July 8, 2004
In this issue
§ Insect update
§ Malformed potato tubers
§ 2004 guidelines for postemergence weed control in dry edible beans
§ Scouting cyst nematodes
§ Twenty-fifth Ag Expo just around the corner
§ Regional reports
§ Weather news
First generation flights have petered out in South and Central Michigan (Allegan, Ingham, Montcalm counties). In most locations, we are past the point a spray would be effective. Flights of first generation corn borer started in the UP at the end of June.
We sighted our first Japanese beetle adults in soybean fields at the end of June. Japanese beetle adults are rarely a problem in soybean, although they will feed on the leaves. They are rarely a problem in corn unless they clip silks to within a half-inch of the ear during pollination. This is especially important in seed corn production. Adults are often found clipping silks with their friend, the...
Adults of WCR have emerged in Indiana and Ohio, and they should begin to emerge in Michigan over the next one to two weeks. We found pupae this week in continuous corn in Central Michigan. There were already reports of root damage and lodging in corn in the states to the south, especially in Illinois. There have even been reports of heavy damage in fields treated with soil insecticides. With the heavy rains in May and early June (which equaled off-target movement of soil insecticide plus the potential for poor/ shallow root development in wet soils), be on the look out for lodged corn in Michigan, particularly if windy storm fronts move across the state.
Helpful Internet link: July 9 newsletter article on CRW damage in Illinois http://www.ipm.uiuc.edu/bulletin/article.php?issueNumber=16&issueYear=2004&articleNumber=1
These are numerous in many locations! Extension agents report that alfalfa cutting schedules have been variable. Thus, large numbers of leafhoppers are jumping from field to field, suddenly appearing in large numbers in a given area when a neighboring field has been cut. PLH can be devastating to alfalfa and dry beans. As it feeds, it injects saliva into the plant that acts like a toxin, causing stunting, leaf curling, and a distinctive yellowing symptom called hopperburn. However, PLH is relatively easy to kill. In alfalfa, use a sweep net to sample across the field. Thresholds vary by plant height from 2 per 10 sweeps in alfalfa regrowth, to 20 per 10 sweeps in 12-inch alfalfa. In dry beans, examine entire trifoliate leaves. The threshold is only 1 PLH per trifoliate. Newly hatched PLH nymphs are very tiny, so you need sharp eyes to see them. Yet it is important to count the small as well as large nymphs because they grow very quickly. This year I have noticed more PLH on soybeans (which we sample routinely for aphids) than in previous years. PLH is usually not reported to cause yield loss in soybeans, but feeding can result in injury - leaf edges turn yellow and the leaves cup downward. The threshold is one PLH per trifoliate (similar to dry beans).
Good news, as aphid numbers continue to be low in Michigan and surrounding states. However, we aren’t out of the woods yet. Continue to examine fields though July into early August, especially if temperatures increase. Don’t confuse potato leafhoppers for soybean aphids (see the chart which follows this article). One concern is for the threshold of 250 aphids per plant recommended for R1-R3 stage beans. We have noticed many beans already initiating flowering (R1 stage) or even at full flower (R2 stage), although the plants are quite small and aphids aren’t present. We are not sure if the 250 threshold will be applicable to later-stage beans if aphids increase in early August.
I’ve received several calls about leafminers in corn. The leafminer adult is a small, pretty fly with patterned wings. The larvae (maggots) live in mines between the upper and lower leaf surface of corn leaves. CBL is present every season, but in some locations and years it is numerous enough to draw attention. Several years ago, there were widespread reports of damage by corn leafminers in Michigan. However, there is little you can do about this pest. First, damage is usually thought to be non-economic – i.e. the corn compensates for the damage by the end of the season. Second, insecticides cannot reach the maggots, since they are safely protected within the leaf itself. Finally, the maggots are attacked by a wasp that can sting the larvae through the leaf surface. Often, a CBL infestation is eventually controlled by this wasp.
