 |
 |
|
|
|
Insect update
Christina DiFonzo, Entomology
|
Alfalfa
With the cool spring and delayed insect development,
alfalfa weevil larvae (some quite small) and potato
leafhopper (PLH) are being found together in alfalfa. If a field
is still not harvested, then cutting in the next few days will kill
many weevils, plus PLH eggs and some nymphs. Watch regrowth for
damage from both insects. For weevils, the threshold for treatment
is 6 to 8 weevils per square foot, or 25 percent of the new tips
with feeding damage. For PLH, the threshold is only 20 insects per
100 sweeps (= 1 PLH in 5 sweeps) in 3-inch alfalfa. Some fields
were already harvested a while back, but small weevil larvae are
still present. In this case, use the weevil thresholds you would
normally use before first cutting; that is 40 percent of the stems
with feeding damage. For PLH, the thresholds increase to 50 per
100 sweeps in 3- to 8-inch alfalfa, and 100 per 100 sweeps (= 1
insect per sweep) in 8- to 12-inch alfalfa.
There are numerous insecticides registered for
alfalfa that include both weevils and PLH on the label. These include
such products as Ambush, Baythroid, Furadan, Imidan, Lannate, Lorsban,
Mustang, Pounce and Warrior. While good on PLH, the Dimethoate label
indicates only "reduction of alfalfa weevil larvae" and may not
be the best choice if trying to optimize weevil control. However,
if your major concern is PLH, and small weevils are still present
in the field below threshold, Dimethoate will likely provide enough
suppression of the weevil population.
To end on a positive note, the timely rainfall
and good plant growth we've seen this spring helps alfalfa tolerate
insect feeding better.
Soybean
Bean leaf beetle (BLB) adults are really cooking
in soybean. These beetles are very distinctive - ranging in color
from greenish to yellow to red, with a black triangle behind the
head, a black edge around the abdomen, plus 4 black, square spots
on the abdomen. Adults overwinter in leaf litter and wooded field
margins. In the spring, these adults emerge and eventually move
to soybean fields to feed. The adults chew round holes in the leaves.
Young soybeans (V1-V2 stage) can tolerate considerable injury -
up to 50 percent defoliation - without yield loss. Published thresholds
for V2 soybean range up to 6 beetles per plant because soybeans
can compensate for early defoliation. Thus treatment is generally
not needed at this point in the season, unless defoliation across
the entire field is over 50 percent and there are multiple beetles
per plant. The main concern with BLB is actually for damage by the
summer generation later in the season. At that point, the beetles
feed on pods, damaging developing seeds.
Soybean aphid is present in some fields.
We estimate 1 in 20 plants in a couple of our fields on the MSU
campus have aphids. We have even found isolated plants with up to
50 to 100 aphids, with ants tending and protecting the colony. Some
of the aphid colonies are made up of non-winged mothers with babies.
This indicates that aphids have been present in the field for 7
to 10 days, and that the beans were colonized just after emergence.
There is buckthorn in woodlots around the campus, and this is the
likely source of the aphids colonizing the plots. It is too soon
to know if predators will clean up these isolated infested plants,
or if aphid numbers will increase.
|
|
|
Magnesium deficient corn
Carrie Laboski
Crop & Soil Sciences
|
There have been several reports of magnesium (Mg)
deficient corn in Southwest Michigan. Magnesium deficiency symptoms
often appear early in the growing season in cold wet soils and may
disappear as the soil warms and dries. Here's what to look for if
you suspect Mg deficiency: The first symptoms appear as interveinal
chlorosis in the older leaves. The leaf margins then become reddish/purple.
See Figure 1.
However, one should verify whether or not there is adequate soil
Mg.
Magnesium deficiency shows up on acidic sandy soils.
And large applications of potash can induce the deficiency. If the
soil test Mg level is below 75 lb Mg/a or if potassium (K) exceeds
Mg as a percent of exchangeable bases, the soil may not be able
to supply adequate Mg. A long-term solution on acid soils is to
lime the soil using an appropriate amount of dolomitic lime. On
non-acidic soils, Mg deficiency may be corrected by broadcasting
50 to 100 lb Mg/a, or banding 10 to 20 lb Mg/a. Acceptable sources
of Mg include: magnesium sulfate (Epsom salts), potassium-magnesium
sulfate, and finely ground magnesium oxide.
If the deficiency is severe and/or soil Mg levels
are low, then foliar applications of Mg at a rate of 1 to 2 lb Mg/a
is recommended. This can be achieved using 10 to 20 lb of Epsom
salts applied in at least 30 gallons of water.
