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corn earworm
All Crops Treasure Valley - Idaho
corn earworm
Posted on: August 6, 2010 by Jerry Neufeld
The University of Idaho CIS 366 entitled “Timing Corn Earworm Control,”states that summer moths will begin laying eggs in fresh corn silk at approximately 1300 growing degree days (GDD). Egg hatch and larvae attack will begin about 73 GDD later.
According to the Oregon State University GDD model for Corn Earworm (http://uspest.org/cgi-bin/ddmodel.pl?clm), we are currently at 1204 GDD in the Caldwell area. We are accumulating approximately 19-20 GDD per day. We will hit 1300 GDD in the Caldwell area on approximately 8/10, and hit 1373 GDD on approximately 8/14. Those fields with fresh silk at 1373 GDD are most vulnerable to attack from corn earworm larvae.
The following information was taken from CIS 366 regarding corn earworm.
Corn can be “scouted” for corn earworm eggs to predict possible infestation levels. Examine 10 silk masses (about 2-day old) on each edge of a field but only in those fields which are beginning to silk or are silking. Examining a field in late silk for the first time is worthless; most of the eggs, if any were present, are already hatched, and the damage cannot be prevented.
When the egg counts average 1 egg per 2 silk masses, about 100% ear infestation will occur in the field and other fields of like maturity in the vicinity. With 1 egg per 2 silk masses, about 1 inch of each ear tip will be damaged; 1 egg per silk mass will result in about 2 inches of the ear tip damage, etc. When the days and nights are warmer than usual, the damage may double because the earworm will develop faster than the corn.
Fields should be scouted about every 2 to 4 days, depending on temperatures. Once economic egg levels are reached, determined on the basis of damage expected, further scouting is unnecessary. All fields which silk after that time in that vicinity will be subject to damage.
No chemical control will control worms in the ears, so sprays must be timed to control the larvae on the silk before the worms enter the ears. Make the first application when the plants are 50 percent silk, and repeat in 5 to 7 days or as necessary.
For control information from the 2010 Pacific Northwest Insect Management Handbook go to the following web address: http://uspest.org/pnw/insects. In the drop down boxes click on “commercial vegetables” and then “sweet corn.”
Dr. Jim Barbour from the UI Parma R and E Center, Terry Clinton from Crookham Company and I are once again collaborating on a project to trap corn earworm moths across the Treasure Valley. We set out 14 traps at various locations from near Melba to near Weiser. I will check the traps every few days and post the moth counts to this website. Below are the moth counts from earlier this week. Purdue University recommends the treatment threshold to be 10 moths per trap per night.
Weekly Corn Earwom Counts, 2010
Location 8/5
South of Melba, #1 1
N of Melba 0
Kuna 1
SE of Nampa 0
S of Nampa 0
Map Rock Rd & Deer Flat 0
S of Upper Dam, Lake Lowell 5
West of Marsing 9
S of Homedale 7
NE of Wilder 0
East of Parma 4
NW of Caldwell 0
S of Caldwell 0
Near Weiser 1
Total 28
corn earworm
All Crops Treasure Valley - Idaho
corn earworm
Posted on: August 6, 2010 by Jerry Neufeld
The University of Idaho CIS 366 entitled “Timing Corn Earworm Control,”states that summer moths will begin laying eggs in fresh corn silk at approximately 1300 growing degree days (GDD). Egg hatch and larvae attack will begin about 73 GDD later.
According to the Oregon State University GDD model for Corn Earworm (http://uspest.org/cgi-bin/ddmodel.pl?clm), we are currently at 1204 GDD in the Caldwell area. We are accumulating approximately 19-20 GDD per day. We will hit 1300 GDD in the Caldwell area on approximately 8/10, and hit 1373 GDD on approximately 8/14. Those fields with fresh silk at 1373 GDD are most vulnerable to attack from corn earworm larvae.
The following information was taken from CIS 366 regarding corn earworm.