Helpful Internet link: University of Nebraska CBL bulletin: http://ianrpubs.unl.edu/insects/nf374.htm
CBL pictures: http://entomology.unl.edu/fldcrops/cornpestkey/cornblotch.htm
Helpful Internet link: Iowa State insect pictures, potato leafhopper and soybean aphid http://www.ent.iastate.edu/imagegal/homoptera/
|
Characteristic |
Potato leafhopper |
Soybean aphid |
|
Shape |
Elongate, torpedo shaped. |
Fat, roundish |
|
Color |
Bright, lime green |
Dull green - often take on the shade of the leaf they are feeding on |
|
Numbers |
Solitary individuals, do not hang out in groups |
Colony-formers. Small colonies made up of a mom with babies, or a group of sisters. Under heavier infestations, hundreds crowd together on a leaf |
|
Location on plant |
Undersides of leaves, often lower on the plant. |
Undersides of leaves, prefer newest growth. |
|
Movement |
Fast! Walk in a crab-like fashion - in other words, can move forward, backward, and sideways. |
Slow. Sometimes have to be poked to make them walk. |
|
Associated insects |
None |
Eggs, larvae, and adults of predators such as ladybugs, lacewings, and pirate bugs. SBA is also sometimes tended by ants. |
Potato tubers submitted to MSU Diagnostic Services contained numerous growth cracks and splits. These symptoms are characteristic of injury from ALS-inhibiting herbicides that might have drifted, been misapplied, or persisted in the soil. These herbicides can cause various tuber malformations, including folded, split, cracked, knobby tubers with rough, discolored skin.
These particular tubers were tested in the lab for the presence of several imidazolinone and sulfonylurea herbicides. We were able to detect halosulfuron in the injured tubers at 1.7 ppm.
It is that time of year again when several dry bean fields will need to be sprayed with postemergence herbicides to control weeds that escaped earlier weed control efforts. Options for postemergence broadleaf weed control in dry beans are limited to Basagran, Raptor, Pursuit, and Reflex (Section 18 in 2004 for use in the Lower Peninsula). Assure II, Select, and Poast are registered for postemergence annual grass control in dry beans.
When looking at these different options there are a few things to consider when using these herbicides alone or in combination. One of the first things to consider is, “What are the weeds that need to be controlled out in the field?” Many times the weeds that top this list are common ragweed, common lambsquarters, and eastern black nightshade. Selection of a herbicide or combinations of one or more of these herbicides will be dependent on the weed complex in the field (Table 1). For example, if common ragweed is the only weed escape, the best option for control would be to use Reflex. However, if common ragweed and common lambsquarters are both present, you may choose to tank-mix Basagran with Reflex. When making these weed control decisions it is important to consider certain guidelines, such as rotational crop, herbicide use rate, and adjuvant selection. Several of these guidelines follow in this article.
All postemergence broadleaf herbicides, except Basagran, have rotational crop restrictions. Some of these restrictions may influence your herbicide selection, depending on your cropping system. For example, the rotation restriction for Reflex is 10 months for corn and 18 months for alfalfa, sugar beets, potatoes, cucumbers, canola, and tomatoes. The rotation restriction for Raptor is 18 months for sugar beets (extended to 26 months if pH is less than 6.2) and canola. Pursuit’s rotation restriction is potentially over 40 months for sugar beets and is 40 months for canola, cucumbers, and tomatoes.
The use rate for Raptor is 4 fl oz/A in edible legumes. For Reflex the use rate is 1 pt/A and this can only be used once in a two-year period. Common ragweed less than 4-leaf will be controlled ½ pt/A of Reflex. Pursuit is generally used at 2 fl oz/A and Basagran rates range from 8 fl oz to 2 pt/A depending on weed species, size, and herbicide tank-mixture.