If you suspect spots of Mg deficiency in a field,
take plant samples in the affected and unaffected areas and send
them to a lab for analysis, in addition to soil sampling. This can
confirm Mg deficiency.
|
|
|
Presidedress Soil Nitrate Test results
Darryl Warncke
Crop & Soil Sciences
|
In looking over the results of the Presidedress
Soil Nitrate Tests (PSNT) from the MSU Soil & Plant Nutrient
(SPN) Lab, the difference between the manured and non-manured fields
is very apparent. The average nitrogen credit for samples received
from manured fields is 150 lb N/A-2 ft with a range from 70 to 285.
For samples from non-manured fields the average N credit is 67 lb
N/A-2 ft with a range from 20 to 150. Many cornfields that have
received manure have more than adequate available nitrogen to meet
the crop's need. No sidedress nitrogen is needed. In some non-manured
fields, more sidedress nitrogen will be needed than is usually applied.
In these situations the PSNT will either save money or improve the
corn yield.
With recent heavy rains in some areas of Michigan
some farmers are asking how much of the preplant incorporated nitrogen
is still in the top two feet or potential rooting zone. A soil sample
to two feet is the best way to get an answer for this, but not too
many people are anxious to pull soil samples two feet deep. A general
guide developed by my predecessor indicates that in sandy soils
already wetted to field capacity the nitrogen might move 12 inches
for each inch of rain received. Under similar moisture conditions
in finer textured soils the nitrogen might move 4 inches for each
1 of rain received. Following heavy or continual rainfall events
nitrogen loss by denitrification is more likely in fine textured
soils than in sandy soils that drain well.
|
|
|
Diagnosing plant growth problems
Darryl Warncke
Crop & Soil Sciences
|
Each year plant growth abnormalities show up in
a variety of crops grown on a range of soil types. These might be
due to a nutrient deficiency, disease, insects, nematodes, pesticide
injury, tillage or some other cause. In diagnosing a plant growth
abnormality, first observe the field noting where in the terrain
or landscape the problem is located and whether there is a pattern.
Observe the plant closely noting the nature or pattern of the abnormality
or injury. Look at both the top and bottom sides of the leaves as
well as the stem for the presence of injury or insects. Split the
stem open to determine whether or not there is any discoloration.
Use a spade or shovel to dig up the roots and gently remove the
soil. Observe the roots for color and growth habit.
When a nutrient deficiency is suspected, collect
plant or leaf tissue samples from the problem area and from a good
area in the field. Even though interpretation guidelines exist for
"normal" element concentrations in various crops there are variations
in varieties. The "good" sample serves as the reference. Also, collect
soil samples from the problem and good areas and have them analyzed
for available nutrient levels. A quick soil pH measurement can sometimes
help determine which elements might or might not be the cause of
a deficiency.
The last two years magnesium deficiency has been
observed in corn during the early growth. This is more likely to
occur on sandy soils, especially if the soil pH is below 6.0. Application
of high amounts of potassium might also contribute to magnesium
deficiency. Manganese deficiency is frequently observed in soybeans,
especially when the soil pH is above 6.5. Boron deficiency is more
likely to occur in second or third cutting alfalfa if rainfall and
soil moisture is below normal. Observed nutrient deficiencies can
be corrected by spraying the appropriate nutrient on the foliage.
Suggested rates are 0.5 to 2 lb Mg/A, 0.5 to 2 lb Mn/A and 0.3 lb
B/A. A regular soil testing program can help in diagnosing plant
growth problems and/or in preventing nutrient deficiencies from
developing.
|
|
|
Fusarim head blight (scab) of wheat
probability for Michigan
Pat Hart
Plant Pathology
|
The models predicting the potential for fusarium
head blight of wheat can be found by clicking on the link at: www.cips.msu.edu.
Model 2 is the only appropriate model to use at
this time. This model predicts a very low probability for head blight
to develop in Michigan this year. Generally, temperatures were too
low during times when rain or relative humidity was favorable for
disease development. The warm weather over the past week has really
accelerated wheat growth, and most of the state is past the window
when Folicur can be applied.
|
|
|
Stripe rust in wheat
Pat Hart
Plant Pathology
|
Stripe rust of wheat is caused by the fungus Puccinia striiformis. Stripe rust is usually
a problem in wheat when cool temperatures occur throughout the wheat-growing
season. The disease is favored by temperatures in the 50's and 60's
and is inhibited when there are several days of temperatures in
the mid-80's. Stripe rust was observed in wheat on the MSU campus
last week. The overall incidence was low, and severity was low to
moderate. Continued development should be slowed or stopped as temperatures
in the mid-80's are expected over the next week.