Corn can be “scouted” for corn earworm eggs to predict possible infestation levels. Examine 10 silk masses (about 2-day old) on each edge of a field but only in those fields which are beginning to silk or are silking. Examining a field in late silk for the first time is worthless; most of the eggs, if any were present, are already hatched, and the damage cannot be prevented.
When the egg counts average 1 egg per 2 silk masses, about 100% ear infestation will occur in the field and other fields of like maturity in the vicinity. With 1 egg per 2 silk masses, about 1 inch of each ear tip will be damaged; 1 egg per silk mass will result in about 2 inches of the ear tip damage, etc. When the days and nights are warmer than usual, the damage may double because the earworm will develop faster than the corn.
Fields should be scouted about every 2 to 4 days, depending on temperatures. Once economic egg levels are reached, determined on the basis of damage expected, further scouting is unnecessary. All fields which silk after that time in that vicinity will be subject to damage.
No chemical control will control worms in the ears, so sprays must be timed to control the larvae on the silk before the worms enter the ears. Make the first application when the plants are 50 percent silk, and repeat in 5 to 7 days or as necessary.
For control information from the 2010 Pacific Northwest Insect Management Handbook go to the following web address: http://uspest.org/pnw/insects. In the drop down boxes click on “commercial vegetables” and then “sweet corn.”
Dr. Jim Barbour from the UI Parma R and E Center, Terry Clinton from Crookham Company and I are once again collaborating on a project to trap corn earworm moths across the Treasure Valley. We set out 14 traps at various locations from near Melba to near Weiser. I will check the traps every few days and post the moth counts to this website. Below are the moth counts from earlier this week. Purdue University recommends the treatment threshold to be 10 moths per trap per night.
Weekly Corn Earwom Counts, 2010
Location 8/5
South of Melba, #1 1
N of Melba 0
Kuna 1
SE of Nampa 0
S of Nampa 0
Map Rock Rd & Deer Flat 0
S of Upper Dam, Lake Lowell 5
West of Marsing 9
S of Homedale 7
NE of Wilder 0
East of Parma 4
NW of Caldwell 0
S of Caldwell 0
Near Weiser 1
Total 28
Iris Yellow Spot Virus
Onion Treasure Valley - Oregon
Iris Yellow Spot Virus
Posted on: July 21, 2010 by Jerry Neufeld
Lynn Jensen from the OSU Malheur County Extension office is reporting that Iris yellow spot virus has been confirmed in Malheur County. Make sure onion fields are maintained at an adequate fertility level, and that the soil moisture level is kept at about the 20 centibar level. Make thrips control insecticide applications every 7 - 10 days.
Organic Field Day Offered
Announcements All Locations
Posted on: July 20, 2010 by Nora Olsen
Organic Field Day Offered
M&M Heath Farms, Buhl, Idaho
Wednesday, July 28
Registration at 9 am. Tour from 9:30 to 12:30 pm, followed by lunch.
Cost is $15
Mike Heath of M&M Heath Farms in Buhl, Idaho and Jennifer Miller with the Northwest Coalition for Alternatives to Pesticides invite you to attend an organic field day on Wednesday, July 28.
Mike Heath has been farming organically for 28 years and currently runs 450 acres of certified organic production. He produces dry beans, grains, potatoes, hay, tomatoes, winter and summer squash, and a variety of other vegetables, as well as livestock.
Heath will describe his rotation, organic fertility management, and pest and weed management. He will provide a tour of his various potato varieties, dry beans, Austrian winter pea seed crop, new alfalfa stand, and squash, as well as his planters, cultivators and other equipment.
Last year, Heath participated in the Farm Bill EQIP-Organic Initiative through the Natural Resources Conservation Service. Mike Cothern from the Natural Resources Conservation Service in Twin Falls will be on-hand to discuss this program and others available to organic farmers.
The field day will also include updates from University of Idaho researchers on organic disease management, fertility management, and the Idaho Foundation Seed Program.