Raptor alone provides fair control of foxtails. Foxtail control is good when Raptor is tank-mixed with Basagran at 8 fl oz/A + NIS + 28%N (or AMS – ammonium sulfate). Barnyardgrass and crabgrass control are only fair. Assure II, Select, and Poast can be tank-mixed with Basagran, Reflex, or Basagran + Reflex for grass control. However, do not tank-mix Assure II, Select, or Poast with Raptor or Pursuit, because grass control will be compromised.
Basagran alone should be applied with 1 qt/A of a crop oil concentrate (COC). Reflex should be applied with a non-ionic surfactant (NIS) at 0.25 to 0.5% v/v or a COC at 0.5 to 1.0% v/v. Include COC when tank-mixing Basagran + Reflex. Raptor or Pursuit alone should be applied with 0.25% v/v of NIS. To increase control, 28% N at 2.5 gal/100 gal of spray solution or 12 to 15 lb/100 gal of spray solution of AMS can be added to Raptor + Basagran or Pursuit + Basagran applications. The addition of at least 8 fl oz of Basagran to Raptor or Pursuit will “safen” these applications. To control common cocklebur, jimsonweed, or provide good control of common lambsquarters increase the rate of Basagran to 16 fl oz when tank-mixed with Raptor and use COC + 28% N or AMS. Do not add 28% N or AMS when tank-mixing Raptor and Reflex.
Raptor, Reflex, Basagran, or Pursuit should only be applied after dry beans have one fully expanded trifoliate. Do not apply these herbicides once dry beans start to bloom.
The rain-free period is one hour for Assure II, Select, Poast, Pursuit, Raptor, and Reflex. There is not a specified rain-free period on the current Basagran label. However, earlier labels listed the Basagran rain-free period as 8 hours.
Cyst nematode females should be present on the roots of their hosts at this time. Soybeans and sugarbeets are two economically important plants grown in Michigan that are hosts for cyst nematodes. The soybean cyst nematode (SCN) is a major limiting factor in soybean production but will also feed on dry beans, green beans, and peas. The sugar beet cyst nematode (SBCN) is a serious pathogen of sugar beets but will feed on a variety of plants particularly in the Chenopodiaceae (sugar beet, red beet, mangolds, and spinach) and Cruciferae (cabbage, kale, Brussels sprouts, broccoli, cauliflower, turnip, rape, and mustards). Other species of cyst nematodes exist in Michigan but are not widely distributed (cereal cyst nematode), are not as economically important (clover cyst), or do not feed on field crops (carrot cyst, turf cyst, and others where weeds are hosts).
Cyst nematode females are approximately the size of a pinhead and are white or yellow in color. To observe them, dig infected plants and gently shake off the soil or dip the roots in a pail of water. Their color contrasts well with soil or the root surface and should be easy to see. Their presence, of course, indicates a cyst nematode problem.
This is an excellent time for growers evaluating different varieties to score them for cyst nematodes. The numbers of females present on roots are indicative of their developmental success on the plants in question. For instance, soybean varieties with resistance to soybean cyst nematode should have very few females on their roots, whereas SCN-susceptible varieties should have hundreds depending upon the level of the initial infestation. Soybean growers should dig some plants and inspect them for SCN females. Make notes as to their abundance. If many females are present, the population density of SCN is sure to increase over the growing season. If you’re growing an SCN-resistant soybean variety, if SCN females are abundant, you’ll probably want to consider another variety the next time you grow soybeans.
The only way to assess cyst nematode population densities in the soil is to collect samples and submit them to a Nematode Diagnostic Lab for analyses. Producers of any of the crops listed in the first paragraph should collect samples every fall before any of those crops are grown regardless of whether it is already known cyst nematodes exist in a field. Management strategies and tactics will be based upon the numbers of cyst nematode eggs and second-stage juveniles recovered from those samples. Cyst nematodes are major limiting factors in the production of their host crops. Ignoring them can result in significant yield losses.
