The cranberry toad bug, Phylloscelis rubra (Figure 1), is a pest of concern to cranberry growers in New Jersey. A recent study demonstrated that even relatively low densities of this insect can cause significant injury to cranberries (Rodriguez-Saona et al., 2020. “Characterizing the Feeding Injury Caused by Phylloscelis rubra (Hemiptera: Dictyopharidae) to Cranberries,” Journal of Insect Science, 20(6), 37, https://doi.org/10.1093/jisesa/ieaa143). Thus, monitoring for this insect from now through mid-August is critical.

Cranberry toad bug

Life cycle. Cranberry toad bugs feed exclusively on cranberries. This insect has a single generation per year and overwinters as eggs. Nymphs appear from the end of June through early September, while adults are present from the end of July through October (harvest). Eggs are laid from the end of August through October.

Damage. Feeding damage can be noticed in two stages. First-stage feeding damage on vines causes the leaves on new growth to close in towards the branch. Second-stage feeding results in a color change in the new growth, turning it from reddish to brown. This damage can be seen from July until harvest and will cause the branches to die and the berries to shrivel up. Heavy infestations will result in dwarfed berries.

Management. To determine infestation, lightly sweep problematic beds; the bugs should be easy to catch in sweep nets as they are very active. Currently, no threshold has been established for this pest. Therefore, insecticide applications should be based on the relative number of bugs per sweep compared with other sites and the previous history of infestation. If needed, growers can use the following control options: Sevin (broad-spectrum carbamate), Diazinon (broad-spectrum organophosphate), Danitol or Fanfare (pyrethroids), and Actara or Assail (neonicotinoid insecticides, effective against piercing-sucking insects). If infestation is high, treatments should be applied now (early through mid-August) for best control.

Most beds are either out of bloom or should be coming out of bloom soon. If Sparganothis fruitworm trap counts have been high and you haven’t already treated, you should consider doing so in the next few days after honey bees are removed to prevent damage to berries. The best post-bloom treatment options are Diazinon, Intrepid, Altacor, or Delegate. All treatments for lepidopteran pests should be completed before the end of this week to avoid significant fruit injury. Additionally, please monitor the weather conditions, as there will be several rainy days this week.

Root-feeding Pests of Cranberries

If your beds show damage caused by root-feeding insects, you should consider treatment with Imidacloprid (e.g., Admire Pro, Alias 4F, Alias 2F) after bees are removed. The presence of root-feeding insects will be indicated by dead patches (see Picture 1). Pull up dead vines and search through the root zone and soil for grubs and worms. Imidacloprid (Admire Pro or other generic insecticides) is labeled for controlling cranberry rootworm, white grubs (Phyllophaga spp.), and other scarabs in cranberries.

White grubs, Phyllophaga spp. Several species of white grubs infest cranberries in New Jersey, with P. georgiana being the most abundant. These grubs are C-shaped and often found near bog margins.

Picture 1. Damage caused by root-feeding insects.

The adults are reddish-brown and nocturnal. While the grubs attack cranberry roots, the adults have not been reported to feed on cranberries (see Picture 2 of grubs and adults in cranberries). The life cycles and abundance of white grub species in New Jersey are not well known. However, it is likely that Phyllophaga grubs have a 3-year life cycle based on previous reports and our observations. Eggs are laid in late June and July, hatching in July. First instars can be found in late July and August, turning into second instars by the end of August to September. The second instar grubs will overwinter. The following year, these grubs will feed until June and molt into third instars, which will overwinter again. In the subsequent year, the third instars will feed for a while before pupating in June. Pupation occurs in July-August, with adults appearing in the soil in August-September. These adults will remain in the soil and overwinter, emerging in June to mate and lay eggs, thus completing the cycle.

Cranberry rootworm (Chrysomelidae). Pupation starts in late May, with beetles emerging in early June. Adults (see Picture 3) are nocturnal and

Picture 2. Developmental stages of Phyllophaga georgiana.

hide in leaf litter, but can be easily picked up with a sweep net. Females feed on foliage before laying eggs. Young larvae feed on roots, with feeding continuing until October. In the fall, the mature larvae (see Picture 4) move down into the soil to overwinter. Holding water will delay the onset of pupation. The 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 is most effective against early (1st-2nd instar) grubs and should be applied after bees are removed from the beds. Due to the 3-year life cycle of these pests, treatment should be continued for 2-3 consecutive years to ensure effective control. Imidacloprid, a neonicotinoid insecticide, is registered for use in cranberries against cranberry rootworm and scarab grubs. This insecticide acts as a contact and stomach poison, affecting the insect nervous system. It is highly systemic and toxic to honey bees, so it should only be used as a post-pollination insecticide. Imidacloprid can be applied by ground or by chemigation, but aerial application is prohibited. The insecticide has a long residual activity (over 100 days) as long as it is not directly exposed to the sun.

Picture 4. Cranberry rootworm larvae.

Picture 3. Cranberry rootworm adult.

