Archives for June 2018

Potato | Tomato Disease Forecast 6-15-18

Click to View | Download Report 6-15-18

Potato Disease Forecasting Report

We will be tracking DSVs for Late blight development and calculating P-days for initiating the first early blight fungicide application.

The first late blight fungicide application is recommended once 18 DSVs accumulate from green row. Green row typically occurs around the first week in May in southern NJ. An early season application of a protectant fungicide such as mancozeb (Dithane, Manzate, Penncozeb) or Bravo (chlorothalonil) as soon as the field is accessible is suggested. Please be vigilant and keep a lookout for suspect late blight infections on young plants. No late blight has been reported in our region to date.

Remember the threshold for P-days is 300!  Once 300 P-days is reached for your location, early blight fungicide applications should be initiated. Growers who are interested in using this model should choose the location above that is closest in proximity to their farming operation and should regularly check the Cornell NEWA website (http://newa.cornell.edu) where this information is compiled from. Click on Pests Forecasts from the menu, select your weather station, and click on tomato diseases, set accumulation start date, and a table of daily and total DSVs will be generated.

Tomato Disease Forecasting Report

Disease severity values (DSVs) for early blight, septoria leaf spot, and tomato anthracnose development are determined daily based on leaf wetness (due to rainfall, dew) and air temperature.

On a daily basis DSV values can range from 0 to 4 where 0 = no chance for disease development to 4 = high chance for disease development. DSVs are accumulated during the production season.

Fungicide applications are based on an individually determined DSV threshold. The first fungicide application for the control of these three diseases is not warranted until 35 DSVs have accumulated from your transplanting date. After that, growers can base fungicide applications on different DSV thresholds.

Reports generated by Ryan Tirrell

Rutgers, The State University of New Jersey

Vegetable Disease Update – 6/14/18

  • Dickeya dianthicola has been confirmed on ‘Norwis’ potato in New Jersey from seed originating from Prince Edward Island. This is the first report of Dickeya on potato in NJ this growing season. All potato growers should continue to scout their fields on a regular basis. Please contact your county agent if you find suspect plants.
  • Pectobacterium spp. has been confirmed in southern NJ in ‘Dark Red Norland’ potato originating from P.E.I and in ‘Atlantic’ originating from Maine.
  • Late blight was reported on tomato being sold as transplants in a retail operation last week near northeast Philadelphia. There has been no new information to date. Growers of tomato and potato should continue with their regular fungicide maintenance programs.
  • Basil downy mildew was reported in potted basil being sold at a retail location in southern New Jersey.
  • Bacterial leaf spot has been confirmed in pepper.

Research on False Blossom and Blunt-nosed Leafhoppers

Blunt-nosed leafhoppers are vectors of a phytoplasma that causes false blossom disease in cranberries. This disease

Person researching

Nakorn Pradit, graduate student, Entomology

causes abnormalities in flowers, which include shortened, discolored and streaked petals, enlarged calyx, straighten inflorescence, and abnormal development of floral parts into leaves (phyllody). False blossom imposed a severe threat to the cranberry industry in the US in the first half of last century. However, in the second half of last century, management of leafhoppers through the development of resistant varieties and effective chemical controls reduced its incidence. Recently, the disease has re-appeared in many New Jersey cranberry farms due to changes in management practices and the use of new (possibly more susceptible) varieties. To address this issue, the entomology program at the Rutgers PE Marucci Center is conducting studies to understand the effects of phytoplasma-infected cranberry plants on resistance to leafhoppers and other insect herbivores. This research is being led by Nakorn Pradit, PhD student in the Department Entomology (Rutgers U.). We are asking two main research questions: 1. Are phytoplasma-infected cranberry plants more resistant or susceptible to leafhoppers and other non-vector insect pests? and 2) what are the mechanisms of this resistance/susceptibility? These studies will help identify possible mechanisms of insect pest resistance in cranberries and develop tools for improving control methods against insect vectors and other pests of cranberries.

 

IPM Update 6/06/18

Sweet Corn

European corn borer (ECB) moths have declined in black light traps, and numbers are now very low.  The highest activity now in central Morris County (see ECB map).   As is normal, when the adult generation winds down, feeding increases.  IPM technicians have reported dramatic increases in feeding in whorl and pre-tassel stage plantings in the all counties.  Numbers of infested plants have exceeded 30% in many areas.  [Read more…]

Managing Thatch

Recently received a couple of questions about managing thatch. One question was concerning the recent trend in the industry to not core putting greens and only use solid tines.  Non-coring programs rely on topdressing to dilute the organic matter (thatch) that accumulates, thus forming a mat layer as opposed to a thatch layer. Turgeon defines […]

Insect Update

Cranberry beds are in bloom. If insects have been effectively managed prior to bloom, we recommend no sprays at this time. A reminder: when bees are present your only choices of insecticides are insect growth regulators (IGRs) such as Intrepid 2F or Bt products such as DiPel.

During bloom we recommend monitoring insect populations using pheromone traps. Pheromone traps should be used particularly to monitor activity of Sparganothis fruitworm and blackheaded fireworm, two key pests in New Jersey.

Sparganothis fruitworm- Adult flight started a few weeks ago and we should be at peak flight activity by next week (see DD model below). Damage by the second generation larvae begins after the eggs hatch, usually 9-12 days after they are laid. These larvae will feed on foliage and fruit. Larvae will partially feed on berries, causes scoring of the fruit. However, particularly on Ben Lear, larvae may feed inside the fruit. Insecticide treatment should target small larvae. Pheromone traps can be utilized to time insecticides sprays. If treatment is required, sprays should be applied two weeks after peak moth flight and/or earlier if using an IGR. If trap counts indicate a low population that requires management, a single insecticide application may be made post-bloom. If trap counts are high, then an early application of an IGR may be used when the first eggs start to hatch. This would be followed by a second application soon after bloom. Your post-bloom options are Diazinon, Altacor, Delegate, or Intrepid.

As indicated above, controlling fruitworm populations is often very difficult and many require multiple applications depending on pest pressure. Sparganothis fruitworm populations in Massachusetts are resistant to organophosphate insecticides (e.g. Diazinon, Lorsban). Thus, organophosphates should be used with care, i.e., always rotate insecticides with different modes of action. Organophosphate insecticides will also negatively affect natural enemy populations. Delegate and Altacor are insecticides belonging to relatively new modes of action; these are registered against fruitworms and can be used as an alternative to organophosphates post-bloom.

Degree-day model for Sparganothis fruitworm

Sparganothis degree-day model

Sparganothis degree-day model benchmarks

The figure details life history benchmarks of interest for Sparganothis fruitworm and associated degree-day estimates from March 1. Flight initiation is predicted around 595 DD, at a lower temperature threshold of 50 °F. Based on this model Sparganothis fight was initiated in our region (Chatsworth, NJ) about a week ago. So far, we have accumulated (starting April 15) 763 DD, which means that egg laying has started (depending on the DD accumulations specific to your farm); however, eggs are not expected to hatch until later this month. Also, a reminder that a single insecticide application aimed at Sparganothis larvae will likely have the greatest effect if it is timed between the beginning and the peak egg-hatch/larval-emergence, which is approximately 895-1,400 DD. I will keep you updated on these DD predictions as the season progresses.