As it has since its inception, Ag Expo, set for July 20-22 at Michigan State University (MSU), will feature a variety of educational and informational demonstrations and activities. This year, two of those programs will earn participants restricted use pesticide (RUP) applicator credits.
July 20 at 10:00 AM, Jim Kells, MSU professor and Extension weed specialist, Department of Crop and Soil Sciences, will present New Weed Control Strategies for Herbicide-Resistant Corn. This program will give participants the chance to view research on herbicide-resistant corn and discuss weed control strategies.
At 1:00 PM, Willie Kirk, MSU plant pathologist will present Host
Development and Growth Stages in Sugar Beet and Potatoes. He will focus on sugar
beet and potato research at MSU. This program will be repeated July 21 at 1:00
PM.
Participants can earn one RUP credit for Kells’ program and one for attending the Kirk program (no additional credit earned for attending the Kirk program twice).
There is no charge to attend the sessions, though preregistration is required. For more information call 517-355-3776 or e-mail agexpo@canr.msu.edu
Other demonstrations will focus on haying and tillage equipment, horse pasture management, developing a comprehensive nutrient management plan and the USDA’s new animal identification system.
Expo visitors will have the chance to consult with MSU research and Extension specialists in the College of Agriculture and Natural Resources (CANR)-sponsored tent focused on Serving People and Communities. This tent will feature the work of Michigan Agricultural Experiment Station researchers; MSU Extension; the MSU Product Center for Agriculture and Natural Resources; AgrAbility; IPM resources; insect, weed, nematode and disease diagnosticians; MSU Product Center projects staff members, National Food Safety and Toxicology initiatives; Project GREEEN and Animal Initiative studies.
The MSU Land Policy Program will bring 13 programs centers and institutes together (12 from MSU, one at Wayne State) in one tent to focus on land use and development education.
The Michigan Agriculture Environmental Assurance Program (MAEAP) will also host a tent focused on nutrient management education. MAEAP partner organizations include governmental agencies, agricultural organizations, commodity groups and educational institutions.
Other MSU participants include the Department Biosystems and Agricultural Engineering, the Department of Forestry, the College of Veterinary Medicine, the MSU Student Organic Farmers and the MSU Extension Bulletin office.
Ag Expo
will run from 9:00 AM to 5:00 PM July 20, 9:00 AM to 8:00 PM July 21 and 9:00
AM to 3:00 PM July 22. All Ag Expo events and parking at Farm Lane and Mt. Hope
Road are free.
For more information about Ag Expo, call 1-800-366-7055, visit www.agexpo.msu.edu or e-mail agexpo@canr.msu.edu
Corn growth has been irregular across the region.
Some corn has really taken off with warm weather, advancing growth stage, and
continued rainfall. Other corn seems irreparably stunted from early season flooding.
Likewise, weed control has ranged from excellent to poor. Giant foxtail and
ragweed are common escapes in fields I’ve walked.
Soybean crops are developing well. The tallest field I’ve been in is knee high. Most other fields are considerably shorter. All fields have adequate stands ranging from 80,000 to 150,000 plants per acre. Exceptions are low areas where standing water killed plants earlier in the season. Many of these areas were not replanted due to continued excess moisture. There are reports of soybean aphids in our region, but I have not been in infested fields yet.
Farmers have begun wheat harvest. It is not uncommon to see headlands taken off. It’s too early to get yield reports from growers. Expectations are for below average yields.
The weather has been somewhat cooler than normal, especially at night, over the last week in Southwest Michigan. Heavy rainfall on the weekend of July 4 provided one to three inches of precipitation over the majority of the region.
In alfalfa, we finally had a window of opportunity to harvest the last of the first cutting hay, as well as some of the second cutting during the week before the holiday weekend. Potato leafhoppers continue to be a potential problem in some areas. Watch the re-growth for potato leafhoppers before your alfalfa yields are reduced by this pest.
