As we approach the end of July, growers need to start monitoring for the cranberry toad bug, Phylloscelis rubra (Figure 1). In a recent study,

we showed 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 the end of July through mid-August is critical.

Life cycle. Cranberry toad bugs feed only on cranberries. This insect has a single generation per year. It overwinters as eggs. The nymphs appear by the end of June through early September, and the adults from end of July through October (harvest) (Figure 2). Eggs are laid from end of August through October.

Damage. Feeding damage can be noticed in two stages. 1st-stage feeding damage on vines causes closing in (towards the branch) of the leaves on the new growth. 2nd-stage feeding causes changed in color (reddish to brown) of new growth. The damage can be seen from July until harvest. This damage will cause dying of the branch and the berries to shrivel up (Figure 3). Heavy infestation will result in dwarfed

berries.

Management. To determine infestation, lightly sweep problematic beds (bugs should be easy to catch in sweep nets as they are very active). Currently there is no threshold established for this pest. Thus, insecticide applications should be based on the relative number of bugs per sweep compared with other sites and previous history of infestation. If needed, growers can use the following control options: Sevin 4F (broad-spectrum carbamate), Diazinon, Imidan 70W (broad-spectrum organophosphates), Actara or Assail 30SG (neonicotinoid insecticides, effective against piercing-sucking insects). If infestation is high, treatments should be applied in early August for best control.

Sparganothis Fruitworm Degree-Day Update: as of July 07, 2021

Based on our degree-day (DD) model for Sparganothis fruitworm, the window for egg hatch is between 895 and 1,890 DD (see chart). As of July 07, Sparganothis has accumulated 1,251 DD (using April 15 as biofix). This indicates that most eggs should have hatched by now and fruit is susceptible to infestation. Most beds are out of bloom (early varieties) or should be coming out of bloom. If trap counts have been high and you have not done so already, then you should consider treatment in the next few days to prevent damage to berries. Your best post-bloom options are Diazinon, Intrepid, Altacor, or Delegate. All treatments for lepidopteran pests should be done before the end of this week to avoid substantial injury to fruit.

Root-feeding Pests of Cranberries

If your beds have damage caused by root-feeding insects, you should consider treatment with Imidacloprid (e.g. Admire Pro, Alias 4F, Alias 2F) after bees are removed. Occurrence of root-feeding insects will manifest by the presence of dead patches (see picture). Pulling dead vines and searching through the root zone and soil are needed to reveal the presence of larvae. 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 adults 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 insta

rs, 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.

Cranberry rootworm (Chrysomelidae). Pupation starts in late May and beetles emerge in early June. Adults (see picture) 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, and feeding continues until October. The mature larvae (see picture) 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.

Based on our degree-day (DD) model for Sparganothis fruitworm, first eggs hatch at about 895 DD (see chart). As of June 27, Sparganothis has accumulated 991.5 DD (using April 15 as biofix). This indicates that eggs have started to hatch, and fruit will become susceptible to infestation since larval injury to fruit usually begins after the eggs hatch. According to our model, peak flight should have occurred about a week ago (around June 20). Insecticide applications are usually recommended 10-14 days after peak flight (i.e., June 30-July 4). Most beds should be close to the end of bloom. If trap counts have been high, growers should consider treatment by the end of next week (depending on the variety and time of winter flood removal) to prevent damage to berries. If spraying when bees are present, your option is to use an insect growth regulator (IGR), such as Confirm or Intrepid, or the diamide Altacor. Our “standard” recommendation has been, however, to wait until bees are removed to apply an insecticide. Your post-bloom options include the organophosphate Diazinon, the diamides Altacor, Verdepryn, or Exirel, the spinosyn Delegate, or the IGR Intrepid. Timing of insecticide application is critical; so, if needed, do not wait too long to manage this pest.

Based on our degree-day model for Sparganothis fruitworm, flight initiation is expected at around 596 DD (see chart). As of June 06, Sparganothis has accumulated 706 DD (using March 1 as biofix; based on Wisconsin conditions) or 554 DD (using April 15 as biofix; a more realistic biofix based on the time when winter flood is removed from New Jersey beds). This indicates that flight activity has likely just started or will start in the next few days. Growers are advised to place pheromone traps for monitoring this pest as soon as possible if they haven’t done so already.

