remain. In a recent article, we discussed the potential corn grain yield loss associated with dry soil conditions. This information is summarized in Table 1. This article will further explore the fundamental stages of corn grain yield determination. Of course, corn grain yield involves the continuous interaction of genetic, climatic, soil, plant pest and nutrient factors present for a specific growing season. However, from a crop management standpoint, it is helpful to characterize the most critical stages of development in the life of a corn plant with respect to determining final grain yield. The following are four critical stages in the development of a corn plant that are fundamental to determining corn grain yield. The first of these critical stages is emergence. Corn does not have the ability to compensate for poor stands as well as other crops such as soybeans. Establishing a uniform, optimum population stand is the first step in developing corn grain yield potential. Studies on the genetic evolution of corn indicate that modern hybrids tolerate field stress associated with higher plant populations better than their earlier genetic predecessors. Growers should continually evaluate the carrying capacity of their fields by putting in a few strip trials to determine the optimum plant population for each field. Keep in mind that as corn genetics continue to evolve, you will likely need to continually adjust your planting population upward to find that optimum plant population for each field. In general, much of the state had good to excellent conditions for corn emergence in 2007, and plant stands are quite good. The second critical growth stage is when the plant determines the number of kernel rows and the number of potential kernels (ovules) per row. This is primarily determined during the rapid phase of corn vegetative growth, which generally occurs in early to mid-July in Michigan. The number of kernel rows per ear is heavily influenced by genetics and is generally determined by growth stage V12, which corresponds to the 12 leaf collar stage. The number of potential kernels per row is being determined at V12 and is usually completed a week to 10 days prior to silking (V17). The number of potential kernels per row is strongly influenced by field conditions. Managing corn to reduce environmental, pest, moisture and nutrient stress during this time will maximize the potential number of harvestable kernels. This stage, along with the pollination stage described in this article, determines the “sink” which the corn leaf canopy will work to fill with photosynthetically derived starch. Follow a plan to ensure adequate nutrient levels, and minimize stress from pests such as weeds and insects during this critical period to establish the potential for high yield. The hardest hit areas of the state likely suffered yield loss during this critical stage of ear size determination. Other areas of the state came through this stage of development in fairly good shape with less significant to minimal yield loss. The third critical stage is pollination. Successful pollination is required to convert potential kernel numbers to actual developing kernels. Pollination occurs when a pollen grain is shed from the tassel, lands on an emerged silk, grows down the length of the silk and successfully fertilizes the ovule. It generally takes two to three days for all the silks on an ear to be exposed and pollinated. Pollen shed generally occurs in the late mornings and early evenings and the pollen shed period typically lasts from one to two weeks. From a management perspective, there is not a lot that can be done to ensure good pollination since it is highly dependent upon the weather. Droughty conditions can de-synchronize pollen shed and silk emergence and also can desiccate silks and pollen grains. This results in barren ears or in short ears with barren tips. Insect pests such as adult corn rootworm beetles can feed on emerging silks and reduce pollination, and therefore should be scouted during silk emergence. Finally, because the tassel and all leaves are completely exposed, the plant is especially vulnerable to hail damage at this stage. Most of the corn in the state has now completed the pollination stage of development. The high variability of rainfall across the state during this period has translated to high variability in pollination success. To assess pollination, remove the husk from developing ears and vigorously shake. Silks on successfully pollinated kernels will drop off and silks emerging from unpollinated kernels will stay fast. The final critical growth stage for determining corn yield is the grain fill or kernel development period. The grain fill period which begins at pollination and ends at kernel black-layer formation generally takes from 60 to 70 days (855 to 1200 GDD) for Michigan conditions depending upon climate, planting date and hybrid relative maturity. The size and weight of harvested kernels are determined at this time and under adverse conditions, kernel number can also be reduced. Stress on the corn plant during the grain fill period can affect final yield by reducing either of these factors. Although field and machinery conditions can still influence final harvestable yield, the corn plant photosynthetic factory has completed its work at the kernel black-layer formation stage of development. Table 1. Effect of four consecutive days of visible wilting on corn grain yield.