Registration starts at 9 am, with the tour from 9:30 am to 12:30 pm. Lunch will be served. The cost is $15. RSVP with Jennifer Miller by Friday, July 23 at jmiller@pesticide.org or 208-850-6504.
Driving directions are available at www.pesticide.org.
Powdery Mildew in Sugarbeets
All Crops All Locations
Powdery Mildew
Posted on: July 14, 2010 by Jerry Neufeld
As of today (July 14) powdery mildew has still not been found in Treasure Valley sugarbeets.
UI CALS Twilight Tour
Announcements Magic Valley
Posted on: July 9, 2010 by Jerry Neufeld
Attached is a flyer with information about the July 21 UI CALS Twilight Tour at the Kimberly R and E Center.
Powdery Mildew in Sugarbeets
Sugarbeets Treasure Valley - Idaho
Powdery Mildew
Posted on: June 25, 2010 by Jerry Neufeld
The Amalgamated Sugar Company Field Representatives are saying that now is the time to plan your treatments for powdery mildew in sugarbeets. While mildew has not yet been found in the Treasure Valley, White Satin Field staff say the modes of action of the mildew chemistries work best if treatments are applied before mildew is found in the field. They are recommending mildew treatments begin in the west end of the Treasure Valley the week after July 4 regardless of whether or not your fields are surface or sprinkler irrigated. You may also want to include an insecticide treatment for black bean aphid or loopers in the mildew tank mix. Contact your Amalgamated Fieldman for information regarding these treatment recommendations and rotation of chemistries.
Confirmed late blight in Washingon
Potato All Locations
Late Blight
Posted on: June 25, 2010 by Jerry Neufeld
Below is information on Late Blight from Philip B. Hamm, Supt at the OSU Hermiston Agricultural Research & Extension Center.
Late blight was confirmed in the Columbia Basin today at two locations; south of Kennewick (Horse Heaven Hills) and near Burbank WA. There are few additional details at this time. Frankly, I am surprised that we haven’t seen this disease problem earlier, given the favorable weather conditions. We expect there are other infections waiting to be found….Keep scouting and bring any suspects in to the lab for confirmation.
Weekly applications of protectant fungicides (manzate and chlorothalonil) are recommended through July. Use of Omega for white mold control provides protection against late blight. Use of a phosphorus acid product may be beneficial for protecting tubers against late blight and pink rot.
Keep checking the late blight hot lines in both Oregon and Washington for further details.
The Oregon Hot Line is 1-800 705 3377
Washington 1 (800)-984-7400
Please let me know if you have any questions.
Phil
Philip B. Hamm
Professor of Plant Pathology &
Superintendent
Hermiston Agricultural Research & Extension Center
Oregon State University
2121 South First Street
Hermiston OR 97838
Phone: 541 567 8321
Loose Smut on Wheat
Small Grains Magic Valley
Loose Smut
Posted on: June 25, 2010 by Jerry Neufeld
Loose smut on wheat was observed in Jerome County. Infected heads are blackened (picture 1) and spikelets are transformed into dry, olive-black masses of spores (pictures 2 & 3). Spores are spread by wind or splashing rain. Only a bare rachis will remain. Before heading, infected plants might have dark green, erect leaves with possible chlorotic streaks. Fungus survives in infected seeds, which remain fully germinable and are not visibly altered. Control is only possible by planting certified disease free seeds, resistant cultivars, and chemical seed treatments.
This information was provided by UI Extension Plant Pathologist Dr. Oliver Neher.
Downey MIldew
Alfalfa Magic Valley
Downey MIldew
Posted on: June 21, 2010 by Jerry Neufeld
Downey Mildew on Alfalfa was observed in the Rupert area. Cool and humid conditions are conducive to the development and spread of Downy Mildew. Initial symptoms include chlorotic tissue either as localized areas on leaflets or entire leaves and stems if infection is progressing. Infected leaves can show symptoms of twisting and/or curling of the leaf margin. Lower leaf surfaces will show white to pale violet down growth. Fungus needs near 100% relative humidity to reproduce and is spread primarily by wind and splashing rain. Disease cycle can be repeated every 5 days depending on environmental conditions. Please consult the PNW handbook pdf below for control alternatives.
