If your beds have damage caused by root-feeding insects, you should consider treatment with Imidacloprid (e.g. Admire Pro, Alias 4F, Alias

Symptoms caused by grub injury in cranberries

2F) after bees are removed. Occurrence of root-feeding insects will manifest by the presence of dead patches (see picture). Pull dead vines and search through the root zone and soil for grubs and worms. Admire Pro (imidacloprid) is labeled for the control of cranberry rootworm, white grubs (Phyllophaga spp.), and other scarabs in cranberries.

White grubs, Phyllophaga spp. There are several species of white grubs that infest cranberries in New Jersey, the most abundant being P. georgiana. Grubs are C-shaped and often found near bog margins. Adults are reddish brown and nocturnal. Grubs attack the cranberry roots; adults have not been reported to feed on cranberries. See pictures of grubs and grub damage in cranberries. The life cycles and abundance of white grub species in New Jersey is not well known. Most likely, Phyllophaga grubs have a 3-year life cycle (based on previous reports and our own observations). Eggs are laid in late-June and July, and will hatch in July. First instars can be found in late-July and August and turn into second instars by the end of August-September. The second instar grubs will overwinter. These grubs will feed the following year until June and molt to third instars, which will overwinter. The following year, the third instars will feed for some time and then begin to pupate in June. Pupation will take place in July-August. Adults will appear in the soil in August-September. Adults will remain in the soil and overwinter. They will emerge in June, mate, and begin to lay eggs, completing the cycle.

Phyllophaga grubs

Cranberry rootworm (Chrysomelidae). Pupation starts in late May and beetles emerge in early June. Adults are nocturnal and hide in leaf litter. Adults can be easily picked up in a sweep net. Females feed on foliage before laying eggs. Young larvae will feed on roots, feeding continues until October. The mature larvae move down the soil in the fall to overwinter. Holding of the water will delay onset of pupation. Rootworm has a 1-year life cycle. Entomopathogenic nematodes (Heterorhabditis bacteriophora) can be used to control cranberry rootworm.

Use of Imidacloprid. If treatment is needed, use imidacloprid (Admire Pro or other generic insecticides such as Alias 4F) to control white grubs and rootworms. Imidacloprid works best against early- (1st-2nd) instar grubs. Imidacloprid should be used after bees are taken out of beds. Because of the 3-year life cycle, treatment should be continued for 2-3 consecutive years to ensure control. Imidacloprid (active ingredient) is a neonicotinoid insecticide registered for use in cranberries against cranberry rootworm and scarab grubs. This insecticide is a contact and stomach poison that affects the insect nervous system. It is highly systemic and toxic to honey bees; therefore, can be used only as a post-pollination insecticide. Imidacloprid can be applied by ground or by chemigation. Aerial application of this product is prohibited. Imidacloprid has a long residual activity (> 100 days) as long as the insecticide is not directly exposed to the sun. Admire Pro can be used at 7-14 fl oz/acre. A maximum of 14 fl oz of Admire Pro can be used per acre per season. The PHI is 30 days.

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.