Andy Wyenandt

This is an archive of Dr. Wyenandt's posts on the Plant and Pest Advisory.

March 12, 2014

Greenhouse Sanitation Important for Disease Management

Proper greenhouse sanitation is important for healthy, disease-free vegetable transplant production.

Efforts need to be made to keep transplant production greenhouses free of unnecessary plant debris and weeds which may harbor insect pests and disease. Efforts need to be taken throughout the transplant production season to minimize potential problems.

  • All equipment, benches, flats, plug trays and floors should be properly cleaned and then disinfested prior to use.
  • Any weeds in or around the greenhouse structure should be removed prior to any production.
  • Any transplant brought into the greenhouse from an outside source needs to be certified ‘clean’, as well as, visually inspected for potential insects and diseases once it reaches your location.

Remember, disinfestants, such as Clorox, Green-Shield, or hydrogen dioxide products (Zerotol – for commercial greenhouses, garden centers and Oxidate – commercial greenhouse and field), kill only what they come into direct contact with so thorough coverage and/or soaking is necessary. The labels do not specify time intervals for specific uses, only to state that surfaces be ‘thoroughly wetted’. Therefore, labels need to be followed precisely for different use patterns (i.e., disinfesting flats vs. floors or benches) to ensure proper dilution ratios. Hydrogen dioxide products work best when diluted with water containing little or no organic matter and in water with a neutral pH.

Filed Under: Vegetable Crops
February 18, 2014 and

Commercial Vegetable Recommendations 2014 Available Online

The Rutgers Commercial Vegetable Production Recommendations for NJ, newly updated for 2014, is available for free download. Each section, crop, and topic is available separately.

Having printed copies in your pesticide building or in pickup truck is also desirable. Contact your County Extension Office  to purchase printed editions.

Filed Under: Commercial Ag Updates, Vegetable Crops
January 8, 2014

Mitigating Losses to Pepper Anthracnose

Pepper Anthracnose

Pepper Anthracnose

In recent years, pepper anthracnose caused by Colletotrichum spp. has become a significant problem on some farms in southern New Jersey.

Unlike in tomato, where symptoms are only present in mature (red) fruit, pepper anthracnose can infect pepper fruit at any growth stage. [Read more…]

Filed Under: Vegetable Crops Tagged With:
October 21, 2013

Late Blight Confirmed on Organic Tomato in South Jersey

Late blight was confirmed in an organic tomato field late last week south of Bridgeton, New Jersey. As a note, growers who are still picking tomatoes should continue to scout up until the final pick and destroy field as soon as possible once harvesting is finished either by applying gramoxone or discing under plant material. Growers with late blight issues this growing season should be especially diligent. The threat of late blight in our area will remain up until the first frost. Late blight has the potential to overwinter in our area on infested potatoes left in cull piles or unharvested tubers left in the field.

Filed Under: Organic Production Tagged With: ,
October 4, 2013

Angular Leaf Spot in Fall Transplanted-Strawberries

There have been a few reports of angular leaf spot (ALS) caused by the bacterium, Xanthomonas fragariae, in strawberry in the northern part of New Jersey. Often considered a minor pathogen, ALS can cause serious leaf and calyx infections ruining the marketability of fruit if left uncontrolled. Like all bacterium, the pathogen will infect leaves and the calyx through natural openings or wounds.

Fig. 1. Water-soaked lesions caused by angular leaf spot on infect strawberry leaf. Photo by P. Nitzsche

Infections can often start in production operations and come in on infected bare root transplants or cuttings. Symptoms on leaves include initial small, irregular water-soaked lesions (Figure 1).


Fig. 2. Reddish-brown lesions on infected strawberry leaf caused by angular leaf spot. Note the translucent spots when held up to light. Photo by P. Nitzsche

As disease progresses lesions will enlarge and coalesce forming reddish-brown spots on leaf surfaces which later become necrotic and translucent (Fig. 2). Holding infected leaves up to the light will reveal this diagnostic feature.


Importantly, in severe outbreaks in the spring, the bacterium can spread to fruit causing the calyx to turn brown and dry out ruining the marketability of infected fruit (Figs. 3 & 4).

Fig. 3. Angular leaf spot infections on calyx of infected strawberry fruit. Photo by P. Nitzsche

Fig 4. Strawberry fruit infected with Angular leaf spot. Note the brown, dried up calyx.




The pathogen is easily spread via overhead irrigation and during rain and can be moved around the field during harvest. The bacterium may overwinter on infected plant debris buried in the soil for up to one year. The best method for controlling angular leaf spot is to buy clean transplant material. Conventional or organic copper-based products can help suppress the development of ALS, and should be applied at a low rate to avoid phytotoxicity in leaves. Weekly, preventative applications of 0.3 lb fixed copper have been shown to be effective in reducing ALS if applied early enough when disease pressure was still low.

Filed Under: Vegetable Crops Tagged With: ,
September 27, 2013

Vegetable Disease Briefs – 9/28/13

Basil downy mildew remains active. The weather this time of year is ideal for downy mildew development across many crops. Growers should remain diligent going into the fall with regular scouting and preventative fungicide applications. [Read more…]

Filed Under: Vegetable Crops