This information was provided by UI Extension Plant Pathologist Dr. Oliver Neher.
Stripe rust in winter wheat
Small Grains All Locations
Stripe rust
Posted on: June 16, 2010 by Juliet Windes
Stripe rust has been reported in southern Idaho on Moreland hard red winter wheat south of Burley. (Report was confirmed June 16, 2010.) Scout your winter and spring wheat for stripe rust starting immediately. Varieties with "High temperature adult plant resistance" (such as the soft white spring wheat Alturas) may be vulnerable to stripe rust as the temperatures have NOT been warm enough to activate this type of resistance!Current weather continues to be extremely conducive to the spread of this disease. Refer to the Southern and Eastern Idaho Cereals Extension website for more information.
Small Grains Disease becoming widespread
Small Grains All Locations
Pythium species
Posted on: June 16, 2010 by Juliet Windes
I have examined several wheat and barley samples lately that have had no obvious stem base lesions, but have had dying of lower leaves and severe root rot. I could find no runner hyphae typical of take–all, no stem rot lesions similar to that of Fusarium, no eyespot lesions of Tapesia (formerly Pseudocercosporella).
These have all had (sudden onset of) yellowing symptoms on the leaves, chlorosis and poor overall plant health. Some leaf symptoms look typical of virus infections. Some root systems exhibit extreme damage, with very little to no viable roots left.
I believe these plants are suffering from Pythium root rot, also called browning root rot. Please see the following internet documents as references:
http://ipm.illinois.edu/bulletin/article.php?id=970
http://www.ipm.illinois.edu/diseases/rpds/113.pdf
There is very little we can do at this point to control these infections. Seed treatments with metalaxyl-based fungicides will help control or reduce seedling infections, but will not be effective at this late stage. The disease will be exacerbated with over-watering! If the weather comes off hot and dry, then there will NOT be sufficient root mass to support the plants or grain fill. Stressed plants will also exhibit foliar symptoms of other disease organisms: for example barley scald and spot blotch will take advantage of weakened barley.
There are no resistant varieties.
Stripe Rust
Small Grains Treasure Valley - Idaho
Stripe Rust
Posted on: June 14, 2010 by Jerry Neufeld
Below is some information about stripe rust that specific to the Treasure Valley. UI Cereals Specialist Dr. Brad Brown provided this information.
There were pest alerts posted last week for stripe rust in wheat that were not particularly specific for the Treasure Valley. Most of our winter wheat has already flowered which is the end of the window for labeled applications of fungicides for stripe rust. Some fungicides can’t be applied after heading. In all cases apply according to the label.
The only wheat that can still be sprayed with a labeled application in western Idaho is possibly late fall planted winter wheat that may still be flowering, or spring wheat that is spring planted and some of it may be flowering now. Our spring wheat varieties that were early fall planted (mostly hard red spring) are further along than our winter wheat so are outside the label for fungicide applications. Late fall planted spring wheat should be further along than winter wheat planted the same day.
While there is some stripe rust present at the Parma R & E Center, the incidence is considerably less than 1% in varieties where it is found and most varieties don’t have any pustules present. If you suspect that you have stripe rust in wheat that has not flowered and would like some confirmation before spending your money on a crop that isn’t worth much to begin with, bring it to the Parma R &E Center and Dr. Krishna Mohan, Extension Plant Pathologist will examine it. If pustules are present it is a swift diagnosis. If pustules are not present, then Dr. Mohan can confirm by incubating for two or three days until rust pustules develop. The only pustules of rust that we have seen in the Parma trials are on winter wheat. There is also a tiny bit of leaf rust showing in one spot, but it is not as widespread as the stripe rust, which is pretty isolated.
