Vol. 20, No. 12, June 30, 2005

Christina DiFonzo, Entomology

Soybean aphid numbers continue to climb across Michigan. In fact, we are more heavily infested than many of the states around the Great Lakes. We have numerous field plots in which 100 percent of the plants are infested with an average of 90 to 100 aphids per plant. However, none of our plots are truly over the 250 threshold, when aphids are directly counted and averaged. We expect that they will go over threshold within the next two weeks. Many fields are beginning to flower, so the timing for spray applications will be quite good. Remember to think timing and coverage for soybean aphid control.

This week, winged aphid production and flight began in infested fields. This is important for several reasons.

First, these winged individuals will move around the landscape and land on previously uninfested fields. For example, we counted two to seven winged aphids per plant on Gaucho treated beans on June 28 at MSU. If you live in an area that lacks buckthorn, you used a seed treatment that killed the initial flight of aphids from buckthorn, be ready to walk fields after July 4 because this new flight of aphids will colonize your clean fields. Also, if you sprayed early (within the last two weeks), be prepared to start scouting again, because your fields will be re-infested by winged migrants from neighboring fields.

Second, winged aphids spread viruses in vegetable crops, so watch for an increase in symptoms of CMV, WMV2, ZYMV, and other viruses in two to three weeks.

I am trying to get aphid information out to agribusiness and growers in numerous ways. This includes the CAT Alert newsletters, plus the MABA Ag Fax, the Michigan Soybean Promotion Committee, Farm Radio interviews and DTN. Also, I will be doing a call-in show for DTN on Tuesday, July 12, at 9:00 PM. The web site with more information, and a way to listen to the show after the fact is at: http://www.dtn.com/dtn_onair.cfm

Corn borer numbers are still high as well. There are a few reports of spraying in southern Michigan, especially areas with seed corn production. While I have not had a report of field corn over threshold, people do report shot-holing damage on up to 40 percent of the plants, close to the 50 percent threshold.

Pea aphid numbers are high in some alfalfa fields – presumably it is a good aphid year in general in Michigan. I looked at a field this week that had a heavy pea aphid infestation before, then after cutting as the aphid concentrated on the new growth. However, by the time I looked at the field within a day or two of the phone call, most of the aphids were dead. They were infected with naturally occurring fungi that attack and kill aphids under humid, warm environmental conditions. The good news is that once these fungal diseases start, they can move around the landscape to aphid species in other crops, for example, to soybean. While I haven’t seen any infected aphids on soybean yet, in previous years we observed infected soybean aphids in August, under the same conditions that lead to white mold.

Jan Byrne, MSU Diagnostic Services
Sandy Perry, SBR Sentinel Plot Coordinator

MSU has established 20 sentinel plots around the state to be scouted weekly looking for the first appearance of Asian soybean rust (SBR) in Michigan. Scouting is occurring in at least 25 soybean-growing states and, to date, rust infection has been reported on volunteer soybeans in one county of southwest Georgia (those plant have been destroyed) in one sentinel plot in northern Florida and at one site in Alabama. Six counties in Florida have reported Asian soybean rust infections on kudzu – a rampantly growing invasive vine found in the South. The kudzu infections are of concern because kudzu is an alternate host on which SBR can overwinter and serve as a reservoir for infections that could spread to soybeans. A United States map with the scouting locations and SBR detection locations can be found at http://www.sbrusa.net/

The Michigan sentinel plots are located in Berrien, Cass, St. Joseph, Hillsdale, Lenawee, Monroe, Van Buren, Calhoun, Jackson, Washtenaw, Eaton, Ingham, St. Clair, Saginaw, Tuscola, and Sanilac counties. The scouting is being done by 12 Extension educators with field crops area of expertise.

In the last week six soybean samples have been submitted to MSU Diagnostic Services and tested for SBR. Two samples came from sentinel plots. All six samples tested negative for SBR using real time PCR technique. The diseases found on the leaves were Septoria brown spot and bacterial blight, both common diseases found on soybeans in Michigan.

Following is the compilation of the 15 scouting reports submitted between June 22 and 29.

Growth stage: ranged from V4 to R1.

Plant height: ranged from 7 to 18 inches.

Degree of canopy closure: ranged from 20-95 percent.

Soybean diseases present: Diseases were indicated on 13 reports. Brown spot was predominate (12 reports) with bacterial blight and Phytophthora stem canker each indicated twice.

Soybean insects present: Soybean aphids were indicated in nine of the reports. Quantities ranged from less that 1 per leaf up to 0-100 per leaf.

