Avoiding Plectosporium blight in cucurbit fields.

Plectosporium blight, also known as Microdochium blight or White speck, caused significant problems in some pumpkin fields last summer in New Jersey. The soil-borne fungal pathogen, although somewhat uncommon, can unexpectedly show up in some years and cause significant losses if left uncontrolled. The fungus survives in the soil on decaying plant debris where it can remain saphrophytic by surviving off organic matter. Infection is characterized by the production of numerous light tan to “bleached” spindle shaped lesions that develop on vines and the undersides of infected leaves. Heavily infected vines and leaves can die leading to premature defoliation and subsequent sunscald on fruit. In cases of heavy disease pressure, spores that are produced on the bottom sides of leaves fall and infect the topsides of fruit laying beneath the canopy. Infection of stems leads to premature browning and drying reduce their longevity. Fruit infection, in most cases, remain mostly cosmetic in nature reducing fruit quality and may predispose fruit to other opportunistic fruit rots. Plectosporium blight often shows up during periods of prolonged wet weather where the soil remains wet for extended periods. “Hot spots” typically appear in fields before the pathogen is further spread by driving rains and wind.

From a production standpoint, stay away from fields with known history of the disease for as long as possible; provide adequate spacing between plants in- and between rows (i.e., avoid the overcrowding of plants); avoid over (preplant) fertilization that can lead to thick, dense canopies; avoid overhead irrigation (if possible); avoid planting in area of a field that remains heavily shaded where soils tend to dry too slow.

Controlling Plectosporium blight begins with regular scouting, recognizing symptoms, and identifying “hot spots” in the field. Protectant fungicides, such as chlorothalonil, as well as those used in weekly maintenance spray programs for cucurbit powdery mildew control will help control Plectosporium blight as long they applied on a weekly schedule with a high volume of water with thorough coverage. To help improve control on the undersides of leaves, a FRAC code 11 fungicide such as Quadris Top or Pristine, can be added to the tank mix. Remember, FRAC code 11 fungicides have translaminar activity and will move from the top surface of the leaf to the bottom. Growers who grow powdery mildew resistant varieties need to remember to scout their fields regularly even if cucurbit powdery mildew has not been detected on the farm or if regular maintenance sprays haven’t begun.

 

White speck lesions covering pumpkin

White speck lesions covering the surface of immature and mature pumpkin fruit. White speck will only cause cosmetic injury to fruit.

White speck on vine and stem of infected pumpkin plant

White speck on vine and stem of infected pumpkin plant. Note the numerous small, white diamond shaped lesions.

 

 

 

 

 

 

 

Plectosporium blight caused trouble in cucurbit fields in 2019

Plectosporium blight, also known as Microdochium blight or White speck, caused significant problems in some pumpkin fields last summer in New Jersey. The soil-borne fungal pathogen, although somewhat uncommon, can unexpectedly show up in some years and cause significant losses if left uncontrolled. The fungus survives in the soil on decaying plant debris where it can remain saphrophytic by surviving off organic matter. Infection is characterized by the production of numerous light tan to “bleached” spindle shaped lesions that develop on vines and the undersides of infected leaves. Heavily infected vines and leaves can die leading to premature defoliation and subsequent sunscald on fruit. In cases of heavy disease pressure, spores that are produced on the bottom sides of leaves fall and infect the topsides of fruit laying beneath the canopy. Infection of stems leads to premature browning and drying reduce their longevity. Fruit infection, in most cases, remain mostly cosmetic in nature reducing fruit quality and may predispose fruit to other opportunistic fruit rots. Plectosporium blight often shows up during periods of prolonged wet weather where the soil remains wet for extended periods. “Hot spots” typically appear in fields before the pathogen is further spread by driving rains and wind.

From a production standpoint, stay away from fields with known history of the disease for as long as possible; provide adequate spacing between plants in- and between rows (i.e., avoid the overcrowding of plants); avoid over (preplant) fertilization that can lead to thick, dense canopies; avoid overhead irrigation (if possible); avoid planting in area of a field that remains heavily shaded where soils tend to dry too slow.