Based on our degree-day model for Sparganothis fruitworm, flight initiation is expected at around 596 DD (see chart). As of May 30, Sparganothis has accumulated 607 DD (using March 1 as biofix) or 455 DD (using April 15 as biofix; a more realistic biofix based on the time when winter water was removed from most NJ beds). The later biofix indicates that flight activity will start very soon, i.e., within a week from now. Thus, growers are advised to place pheromone traps for monitoring this pest this coming week.

Blunt-nosed leafhoppers (BNLH) continue to be an increasing threat to cranberries in NJ. BNLH has one generation a year. It overwinters as

eggs, which begin to hatch in early May. The nymphs (Picture 1) will go through five instars in about a month. The adults (Picture 2) begin to appear by the end of June and are most abundant in mid-July. Numbers of this species start to diminish by the end of July. The adults have a characteristic blunt head and vary from light yellowish-gray to dark brown. Eggs are laid in June-July. Nymphs and adults get their food by sucking the juices of the cranberry vines with their piercing-sucking mouthparts. This direct injury is, however, not noticeable. They are most important as vectors of false blossom disease (Picture 3). Typical disease symptoms include distinctive branching of the upright shoots (witches’ broom) and malformed flowers where flowers stand erect and petals are redder than normal.

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

1. The most important point in BNLH control is locating the sites of infestation. Monitoring for this insect is accomplished best with an insect sweep net. Nymphs should be monitored before bloom using sweep nets (this time of year). Nymphs before bloom are small; thus, you may need to freeze the samples (to kill them), and then count the number of nymphs under a microscope or using a magnifying lens.
2. To monitor, perform sweep sets of 25 sweeps each. The recommended number of sweep sets is: 1–3 sweep sets per 1–
   

   Picture 2. BNLH adult. Photo by Elvira de Lange.

   10 acres, at least 10 sweep sets per 10–20 acres, and 1 sweep set per 2 acres for more than 20 acres.

3. A challenge for managing BNLH is the fact that they vector a phytoplasma that causes false blossom disease. For this reason, it is difficult to establish economic thresholds for this pest because we do not know the proportion of individuals that are infected in the population. Moreover, this proportion can vary depending on the variety. For instance, we have observed higher incidence of infection in the newer varieties even when populations of leafhoppers are low.
4. Although they need to be tested, based on experience, I came up with the following tentative treatment thresholds: An average of 20 nymphs per sweep set if it is a new variety bed, bed with young plantings, and/or a bed that has a recent history of false blossom. Or, an average of 40 nymphs per sweep set if it is an older bed and older variety with no previous history of false blossom.
5. If BNLH populations are increasing compared to previous years and the beds have not been treated for BNLH for 2-3 years, growers should consider treatment.
6. If growers have treated for BNLH in the previous year and populations are low (average of less than 10–20 BNLH per sweep set), there is no need to treat again. Keep a record of the BNLH numbers and check those same beds again the following year to see if the numbers increase.
   

   Picture 3. False blossom-infected cranberry vine.

7. In most cases, there is no need to apply broad-spectrum insecticides (organophosphates, carbamates) to control BNLH for two or more consecutive years. These insecticides will disrupt the biological control of other pests such as Sparganothis fruitworm and therefore cause increases in insecticide use.
8. If treatment is necessary, we have limited options to manage BNLH. The best timing for insecticide treatment is before bloom to target the young nymphs. We recommend the use of organophosphates such as Lorsban (chlorpyrifos) and Diazinon (diazinon), and carbamates like Sevin (carbaryl). The neonicotinoid Assail (acetamiprid) also works well against nymphs, but we do not recommend the use of neonicotinoids before bloom due to potential negative effects on bees-neonicotinoids are systemic insecticides that can accumulate in the pollen and nectar. A new registered insecticide, Closer (sulfoxaflor), is also effective against BNLH nymphs. Although Closer has a similar mode of action as the neonicotinoids, it belongs to a different class of insecticides. Closer use is prohibited during bloom (between 3 days prior to bloom and until after petal fall).
9. Trials will be conducted this year at the Rutgers P.E. Marucci Center with existing and new insecticides against BNLH nymphs.