June 25, 2008
In this issue
§ Vegetable insect update
§
Downy mildew is in
§ Soil conditions contribute to poor plant growth
§ Asiatic garden beetles beginning to emerge in St. Joseph County
§ Learn from the cover cropping in vegetable systems tour held June 12
§ Regional Reports
§ Weather
Beth Bishop
Entomology
The first flight of European corn borer moths continues
throughout
We are still catching a small number of corn earworm moths in pheromone traps. These are most likely moths that moved into the state on the strong storms a few weeks ago. Sweet corn in silk is attractive to corn earworm females for egg laying. However, growers with silking corn should also be spraying for European corn borer. As long as the silks are well-covered, applications to control corn borer should also control any corn earworm. As a reminder, corn earworm is migratory and we can see very large numbers come into the state on storm fronts. If and when that happens we will update growers.
Most celery, carrot and lettuce growers have recently
sprayed fields to control aster leafhoppers and the number of aster leafhoppers
found last week decreased. Diagnostic
Services tested six populations of leafhoppers collected from celery and
carrot fields in west
Earlier this year, in late May and early June, aster leafhoppers carried very little aster yellows. In mid-June, storm fronts carried new leafhoppers into the state and some of these leafhoppers were infected with aster yellows. Consequently, we have a mixture of old and new, infected and uninfected aster leafhoppers. Growers may wish to be conservative and use the treatment thresholds published last week because of the variability in infection rate.
Celery fields should be treated if the number of aster leafhoppers caught in sweep net samples exceeds three to five leafhoppers per 100 sweeps. Carrot fields should be treated if the number of aster leafhoppers exceeds three to seven per 100 sweeps. Lettuce fields should be treated if the number of leafhoppers exceed two to four leafhoppers per 100 sweeps.
Mary Hausbeck
Plant Pathology
Downy mildew has been confirmed in a small commercial
slicing cucumber field in the
Darryl Warncke
Crop and Soil Sciences
Growing conditions have been variable and challenging across
During flooded or saturated soil conditions 50 lbs N/a or more may be lost by leaching or denitrification. Once soils dry sufficiently, sidedress 40 lbs N/a to enhance root and plant growth. Spraying nitrogen and other nutrients on the foliage of stressed plants may help them get through the stress period. However, under stress conditions plants are less able to absorb nutrients through the leaves, so the benefit may not be as great as anticipated. Urea ammonium nitrate (28 percent nitrogen) is a good source of nitrogen for foliar application as long as the rate does not exceed three gallons per acre. Small amounts of nutrients may be able to be added in with other spray materials, but be sure to check compatibility.
When excess rainfall occurs, the primary nutrient of concern is usually nitrogen. In sandy soils, significant amounts of potassium may also be leached out of the root zone so that topdress application may be beneficial for high potassium requiring crops, celery and tomatoes. Boron is also subject to leaching out of the root zone in sandy soils and muck soils. For celery, celeriac, broccoli and root crops consider spraying 0.25 lb actual boron per acre on the foliage.
Bruce MacKellar
St. Joseph County MSUE educator
Asiatic garden beetle is a new pest in southwest
During MSUE winter meetings last year, we learned that
potato producers in southern
We have been closely monitoring Asiatic garden beetle
activity in
This week the first Asiatic garden beetle adults began to
emerge. The beetles were observed in a seedcorn field in central
MSU Field Crops Entomologist Chris DiFonzo is hoping to develop a method for predicting when Asiatic garden beetle larvae pupate and when adults are likely to emerge. We are looking at both soil and air growing degree day accumulations at the MSU Enviro-weather stations in Mendon and Constantine to chart how these values against adult beetle emergence. It may take several seasons to get a model in place to accurately predict when the adults are likely to emerge.
Chris and Dr. Walt Pett are interested in learning more
about when Asiatic garden beetles enter potato fields to lay eggs. Unlike their
close cousins, the Japanese beetle, Asiatic garden beetle adults are more
active at night than in the daytime. They hope to work with potato producers in
Kate Leich
MSU Department of Community, Agriculture, Recreation and Resource
Studies
June 12 was a wonderful day at the Kellogg Biological Station (KBS); the weather was great, the speakers were fascinating and the cover crops were looking good. We started the day indoors, listening to five talks from professors and Extension educators. PowerPoint presentations from this program are available at http://michiganorganic.anr.msu.edu/. A summary of the workshop is given below and on the main page with links to the presentations.
Anne Verhallen from the Ontario Ministry of Agriculture, Food and Rural Affairs, gave an overview on cover crop attributes in vegetable systems. Her talk was particularly attuned to the audience's interests and there was opportunity for feedback and questions throughout her presentation.
Mathieu Ngouajio, associate professor of horticulture at Michigan State University (MSU), taught us about biofumigant cover crops. We learned about the biochemistry of biofumigants and how this information can help to develop more efficient cover cropping practices.