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| Soybean rust update Soybean rust has recently shown up in the southwest corner of Arkansas, the furthest north it has made it so far this season. Rust has shown up earlier and more extensively in Texas and Louisiana this year. Rust has also been confirmed in plantings of yam bean (jicama) in Mexico. Rust development and spread in these locations as opposed to rust found in Florida or Georgia is of more concern to us in Michigan, because the majority of storms that could carry the rust northward to us originate in the Gulf of Mexico. Conditions in the Southern states are currently favorable for the development of soybean rust. The good news is that there are no storm systems forecast to move up from the Gulf Coast to Michigan for the next couple of weeks. Dry weather throughout much of Michigan has been generally unfavorable for the development of soybean foliar diseases. There has been no soybean rust found in Michigan to date, but if the need should arise, we will have plenty of fungicides to use. The arsenal of fungicides approved for use on soybean rust has been expanded to include Laredo EC (myclobutanil), which was granted a Section 3 supplemental label last week. |
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| Soybean sudden death Over the last few years, the number of fields reported with symptoms of soybean sudden death has been increasing. The first few reports of suspected soybean sudden death are trickling in, so this is a good time to review the disease symptoms and management. Soybean sudden death is caused by a fungus, Fusarium virguliforme (formerly F. solani f.s. glycines). Research shows that there is a definite relationship between soybean sudden death and the soybean cyst nematode. Although soybean cyst nematode is not required for the development of soybean sudden death, it increases its severity. Soybean cyst nematode has been found in all major soybean producing counties in Michigan. A Michigan soybean check-off supported soil testing program for soybean cyst nematode began in 1997. The percentage of soil samples testing positive for soybean cyst nematode has increased over the last few years, to about 65 percent (of an average 1100 samples per year). In fields where soybean sudden death is a problem, a combination of techniques is needed to manage both the cyst nematode and the fungus causing the disease. Choose resistant varieties to limit yield loss. It’s important to look at both soybean cyst nematode resistance and soybean sudden death resistance levels when selecting varieties. Even when soybean cyst nematode resistant soybeans are used, soybean sudden death may be more severe in fields with a history of high levels of SCN. Because SCN is usually present in fields with SDS, it’s advisable to choose an SCN-resistant soybean that has at least moderate resistance to SDS. Growers requiring group II and shorter maturity soybeans have fewer choices for soybean sudden death resistant varieties than longer maturity groups, but there are some varieties available. Information about SCN-resistant soybeans in the Michigan soybean variety trial ratings can be found at: http://www.css.msu.edu/varietytrials/soybean/Soybean_Home_Page.htm. Ratings of SDS resistance for commercially available soybeans has been conducted across a number of locations in Illinois for several years. That information, along with SCN ratings, maturity group and yield can be found at the Varietal Information Program for Soybeans (VIPS) website www.vipsoybeans.org or at the Southern Illinois University SDS North Central Soybean Research Project website, http://www.siu.edu/~soybean/. Avoid early planting. Yield reductions due to SDS are dependent on when infections begin. Early infections result in pod abortion, reduced seed number and size. Avoid early planting, especially in soils that are cold and wet. SDS is often less severe in delayed plantings and in early maturing cultivars, as the onset of the disease doesn’t occur until later reproductive stages. Evaluate your tillage practices. Severity of SDS tends to be greater under no-till or reduced tillage systems than conventional tillage. Reasons for this may include higher soil moisture, cooler soil temperatures and higher loads of the pathogen remaining as inoculum for subsequent soybean crops. Improve drainage SDS is often found in wet areas or poorly drained soils. Minimize soil compaction, wetter, less porous soils resulting from compaction favor the development of SDS. Avoid moving infested soil from field to field on equipment or vehicles. The fungus responsible for SDS can survive for extended periods in soil. Crop rotation is not a primary management tool for SDS because the fungus produces resting spores in the soil and can survive for extended