The wheat crop has reached maturity in most areas. Recent rainfall has slowed down harvest. Weeds do not seem to be much of an issue in most fields at this time. Fusarium can be found in most fields, but keeping the airflow from the fan on the combine can help to keep the level of vomitoxin low by blowing over the infected kernels. Several of the wheat fields have excellent growth and yield potential this season. Even after cleaning up some of the shriveled kernels, I would expect that some growers will have pretty good yields.
The earliest planted corn is just beginning to shoot tassels now. The latest planted corn is still below 4-6 collars. Side-dressing of nitrogen is continuing on the latest planted corn. The fields planted in May are still uneven, and this will undoubtedly mean lost yield potential. European corn borer levels seem to be fairly low in most areas. There is some evidence that the extended first generation moth flight has left a wide variety of larvae sizes in many fields. I have not seen many problems with rootworm feeding in fields I have walked this week. I expect we will begin to see rootworm adult emergence in the next week.
Seed corn is looking like it is beginning to turn the corner. Most fields are beginning to green up nicely after a prolonged period of yellowing from flooding, lack of nitrogen, and cool conditions. The earliest planted seed corn is approaching Vt, and probably will be at tassel emergence by the end of the coming weekend. ECB moth flight seems to have crashed over the last couple of weeks. Larvae range from first instar to fourth (1 inch in length) in fields I have walked. Japanese beetle emergence is well underway. I have not seen any rootworm beetles at this point.
In potatoes, some fungal pathogens are beginning to become evident. We took a sample up to Dr. Willie Kirk for identification this morning. The MSU potato late blight model suggests the disease severity rating was high this week. The model suggests that growers keep protectant fungicide applications at the minimum treatment interval. For more specific recommendations from the MSU Potato Late Blight Prediction Model, visit: http://www.lateblight.org/lowband_choosestn.htm
Soybeans continue to be the most variable crop in terms of stage of development. The earliest planted soybeans are looking pretty good with plants in the early stages of pod development. Plants in these fields are 12 to 14 inches in height. The majority of the crop is about 8 to 12 inches in height. Most of the post emergence herbicide applications have been made. Weed control appears to be very good in most fields. Insect activity has been fairly light. Soybean aphids are either very low or non-existent in the fields that I have walked this week (I have looked at a lot of fields from western Van Buren County to Branch County early this week.). There are quite a few potato leafhoppers in soybean fields this summer. The nymph leafhoppers can be easily mistaken for soybean aphids, mostly because of the similarity in color and size. We will continue to monitor for this pest over the summer. I would be interested in hearing from growers that find the winged stage of soybean aphids in their fields. I have not seen alates yet this season. If we start to see winged aphids, this may indicate that a batch of the insects were deposited into the area by thunderstorm winds. Because the western portion of the region has very few common buckthorn trees in fencerows, the discovery of winged aphids has often marked the beginning of soybean aphid infestations.
Cool, damp weather
persisted over the past two weeks. High temperatures were above 80 degrees only
three times in the past 14 days. Low temperatures have been in the 50’s dipping
to as low as 39 degrees. Rainfall totals have been in the nature of 1 to 1.5
inches for this two-week period.
In alfalfa, second cutting harvest has begun and will continue for the next few weeks as regrowth varies greatly due to delayed harvest of first cutting. Fields need to be monitored for potato leafhopper. Harvesting dry hay continues to be very difficult everywhere.
Wheat has turned and we are now waiting for dry down.
Harvest will likely begin in about one week.
Corn condition and growth stage remains highly variable. Most corn is V5 to
V8.
Soybeans like corn are variable in condition and growth stage. Dry bean planting ended near July 5 with 2/3 of the crop planted in these last two weeks. Early planted beans are growing slowly; root rot is a common problem.
A few days of temperatures in the 80’s and sunshine have sure helped most crops. Temperatures have been below average for this time of year which is not helping to move the late corn crop through development stages. There continues to be areas of poor crops due to weather problems, mostly excessive rainfall.
