- Cucurbit downy mildew has been reported on cucumber in southern New Jersey. This is the first report in the state this growing season. For a review of CDM control please click here. To track the progress of CDM on your phone or PC please visit the CDM forecasting website.
- Cucurbit powdery mildew season is here. For a review of CPM control strategies please click here.
- No reports of Late blight in region. To track the progress of Late blight in the US please click here.
- Aerial stem rot has been reported on potato in southern New Jersey. The pathogen is an opportunistic bacterium in the field which infects vines that have been damaged by wind and heavy rains.
- There have been a few reports of Southern blight (Sclerotinia rolfsii) on tomato and pepper. Southern blight is much more common in vegetable areas south of the state where summer temperatures remain hotter (above 90°F) for longer periods of time. Like white mold, caused by Sclerotinia sclerotiorum, it can survive in the soil for many years. Symptoms of Southern blight include infection at the base of the stem at the soil-line. The resulting infection will girdle the plant causing wilt and death. The fungus will produce white, cottony mycelium and very small, spherical sclerotia which are often have a white to tannish, brown color as they mature. For more information on Southern blight from NCSU please click here.
- Collar rot caused by Alternaria has been reported on processing tomato in New Jersey. It is the same pathogen that causes Early blight in tomato. Tomato growers who have not switched to more specific fungicides for Early blight and anthracnose fruit rot control should consider doing so. For more information from NCSU please click here.
- Bacterial wilt has been reported in tomato in New Jersey.
- Rhizoctonia root and crown rot has been reported on sugar beet in southern New Jersey. For more information from the University of Idaho please click here.
- Bacterial leaf spot has been reported in pepper. For more information on BLS and copper resistance please click here.
- Pepper anthracnose is a serious problem in all bell and non-bell peppers, especially in fields with a history of the disease. For more information on controlling pepper anthracnose please click here.
- Phytophthora blight has been reported in pepper and cucurbit crops. For more information please click here.
- Basil downy mildew (BDM) has been reported in southern New Jersey on BDM susceptible sweet basil. All growers are encouraged to initiate preventative fungicide programs on DMR and non-DMR basil. For control options and to follow the progress of BDM in the US on your phone or PC please click here.
- Downy mildew has been reported in kale seedlings in a hydroponic greenhouse in PA. As a note, kale and related crops should be scouted on a regular basis. For more information on downy mildew in brassica crops from UMASS-Amherst please click here.
- Bacterial canker has been reported in fresh-market tomato. For a review of bacterial canker in tomato please see report by Dr. Sally Miller at The Ohio State University by clicking here.
- Diplodia leaf streak, a fungal disease, was identified in sweet corn this past week. Symptoms include the development of numerous pycnidia which produce conidia within the lesions on infected corn leaves. For nice reviews, please see report by Dr. Kiersten Wise and colleagues from the University of Kentucky and report by Dr. Steve Johnson at the University of Maine.
- White mold, caused by Stromatina cepivorum, has been reported in garlic. For more information, please see report by Crystal Stewart and Frank Hay from Cornell University.
- Angular leaf spot has been reported in summer squash. Look for angular lesions delimited by leaf veins and ‘shotholes’ in infected leaves that develop after periods of hot, dry weather.
- Bacterial leaf spot has been reported in sweet basil. BLS of sweet basil is a relatively new disease of basil in the US. The bacterium has a large host range and can survive and overwinter in the soil on infested plant debris. Disease development is favored by hot, humid, rainy weather. Periods of hot, dry weather will help mitigate disease development.
- With the on and off again heavy rains we have been getting, along with warmer weather, all growers should consider applying at-transplanting fungicides for root rot control. Please click here to see these articles.
- For a quick review on managing fungicide resistance development using tank mixes and fungicide rotations, and information on FRAC group 4, FRAC group 7, and FRAC group 3 and FRAC group 11 fungicides please click on hyperlinks.
- For more information on the control of the diseases mentioned above please see The 2020/2021 Commercial Vegetable Production Recommendations Guide which is available for free online! With many county offices running reduced hours or being closed this is the easiest way to obtain the newest recommendations.
Search Results for: basil downy mildew
July 8, 2020 Andy Wyenandt
Vegetable Disease Update – 7/8/20
June 26, 2020 Andy Wyenandt
Vegetable Disease Update – 6/26/20
- Cucurbit powdery mildew season is here. For a review of CPM control strategies please click here.
