In this issue
§ Soybean aphids still a problem
§ Asian soybean rust sentinel plot scouting report: August 4–11
§ Regional reports
§ Weather changes in progress
Aphids continue to plague growers. Some fields have been sprayed two to three times, others once, still others not at all. Later in the season, when pods begin to fill, we've always known that the threshold for aphids increases from 250 to some higher number. Unfortunately, research data is not available to define that later season number – one rule of thumb that I use in larger, fuller plants is 1000 aphids per plant, but again that has not been confirmed with research, but clearly a plant that is four feet tall can withstand more than 250 small aphids. Instead, when we get later in the season, I evaluate fields using additional characteristics that give me the “feel” of the aphids population, and to define fields that probably do not need to be sprayed immediately – wait a few days and see what happens. Remember, the second half of the aphid spray recommendation: 250 (early in the season) or 1000?? (R5 or later) aphids per plant with increasing populations.
Here is a quick list of such characteristics:
There are less than, say, 1000 aphids per plant. Most aphids are small, newly deposited nymphs. Aphids are not growing in size very quickly, and appear not to be doing very well on the plants. Tiny babies are very common, but they do not appear to “grow.” Instead they appear the same each day (Likely predation is removing many of the older individuals so these really are new babies each day.).
Although aphids are present on every plant, populations do not appear to be increasing. Aphid numbers per plant overall in the field are instead remaining static or increasing slowly.
Beans do not appear stressed: adequate water; green, healthy foliage; tall canopy.
Beans do not have signs of classic aphid infestation, that is, no or little new honeydew, aphids lined up on the stem, etc. There may be signs left over from a previous infestation, for example honeydew and mold, or white skins shed from aphids.
Presence of fungus in the fields is killing aphids. Fungal pathogens are beginning to wipe aphids out at certain locations. Recent foggy mornings, with extended dewiness, are perfect for outbreaks of beneficial fungi. Aphid populations can crash in a matter of days. Aphids attacked by fungus turn pink or tan, and appear fuzzy under a hand lens. In addition to killing aphids, certain fungi also kill spider mites and potato leafhopper.
Many natural enemies are present in the fields.
Fields such as this probably do not merit spraying immediately. If possible they should be resampled in three to four days.
1. Field canopy is tall and dense – obvious difficulty moving equipment in the field will cause poor coverage of insecticide. We have already seen spectacular examples this season of poor coverage leading to the need for additional sprays. By spraying and getting poor coverage, many beneficials die, while aphid control is weak.
2. Pre-harvest interval of available insecticides is too
close. PHIs (days) for some aphid insecticides are
the following: Ambush/ Pounce/ permethrin: 60; Warrior:
45; Lorsban and other chlorpyrifos
products: 28; Asana, Mustang Max, and dimethoate: 21;
Penncap: 20.
These two factors may “clinch” the decision not to spray.
Meanwhile, winged aphid numbers continued to be high in
suction traps over the last few weeks with
I realize that many people are frustrated with aphids right now, but this is expected! First, this season has been different in that we had the earliest colonization we've ever seen and a heavy winged aphid flight in midseason. Combine this with some of the earliest planting of soybean, and you get fields that have to be resprayed, simply because of how long aphids have been present in the fields.
Second, due to the threat of rust plus our experience with yield loss due to aphids in 2001/2003, this is really the first season that so many people are actually walking soybean fields on a regular basis. As a researcher sampling aphids for the last four to five seasons, I've experienced frustration towards the end of each season, trying to define later-season threshold, decide which fields should be treated, and when too late is really too late. Now many others are getting to experience to the frustration, too (misery loves company).
But don't despair! If you are frustrated by aphids right
now, it’s because you are in the
field, watching aphid populations rise and fall for sometimes
mysterious reasons. In general, producers have done a great job this year
walking fields, following aphid populations, observing other insects in soybeans,
asking a lot of questions and making spray decisions. Notice that there are
very few "black" soybean fields this year compared to 2001/2003,
because people have done a much better job of management, even if it is
frustrating at times. The second reason not to despair is that within the next
7 to 14 days, aphid populations will fall. Fungus is going to move into more
fields, crashing populations. Maturing beans are a much lower quality host, so
aphid increase will slow. And as the days get shorter, temperatures cooler, and
plant quality less, the aphid population will switch over to winged males and
females that leave soybean for buckthorn. The end is near!
Ten reports were filed from the 20 soybean sentinel plots during the reporting week.
No soybean rust has been found on soybeans or other plants
in
Growth stage: Three plots are at R4 and seven plots are at R5.
Plant height: Two
plots ranged from 20 to 30 inches, and eight plots ranged between 36 and 48
inches.
Degree of canopy closure: All plots ranged between 95 and 100 percent closure.
Soybean diseases present: Downy mildew is present in half the plots at low to moderate levels but the incidence is increasing. Brown spot remains at low levels in three plots.
Insects present: Two plots have recently been sprayed for soybean aphids, three plots have per plant populations of soybean aphids ranging from 250 to 420 with honeydew and sooty mold present, two plots have low incidence of soybean aphids and three plots report no soybean aphids. Spider mite damage was noted on 5 to 10 percent of the leaves in one plot.
There is no MSU Diagnostic Services report this week.
New reports of soybean rust in the
It has been hot and dry over the past two weeks. We are now over 25 days of 90-degree temperatures this summer. Some scattered and light showers have fallen, but nothing widespread. The last thing we need is an August as stressful as was June and early July.
Alfalfa has a lot of potato leafhoppers. The third cutting is about half finished. The alfalfa is growing well given the dry conditions. The heat has caused the second and third cuttings to mature much quicker than normal. Prices have held up fairly well, one report of $2.50 per small, square bale for first cutting and $3.00 per bale for second cutting. Most hay was put up without rain this summer and is nice and dry and green.
