As we approach the end of bloom, growers should consider the need for any post-bloom applications. The main pest targets for these applications are mainly Sparganothis fruitworm and spotted fireworm.

Sparganothis fruitworm (SPARG) – If your farm has high pheromone trap counts, you should consider managing this pest as soon as bees are removed. The timing for this 1st post-pollination spray is at 2 weeks after peak pheromone trap catches, which usually coincides with this time of the year.

Spotted fireworm (SFW) – SFW is one of the most important pests in New Jersey. Male SFW moth catches typically peak in the second through third week in June. Although trap catches give an indication of population size, these numbers not always correlate with numbers of egg masses. This insect becomes a problem in “weedy” beds because female moths lay their eggs predominantly on weeds. Thus, growers need to monitor for the presence of SFW egg masses on weeds (broadleaf species and grasses). Keeping beds clean from weeds will keep this insect under control. Egg masses should be hatching by now. SFW larvae from this generation feed on foliage as well as fruit.

Control Options – Insect Growth Regulators (IGRs) (e.g. Intrepid and Confirm) are effective against SPARG. Alternatively, if you have used IGRs intensively (e.g. last year and this year as a pre-bloom or bloom spray), and would like to rotate with other chemistries, you may want to use Altacor, Delegate, or the broad-spectrum insecticides Diazinon, Imidan, or Lorsban. Broad-spectrum insecticides are also a choice if you have high blunt-nosed leafhopper populations (see below) because Intrepid, Delegate, and Altacor will have no effect against this insect. IF YOU ARE AN OCEAN SPRAY (OS) GROWER PLEASE CHECK RESTRICTIONS ON THE USE OF THESE INSECTICIDES. Lorsban in particular can’t be used by OS growers after bloom due to maximum residue limits (MRLs) for exporting cranberries. If you are an OS grower and want to use a post-bloom application to control SPARG then Delegate, Altacor, Diazinon (no aerial application allowed), or Imidan would be your options.

Blunt-nosed leafhoppers– The best timing for controlling blunt-nosed leafhoppers is before bloom when they are immatures. At this time of the year, most of the population are adults and already laying eggs. If you did not spray before bloom and have a high leafhopper population, you may consider a post-bloom application to prevent from an increase in population size. You may also consider spraying next year to control for those immatures that will emerge from the already laid eggs. I list the best products against leafhoppers. As indicated above, if you are an OS grower please check insecticide use restrictions based MRLs.

Recommendations for leafhopper control

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.