- Cucurbit downy mildew has been reported on cucumber in western MI and as far north as North Carolina on cucumber. For a review of CDM control please click here. To track the progress of CDM on your phone or PC please visit the CDM forecasting website.
- No reports of Late blight in region. To track the progress of Late blight in the US please click here.
- Basil downy mildew (BDM) has been reported in southern New Jersey on BDM susceptible sweet basil. All growers are encouraged to initiate preventative fungicide programs on DMR and non-DMR basil. For control options and to follow the progress of BDM in the US on your phone or PC please click here.
- Bacterial canker has been reported in fresh-market tomato. For a review of bacterial canker in tomato please see report by Dr. Sally Miller at The Ohio State University by clicking here.
- Diplodia leaf streak, a fungal disease, was identified in sweet corn this past week. Symptoms include the development of numerous pycnidia which produce conidia within the lesions on infected corn leaves. For nice reviews, please see report by Dr. Kiersten Wise and colleagues from the University of Kentucky and report by Dr. Steve Johnson at the University of Maine.
- White mold, caused by Stromatina cepivorum, has been reported in garlic. For more information, please see report by Crystal Stewart and Frank Hay from Cornell University.
- Angular leaf spot has been reported in summer squash. Look for angular lesions delimited by leaf veins and ‘shotholes’ in infected leaves that develop after periods of hot, dry weather.
- Phytophthora blight has been reported in pepper and cucurbit crops.
- Rhizoctonia and Pythium root rot have been reported in pepper. For a review of identifying and controlling root rots please click here.
- Septoria leaf spot and bacterial blight have been reported in parsley.
- Timber rot, or white mold, has been reported in tomato.
- White rust and Cercospora have been reported in spinach.
- Bacterial leaf spot has been reported in sweet basil. BLS of sweet basil is a relatively new disease of basil in the US. The bacterium has a large host range and can survive and overwinter in the soil on infested plant debris. Disease development is favored by hot, humid, rainy weather. Periods of hot, dry weather will help mitigate disease development.
- Sand blasting has been reported on a number of leafy green and other crops these past few weeks. Injury from sand blasting predisposes plants to bacterial infections. Remember, all bacteria need a wound or a natural opening, such as a stomata, to gain entry into the plant. Fields with extensive injury need to be scouted regularly, and most likely will need to be sprayed regularly with a copper fungicide or disinfectant-type product to help mitigate infection and spread.
- For a review on how to avoid sunscald injury on transplanted crops please click here.
- With the on and off again heavy rains we have been getting, along with warmer weather, all growers should consider applying at-transplanting fungicides for root rot control. Please click here to see these articles.
- The 2020/2021 Commercial Vegetable Production Recommendations Guide is available for free online! With many county offices running reduced hours or being closed this is the easiest way to obtain the newest recommendations.
- For a quick review on managing fungicide resistance development using tank mixes and fungicide rotations, and information on FRAC group 4, FRAC group 7, and FRAC group 3 and FRAC group 11 fungicides please click on hyperlinks.
June 12, 2020 Andy Wyenandt
Vegetable Disease Update – 6/12/20
- Cucurbit powdery mildew season is here. For a review of CPM control strategies please click here.
- Cucurbit downy mildew has been reported as far north as southern Georgia on cucumber and cantaloupe and in South Carolina on cucumber. For a review of CDM control please click here. To track the progress of CDM please visit the CDM forecasting website.
- No reports of Late blight in region. To track the progress of Late blight in the US please click here.
- Basil downy mildew has been reported central TN from basil started in the greenhouse and in the field in southern FL to date. None has been reported in the region. To follow the progress of BDM in the US please click here.
- Angular leaf spot has been reported in summer squash. Look for angular lesions delimited by leaf veins and ‘shotholes’ in infected leaves that develop after periods of hot, dry weather.
- Phytopthora blight has been reported in squash.
- Rhizoctonia and Pythium root rot have been reported in pepper. For a review of identifying and controlling root rots please click here.
- Septoria leaf spot and bacterial blight have been reported in parsley.
- Bacterial canker and speck have been reported in fresh-market tomato.
- Timber rot, or white mold, has been reported in tomato.
- White rust and Cercospora have been reported in spinach.