A good source of information on stripe rust, including
excellent pictures, can be found at:
www.oznet.ksu.edud/path-ext/factSheets/Wheat/Wheat%20Strip%20Rust.asp.
Fungicides are not recommended as the disease is not widespread
in Michigan and as warmer daytime temperatures prevail.
|
|
|
|
|
|
1
- Southeast
Ned Birkey
|
Weather
Weather has been mixed, with 2 inches of rain last Thursday
(June 12), followed by foggy weather, then clearing, then repeat.
At least the temperatures are higher, which is helping growing degree
day accumulations.
Commodity reports
Alfalfa is getting harvested with the final first
cutting finishing up now. Prices started at $2.50 per small square
bale. The quality of this first cutting is highly variable. The
second crop is off to a nice start however.
Corn is growing nicely with advanced fields
at the V6 stage. Sidedressing is going on. European corn borer trap
counts at Dundee this week, 147, 87 and 496 for the three traps
and 2, 4 and 11 for the traps in southern Wayne County.
Soybeans have not had enough sunlight to
do much growing. Bean leaf beetles are feeding and causing some
economic damage.
Wheat is finished flowering. Septoria is
on the flag leaf, though some fields have very little powdery mildew.
Miscellaneous
We simply need more sunshine. Fortunately, we have not
turned off hot and dry, as in the past two summers however.
|
|
|
2 - Southwest
Mike Staton
|
Weather
We were dry until spotty thunderstorms moved through
the area on June 18th. Warmer temperatures have prevailed
over the past week with highs in the lower-80's and lows in the
mid-50's.
Commodity reports
In corn, early-planted fields are in the
V5 to V6 growth stages. Magnesium deficiency is still prevalent
and has produced yellow, stunted plants in the early-planted cornfields.
No European corn borer feeding has been detected in our tallest
corn.
Early-planted soybeans have reached the
V3 growth stage. Later-planted fields have emerged evenly and quickly
to produce uniform stands.
Powdery mildew is common in most wheat fields.
However, the flag leaves are not severely infected.
Alfalfa harvest is nearly completed. Monitor
regrowth for potato leafhoppers.
|
|
|
3 - West
Central
Fred Springborn
|
Weather
A week of summer-like weather has improved crop
conditions dramatically in the Montcalm area. High temperatures
have been in the 80's five out of the last seven days with mostly
clear skies. We did receive a few rain showers late last week but
they yielded very little rainfall, just a few hundredths of an inch
in most locations. Low soil moisture levels are starting to be of
concern in some crops such as second cutting alfalfa and newly planted
dry beans. Low soil temperatures have made it up into the 60's!
Commodity reports
The bulk of alfalfa haylage harvest is complete.
Fields that were cut early are regrowing nicely with 2 to 6 inches
of growth. Alfalfa weevil is present in the Montcalm area. Alfalfa
that has not yet been harvested in Newago County is showing extensive
damage in some locations. Leafhopper levels are low at this time.
Regrowth of alfalfa should be monitored carefully. Harvest of legume
grass mixed hay is going full speed ahead as much of this hay is
harvested as dry hay.
Early-planted oats are in, or close to being
in, boot. Flowering is complete in rye. Wheat for
the most part is in good condition at Feeke's growth stage 10 to
10.5. There is some powdery mildew on flag leaves of susceptible
varieties. A low population of cereal leaf beetles have been observed
in small grains.
Corn growth stages vary from V1 to V6. This
crop has really taken off this week. There is a quite a bit of variability
of growth stage and individual plant condition within the field
of much of the early planted corn
Sugar beets are growing well. Some spinach
leafminer feeding has been observed. Weed control has improved.
The most common problems encountered have been herbicide carryover
and soil pH issues.
Soybean planting is complete. Soybean growth
stages vary from just planted to V3. Dry bean planting is progressing
rapidly with 65 percent completed. Most of the rest of this crop
will likely be planted this week.
|
|
|
4 - Central
Paul Gross
|
Weather
The region benefited from a week of warm dry temperatures.
There were light and very scattered showers over the region on Wednesday
evening (June 18) that will not keep farmers out of the fields.
Windy conditions have caused problems with herbicide applications
and there have been reports of drift. One must wait for wind speeds
below 5 mph and never spray when winds exceed 10 mph. A wind meter
would be an excellent investment to accurately measure wind speed
before applications and record keeping requirements.