Fire blight outlook
Tree Fruits Treasure Valley - Idaho
Fire blight / Coryneum Blight
Posted on: June 14, 2010 by Tony McCammon
Fire Blight infections on apples and pears through Thursday are extremely likely any late blooms, recent pruning cuts, or new succlent growth are susceptable. As blossoms are the primary infection site there is not any need to make an application. Numerous serious blight outbreaks have occurred in past when degree hours near or exceed 70 degrees and blossoms are wetted by rain, 2+ hours of dew, or light irrigation.
The use of chemical to control Fire Blight is recommended during bloom. Do not use antibiotics on trees after bloom; they are ineffective. Management for fire blight through the summer envolves pruning out new infections.
Coryneum blight (also known as shot hole) infections are showing up in orchards now, and in some areas, are worse than usual due to the cool, wet spring. Coryneum blight is caused by a fungus that overwinters in buds, causing small gummy cankers. From there, it spreads to leaves and later, to developing fruit by rain water slashing on infected areas.
Captan or a copper product like Kocide are most effective against this disease when sprayed at 50% leaf fall in the Fall and again in February. Use Captan or Bravo Weather Stik at shuck fall in the spring.
Right now I recommend, where practical, pruning out the dead, diseased, or dying branches. Make sure your sprinklers in the lawn are not hitting the trees. This fall and winter hit it with Captan or a copper product. In the Spring hit it with Captan, bravo, or spectracide immunox. During May and June I would be careful what you use. I do not recommend Captan after shuck fall. Spectracide immunox, however, can be applied up to the day of harvest.
Late Blight Information
Potato All Locations
Late Blight
Posted on: June 14, 2010 by Jerry Neufeld
A new feature at the USPESRT.ORG website (http://uspest.org/wea) features late blight risk maps that are updated frequently. For example, if you go to http://uspest.org/risk/tom_pot_map?state=ID you will see the Tomato-Potato Late Blight Risk map for Idaho. If you click on a pin, it brings up the full model for that weather station. For example, if you click on http://uspest.org/risk/models?sta=PMAI&mdl=tplb
it will bring up a page with specific information for Parma, ID. The late blight graph (top left of page) shows the change in infection risk due to temperature and moisture over the default period (past 14 days + forecasted 7 days).
If sufficient inoculum is nearby, infection is very likely if the risk index exceeds 4. This is the Smith version of the tomato-potato late blight risk model and is documented at http://uspest.org/npdn/riskdoc.html#TPLB.
Below is an explanation of the risk index:
1 = conditions are favorable for fungal spore formation if there are lesions on plants in the area,
3 = Conditions are favorable for infection if there is inoculum (spores) in the area.
4= The latent period following infection is completed, you will see the lesions of the new infections in the field.
These models reflect only weather induced sporulation and infection conditions, not whether inoculum is actually present in the area. Scout regularly to determine if there is inoculum in the area. As with all weather driven pest models, use with caution and be sure to verify the validity of weather data inputs for all sites. Plants are the most vulnerable to late blight after canopy
closure. Site specific irrigation events are not reflected in this weather data and may result in different risk levels.
Carla Thomas, Plant Pathologist with UC Davis provided this information.