periods in the soil, but rotating out of soybeans for at least two years does help to reduce SCN populations. Early symptoms of SDS show up on the foliage as small, round, light green to yellow spots between the leaf veins. As the disease progresses, these spots are replaced by brown to tan areas surrounded by chlorotic tissue. Check wet or poorly drained areas of fields for plants with symptoms of SDS. A brown, grayish brown, or reddish brown discoloration shows up in the vascular (water conducting) tissues of the lower stem and root. Root systems are smaller than normal and show some degree of decay. Discoloration appears on the lower part of the taproot first. Dark blue to blue-green areas may be visible on the root surface where the pathogen has produced spores, but aren’t always present. Frequently, plants lose their leaves, but leaf petioles remain attached. Distinguishing soybean sudden death from brown stem rot Brown stem rot (BSR), caused by the fungus Phialophora gregata has very similar leaf symptoms. BSR causes browning of the pith, SDS does not. BSR does not cause root decay, but SDS does. BSR typically shows up later in the season (around R5-R6) than SDS. This information, along with color photos of disease symptoms, is available as a fact sheet at: http://www.ipm.msu.edu/cat07field/pdf/7-26SDS.pdf |
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| Asian soybean rust sentinel plot scouting report for July 12 to July 26 Joe Svoboda and Cassandra Bates MSU Diagnostic Services There were 19 physical samples received from Michigan’s sentinel plots during the past two weeks. The following is a compilation of the reports. Growth stages: one plot = V8, seven plots = R1, six plots=R2, three plots = R3, two plots = R4. Plant height: Ranged from 10 to 30 inches and averaged 20 inches. Degree of canopy closure: Ranged from 35-100 percent. Soybean diseases present: Four samples with Septoria, eight samples with bacterial leaf spot, one sample with downy mildew and seven samples with no pathogens. There was no soybean rust detected on any of the samples. |
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| Two-day workshop on building healthy soils in vegetable and grain crops for organic and sustainable systems Wednesday and Thursday, August 29-30, 2007 9:30 AM to 4:30 PM Location: Morgan Composting 4281 US 10, Sears, Michigan 49679. Phone 231-734-2451 Presenting Dr. Paul Hepperly, Rodale Research Institute. He will share new perspectives of Rodale’s on-farm research of compost and compost teams. (See Using compost to enhance soil fertility and improve disease suppression). Schedule Wednesday, August 29: Maximizing the benefits of compost in field crops. Thursday, August 30: Building the soil and suppressing disease with compost and compost teas. Lunch is included from locally grown food and mostly organic. Early-bird registration: $25 for one day or $40 for both days. Registrations postmarked after Aug. 20: $35 for one day or $50 for both days 517-282-3557 or sorrone@msu.edu or www.michiganorganic.msu.edu Make checks payable to Michigan State University and send to: 303 Natural Resources, East Lansing, MI 48824. |
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| Regional reports 1 -- Southeast Ned Birkey Weather Weather has been fairly normal for temperatures, but precipitation is still seriously lacking. Some locally heavy rain came on Wednesday, July 25, but no general rains have covered the area since Memorial Day weekend. With fairs going on in Washtenaw and Lenawee counties this week and Monroe County next week, we are almost guaranteed to have some rainy and stormy weather. Crop reports Alfalfa has had the second cutting removed, with about half the normal yield. The dry conditions have made baling much more timely than the first cutting. Potato leafhopper numbers are down. Corn is still suffering from the dry conditions. There are fields with three foot tall corn plant tasseling, near six-foot tall tasseling corn and near eight-foot tall tasseling corn. The fields that appear normal size and growth are fewer than the ones that show severe moisture stress. Corn borer numbers are extremely low. Variant western corn rootworms are found in adjacent soybean fields’ yellow sticky traps in higher than expected numbers, though well below the five per day per trap threshold. Most fields are at the R2 blister growth stage of development. Oats have been harvested with below average yields. Some people here place a higher value on oat straw than wheat straw. Soybeans are growing, though very slowly. Very few aphids are being found in traps in Washtenaw and Lenawee counties. Spider mites are moving into soybean field margins at damaging levels in some fields. Bean leaf beetles, grasshoppers and Japanese beetle numbers are low. Soybean cyst