Commodity reports
The largest corn is about V-6 with some later
planted fields just emerging. Most of the stands are very good.
The near ideal weather over the past week has brought some good
color back to many fields. There are still some fields that are
yellow and showing signs of magnesium deficiency. Light cutworm
pressure has been in a few fields.
Soybeans
are progressing rapidly. The early-planted fields have trifoliate
leaves. Some of the later planted fields are emerging very quick.
Weed pressure is high in many fields and herbicide applications
are being made.
Wheat ranges from flowering to just heading.
Many fields have powdery mildew and septoria. At this point it has
not moved to the flag leaf. Fields should be scouted on a regular
basis. Last year several fields were infested with armyworm. None
have been seen at this time.
Alfalfa harvest should wrap up this week.
This is the first time in a couple of years farmers have been able
to make first cutting without it getting rained on because of the
nice weather. There are reports of alfalfa weevil on the new growth.
Fields should be scouted to determine pest levels. The new seedings
look very good.
Dry bean planting should wrap up this week.
Sugar beet fields
look very good. Leafminers are present in many fields at low levels.
Nitrogen applications are being made.
|
|
|
|
5
- Thumb
Mark Seamon
|
Weather
Sunshine and warm temperatures have been the dominant
weather factors this week. Crops are enjoying these conditions with
fast growth. European corn borer moth traps have showed very limited
flight up to this point.
Commodity reports
The first cutting of alfalfa is getting
wrapped-up by most growers. Regrowth on early harvested fields looks
good due to adequate soil moisture and warm temperatures
Sugar beets are growing very well
in this area. Beets in 22-inch rows are covering about 75 percent
of soil surface. Spinach leaf miners can be found in most fields
but at pretty low levels.
The corn has finally gotten the weather
that it has been waiting for. Improved growth and healthy appearance
have changed this crop from fair to good this week. Nitrogen sidedressing
is going strong in later planted corn, but early corn is pretty
well finished.
Most wheat fields are completing flowering
this week. Later fields are in early flowering stage. Powdery mildew
and Septoria can be found in the lower canopy but most flag leaves
are clear of disease. Cereal leaf beetle feeding on the flag leaf
is the most prevalent problem with that leaf, but not near a treatment
threshold.
Most soybean fields are showing good stands,
and later planted soybeans are showing good emergence. Bean leaf
beetles have been found in a few fields. The most advanced fields
in this area have 3 trifoliates expanded but this sure isn't the
norm.
The few acres of dry beans that are being
grown this year were mostly planted this week. Field conditions
were good at planting. Early planted beans have had a struggle in
the past couple of weeks. They are now emerging but not very vigorous
in growth or stand.
|
|
|
6 - Northern
Lower Peninsula
Dave Glenn
|
Weather
Sunny and warm weather the past week has kept fieldwork
at peak levels. Temperatures in the 80's have lasted the past five
days, but cooler night temperatures (in the 50's) still holding
on. Soil temperatures are finally creeping up into the 60-70's.
Soil moisture has been excellent for planting and fieldwork.
Commodity reports
Corn is really growing now with movement into
the V3-4 overall. The warmer temperatures have helped a lot. Most
fields have been grassier than normal this year, with a lot of post
controls having to be applied this year.
Wheat is at heading
in most fields now with some late fields a few days away. Powdery
mildew is starting in on the lower canopy of most fields, but not
moving up the stem and into the upper leaves yet. Some fields still
remaining yellow.
Soybeans are
now all emerged and growing well.
Dry beans are
still being planted, which is very late for this area. The cooler
temperatures and rain a week ago has kept some fields from being
planted. Most should be done by the end of this week.
First cutting of alfalfa
is well underway with tonnage being down a little from previous
years. Most established yields are weedy with grasses and dandelions.
No serious pest problems noted or reported yet. New seedings last
year look very good.
|
|
|
Weather
news
Tracy Aichele
Agricultural Meteorology
Geography
|
The weather should be clear through the weekend
as dry air moves in behind the front. The next chance of rain is
forecast for Monday (June 23).
In the coming week, temperatures should stay warm,
dipping a bit on Thursday, but climbing to the upper 70's and 80's
over the weekend. Low temperatures Thursday and Friday will be in
the 40's. Growing degree day accumulation is still below normal
in most parts of the state. In the 6-10 day forecast, above-normal
temperatures and above-normal precipitation are expected. The 8-14
day forecast calls for above-normal temperatures and normal precipitation.
|
|
| Back
to top |
