Based on our degree-day (DD) model for Sparganothis fruitworm, first eggs hatched at about 900 DD (see chart). As of July 02, Sparganothis

Sparganothis degree-day model benchmarks

has accumulated 1,212 DD (using April15 as biofix). This indicates that most eggs should have hatched by now and fruit is susceptible to infestation. Most beds should soon be out of bloom. Thus, if trap counts have been high, then a post-bloom application might be necessary. Growers should consider treatment in the next few days (as soon as bees are removed) to prevent damage to berries. Your best post-bloom options are Diazinon, Altacor, or Delegate.

Sparganothis degree-day model benchmark

Based on our degree-day (DD) model for Sparganothis fruitworm, peak flight is expected at around 884 DD and first eggs hatched expected at 895 DD (see chart). As of June 21, Sparganothis has accumulated 951 DD (using April 15 as biofix). This indicates that we have passed peak flight and eggs have just started to hatch. I will keep you updated as the season progresses.

We would like to invite all cranberry growers to the 2018 Cranberry Growers Twilight Meeting.

Location:  P.E. Marucci Center, 125A Lake Oswego Rd., Chatsworth, NJ

Date:        July 03, 2018

Time:        5:00 P.M. to 8:00 P.M

Agenda

5:00-5:30 PM   “Pesticide Regulation and Safety Update”, Patricia Hastings, Pesticide Safety Education Program Coordinator

5:30-6:00 PM   Dinner

6:00-6:30 PM   “Monitoring for Cranberry Insects”, Dr. Cesar Rodriguez-Saona, Extension Specialist, Entomology

6:30-7:00 PM   “Update on Cranberry Diseases”, Dr. Peter Oudemans, Extension Specialist, Pathology

7:00-7:30 PM   “Update on Herbicide Registration and Weed Management for NJ Cranberry”, Dr. Thierry Besancon, Assistant Extension Specialist, Weed Science

7:30-8:00 PM “Frost Damage in Cranberries”, Dr. Nicholi Vorsa, Professor and Director, Rutgers P.E, Marucci Center

Pesticide credits will be issued at the conclusion of the meeting.

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

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.

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 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.

Based on our degree-day model for Sparganothis fruitworm, flight initiation is expected at around 596 DD (see chart). As of June 4, Sparganothis has accumulated 626 DD (using April 15 as biofix) or 586 DD (using April 25 as biofix). This indicates that flight activity has just started or will start soon. Growers are advised to place pheromone traps for monitoring this pest at this moment, if they haven’t done so already.

Sparganothis fruitworm adult

Sparganothis fruitworm degree-day model