No Asian soybean rust was found in any of the sentinel plots.

MSU Diagnostic Services reports the following pests and problems found on field crop samples submitted in the last week:

Soybeans – In addition to the Septoria brown spot and bacterial blight diseases mentioned above, samples were submitted with herbicide injury, poor root development due to soil compaction, and mealybug.

Sugar beets – Severe bacterial leaf spot (Pseudomonas syringae pv. aptata) on two sugar beets samples.

Darryl Warncke
Crop & Soil Sciences

Over the past couple of weeks the field Extension educators have commented about several good soil fertility points.

Compost application
Application of manure or compost made from manure coming from egg laying operations has a liming benefit. This is because of the calcium carbonate added (shell or limestone) in the feed. Depending on the amount applied, the soil pH may be increased or at least maintained over time.

Potassium management
Increasing use of no-till corn and soybean production is providing a challenge for getting adequate potassium into the root zone. Potassium is frequently broadcast on the soil surface to maintain or buildup the potassium status. This results in a high potassium concentration in the surface two inches of soil, but lower levels in the root zone. Growers need to consider including some potassium in the starter fertilizer or using deeper bands of potassium. Several reports have been received over the past two years of low soil potassium levels in established soybean fields, primarily in sandy soils. Potassium broadcast over the top of established soybeans in a low potassium situation on sandy soils may provide adequate potassium for the crop. With adequate rainfall the potassium will be moved into the root zone. However, this may not work on loam and clayey soils because potassium is held more tightly against movement.

Manganese deficiency
Soybeans and wheat are the two field crops most likely to develop manganese deficiency, although other crops may also be affected. Manganese deficiency results in yellowing between the veins of soybeans and an alternating yellow/green pin striping on wheat. Manganese deficiency is most likely to occur under the following conditions:

a)            In higher organic matter soils with soil pH above 6.5 (likely to occur in depressional areas in fields),

b)            Acid soils that are limed to above pH 6.5.

When incorporated into the soil, manganese is readily converted into rather unavailable forms. Therefore, manganese deficiency is likely to reoccur in the same areas year after year, especially when manganese sensitive crops are grown. The best way to correct a manganese deficiency in a growing crop is to spray manganese (0.5 to 1.0 lb/ acre) on the foliage.

Christy Sprague
Crop & Soil Sciences

Want to sharpen your diagnostic skills and stay on top of the latest information in production agriculture? If so, the third annual MSU Crop Management and Field Diagnostic School is for you. This event is scheduled for July 27 at the MSU Plant Pathology Research Center on the south side of the MSU campus and is open to all who are actively involved in production agriculture (growers, agri-business reps, Extension educators, and agency personnel).

The school will focus on such topics as scouting and using appropriate application technologies to manage Asian soybean rust and soybean aphid; fine-tuning fertilizer recommendations; diagnosing herbicide injury and sharpening weed identification skills; and diagnosing and management of nematodes and plant disease problems in field crops.

The $125 registration fee is due July 15. Participation is limited to the first 125 paid registrations. For more information contact any MSU Extension office or call 517-355-0271, ext. 108 or e-mail lisaingr@msu.edu. A brochure with the registration form can be found at: http://www.ipm.msu.edu/CAT05_fld/pdf/2005diagnosticschool.pdf

Approval is pending for RUP credits and 6.0 continuing education units for certified crop advisors (CCA).

Ned Birkey

Weather
The weather has not changed this week from last week, which is hot and dry with widely scattered and localized heavy showers. We had only five days of 89 or 90 degrees all of last year. Already in June we have had 11 days of 88 to 97 degrees, including the past five days in a row. This weather is becoming as stressful to farmers as it is to the crops!

Commodity reports
Alfalfa first cutting is complete and even one farmer’s second cutting. Regrowth is very good considering the lack of precipitation. Potato leafhoppers are evident, but surprisingly are at lower numbers that expected. The Monroe County Extension office has two high-quality sweep nets for sale for $40 each.

Corn is growing slowly except that on sandy soils. Advanced fields are V10 or about 48 inches tall. European corn borer trap counts are down substantially this week, signaling the end of the first (overwintering) generation. Most fields have plants that exhibit rolling of leaves on lighter soils.

Soybeans do not seem to be growing much, except that fields are blooming, so we are at the R1 growth stage. Most fields remain short with perhaps 50 to 75 percent row closure for drilled soybeans. Aphid populations have diminished somewhat this past week, but spraying continues in some fields. Beneficial insects, such as lady bird beetle larvae and Asian lady bugs are more evident in soybean fields this week. Varieties treated with Cruiser Max did not exhibit aphid populations compared to adjacent varieties. Spider mites and soybean cyst nematodes are also found in fields. Manganese deficiency is also apparent on high pH soils.

