Late blight (US23) was confirmed on tomato in a small, retail greenhouse operation in western Maryland (Garrett Co.) today. This is the first report of Late blight on tomato or potato this growing season. US23 has been the most prevalent genotype found in the region the last few years and can infect tomato or potato. While the current report not an immediate threat to NJ, all tomato and potato growers should scout fields on a regular basis as long as wet weather pattern continues. At this time, general protectant fungicide programs that have been initiated will help protect against Late blight. Importantly, in order for Late blight to appear this early in our region it must either have survived on an infested potato tuber left in the field or in a cull pile. For more information on the control of late blight please see the 2016 Mid-Atlantic Commercial Production Recommendations Guide.
Organic Farm Advisory
The Plant & Pest Advisory serves NJ growers by reporting on important pests and recommending responses that are grounded in reproducible trials.
Articles in this section contain information helpful to the NJ commercial organic grower.
Sharing organic practice trial results between land-grant universities is a cost effective way to create a common knowledge base built on the strengths of individual programs. In the sidebar, find institutions with programs in organic agriculture which augment knowledge developed at the Rutgers New Jersey Ag Experiment Station.
Rutgers Cooperative Extension Field Guides: These concise guides help with decision making from pre-planting to harvest. For each crop listed, learn what pests to proactively look for as the season progresses, how to look for them, and when to take action.
Wet Weather Ripe for Strawberry Fruit Rots
Anthracnose Fruit Rot of Strawberry
Fruit rots in strawberry can cause significant losses if not recognized early and controlled. The use of good cultural practices such as: keeping fields weed-free and promoting good drainage; long crop rotations, and preventative fungicide applications are critical.
Pathogens such as anthracnose, gray mold (Botrytis), and leather rot can become systemic problems in strawberry plantings once established. All three fungal diseases are soil-borne and once in fields can be difficult to manage over the lifetime of the planting.
For growers new to strawberry production and/or those just looking for valuable resource(s), please visit Cornell University’s strawberry production website here. An Organic Strawberry Production Guide is also available.
The use of mulch (matted rows) to prevent/reduce soil splashing and keeping fruit from coming into direct contact with the soil surface can be beneficial in organic production systems where conventional fungicides cannot be used. Use of long crop rotations and staying away from areas of the farm with known instances of any of these pathogens is also important. Remember that same species of Colletotrichum that causes fruit rot in pepper and other crops can also infect strawberry.
Damping-off: Identifying and Controlling Early-season Pathogens
It is extremely important to know which pathogen is causing damping-off problems and which fungicide to properly apply. The key to controlling damping-off is being proactive instead of reactive. Always refer to the fungicide label for crop use, pathogens controlled, and application rates.
Damping-off is caused by a number of important vegetable pathogens and is very common during the spring. Damping-off can kill seedlings before they break the soil line (pre-emergent damping-off) or kill seedlings soon after they emerge (post-emergent damping-off). Common pathogens that cause damping-off include Pythium, Phytophthora, Rhizoctonia and Fusarium spp.
Control of damping-off depends on a number of factors. First, is recognizing the conditions which may be leading to the problem (i.e., weather/greenhouse growing conditions) and second, identifying the pathogen causing the problem.
Conditions Favoring Damping-off
Although all four pathogens are associated with damping-off, the conditions which favor their development are very different. In general, Phytophthora and Pythium are more likely to cause damping-off in cool, wet or overwatered soils that aren’t allowed to dry out due to cloudy weather or cooler temperatures. Conversely, Rhizoctonia and Fusarium are more likely to cause damping-off under warmer, drier conditions especially if plug trays are kept on the dry side to help reduce transplant growth. [Read more…]
Controlling Purple Spot in Asparagus
Purple spot, caused the soil-borne fungus, Stemphylium vesicarium, can cause problems during cool, wet spring weather. Symptoms, just like its name, include numerous, sunken oval-shaped spots on spears during the harvest season and more importantly on ferns and stalks during the summer months as long as conditions are ideal for its development. Often, purple spot will disappear as quickly as in appears on spears during the spring production season depending on the weather conditions.
Purple spot in asparagus (Photo by Mary Hausbeck, Michigan State University)
Heavy purple spot infection during the summer will lead to premature defoliation which will decrease carbohydrate reserves for the next production season. Control of purple spot can be difficult because of management issues (i.e., the need for fall mowing and/or removing, burying, or burning of old fern material in the field) and because fungicides can’t be applied during the harvest season. Growers who had pre-mature defoliation issues last year may expect problems this spring. Controlling purple spot begins with preventative fungicide applications during summer and fall by reducing infections to ferns and stalks. Weekly scouting and timely fungicide applications once fern stalks are full size should be done. Apply and rotate azoxystrobin at 6.2 to 15.5 fl oz 2.08F/A or chlorothalonil at 2.0 to 4.0 pt/A.
Organic asparagus growers, as well as conventional growers, need to take appropriate preventative measures to help reduce inoculum loads by completely removing, or by chopping and burying old fern material at the end of each growing season. Remember, any plant material that is infected and left to overwinter in the field may act as a source of inoculum the next growing season. For more information on organic asparagus production please see ATTRA’s Organic Asparagus Production.
Organic Production: Suppressing Soil-borne Pathogens
Pathogens such as Fusarium, Pythium, Phytophthora, Thielaviopsis and Rhizoctonia that cause pre- and post-emergent damping-off can cause serious problems in organic (and conventional) transplant production.
The key to controlling and/or suppressing damping-off pathogens with biological controls is keeping the biological populations high and continually present on root surfaces of the host, and by following good cultural practices. [Read more…]
Organic Options:
Cabbage Maggot & Pest Control Efficacy
A round table meeting of the Organic Farm Advisory group took place this week with discussion on the successes and problems of last season. The need for relative efficacy continues and brings up the chance to revisit a timely article that was the result of last year’s discussion.
What are my organic treatment options and how well do they work? As an organic grower, I sometimes accept less control, and more costly treatment than conventional farmers, but the information on efficacy is unclear. If Rutgers isn’t doing efficacy trials, can you sift through the literature to tell me what others have found that definitely works?
Control of cabbage root maggot (CRM) is a timely example that illustrates the ‘struggle for relative efficacy’ in making organic recommendations when compared with conventional options. Forsythia in bloom–any day now–occurs at about the same time that farmers can expect CRM to damage their transplanted cole crops. Even light CRM infestations can kill small seedlings and transplants, delay crop development, and render root crops unsaleable. Higher populations can kill older plants or reduce yield.
- monitoring and control of CRM in cole crops.
- the use of online weather station degree-day (DD) data to predict CRM activity and timing of treatment – instead of relying on phenology.
- how the lack of field research capacity makes recommendations difficult for organic pest controls in comparison with conventional controls.
- why talent scouting (sifting through the literature) is an adjunct to research capacity, not a replacement.