Potato leafhoppers are the biggest concern in alfalfa now. Cutting of alfalfa has been effective in lowering populations in fields but they are quick to rebound in regrowth.
Variable is the key word in sugar beets. There are several fields that look great and several that look poor, but most are somewhere in between. Unconfirmed reports of Cercospera leafspot have been made. The Beetcast leafspot prediction model is now showing Disease Severity Indexes (DSI) from 35 to 60. One strategy for cercospera control is to start to treat when the DSI reaches 55. Check local weather station data and DSI at www.MichiganBeets.com for your area.
The Thumb region is a place where you can find corn from 12 inches to 6 ft in height. The later planted corn is looking really good (Just don’t look at the calendar or expected growing degree days left in this season.).
Most wheat is now drying down. Some fields are not showing much green color anymore. Some of this loss of green color appears to be related to foliar disease that caused premature death of leaves. Most grain is in hard to soft dough stage.
Most soybean fields seemed to really make good use of the sunshine and few days of warm temperatures. Blossoms can be found in early-planted fields. A few soybean aphids have been found in Saginaw County but very limited.
Just to be consistent with all of the other crops, dry beans are variable. Some fields look very good while others have variable stands due to heavy rains shortly after planting.
Continued cool, wet weather has plagued the area for the week. Up to 2.5 inches of rain fell from Sunday to Tuesday (July 4-6) adding to already soggy fields. Cool weather, lows in the 40s and 50s and highs in the 60s, has not been summer-like or crop friendly.
Corn is variable. Some corn is looking great and is about knee high and growing, the later planted corn is yellow, short, and seems to be waiting for warmer weather. Many areas are flooded out, up to 20 percent.
Wheat is fully flowered and looking good so far. I have not seen signs of scab yet or armyworms. We could have a good harvest this year.
Soybeans are slow growing, still yellow, and very, very short. Weeds are overtaking the soybeans in most fields. Glyphosate sprays have been going on in between rains. No aphids have been found.
Dry beans are emerging fast, but still behind schedule. Most beans are unfolding the first trifoliate.
Most alfalfa has been cut with yields at or just above normal in yield. Rains have thwarted most harvest operations.
Rye is turning color and should be a good crop this summer. Oats are variable in quality with many washouts and yellow areas. Potatoes are slow also this year. Losses in fields are ranging from 5 to 40 percent. Potato leafhopper are present in alfalfa, potatoes, and dry beans.
An upper air troughing feature centered over the Upper Peninsula Thursday morning (July 8) will dominate weather conditions across Michigan for another 24 hours with unseasonably cool temperatures and a continuing chance for showers in northern sections of the state. Look for high temperatures to remain in 60's north to the low 70's south with low temperatures generally in the 40's and 50's. There will be a chance for scattered showers mainly during the afternoon and evening hours with best odds of precipitation in northern sections of the state. Most precipitation that does fall should remain on the light side with totals less than 0.25 inches. The trough will slowly move east of the region by late Friday and be replaced by a weak ridging feature for the weekend and early next week. A warm front will move northward through the state on Saturday and initiate a warming trend with high temperatures returning to the upper 70’s north to mid 80's south by Sunday and continuing into early next week.
With southerly flow behind the front, there will also be an increase in available moisture and an almost daily chance for showers and thunderstorms. Best chances for widespread rainfall will likely be Sunday or Monday.
The latest 6-10 day and 8-14 day medium-range outlooks, covering July 13-17 and 15-21, call for an upper air ridging pattern slowly edging westward from the central U.S. into the Rocky Mountain region, leaving Michigan under weak northwesterly flow aloft. Mean temperatures for the 6-10 day time frame are forecast to range from near normal in eastern sections of the state to above normal in the west. For the 8-14 day period, mean temperatures are forecast to return to below normal levels. Precipitation totals in the 6-10 day time frame are forecast to range from below normal in northern sections of the state to above normal in the southwest, while below normal totals are expected statewide during 8-14 time frame.