Stripe rust possible
Small Grains All Locations
Stripe rust
Posted on: June 11, 2010 by Juliet Windes
While a small amount of stripe rust in wheat was confirmed by Brad Brown in southwest Idaho, it has not been confirmed in southeast Idaho and Magic Valley YET. However, flecking symptoms similar to early infection were seen in Aberdeen in Moreland hard red winter wheat. Due to extremely conducive weather conditions and widespread infection in Washington state, it is highly recommended that consultants and growers scout for stripe rust in all wheat. The wet and cool weather has prevented the resistance in varieties with High Temperature Adult Plant resistance from being activated, so varieties such as Alturas may be showing susceptible reactions. Consider spraying (especially susceptible varieties) in advance of infection. Please report stripe rust infections to Juliet Windes (208-529-8376) and / or Brad Brown (208-722-6701 ext 216). Additional information and pictures can be found at http://www.ag.uidaho.edu/scseidaho
Colorado Potato Beetle
All Crops Treasure Valley - Idaho
Colorado Potato Beetle
Posted on: June 10, 2010 by Jerry Neufeld
Dr. Mike Thornton, from the UI Parma Research and Extension Center, is reporting that overwintering Colorado Potato Beetle adults are beginning to emerge in southwest Idaho. This overwintering adult stage does not do any damage; however, females are beginning to lay eggs in potato fields. We could see the damaging larvae appear in about 7 to 10 days depending on temperatures. This is the time for growers to be scouting for CPB, especially if they are using "soft" foliar insecticides that target control of early instar larvae.
» http://uspest.org/pnw/insects
» CPB Eggs
Colorado Potato Beetle
All Crops Treasure Valley - Idaho
Colorado Potato Beetle
Posted on: June 10, 2010 by Jerry Neufeld
Dr. Mike Thornton, from the UI Parma Research and Extension Center, is reporting that overwintering Colorado Potato Beetle adults are beginning to emerge in southwest Idaho. This overwintering adult stage does not do any damage; however, females are beginning to lay eggs in potato fields. We could see the damaging larvae appear in about 7 to 10 days depending on temperatures. This is the time for growers to be scouting for CPB, especially if they are using "soft" foliar insecticides that target control of early instar larvae.
» http://uspest.org/pnw/insects
» CPB Eggs
Sugarbeet Leafminer
Sugarbeets Magic Valley
Leafminer
Posted on: June 10, 2010 by Jerry Neufeld
Heavy leafminer activity has been observed in several sugar beet fields across the Magic Valley. Maggots feed between the upper and lower leaf surfaces, leaving irregular transparent windows, blotches, and winding tunnels. Eggs are tiny, white, and cigar shaped and are laid on the underside of leaves and cotyledons; they may be laid singly or in groups of two or more. Eggs may be readily observed without magnification. Under very warm conditions, eggs may hatch within four days, but will take longer to hatch under the cooler conditions that we have experienced this spring. There are no formal economic thresholds for insecticide treatment decisions for leafminers, but treatment should be considered if fields are under heavy pressure. To scout a field, sample ten plants in each of several representative areas across a field. Record the average number of eggs and mines per plant observed in each area. Foliar insecticides should be considered within a few days after the first appearance of mines or before most eggs have hatched. Alternatively, systemic granular insecticide should still be effective if applied (and activated) shortly after most larvae have tunneled into leaves. Insecticide seed treatment should also provide control against early-season leafminer attack, which is expected to be more damaging than later-season attack. For current information on registered insecticides, consult the Pacific Northwest Insect Management Handbook (http://uspest.org/pnw/insects).
This information was provided by Dr. Erik Wenninger, UI Extension Entomology Specialist.
» http://uspest.org/pnw/insects
Late Blight Forecast
Potato All Locations
Late Blight
Posted on: June 9, 2010 by Jeff Miller
A forecast for predicting the occurrence of late blight was developed at the University of Idaho in 2004 by Donna Henderson and Jeff Miller. Many different weather variables were analyzed for data collected from 1995 to 2004 in an attempt to relate outbreaks of late blight with weather. The most efficient prediction of late blight was related to the number of late blight favorable periods and the amount of rain in April and May. A favorable period was any hour the air temperature was between 50 and 80 F and the relative humidity was above 80%. While the model was not perfect, it was accurate about 80% of the time in predicting the occurrence of late blight.
Forecasts in 2010 were generated using data from Parma, Twin Falls, Rupert, Aberdeen, Fort Hall, and Rexburg. Based on the forecast, late blight is expected in Twin Falls, Rupert, Aberdeen, and Fort Hall. Any actual outbreak of late blight will be influenced by fungicide spray programs, presence of potential inoculum sources, and weather later in the season.