Darryl Warncke, MSU professor and Extension specialist in the Department of Crop and Soil Sciences, talked about nutrient management using cover crops. He provided a lot of interesting information about the dynamics of nutrient cycling and how understanding those dynamics can help improve nutrient availability.
George Abawi, professor of plant pathology at
Daniel Brainard, assistant professor of horticulture at MSU, spoke about cover crop mixtures for integrated weed and nitrogen management. Throughout his talk he made points about the financial pros and cons of cover cropping.
During the second half of the day we ventured into the KBS fields to examine cover crops from another angle. Sieg Snapp of KBS introduced us to perennial wheat. We got a good look at the wheat's roots, and had discussion about the differences and similarities between perennial and annual wheat (e.g., gluten content). We witnessed a demonstration of a crimper in use; this piece of equipment is useful in killing a cover crop by breaking its stems, yielding a nice, green mulch.
Photos of the meeting are posted at http://michiganorganic.anr.msu.edu/. If you have any questions, please contact Vicki Morrone (sorrone@msu.edu) or Kate Leitch (leitchka@msu.edu).
Ron Goldy
Temperatures were below normal for the period with lows from 47°F to 53°F and highs from 66°F to 81°F. There was a trace to 0.1 inches of rain across the immediate area. Soil moisture levels continue to drop and in many soils irrigation is necessary.
Watermelon and cantaloupe look good, but growth has slowed due to cool temperatures.
Cucumber, yellow squash and zucchini harvest continues from tunneled plantings. Some pollination problems have been observed. This may be due to the earliness of the planting and bees not yet finding it, or it may be weather related since we experienced some cool, windy conditions seven to ten days ago when these crops would have been in bloom.
Pumpkins are mostly planted and are growing well.
Onions are starting to bulb.
Pepper and tomatoes are growing as well as expected given the cool temperatures.
No serious disease or insect pressures have been reported in the area.
Bill Steenwyk
Temperatures remained cooler than desired, but have warmed in recent days. Many fields could benefit from a little rainfall, even as we recover from the early June flooding, however storm clouds are gathering as this article is being written. Crop growth and development varies, and continued warmer temperatures will be important to advance. As reported for the past two weeks, muck and poorly drained upland soils suffered from the June 7 - 8 storms. However, we are still discovering the extent to which fields are or are not recovering in terms of yield quantity, quality and timely maturity. Many are wisely, sidedressing additional nitrogen to replace what was lost from leaching and denitrification. One grower intended to sidedress urea and hope for rain to incorporate the nitrogen into the soil. Let me remind everyone that any fertilizer product containing the ammonium form of nitrogen must be incorporated mechanically or by irrigation/rainfall to avoid major nitrogen loss. When left on the surface, much of that expensive nitrogen will be converted to ammonia gas and simply float away.
On muck soils, celery, radishes, lettuce, cabbage and sweet corn are being planted, transplanted or replanted. Post-flood plantings look good overall.
Onions are quite variable with healthy and water-stressed fields growing near each other. Bulb initiation is beginning. In some cases, the onion plant hasn't developed enough leaf tissue to support good bulb development.
Leeks have been stressed, but should recover.
On upland and some muck soils, cabbage looks good. Sweet corn is growing again, with the earlier plantings exceeding two feet. Corn borer trap counts as of June 24 were less than one per trap.
Vine crops are
growing, although significant acreages of squash
in some areas of
Tomatoes and peppers are doing well overall and in flower or developing fruit.
Peas are being harvested.
Norm Myers
With the exception of yesterday,
Asparagus growers are in the midst of shutdown and so are many of the processors. However, the largest processor will receive into next week. We are also riding a very hot fresh market and I am sure that some growers will pick through the weekend for that market. Growers are still getting good yields and good quality, probably as a result of the abundant rain and cool temperatures. Most growers feel that they will be a little ahead of last year’s production, but it is important to remember that 2007, was a record low year for asparagus.
Fortunately, growers all sprayed their carrots last week as a result of the new aster leafhopper threshold and scouts are not reporting finding new leafhoppers this week. We are setting out our Tom-Cast sensors this week, but don’t anticipate any disease yet.
Zucchini, pumpkins and pickles are emerging normally except where they were planted on heavy soils and needed to be replanted.
In sweet corn, I had only one catch in each of my European corn borer traps, but I did catch five corn earworms. So far nothing has been caught in my western bean cutworm traps.
Jim Breinling
The only rainfall reported during the past week was 0.06 inch at the Ludington Enviro-weather station. Temperatures in the area were below normal with highs generally in the low 70s and lows about 50°F.
Crown maggots were found in spinach on Friday, June 20 above a threshold level of one per 100 plants. Also, some leaf feeding on new growth was observed, but no chewing type insects could be found.
Harvest of processing peas
was completed during the past week in
Early planted fields (April 15) of carrots are now at 0.25 inch in diameter and up to ten inches in length depending on variety and type. They will be approaching the start of harvest in approximately six weeks.
In cucurbit crops, reports of some replant due to cold temperatures and then wet weather. Fields of winter squash are now at the three true leaf stage of growth.