nematodes can easily be found and perhaps the early stages of sudden death syndrome. As mentioned above, variant western corn rootworms can be found in soybeans, at higher numbers than in the past few previous years. The only time we had a field above threshold was in 2000. Levels found this week are at half of the threshold number. Most fields are at the R3 beginning pod stage of development. Wheat harvest has been completed with very good test weight and good yields. Nabisco is very pleased with the quality and is shifting to use more white wheat and less red wheat. The MSU Wheat Variety Trial results are now available free of charge, at http://www.css.msu.edu/varietytrials/ or at the Monroe County Extension office. Miscellaneous Although commodity prices are very good compared to the past several years, farmers are generally worried about lower than normal yield prospects based upon poor plant growth and development. It is far too early to accurately estimate corn and soybean yields. |
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| 2 -- Southwest Bruce MacKellar Weather Storms associated with a reverse (northeast to southwest) airflow pattern brought significant rainfall to some portions of the southwest region on July 25. Portions of western Van Buren, Berrien and Cass counties picked up 1.0 to 2.0 inches of precipitation. Some of these same areas also received heavy rainfall during thunderstorms on July 18-19. Additionally, there were heavy rainfall totals in a narrow line north and south of the Battle Creek area to the Coldwater area from the July 25 activity. Elsewhere, the region remains extremely dry. Crop reports Irrigated commercial corn continues to look good. We have seen an increase in western corn rootworm variant activity in rotated fields this year, as is evidenced by the level of leaf windowpane feeding from adult beetles on several commercial and seed corn fields. We are in the process of digging roots from some representative fields to evaluate rootworm larval feeding damage on fields over the next week. Non-irrigated corn that was fortunate enough to have received measurable rainfall has been helped slightly by the moisture and cloudier conditions, but the majority of the crop has suffered irreversible losses due to the drought stress at this point. Some fields will have suffered more than 70-80 percent loss of yield potential. The severity of the loss level is dependent upon the amount of rainfall received. The early planted corn is now in the early grain fill (blister) stages of development (R2-R3). Seed corn continues to grow well where adequate irrigation has been maintained. Detasseling is still underway due to the spread out planting schedule this spring. Male row destruction has begun on the earlier planted fields. Some fields continue to be treated with fungicides, mostly quadric or headline, for control of rust and potential gray leaf spot. Insecticide applications to control western corn rootworm adults and Japanese beetles are also common. We have seen some seed corn fields with spider mite injury on the lower leaves. Affected plants have a bronzed appearance with lots of webbing visible along the lower surface of affected leaves. Check with your seed corn company agronomist or field representative for treatment thresholds and miticides to use before you consider treating seed corn fields. (view image) In soybeans,spider mites are the biggest pest challenge in the dry southwest region. Most fields have at least some populations of spider mites right now. (view images) Many fields may not be showing visual symptoms yet, but it is going to be worthwhile to watch your fields carefully for the rapid development of this pest. At 1/50 to 1/64 of an inch in length, it is really hard to see spider mites on the leaves. Tapping suspect leaves over a sheet of white paper can help you to identify the pest; you likely have spider mites if the “dust grains” begin to move on the paper. The visual symptoms of spider mite infestation start out as leaves with a stippled or yellowed appearance. With more severe feeding, the leaves take on sort of a bronze appearance. Plants that have had high levels of spider mite activity may loose their leaves and die. Dry conditions help this pest become established by reducing the level of pathogenic fungi that help keep their populations in check. Hot conditions help mites by speeding up their reproductive capacity. Mites can “surf” the air currents and move from field to field when the wind catches a sting of their web. Irrigated fields are often considered to be less vulnerable to spider mite infestation. We have seen plenty of spider mite activity on dry corners move out into the irrigated portions of the fields in the past, so scouting for this pest is the best approach to determine if