Our current recommendation is to plan on spraying at row closure and then continue on a 10-14 day schedule. This recommendation may be modified depending on subsequent weather patterns.
A useful discussion of fungicides effective against late blight can be found at following link: http://www.millerresearch.com/reports/Overview_of_Fungicides_for_Late_Blight.pdf
The evidence indicates that the late blight outbreak in southern Idaho in 2009 came from diseased tomatoes. We also have evidence that this may have happened in western Idaho in 2005. In 2009, a severe outbreak of late blight in the Northeast U.S. was linked to transplanted diseased tomatoes. If you are buying tomato transplants from a garden center in your area, keep an eye out for sick-looking plants. If you find any suspicious lesions, please contact us or an extension specialist from the University of Idaho for confirmation of late blight. Dr. Phillip Wharton of the University of Idaho has authored a publication on the impact of tomatoes with respect to potato late blight and it is included on a previous post. For more information on late blight in Idaho you can call the University of Idaho late blight hotline (1-800-791-7195). Or for instant updates on the status of late blight and other diseases in the state you can sign up for SMS text message notifications by texting “follow potatodiseases” to 40404.
Late blight was only confirmed in one area in southern Idaho last year. There are no cull piles or any apparent overwintering sources for the pathogen in the 2009 affected area. Potato seed can also be a source.
» http://www.millerresearch.com/reports/Overview_of_Fungicides_for_Late_Blight.pdf
Late Blight Information
Announcements All Locations
Late Blight
Posted on: June 9, 2010 by Jerry Neufeld
Click on the pdf below for additional information from UI Plant Pathologist Dr. Phillip Wharton about Early and Late Blight in potatoes.
Late Blight Leaflet
Announcements All Locations
Late Blight
Posted on: June 9, 2010 by Jerry Neufeld
Tomato and Potato Late Blight Alert Leaflet
In 2009, many gardeners and commercial farmers in the Northeast saw their entire crop of lovingly cared for tomatoes overcome with late blight and rot on the vine, while the plants withered up and died. Late blight is devastating on both tomato and potato plants and once the disease has taken hold of the plant there is very little that can be done to halt its progress. Last year the disease is thought to have started in tomato transplants and then spread from diseased tomato plants to healthy tomato and potato plants in surrounding gardens and commercial fields. Late blight can infect and kill plants within 10 days and the spores of pathogen can be carried in the air. The disease outbreaks that occurred in the Northeast last year were mainly due to a new strain of the late blight pathogen called US22. There was also an outbreak of late blight reported on potatoes in southeastern Idaho last summer. Fortunately, it was limited to only a couple of fields. However, what is worrying is that it was identified as being caused by the new US22 strain of late blight, suggesting that it also came from infected tomato plants. There were no confirmed reports last year in Idaho of late blight on tomatoes, but the presence of the US22 isolate suggest that late blight was probably more widespread in southeastern Idaho than reported. Idaho potato growers were extremely lucky last year. In the Northeast, the US22 isolate spread quickly from tomatoes to potatoes and caused widespread losses in commercial potato crops. This year there have already been reports of late blight found on tomatoes bought in a Walmart store in Kentucky, and those plants were identified as being produced in Michigan. With all the unseasonably wet weather we have been having in Idaho in the past few weeks it is important that people remain vigilant for signs of late blight in tomatoes and potatoes. The attached leaflet (click on the pdf below) is designed to help homeowners and growers identify diseased plants and informs them of what steps they can take if they think they have late blight on their plants.
For more information on late blight in Idaho you can call the University of Idaho late blight hotline (1-800-791-7195). Or for instant updates on the status of late blight and other diseases in Idaho you can follow us on Twitter at “http://twitter.com/potatodiseases” or sign up for SMS text message notifications by texting “follow potatodiseases” to 40404.