Wheat harvest will begin next week with early fields east of Toledo, Ohio already combined. Few fields show any green tissue, while most fields are very yellow. The MSU Wheat Variety Trial in Lenawee County is signed and ready for public observations. It is located on Holloway Road, a half-mile east of Britton Road, south of Britton, Michigan.

Miscellaneous
Commodity prices tanked this week, but not before some farmers were able to sell some old crop corn and soybeans. Was last week the high price for the year for corn and soybeans? The USDA acreage report at 8:30 AM today (June 30) will give some idea of what farmers planted.

Bruce MacKellar

Weather
Once again, the levels of crop stress vary widely within the region. Rainfall totals from widely scattered thundershowers ranged from 1.5 to virtually no rainfall. The general pattern is that areas to the east of US 131 have received more rainfall than areas to the west. High temperatures in the 90s over the past week have meant that many fields have shown signs of heat and moisture stress. In places where soil moisture has been adequate, the heat has spurred on crop development at a feverish pace.

Commodity reports
Early planted commercial corn is well above shoulder height with the majority of the crop at waist height or more. Corn continues to grow well in all but the driest of spots. Pest activities seem fairly light at this point. There is some European corn borer feeding on leaves, but commercial corn remains below threshold. I have not seen emergence of rootworm beetles yet. In fields that I have looked at, there has been virtually no incidence of root pruning from rootworm beetle larvae feeding at this point.

Seed corn growers have been very busy with cultivation and sidedress nitrogen application over the past week. Many of the early-planted fields have grown beyond this stage now. Some fields have been treated for corn borers. Japanese beetles have recently begun to emerge in St. Joseph County with some plants showing signs of leaf feeding.

Soybean aphids have been found in many fields in southwest Michigan, but most fields are still way below threshold. In areas that have been extremely dry, there have been some reports of spider mite feeding damage. Both of these pests will be helped by dry and hot weather conditions. Where I have seen aphids, there has been good Asian ladybeetle activity. Keep an eye out for these pests. We have also begun to see defoliation from early Japanese beetle feeding in some fields. The soybean rust sentinel plots have revealed a little lingering brown spot problems, but little else in the way of soybean leaf diseases. Growth stage ranges from pre-R2 and R1, to the late vegetative growth stages. We will be evaluating MSU trials to look at the effect of seed insecticide treatment on soybean aphid development.

Second cutting harvest of alfalfa is underway between threats of rain. The good news is that most of the alfalfa that has been harvested has looked very good. Growers should still be monitoring leafhopper numbers, especially when the re-growth is very small.

Wheat is approaching the dry-down stage. The crop looks good with little incidence of head scab. Yields will be variable depending on the moisture that was available earlier in the season.

Fred Springborn

Weather
The weather this week has been very summer-like. Much of eastern Montcalm County still has adequate topsoil soil moisture at this time, as you go west topsoil moisture becomes more of a concern. Many parts of the region, particularly to the north and west, remain dry and are in need of rain. High temperatures have been in the upper 80s to lower 90s. Low air temperatures have been in the 60s.

Commodity reports
Oats are headed. Wheat is turning. There is very little evidence of head scab in this year’s crop.

Corn growth has progressed. Much of the crop is in the V9 to V12 growth stage (waist high and taller) leaf rolling was observed this week in corn on the lighter soils in Montcalm. Much of the corn crop in Newago County is suffering from moisture stress. Armyworm has been observed in a few fields and bears continued scouting. European corn borer moth flight is decreasing with very low numbers of moths being caught in pheromone traps this week.

Dry bean planting is essentially complete. Most of this crop has emerged well and is experiencing overall good growing conditions. Soybean aphid has been observed in low numbers in soybeans.

Second cutting alfalfa is underway. Potato leafhoppers are present in alfalfa fields and should be monitored. Alfalfa weevil is still present in a few fields in Newago County.

Paul Gross

Weather
Parts of the region received at least one inch of rain over the past week. With the adequate to surplus soil moisture, crops have been growing rapidly. At this point in the growing season most farmers are pleased with their crops, however, there is a lot of growing season still ahead.

Commodity reports
Corn is growing rapidly and generally looks very good. We are starting to see feeding from first generation corn borer. There are no real other problems at this time.

Soybeans are just beginning to flower. Growth is very good as most fields canopy. Scout fields for soybean aphids over the next week. There have been very few found at this date.