Controlling Plectosporium blight begins with regular scouting, recognizing symptoms, and identifying “hot spots” in the field. Protectant fungicides, such as chlorothalonil, as well as those used in weekly maintenance spray programs for cucurbit powdery mildew control will help control Plectosporium blight as long they applied on a weekly schedule with a high volume of water with thorough coverage. To help improve control on the undersides of leaves, a FRAC code 11 fungicide such as Quadris Top or Pristine, can be added to the tank mix. Remember, FRAC code 11 fungicides have translaminar activity and will move from the top surface of the leaf to the bottom. Growers who grow powdery mildew resistant varieties need to remember to scout their fields regularly even if cucurbit powdery mildew has not been detected on the farm or if regular maintenance sprays haven’t begun.

 

White speck lesions

White speck lesions covering the surface of immature and mature pumpkin fruit. White speck will only cause cosmetic injury to fruit.

White speck on vine

White speck on vine and stem of infected pumpkin plant. Note the numerous small, white diamond shaped lesions.

 

 

 

 

 

 

 

Veg IPM Update: Week Ending 10/05/16

Sweet Corn

16cew1005aCorn earworm moth (CEW) activity has been fairly steady over the past week.  Patches of locally higher activity remain within a generally low population (see CEW map).  Catches are now rising and falling with night time temperatures.  It is advisable to incorporate materials into the spray program that have different modes of action from the pyrethroids.  This includes IRAC 28 materials like Coragen, Exirel and Besiege, as well as IRAC 5 (Radiant, Entrust (OMRI approved), and Blackhawk)).  Growers should be checking CEW activity frequently, and adjust spray schedules according to local activity.  On this map, green areas correspond to a 3-4 day silk spray schedule, while blue is 4-5 days.

The highest nightly CEW catches for the previous week are as follows:

Centerton   3 Denville   1 Milford   1
Green Creek   2 Eldora   1 New Egypt   1
Blairstown   1 Farmingdale   1 Sergeantsville   1
Califon   1 Jones Island   1 Tabernacle   1

 

 

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Veg IPM Update: Week Ending 9/28/16

Sweet Corn

European corn borer (ECB) moths are nearly non-existent now.  There are no particular areas of higher activity, and  no map will appear in this edition. It is unlikely that we will realize any further injury from this pest this season.

Nearly all remaining sweet corn plantings are now in the silk stage.  Fall armyworm (FAW) however, continues to be a threat to these sweet corn plantings.  We should expect this pest to be with us at some level for the remainder of the sweet corn growing season.   FAW do not respond well to pyrethroid insecticides.  The most useful products are those in the IRAC group 28 class (Coragen, Exirel) or the IRAC group 5 class (Radiant, Entrust), or combination products including these classes.  See the 2016 Commercial Vegetable Recommendations Guide for insecticides effective against FAW.

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Veg IPM Update: Week Ending 9/21/16

Sweet Corn

European corn borer (ECB) moth numbers have decreased this past week such that only a handful of moths were captured.  There are no particular areas of higher activity, and  no map will appear in this edition. It is unlikely that we will realize any further injury from this pest this season.

The highest nightly ECB catches for the previous week are as follows:

Cinnaminson   1 Milltown   1
Clinton   1 Pedricktown   1
Hillsborough   1 Sergeantsville   1

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Veg IPM Update: Week Ending 9/14/16

Sweet Corn

16ecb0914aEuropean corn borer (ECB) moth numbers increased slightly this past week.  At the present time, highest activity is in western areas from the Delaware Bay shore northward to Warren County (see ECB map). This partial third flight should not present much of a threat to host crops.  This is particularly true in light of the dominance this year of fall armyworm (FAW). FAW will probably remain the larger threat, and treatments for this pest will eliminate ECB in the process. See the 2016 Commercial Vegetable Recommendations Guide for insecticide choices.

 

 

The highest nightly ECB catches for the previous week are as follows:

Allentown   1 Lawrenceville   1
Crosswicks   1 Pennington   1
Downer   1 Phillipsburg   1
Georgetown   1  Sergeantsville   1

 

There has been little change in the fall armyworm (FAW) situation in the north and central areas.  Joe Ingerson-Mahar indicates that re-infestation rates in younger corn in the southern counties have declined somewhat.  Infestations continue throughout NJ, with damaging infestation rates in all parts of the state.  We should expect this pest to be with us for the remainder of the sweet corn growing season.  Treat when FAW alone or in combination with ECB damage exceeds 12% plants infested.  FAW do not respond well to pyrethroid insecticides.  The most useful products are those in the IRAC group 28 class (Coragen, Exirel) or the IRAC group 5 class (Radiant, Entrust), or combination products including these classes.  See the 2016 Commercial Vegetable Recommendations Guide for insecticides effective against FAW.

  [Read more…]