Snap bean
planting is now in full swing in the area. Planting was delayed about a week
due to cool weather, which was fortunate that no plantings were in before the
heavy rains occurred. The fields in
June 21 -24. Trap counts on June 23 were 11 - 0 - 5.
Sweet corn
development at the
Hannah Stevens
The cool and wet conditions persist with the maximum temperatures barely reaching 80°F throughout these counties. The area has also received highly variable amounts of rainfall on at least five days this week, from 0.2 inch to two inches have been reported, including wind and damaging hail. Nevertheless, there have been opportunities for sidedressing nitrogen, weed control, tunnel removal and planting of late season cole crops, sweet corn and others. Wild pollinators appear to be in abundance on trees, shrubs and herbs that are in lush bloom in the landscape.
The potato crop is in excellent condition
with some new potatoes due at farmers markets this weekend.
Most untreated onion fields have thrips present, even on small ones. Onion smut may be seen occasionally as well as a small amount of maggot injury. Spring bunching onions as well as very early green bulb onions are being pulled for direct sales. (view photos).
Growers are trying to finish transplanting of the late crop of broccoli, brussels sprouts, cauliflower and cabbage. Imported cabbage worm butterflies were very visible this week in the landscape. Early broccoli is now being retailed.
Alternaria leaf spot was found on a field margin of early carrots.
In sweet corn, corn borer numbers are holding steady at relatively low levels as the first crop of bare soil corn begins to show tassels in the whorl. I did not notice any foliar feeding injury at this time, but I suspect growers will begin to see it soon.
Tunnels have been removed with muskmelons and watermelon quickly vining out, flowering and beginning to fruit. Angular leaf spot is present in one cucumber field (view photo). Growers are watching closely for downy mildew in our location and angular leaf spot, a bacterial pathogen, can resemble this more destructive fungal disease. Nevertheless, angular leaf spot may require treatment as cool and wet conditions persist.
The first crop of radishes
from
Edible podded, snap and shell peas are now at farmers markets.
Sudeep Mathew
We had some isolated showers this past week. Most other
areas were dry with some windy conditions. According to the Enviro-weather
station in
Sweet corn is progressing well. Sweet corn smut was found in a conventionally planted sweet corn field (Photo 1). Leaves were infected, developing small galls, usually on the midrib, causing some leaf distortion. It is usually not economically important, although in some years yield losses in sweet corn may be as high as 20 percent. European corn borer larvae between one-sixteenth and one-eighth of an inch in size were found in sweet corn. A granular application was recommended, however growers who do not have the equipment could put a foliar spray schedule with an interval of five to six days. It is important to make sure the plant is covered at the tassels emerging stage to restrict that caterpillar activity. Not many eggs were found. European corn borer moths in our traps averaged two moths per trap for this week.
Cabbages are forming heads and continue to be harvested in the early planted fields. Cabbage rhizoctonia secondary infection was found in some rotted cabbage heads (Photo 2). It is not wide spread across the fields; the symptoms are only in isolated areas.
Cucumber beetle activities were found at several fields.
Most growers made an insecticide application. Melons, squashes and pumpkins are coming up very well. Since
we heard the news about downy mildew in
Tomatoes are progressing well on stakes. Plants have thick canopy with fruits forming. Fruits are 1.5 to 2 inches in diameter. I have noticed tomato blossoms falling off in some fields. I feel it was because we had many evening temperatures that fell below 55°F this season. There is no serious insect or disease pressure at this time.
Peppers are progressing well. There was some wind damage in few fields (Photo 3).
Snap beans are having a very vigorous growth.
Potatoes are blossoming with good canopy. There are very low numbers of leafhoppers in many fields, but we did find ten leafhoppers in twenty sweeps in a fingerling potato field.
Aaron Pollyea
Geography
Shortwave troughs will be the major effect on the state’s weather over the next couple of days, producing rainfall across the state. Along with a deepening upper air flow with a moist airmass pushed in front of it, the amount of precipitation will be less then a half an inch across the state by the night of Wednesday, June 25. The low should enter our region by Friday, June 27, producing the previously mentioned possible severe weather and rainfall. The warmer temperatures should persist until late this weekend when a slight cooling over the state should occur.
Temperatures during the next few days will be generally steady, with highs Wednesday through Tuesday generally ranging from the upper 70s north to the lower 80s south and lows from the upper 50s to low 60s north to the lower 60s south.
In the medium range forecast, the upper air pattern mentioned above is expected to continue for much of the remainder of June. The National Weather Service 6‑10 day outlook covering June 30 through July 4 calls for below normal temperatures and for precipitation totals to remain at near normal levels. The outlook for the 8-14 day period (July 2- July 8) calls for mean temperatures to range from near normal levels across the lower peninsula to above normal levels in upper peninsula, and for near normal precipitation totals across the state.
Further ahead, it is interesting to note that forecast
guidance is also hinting that the very turbulent, active upper air pattern of
late May and early June may return to the upper