Willie Kirk, Chris Long and Phill Wharton...The 2009 season has been challenging for many growers in the state. Several thousand acres will not be harvested in areas throughout Michigan. This can be whole fields or parts of fields. The appearance of a new strain of late blight has also complicated matters regarding the integrated management of late blight for next season.

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Fred Warner...Potato early-dying disease (PED) is a complex with the lesion nematode, Pratylenchus penetrans and the wilt causing fungus, Verticillium dahliae, usually implicated as the causal agents. Both organisms are pathogens of potato but when present together, they often interact to produce more significant yield losses than they would cause individually.

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Willie Kirk and Jan Byrne...On July 29, the MSU Diagnostic Services center at MSU received a tomato plant that had late blight on both the fruit and foliage. This sample was from a home gardener in Gratiot county. There has been a severe outbreak of late blight on tomatoes in the Northeast, in states including New York

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By Willie Kirk... Potato late blight has been confirmed in potato crops in the Midwest in recent days. During the past year, potato seed has been in short supply. This shortage has resulted in growers procuring their seed from unusual sources.

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Willie Kirk...The Late Blight Risk Monitoring system is now up and running for the 2009 growing season. Five new locations have been added due to the expansion of the Enviro-weather network since last year.

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By William Kirk and PhillipWharton... Potato seed production in the north central United States has been impacted in recent years by unusual, but increasingly regular, meteorological conditions during the tuber development phase in the field.

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Willie Kirk...The main diseases to appear in Michigan fields in 2008 have been Rhizoctonia stem canker, bacterial soft rot and seed-borne fusarium dry rot. Spring and early season conditions have been ideal this year for the sporadic appearance of these diseases although Snowden has been particularly affected by soft rot issues. The disease has not been confined to seed from any single seed lot or grower, but has been a varietal issue. We are investigating this further.

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Willie Kirk...Recent weather conditions may have been suitable for the development of Rhizoctonia diseases and possibly black dot if weather conditions become hot in the next few days. Results of trials across the United States suggest that black dot may be suppressed by an application of a strobilurin or similar fungicide, such as Quadris, Evita, Headline, or Tanos, prior to canopy closure.

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Wesley Everman...Potatoes have a wide variation in growth habit and response to environment, particularly due to genetic variation which can be attributed to its polyploidy nature. It is therefore no surprise to those who grow potatoes that varieties respond differently to herbicide applications. Herbicide options for weed control in potatoes are limited to several compounds that have been around for decades with a few newer ones mixed in.

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 Willie Kirk, Phill Wharton...Fusarium dry rot is one of the most important diseases of potato, affecting tubers in storage and seed pieces after planting. Fusarium dry rot of seed tubers can reduce crop establishment by killing developing potato sprouts. There have been reports of Snowden seed lots affected in 2008 although other seed lots may also be affected.

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Willy Kirk...The NCERA (North Central Research and Extension Activity) 205 group met in East Lansing during late March 2008. The group was composed of members from Michigan, Wisconsin, North Dakota, Minnesota, Colorado and Nebraska potato industries. Michigan attendees included representatives from Walther farms, Black Gold, Lennard Farms and ABC consultants as well as MPIC and MSU. The focus of the group is on pest management and agronomic practices in the North Central region of the United States.

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Willie Kirk and George Bird...Potato plants can become systemically infected with viruses following mechanical transmission or through vectors. Viruses decrease plant vigor and cause mottling, chlorosis and necrosis. Yields are decreased and some viruses cause internal tuber symptoms which can be seen after the affected tuber is cut or peeled. Such crops completely lose their value even though a small proportion of tubers are affected. Some viruses may rapidly kill plants, whereas others cause mild or no symptoms at all and the reaction of different varieties to the same virus can vary.

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 Willie Kirk...A new potato disease scouting guide is now available in addition to seven new high resolution potato diseases MSU Extension bulletins for purchase from the MSU Extension Bulletin Office.

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Walter Pett...Colonies of green peach aphids have been found in several potato fields in lower Southern Michigan.  Green peach aphids vector both persistent (PLRV) and non-persistent (PVY) viruses to potatoes. Hot dry conditions are ideal for rapid flair-ups of aphid populations.

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Beth Bishop...Aster leafhopper numbers remain low in carrot and celery fields in west Michigan. The percentage of leafhoppers infected with aster yellows has also remained low so far this year. Most fields have too few leafhoppers to require insecticide treatment. Treatment threshold is 30 to 35 leafhoppers per 100 sweeps for celery, 40 to 50 leafhoppers per 100 sweeps for carrots and 20 to 25 leafhoppers per 100 sweeps for lettuce.

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Phill Wharton & Willie Kirk...Seven new high resolution potato diseases extension bulletins are now available for purchase at http://www.emdc.msue.msu.edu/ for $1.50 each. The new group of publications includes the recent potato late blight bulletin and bulletins on early blight, pink rot, Fusarium dry rot, Rhizoctonia diseases, potato common scab, white mold and seed piece management. For more information, call 517-353-6740. You can also download these bulletins from this web page http://www.potatodiseases.org/extensionpubs.html as PDF files from our late blight website.

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Steven Gower...Potato plants submitted to MSU Diagnostic Services contained chlorosis followed by necrosis of the newest leaves with the older leaves being normal. In addition to first turning yellow, the newest leaves contained a proliferation of buds and small leaflets. (view image)

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Willy Kirk...Strobilurin-insensitive isolates of Alternaria solani were reported by Dr. Neil Gudmestad (North Dakota State University) for samples of the disease taken from potato fields in southwest Michigan and Dr. Walt Stevenson (University of Wisconsin) for samples taken in Tuscola County, Michigan in 2005. In 2006, it is intended to widen this survey to all potato growing regions of Michigan.

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Willie Kirk...Potato late blight was confirmed in a field in southwest Michigan near the town of Three Rivers. It was found on a variety particularly susceptible to the disease. However, it is highly unlikely that the disease was initiated through seed-borne infection as it appeared seven days after heavy rains and thunderstorms passed through the area.

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Beth Bishop...The recent warm weather has caused the sudden appearance of many insect pests in vegetable fields. Insects that overwinter in Michigan need two major factors to emerge: adequate degree day accumulations and adequate moisture. The cool, wet weather we experienced in mid-May provided sufficient moisture. The very warm weather during the past week has meant a rapid rise in degree days. Consequently, some insect pests such as Colorado potato beetle and European corn borer (see photo), which would normally emerge during several weeks of moderate temperatures, emerged all at once, in high numbers in the hot weather.

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Beth Bishop...Colorado potato beetles have emerged from overwintering and are feeding on potatoes in many areas of the state. (see photo) In most cases, growers applied at-plant neonicitinoid insecticides to control these overwintered beetles.

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Willie Kirk...The recent and continuing stretch of cold, wet weather has resulted in soils that are water saturated and may remain cool and wet for several weeks. These conditions are particularly suitable for the development of lower stem and root-rotting pathogens for example, Phytophthora spp., Rhizoctonia, Pythium, Fusarium and other soil-inhabiting fungi and bacteria such as soft-rots (Erwinia caratovora). Spores of these fungi and water-molds can remain dormant in the soil for many years, and it is likely that with current soil conditions and retarded development and growth of roots, that many plants are vulnerable.

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