treatment is needed. Treatment thresholds are reached when 15 percent of the plants are infested at the flowering to early podfill growth stages. Spot treatment is possible, but it is important to scout the whole field carefully to make sure that spider mites are not prevalent in areas of the field not yet showing visible symptoms of feeding. See Dr. DiFonzo’s article on spider mite control options in this issue for pesticide recommendations. Soybean aphids continue to be found in relatively low numbers in fields in the southwest region. You should continue to monitor fields for soybean aphids as we move into the early podfill stages. Many producers are questioning how much more money they can afford to put into potential rescue treatments of drought stressed crops. Unfortunately, there is no clear answer to that question unless you have a crystal ball that can see the weather for your farm in August. If there is a decent stand of soybeans left in your fields (the plants have not been killed by the drought stress to this point), and if we get enough rain to end the drought soon, these plants will have at least some chance to recover, produce new growth and set new pods. Spider mites can cause significant yield losses, so the decision to treat needs to be completed in a timely manner. In alfalfa and pastures, growth has been virtually non-existent where rain has not fallen. Watch for potato leafhoppers on fields that have received rain or are irrigated. Potato leafhopper numbers remain very high in the southwest region. |
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| 3 -- West Central Fred Springborn Weather A brief rain shower least night, July 25, deposited 1.0 to 2.0 inches of rain across much of Montcalm County. Until last night, dryland crops were under significant moisture stress as rains have been highly variable and light. This will give many who irrigate a much needed break. High temperatures for the last two weeks have been in the upper 70s to low 80s F. Crop reports Wheat harvest is essentially complete. Yields ranged from 30 bu/acre to the mid 90 bu/acre. All high yielding fields were irrigated. Oat harvest will begin in the next week. Corn is variable. Irrigated corn is progressing well with pollination completed. Dryland corn is pollinating now. European corn borer trap catches are very low with most traps catching one to two moths. Corn ear worm trap catches are lighter this week with an average of one moth per trap. Dry bean stands are very good where there was adequate moisture. Where soils were allowed to dry out before planting, stands are poor. Most soybean fields are blossoming. Growth is below average. These are very low numbers of soybean aphids. Alfalfa second and third cutting is underway. Yields are very low, 30 to 40 percent of normal in many cases. Slow, spotty, regrowth due to dry weather is generally seen. Sugarbeets are doing well by and large. Even irrigated beets have shown moisture stress on several days when temperatures were high and humidity was low. |
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| 4 -- Central Paul Gross Weather There was varying amounts of rain across the region over the past two weeks. It has been mostly hit and miss with more areas missed than hit. Reported rainfall amounts range from 0.5 inch to over 2.0 inches. The region is in need of moisture in the very near future to prevent further yield loss. There was hail last week in parts of Isabella County. It is too early to tell the extent of yield loss in corn damaged by the hail. Crop reports The corn crop is in various growth stages ranging from tasseling to pollination. Fields on light soil have permanent yield loss due to drought conditions. Rain will be needed soon to prevent further yield loss. We are seeing lots of corn rootworm adults in many fields. Soybeans are in growing reasonably well considering the lack of rain. There are fields that have bean leaf beetle feeding and light aphid populations. Spider mites are present in some fields. It will be important to scout fields over the next week for mites and aphids. The populations of these pests can explode almost overnight and with drought stressed beans pest injury can compound. The double crop beans have the first trifoliate emerging. Wheat harvest is wrapping up. There are just a few fields of red wheat left to harvest. Most farmers are reporting disappointing yields. The range has been from about 40-90 bushels per acre. Most agree the average is around 60 bushel per acre. The early season wet conditions, dry summer and late planting last fall have contributed to the lower yields. Harvest of second cutting alfalfa is nearly complete. Yields have been very disappointing. Between dry weather and leafhopper damage yields are 50 percent or less. It seems that leafhopper populations are low at this time. Fields scouted this week were below threshold. Keep sweeping these fields for this pest. Growers on a early cutting schedule will begin harvest of third cutting next week. Summer seeding will be planted in the next two weeks. Oat harvest has begun in the southern part of the region and will begin next week in the northern parts of the region. Dry beans are growing pretty well all things considered. The rows are closing in some fields. The crop could use a good shower. Sugarbeets are growing slow and are in need of rain. |