Based on our degree-day model, Sparganothis fruitworm has accumulated 1038 degree-days (DD) as of June 24, using April 15 as the biofix date. This indicates that peak flight activity should have occurred at the end of last week. Historically, we recommend insecticide applications 10-14 days after peak flight. This period will fall between mid- to the end of the first week in July.

Based on our degree-day model, Sparganothis fruitworm has accumulated 867 degree-days (DD) as of June 18, using April 15 as the biofix date. This indicates that flight activity has reached the 25% mark. We anticipate that peak flight will likely occur by the end of this week. This model uses averages across several beds, so there may be slight differences depending on the variety. We will continue to provide updates as the season progresses.

Cranberries have started to bloom, and bees are active in bogs. If insects have been effectively managed prior to bloom, we recommend no sprays at this time. A reminder: when bees are present, your 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 the activity of Sparganothis fruitworm and blackheaded fireworm, two key pests in New Jersey.

Degree-Day Model for Sparganothis Fruitworm

Sparganothis fruitworm adults

Together with Dr. James Shope, Assistant Extension Specialist in the Department of Environmental Sciences at Rutgers University, we have been working on refining a degree-day model for Sparganothis fruitworm using trapping data from New Jersey. According to this model, 25% flight activity should occur at 840 degree-days, and peak flight activity at 952 degree-days (starting on April 15). As of today, Sparganothis fruitworm has accumulated 724 degree-days, indicating that flight should have started but has not yet reached 25%. Note that this model includes data from many bogs and varieties, which may behave differently from the overall model. Therefore, it is advised to monitor closely as the expected peak flight approaches.

New Jersey cranberry growers are increasingly concerned about rising blunt-nosed leafhopper (BNLH) populations. This rise is attributed to changes in pest management strategies, such as the adoption of new reduced-risk products and decreased use of broad-spectrum insecticides, as well as the expansion of high-yielding varieties that seem more susceptible. BNLH is particularly worrisome because it transmits a phytoplasma, a type of bacteria, that causes false blossom disease. Symptoms of false blossom disease include stunted growth, erect sterile flowers (Figure 1), and distinctive branching of upright shoots, known as witches’ broom.

False blossom infected cranberry with erect flowers (left) and uninfected cranberry (right). Photo credit: Beth Ferguson.

Life Cycle

BNLH has one generation per year. Its eggs overwinter and begin hatching in early May. Nymphs go through five instars in about a month. Adults appear in early July, peak in mid-late July, and their numbers diminish by the first week of August. These adults have a distinctive blunt head and range in color from light yellowish-gray to dark brown. Eggs are laid between July and August.

Damage

Nymphs and adults feed on cranberry plant juices using their piercing-sucking mouthparts. This direct injury is not noticeable. However, they are significant as vectors of the phytoplasma that causes false blossom disease.

Management

At this time of the year, we are observing early-instar nymphs, mostly 2^nd instars but also 3^rd instars (Figure 2).

Blunt-nosed leafhopper nymphs. Photo credit: Beth Ferguson

Here are some guidelines to consider when managing BNLH in cranberries:

1. Identify Infestation Sites: The key to BNLH control is locating infestation sites. The best way to monitor for this insect is with an insect sweep net. Before bloom, use sweep nets to monitor nymphs. Since nymphs are small, freeze the samples to kill them, then count the nymphs under a microscope or with a magnifying lens.
2. Sweep-net Monitoring: Perform sweep sets of 25 sweeps each. The recommended number of sweep sets is:

• 1 per 1–10 acres
• At least 10 sweep sets per 10–20 acres
• 1 sweep set per 2 acres for areas larger than 20 acres

3. Lack of Economic Thresholds: Managing BNLH is challenging because they vector a phytoplasma causing false blossom disease. Establishing economic thresholds is difficult due to the unknown proportion of infected individuals in the population, which can vary by variety. Higher infection rates have been observed in newer varieties even when BNLH populations are low.
4. Control Measures: Consider control measures based on BNLH numbers relative to previous years, history of insecticide application, and cranberry variety. If BNLH populations are increasing compared to previous years and the beds have not been treated for BNLH in 2-3 years, growers should consider treatment.
5. Treatment Options: If treatment is necessary, consider the following options to manage BNLH:

• Timing: The best time for insecticide treatment is before bloom to target young nymphs.
• Insecticides: Organophosphates: Diazinon (diazinon), Orthene (acephate); Carbamates: Sevin (carbaryl); Pyrethroids: Fanfare or Brigade (bifenthrin), Danitol (fenpropathrin); Neonicotinoids: Assail (acetamiprid), Actara (thiamethoxam). Note: Do not use before bloom due to potential negative effects on bees, as these systemic insecticides can accumulate in pollen and nectar. Sulfoxaflor: Closer (sulfoxaflor). Although effective in small plot trials at the P.E. Marucci Center, more data are needed to confirm efficacy on larger commercial scales.
• Be aware that, while not scientifically proven, there are claims that Orthene and Sevin may reduce pollinator activity by repelling bees.