- Bacterial leaf spot has been reported in sweet basil. BLS of sweet basil is a relatively new disease of basil in the US. The bacterium has a large host range and can survive and overwinter in the soil on infested plant debris. Disease development is favored by hot, humid, rainy weather. Periods of hot, dry weather will help mitigate disease development.
- Sand blasting has been reported on a number of leafy green and other crops these past few weeks. Injury from sand blasting predisposes plants to bacterial infections. Remember, all bacteria need a wound or a natural opening, such as a stomata, to gain entry into the plant. Fields with extensive injury need to be scouted regularly, and most likely will need to be sprayed regularly with a copper fungicide or disinfectant-type product to help mitigate infection and spread.
- For a review on how to avoid sunscald injury on transplanted crops please click here.
- With the on and off again heavy rains we have been getting, along with warmer weather, all growers should consider applying at-transplanting fungicides for root rot control. Please click here to see these articles.
- The 2020/2021 Commercial Vegetable Production Recommendations Guide is available for free online! With many county offices running reduced hours or being closed this is the easiest way to obtain the newest recommendations.
- For a quick review on managing fungicide resistance development using tank mixes and fungicide rotations, and information on FRAC group 4, FRAC group 7, and FRAC group 3 and FRAC group 11 fungicides please click on hyperlinks.
April 23, 2020 Andy Wyenandt
Understanding phenylamide (FRAC group 4) fungicides
The phenylamide fungicides (FRAC group 4) are a highly active class of fungicides that target oomycete pathogens such Phytophthora and Pythium spp. FRAC group 4 fungicides are also highly effective against downy mildew pathogens such as Pseudoperonospora cubensis (cucurbit downy mildew), Phytophthora infestans (Late blight), and basil downy mildew (Peronospora belbahrii) and many other important pathogens in vegetable production. Like other fungicide classes, FRAC group 4 fungicides have a high-risk for fungicide resistance development. The phenylamides (PA) inhibit ribosomal RNA (rRNA) biosynthesis in oomycete pathogens which inhibits several life stages in oomycetes including hyphal growth, haustoria and sporangia formation. The exact mechanism for resistance is not completely understood although research has shown that PA resistance is control by a single incompletely dominant gene although multiple mutations or mechanisms may be involved in PA resistance development. Pathogens such as cucurbit downy mildew, late blight, and basil downy mildew can be disseminated over vast geographic distances in any given year, thus this migration can be responsible for the introduction of new pathogen genotypes (including PA resistant) to new locations along with local selection pressure due to PA fungicide use resulting in changes in the pathogen population. Additionally, pathogens such as P. infestans and P. capsici (Phytophthora blight) are highly sexually active at the local level, because of the potential presence of two mating types (A1 and A2), you have a “recipe” that is always evolving. Resistance development to PA fungicides is often described as sensitive, intermediate, or resistant based on EC50 (Effective Concentration) values of the different fungicides needed to kill 50% of the pathogen in laboratory assays. This type of collected information is useful in determining what proportion of a given local, or wide geographic pathogen population, may be PA resistant. Recommended resistance management guidelines developed FRAC have not changed since 1997and are intended as general recommendations that must be adapted to respective pathosystems, fungicide use and patterns, and resistance levels.
The following are general recommendations for PA fungicide use as stated by FRAC.
- PA fungicide should be used on a preventative basis; and not used as a curative or on a eradicative basis
- As foliar applications, PA fungicide should always be tank mix with a unrelated fungicide from a different FRAC group
- The total number of PA applications per season should be limited to 2 to 4 depending on label requirements
- PA sprays are recommended for use earlier in the production season during active vegetative growth
- PA should not be used as soil treatments against foliar disease development
Resistance development in P. capsici to mefenoxam has been known for many years in southern New Jersey. This is most likely to the widescale and overuse of mefenoxam in its early days because of the lack of an alternative chemistry, as well as a result of crop rotations where susceptible crops were planted in the same field for many years. In the past decade, there have been several new fungicides from different FRAC groups labeled for oomycete control. These include: Orondis Gold (oxathiapiprolin + mefenoxam, FRAC groups 49 + 4), Previcur Flex (propamocarb, 28), Ranman (cyazofamid, 21), Presidio (fluopicolide, 43), and Phosphites (33) for field use. Ranman, Previcur Flex, and phosphites have greenhouse use labels for Pythium control. Ranman and Previcur Flex can be applied in the transplant water. Orondis Gold, mefenoxam, metalaxyl, and the phosphites are the most systemic of the group and should readily be taken up the by plant via application through the drip. Presidio has locally systemic and translaminar activity and offers protection of the root system via drip. Ranman has protectant-like activity and thus will offer root system protection. Growers with a known history of mefenoxam-insensitivity on their farm should use Presidio, Previcur Flex, or Ranman plus a Phosphite fungicide in rotation in their drip application programs. Importantly, if mefenoxam has not been used in particular fields on any crop for a number of years (more than 5+) the fungus may revert back to being mefenoxam-sensitive and control with these products may return.