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| 5 -- Thumb Mark Seamon Weather Variable rainfall continues to bless some areas while leaving others high and dry. Most areas have received some rainfall, but some areas were very limited. Temperatures have been moderate, which is giving some relief to dry areas. The southern and eastern Thumb areas continue to be very dry. Crop reports Alfalfa regrowth is slow and fighting against potato leafhopper feeding. Sugar beets continue to add growth and roots are sizing up nicely in many fields. Weed control challenges can now be seen with weeds reaching through the crop canopy. Disease severity values accumulation for cercospera leafspot is variable across the beet growing area. A few leafspot symptoms have been confirmed. Be sure to check specific data for a site near you. This can be found at http://www.michiganbeets.com/ The wheat harvest has been finished in most areas. Yield and quality were pretty good considering the weather conditions this year. Corn has pollinated in most areas with a few fields still showing tassel emergence. Many areas received some rainfall and had moderate temperatures that should have allowed successful pollination. This period is also near the maximum water use requirements for corn, so areas that did not receive rainfall may show significant yield loss. The soybean crop has put on significant growth throughout the past couple of weeks. Soybean aphids are still present in most fields, but low in populations (zero to five aphids per plant). Bean leaf beetle feeding can be found in some fields, but well below the threshold of 25 percent defoliation. Some dry fields are showing some spider mite infestations. Dry beans have also added significant growth recently. Where rainfall has been adequate, this crop has good potential. |
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| Weather news Jeff Andresen Agricultural Meteorology Geography An upper air ridging feature anchored across the Great Plains region led to yet another abnormally dry week last week across most of Michigan and the Great Lakes Region (some lucky areas did receive significant rainfall, but were the exception rather than the rule). Since the end of the first week in June, precipitation deficits have grown in many areas to the two to four plus inch range, which unfortunately has also coincided with periods of greatest seasonal plant water needs. The lack of plant available water is currently most acute across southern and interior sections of northern Lower Michigan, and across western and central sections of the Upper Peninsula. \In general, weather forecast guidance for the next couple of weeks does not suggest any major changes that would lead to meaningful relief from the dryness. The short term outlook is more encouraging, however. A cool front is forecast to move through the state Friday, which will bring the best chances for rainfall during the upcoming week. Showers and thunderstorms will be possible in northwestern sections of the state overnight Thursday, and across the Lower Peninsula on Friday possibly lingering into early Saturday across southern sections of the state. Rainfall totals will generally be in the 0.25-0.50 inch category, although some locally heavier totals are possible. Areal coverage of the rainfall is expected to be greatest across southern sections of the state. Fair and dry weather is likely by late Saturday and Sunday continuing through much of the upcoming work week. Temperatures are expected to remain close to seasonal normals during the next few days, with highs ranging from the upper 70's north to mid 80's south and low temperatures from the upper 50's north to low 60's south through Friday. Temperatures will fall back a degree or two following the passage of the cold front Saturday and slowly warm into next week. A broad ridging jet stream pattern is projected across the Upper Midwest for the next one to two weeks, which will likely lead to more warmer, dry weather. Unfortunately for those in need of rain, both 6-10 day and 8-14 day outlooks, covering July 31 through August 4 and August 2-8, call for above normal temperatures and for below normal precipitation totals. |
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