Corn is surprisingly green and tall. A few sample ears showed that pollination was successful, though ear length of the samples were smaller than normal and they were also smaller in diameter. European corn borer numbers are relatively high as we are in the thick of the second generation. Western corn rootworms are present but not in high numbers.
Soybeans are taking a pounding from aphids and spider mites. Most fields are suffering and have been sprayed with insecticides recently. Sudden death syndrome is appearing and soybean cyst nematodes are prevalent. Phytophthora stem rot is also evident, and one farmer is reporting Sclerotinia white mold, though it seems too hot and dry for this disease to become a problem this year. Beneficial insects feeding upon aphids are present, as are the hole-chewing Japanese beetles. Insecticide sprays are not always reaching down into the canopy.
The USDA crop report tomorrow will be read with great interest. An ethanol plant in Blissfield will have their groundbreaking ceremony later this month. The July 1 fire at The Andersons’ Cargill Port of Toledo facility will affect farmers’ grain deliveries and exports this fall.
Scattered rain showers
over the past two weeks have yielded only a few tenths of inch of rain for many
in the southern part of the region while to the north over an inch of rain fell
the week of August 1. Much of
Small grain harvest is essentially complete. There are still a few fields that have
quality and or moisture problems that are still waiting to be harvested.
Corn
maturity is progressing rapidly. European corn borer moth numbers in pheromone
traps have increased this week indicating a possible peak of second generation
moth flight.
Early planted dry bean fields are starting to turn. Most
of this crop is experiencing overall good growing conditions.
Soybean aphid has been observed in high numbers in many fields. Many fields have
been treated. Fields that have not been treated with insecticide have started
showing a decrease in soybean aphid numbers over the past few days.
Potato leafhoppers are
present in alfalfa fields and should
continue to be monitored.
Parts of the region received over one inch of rain in the past two weeks. This has provided very adequate moisture for crop growth. Many farmers are real optimistic about the yield potential in the field. This year, the central region has had the right mix of rain and heat for excellent yields. However most are saying “it’s not in the bin yet.”
The corn crop is outstanding at this time. The crop is maturing rapidly with the record heat of this summer. We expect harvest of corn silage to be much earlier this year. Farmers need to check whole plant moisture over the next few weeks to monitor crop progress to harvest the highest quality corn silage. The biggest problem with corn this year has been corn rootworm. We have seen several fields with lodging because of this pest. Scout fields and make notes to aid in planning for next years corn crop.
Soybeans are R-4 to R-5 and progressing rapidly with the near-ideal growing conditions. The biggest issue is soybean aphids. The populations are at or over threshold and many fields have been treated. We are seeing white mold in many fields. The region has had almost ideal conditions for mold, and it is beginning to show in several fields.
Wheat harvest is complete with most growers disappointed with yields. The quality was very good.
Oats and barley is harvested with yield and quality generally good.
Harvest of third cutting alfalfa is nearly complete. Yield and quality has been very good. Leafhoppers are present and farmers need to continue to scout for this pest.
Dry beans are doing very well. At this point the yield potential looks very good with good stands and few real problems. We expect harvest to be early this year.
High temperatures have been pretty consistent in the past couple of weeks. Rainfall has been limited but a couple of storms have dropped some rainfall in small areas. Most plants do not appear stressed but are using lots of moisture and will need some replenishing soon.
Third cutting of alfalfa is being wrapped up in some places that were able to harvest first and second cutting in a timely manner. Yield of third cutting has been quite a bit less than the first two cuttings.
The sugar beet crop continues to grow and look good in many areas. Weed escapes have made themselves obvious in the past couple of weeks. Micro rate herbicides worked well in some places while other fields could be considered poor weed control. Hoeing has been active where possible with the limiting factors being number of crews to work and the cost per acre for some of the weedy fields. Cercospera leafspot is easy to find with favorable environmental conditions of high temperatures and plenty of leaf wetness (especially from morning dew and fog). Many growers have made a second fungicide application for control.
The good fields of corn continue to look good while some of the injured fields have improved in appearance. Pollination is pretty much wrapped up with good conditions. Temperatures were a little high during pollination, but short breaks in the mornings and evenings helped to fill ears.
Soybeans are showing good yield potential in most areas. Many fields are more than 36 inches in height and podded up to the top node. Rainfall in the next couple of weeks may be critical to the development of those tops pods. Soybean aphids have boomed again in many areas, which has led to a second insecticide application. Many growers have questions about how long we can expect the aphids to stay around but are cautious about allowing high populations to feed on soybeans developing and filling pods.
Some of the injured dry bean fields have recovered significantly while others continue to thrive. The number of pods per plant and beans per pod point to a good crop but we can never be too confident of this crop until they are in the truck.
After several weeks of a persistent ridging pattern across
the central United States, the jet stream will be moving southward during the
next couple of days, resulting in cooler and wetter weather for much of the
Great Lakes region. The cool front that moved across
Temperatures during the next few days will remain near or slightly below normal levels with highs ranging from the low and mid-70s north to mid-80s south and lows from the upper 40s north to low 60s south.
In the medium-range time frame, computer model guidance is
suggesting that the core of the jet stream, normally near its northward-most
range across central Canada at this time of the year, will at lest temporarily
shift southward to the United States/Canada border area. This would result in a
fast-moving, west-to-east jet stream flow over
The NOAA CPC 6-10 day
outlook, covering August 16-20, calls for temperatures to range from below
normal in the Upper Peninsula to near normal in Lower Michigan. A wide range of
precipitation is forecast, ranging from below normal totals across