For more information please see specific fungicide labels, crops sections, and greenhouse uses in Table E-11 in the 2020/2021 Mid-Atlantic Commercial Vegetable Production Recommendations Guide.
Reference:
Hermann, D.C., McKenzie, D., Cohen, Y., and Gisi, U. 2019. Phenylamides: Market trends for resistance evolution for important oomycete pathogens more than 35 years after product introduction (FRAC code 4). Chapter 6 in: Fungicide Resistance in North America, 2nd Ed. Katherine L. Stevenson, Margaret T. McGrath, and Christian A. Wyenandt (eds). The American Phytopathological Society, St. Paul, MN.
Additional resources:
Damping-off: Identifying and Controlling Early-Season Damping-off Pathogens
Understanding Damping-off Pathogens During Seeding and Transplanting
March 21, 2020 Andy Wyenandt
Vegetable Disease Update – 3/21/20
- Late blight has been reported on tomato in central Florida. This is the first report of Late blight in the US this growing season. To follow Late blight outbreaks in the US please sign up for alerts at the USAblight website by clicking here.
- There have been no reports of cucurbit downy mildew in the US to date. To track, monitor, and receive reports on CDM development in the US please click here. For the current understanding of what is happening with the CDM population in the US and current control recommendations please click here.
- There have been no reports of basil downy mildew in the US to date. To track and receive reports on its whereabouts in the US on the new website please click here. For current BDM control options in the greenhouse and field please click on hyperlinks.
- For the updated list of fungicides for use in the control of important diseases in the greenhouse please click here.
- Commercial growers should consider adding at-transplanting or -seeding controls for Phytophthora and Pythium root rots as we head into the spring especially if soils remain wet. For more information please click here. Organic growers can find more information on controlling important root rot pathogens in early season transplant production here!
- Transplant producers need to remember to vent their structures to reduce relative humidity buildup going into the evenings to help reduce leaf wetness during the overnight.
- With strawberry season just around the corner, please click here for information on controlling important fruit rot pathogens.
- The 2020/2021 Commercial Vegetable Production Recommendations Guide is available for free online! With many county offices running reduced hours or being closed this is the easiest way to obtain the newest recommendations.
- For a quick review on managing fungicide resistance development using tank mixes and fungicide rotations, and in FRAC group 3 and FRAC group 11 fungicides please click on hyperlinks.
- To keep up with Rutgers Extension services please click here. We are here to help!
September 18, 2019 Andy Wyenandt
Vegetable Disease Update – 9/17/19
- All cucurbit growers are encouraged to scout their fields on a regular basis and continue to use a downy mildew specific fungicide program. Fungicides that are specific to CDM should be included in weekly fungicide maintenance programs for cucurbit powdery mildew control. To track the progress of CDM in the US please visit the CDMpipe forecasting website here.
- Basil downy mildew has been reported in New Jersey on BDM susceptible and resistant sweet basil lines. All basil growers should continue to scout and follow a BDM specific fungicide program even when using DMR varieties. To track the progress of BDM in the US please visit here.
- Downy mildew has been reported in turnip greens. Growers who have fall leafy greens and cole crops should scout daily and be proactive and initiate a regular downy mildew specific fungicide program. Although its been relatively dry, spotty showers, cooler nights, and longer periods of dew (leaf wetness) have made conditions ideal for downy mildew development across a number of susceptible crops.
- Pepper anthracnose continues to be reported.
- The 2019 Fungicide Resistance Management Guide for Vegetable Crops in the mid-Atlantic Region is now available for FREE online.
- For more information on controlling these and other important diseases please see the 2019 Mid-Atlantic Commercial Vegetable Production Guide. The guide is available for FREE online by following the links on the Plant and Pest Advisory website. Hardcopies of the 2019 guide can be purchased through your local county Extension office.