Wheat is beginning to turn. Harvest is expected to begin in about two weeks, which is expected because Ag Expo is in two weeks. There some light instances of scab in a few fields. It appears that yields will be average with some fields doing poorly.

Drybeans are planted and most have emerged. There is concern that with all the wet weather that the region has received over the past two weeks, root rots will be a problem. There are several fields that had water standing Wednesday night and Thursday morning.

Oats and barley are all headed and the crop really looks good.

Second cutting of alfalfa is under way. There are still a few fields of first cutting being made. It appears that the yields will be very good which will help offset the lower yields of first cutting. Scout fields for leafhoppers as the numbers are getting high.

Mark Seamon

Weather
Variable would describe rainfall across the Thumb during this past week. Hot and humid weather has been consistent and widespread. This weather has been tough on areas that are short on moisture but other areas are coping well.

Commodity reports
Second cutting of alfalfa on early cut fields has provided pretty good yields. Most other fields are waiting for the second cutting.

In sugar beets, row closure has occurred in most fields not injured by rainfall. This is great to have at the end of June. Disease severity values are stacking up in the BEETCAST leafspot prediction model. Watch http://www.MichiganBeets.com web site for updates for your area. When scouting, be sure to identify cercospera leaf spot because bacterial leafspot has been found.

Wheat is maturing nicely with most fields showing color change. Hopefully the hot weather has not compressed the grain fill period too much. Head scab can be found but is very limited.

Where soil moisture has not been limited, the corn crop looks great. Where moisture is a problem, the hot weather is taking its toll with leaf rolling and slow growth. Most variable fields have evened out this week with good growing conditions.

Soybeans have really improved this week. New trifoliates have good color and are developing rapidly. Weed control looks good in most fields, even where weeds got pretty big before an herbicide application. Soybean aphids are easy to find in most fields with some plants hosting 80 to 100 aphids while other fields that are showing very few to no aphids. Be sure to remember the threshold for aphid control is 250 per plant.

Many dry beans were planted early this week while a few growers are still waiting for fields to dry out. Many recently planted fields are emerging nicely. Hopefully the rainfall at emergence won’t cause too much root disease and yield loss.

Jeff Andresen
Agricultural Meteorology
Geography

An upper air ridge across much of the Midwest has brought hot, humid summer-like weather to Michigan for much of the past week. Even though high levels of low-level moisture (the “raw material” of precipitation) have been in place recently with dew point temperatures in the mid and upper 60s to low 70s, there has been a pronounced lack of any atmospheric focusing mechanisms to generate large scale/widespread convection. As a result, the showers and thunderstorms that have developed have been widely scattered with only limited aereal coverage. Looking at the season as a whole thus far, precipitation deficits from the beginning of April now have reached as high as seven inches in some sections of western Lower Michigan with normal rainfall only on the order of 8.0 to 8.5 inches. NOAA Palmer Drought Index values calculated late last week now characterize all but the east central Lower Peninsula in either “moderate” or “severe” drought conditions.

There are prospects for some relief from the dryness and heat in the next 24 hours. A strong cool frontal boundary will make its way into Michigan during the day Thursday, leading to areas of showers and thunderstorms over most areas of the state. Rainfall amounts of 0.10 to 0.25 inches will be possible where rain occurs with the totals limited somewhat by the relatively rapid motion of the individual storms. Due to the forecast of stronger winds aloft Thursday, some thunderstorms may reach severe levels with high winds being the primary threat. Much cooler and drier air will move into the state overnight Thursday and set the state for a fair and cool early weekend.

Warmer weather with the chance for showers and thunderstorms is on tap for early next week (Monday, July 4 and Tuesday, July 5), as yet another frontal boundary moves into the region. Temperatures will remain at much above normal levels one more day Thursday with daytime highs near 80 in northern lake shore areas to the upper 80s to the low 90s south before falling back to the 70s Friday. High temperatures Saturday through Monday (July 4) will gradually warm back from the low 70s north to near 80 south Saturday to the upper 70s north to mid 80s south on Monday. Low temperatures will fall back to the 40s and low 50s Friday morning, warming back into the 50s to low 60s again by Sunday.

The NOAA Climate Prediction Center 6-10 day (for July 5-9) and 8-14 day (covering July 7-13) outlooks both call for temperatures to range from near normal levels in southern sections of Lower Michigan to above normal in the north. Precipitation totals across the state during the 6-10 day time frame are forecast to increase back to normal levels, while below normal precipitation totals are forecast statewide during the 8-14 day period.