Vegetable Crops Edition

Seasonal updates and alerts on insects, diseases, and weeds impacting vegetable crops. New Jersey Commercial Vegetable Production Recommendations updates between annual publication issues are included.
 
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NJ Commercial Vegetable Production Recommendations

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July 1, 2022

Identifying white mold in tomato production

White mold, or timber rot, is caused by the soil-borne fungal pathogen, Sclerotinia sclerotiorum.

High tunnel tomato plant with main stem infected by white mold.

The photo on right shows a high tunnel tomato plant with main stem infected by white mold. Over time the entire plant will slowly collapse looking similar to a wilt or root rot pathogen as the water supply is cut off to the plant.

White mold is common and once introduced into a field or high tunnel it can very difficult to control. The pathogen produces black sclerotia on the surface and inside infected stems. Sclerotia, if they make their way back into the soil, can survive for years causing significant problems.

Infected stems will turn a light brown color and dry up becoming brittle. If the main stem is infected the entire plant will collapse looking like a wilt or root rot issue.

Under hot, humid conditions white fungal growth will develop on the surface of the stems and in some cases sclerotia will develop on the outside of the stem. Breaking open the stem will reveal numerous black sclerotia.

All infected plants and or plant material need to be removed immediately and disposed of properly. Preventative protectant fungicide programs beginning at flowering will help control white mold. Cool, wet weather and poor air circulation favors disease development.

There are a number of control options for conventional and organic growers listed in Table E-11 in the 2022/2023 mid-Atlantic Commercial Vegetable Production Recommendations Guide.

Tomato stem infected by white hold. Note the fungal growth on the surface of the stem.

Tomato stem infected by white hold. Note the fungal growth on the surface of the stem.

White mold of tomato. Note the black sclerotia developing inside the brittle stems.

White mold of tomato. Note the black sclerotia developing inside the brittle stems.

Filed Under: Vegetable Crops Tagged With: , , ,
June 30, 2022

Recognizing Angular Leaf Spot in Cucurbits

Angular leaf spot is common in New Jersey and the region. It often shows up during cooler, wet weather and isolated rain.

Symptoms of angular leaf spot in cucurbit.

Symptoms of angular leaf spot in cucurbit.

Angular leaf spot of pumpkin. Note the 'shot holes' in the leaf.

Angular leaf spot of pumpkin. Note leaf ‘shot holes’.

 

 

 

 

 

 

 

 

Angular leaf spot will first appear as, small water-soaked lesions which will expand until they reach a larger leaf vein resulting in the angular looking symptoms on leaves. Under heavy disease pressure, the bacteria will infect fruit causing small, water-soaked circular spots. In many cases once weather conditions become dry again, infected tissue in leaves will die and fall out leaving the characteristic ‘shot hole’ symptoms. Control of angular leaf spot begins with the application of labeled rates of fixed copper plus mancozeb to help suppress the spread of the disease until hot, dry weather returns.

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June 29, 2022

Vegetable IPM Update 6/29/22

Sweet Corn

Low numbers of European corn borer (ECB) moths remain a sporadic, low component of blacklight trap catches.  Feeding in whorl and pre-tassel stage is now less common, as control has been applied to infested plantings and later blocks (now in whorl stage) have avoided most of the egg laying period.  Slightly higher adult activity is in scattered pockets around the state (see map below at right).  ECB injury over the threshold of 12% of plants infested, while still around, has generally been declining over this past week.   We expect feeding wind down over the next week or so as we move into the period between generations.European corn borer

Weekly distribution of European corn borerLook for the characteristic “shot-hole” type of feeding (photo  below at right) and consider treating when infested plants exceed 12% in a 50 plant sample.  As plantings proceed to the pre-tassel stage, ECB larvae may be found in emerging tassels (see photo at left).  It is a good idea to treat individual plantings as they move into the full tassel/first silk stage one time.  This eliminates any ECB larvae that have emerged with the tassels as they begin to move down the stalk to re-enter near developing ears.

 

Useful insecticides for this particular application include synthetic European corn borerpyrethroids (IRAC Grp 3), spinosyns (including OMRI approved Entrust) IRAC Grp 5), and diamides such as Coragen or Vantacor (IRAC Grp 28) or materials such as Besiege which include the active ingredient in Coragen.  Synthetic pyrethroids alone should NOT be used for corn earworm (CEW) protection on silking corn.  Control with these materials is very inconsistent.

The highest nightly trap catches of ECB for the week ending 6/29/22 are as follows:

Bellemeade   1 Farmingdale   1 Morristown   1
Blairstown   1 Georgetown   1 New Egypt   1
Centerton   1 Lawrenceville   1 Princeton   1
Crosswicks   1 Matawan   1 Sergeantsville   1

[Read more…]

Filed Under: Organic Production, Vegetable Crops
June 29, 2022

Preparing for Anthracnose and Alternaria Leaf Blights in Cucurbit Crops

Anthracnose and Alternaria leaf blight can become problematic in cucurbit crops during long periods of wet, humid weather. Both can cause significant losses if not controlled properly. With the production season in full swing, now is a good time to review a few of these important diseases. [Read more…]

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June 28, 2022

Don’t Rely on Disinfestants for Disease Control

The hot, then windy, then wet weather these past few weeks have brought with it prolonged windy days and rain to many areas. In general, this type of weather is ideal for the development and spread of many vegetable diseases.

By now most growers are on weekly protectant fungicide programs to help prevent disease development. It’s important to remember at this point in the season when disease pressure is high that growers stick with their standard fungicide programs.

Growers should not replace fungicides with disinfestant-type products in their weekly fungicide programs.

Remember, disinfestants only kill what they come into direct and immediate contact with and do not offer any residual activity like fungicides do. Disinfestants should be used in conjunction with weekly fungicide programs and be applied based on specific weather events such as following rainfall or overhead irrigation or after certain cultural practices such as tying or pruning where plant injury or wounding may occur.

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June 28, 2022

Preparing for important fungal diseases in Asparagus during the summer.

Asparagus growers should consider scouting their fields during the summer months for  foliar disease development. Important pathogens that growers need to scout for on a regular basis include Purple spot, Cercospora, and Rust. [Read more…]

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