This article has been adapted from an article written by Dr. Christelle Guédot, University of Wisconsin-Madison, and published in the Cranberry Crop Management Journal – Volume 36 (August 02).

Every 15 years, the Environmental Protection Agency (EPA) performs registration reviews to reevaluate pesticides to assess environmental and occupational risk. In March 2023, the EPA announced that it would accelerate the review process of Diazinon and other pesticides that were due to conclude in 2026. As part of the review process of Diazinon, EPA reached an agreement with the pesticide registrants to develop voluntary mitigation measures by the registrants several years ahead of the normal registration review process to reduce occupational risk. This has led registrants to start implementing these measures this summer and resulted in the shortages observed this summer. For more information about this agreement between EPA and the registrants reached in April, please see https://www.epa.gov/pesticides/epa-reaches-agreement-early-mitigation-measures-initiative-organophosphate-pesticide.

While there was some uncertainty surrounding the supply and forecast of production of the different formulations of Diazinon from Adama and Loveland Products this summer, an official statement was received from Adama stating that they will continue to produce AG500 into 2024 and that they will cease production of Diazinon 50W. For AG500, new labels that will contain occupational risk mitigation measures and endangered species language are expected to be approved by the end of 2023 and should be in place through 2026 when the EPA will complete the registration review process. As for AG600, Loveland Products have informally indicated to the Cranberry Institute that they do not intend to produce Diazinon AG600 any longer. Once stocks of Diazinon 50W and AG600 run out, Diazinon will only be produced and available from Adama in the AG500 formulation. For more information about use pattern of Diazinon AG500, a link to the label can be found at https://s3-us-west-1.amazonaws.com/agrian-cg-fs1-production/pdfs/Diazinon_AG5001t_Label.pdf. It is expected that EPA will announce the notice of the agreed upon mitigation measures later this year and that an interim or final decision will be reached in 2026 under the regular review process timeline.

Based on our degree-day (DD) model for Sparganothis fruitworm, peak flight is expected at around 884 DD (see chart). As of June 22, Sparganothis fruitworm has accumulated 827 DD (using April 15 as biofix; a biofix more realistic to New Jersey practices). Based on the April 15 biofix, egg laying should have been initiated. However, I do not expect peak flight and those eggs to start hatching until mid-next week. Larval injury to fruit usually begins after the eggs hatch. If treatment is required (based on pheromone trap counts), sprays should be done 10-14 days after peak moth captures, ca. 7-11 July. If Sparganothis fruitworm pressure has been high, it may be advisable to treat 3 weeks after the moth flight began (i.e., around 1-4 July) and again 10 days later. When bees are present your option is to use an insect growth regulator such as Confirm or Intrepid. Our “standard” recommendation has been, however, to wait until bees are removed to apply an insecticide. Your post-bloom options include Altacor, Delegate, Exirel, or Intrepid. The timing of insecticide application is critical; so, if needed, do not wait too long to manage this pest.

Degree-day model for Sparganothis fruitworm

Blunt-nosed leafhoppers (BNLH) are important pests of cranberries in NJ because they vector a phytoplasma that causes false blossom disease. BNLH has one generation a year. It overwinters as eggs, which begin to hatch in early May. The nymphs will go through five instars in about a month. The adults 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 plant juices of the cranberry vines with their piercing-sucking mouthparts. At this time of the year, we are observing early-instar nymphs, mostly 1^st instars but also 2^nd instars (Figure 1).

Figure 1. Blunt-nosed leafhoppers early-instar nymphs. Photo credit: Paolo Salazar-Mendoza.

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 (Figure 1); thus, ideally, 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 per 1–10 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. Control measures should be considered based on the number of BNLH relative to previous years, history of insecticide application, and the variety. 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.
5. If treatment is necessary, we have a few 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 Diazinon (diazinon) and Orthene (acephate), carbamates like Sevin (carbaryl), and pyrethroids like Fanfare (bifenthrin) and Danitol (fenpropathrin). Although not proven scientifically, there are claims that Orthene and Sevin can reduce pollinator activity by repelling bees. The neonicotinoids Assail (acetamiprid) and Actara (thiamethoxam) also work well against nymphs, but we do not recommend their use before bloom due to potential negative effects on bees; neonicotinoids are systemic insecticides that can accumulate in the pollen and nectar. Closer (sulfoxaflor) is a new registered insecticide in cranberries with a similar mode of action as the neonicotinoids but that belongs to a different class of insecticides. We have tested Closer in small plot trials at the P.E. Marucci Center and shown that it is effective against BNLH nymphs; however, more data are needed to confirm its efficacy at larger scales in commercial farms.

By now the winter flood is off from most New Jersey cranberry beds. Once the water is removed, the vines will start to initiate bud break. From now until bloom, growers should scout their beds using sweep net sampling for lepidopteran pests (spongy (=gypsy) moth, blackheaded fireworm, spotted fireworm, Sparganothis fruitworm, and cranberry blossomworm), and blunt-nosed leafhoppers (Figure 1).

Figure 1. Spongy moth larva (A); Blackheaded fireworm larva (B); Sparganothis fruitworm larva (C), Spotted fireworm larva (D); Cranberry blossomworm larva (E); Blunt-nosed leafhopper nymph (F). Photo Credits: Elvira de Lange & Dan Schiffhauer.

Spongy moth – Although spongy moth numbers should have dropped compared to the last couple of years, we might see larvae still in places where high infestation occurred, particularly in beds near wooded areas. At this time of the year, the larvae are small (early instars). This insect has one generation a year and overwinters as eggs. Eggs hatch at this time of the year and 1^st instars “balloon” on silken threads from infested trees onto nearby cranberry beds. Thus, spongy moths tend to be one of the earliest caterpillars to show up in cranberry beds, usually during the first week of May. The larvae are quite easy to detect by means of sweep net sampling and are easy to control with most of the insecticides at our disposal (see recommendations below).

Blackheaded fireworm – Blackheaded fireworm eggs overwinter on the bed and usually hatch by around mid-May. It is important to catch the first generation, if possible, because the second generation occurs during bloom and is typically much more destructive. Blackheaded fireworm larvae can be detected by sweep net sampling and it is a good idea to look along the edges of beds where vines first begin to grow. Remember: blackheaded fireworm is much easier to control if detected during the early part of the season.

Sparganothis fruitworm – This insect is a serious pest in most cranberry-growing states.  It completes 2 generations a year and overwinters as an early-instar larva. The larvae from the 1^st generation feed on foliage. In New Jersey, first generation adult moths emerge from mid-June through the first weeks in July; pheromone traps are commonly used to monitor adult flight and population size. The 2^nd-generation eggs are laid on cranberry leaves, and larvae will feed on fruit.

Spotted fireworm – This insect overwinters as a 2^nd instar larva and completes 2 generations a year. The larvae feed between uprights they have webbed together. First-generation larvae injure the foliage causing it to turn brown as if burned. In New Jersey, 1^st-generation adult moths emerge the first week of June, followed by a 2^nd-generation adult emergence in early August. Eggs are laid in masses on weedy hosts. The larvae from 2^nd-generation adults emerge in mid-August and may feed on fruit. Populations of spotted fireworm are regulated by their natural enemies, particularly Trichogramma wasps that parasitize the eggs.

Cranberry blossomworm – Adults lay their eggs in October in cranberry beds. The eggs overwinter and hatch over a period of several weeks. Early instars can be found during the first week of May. Larvae go through 6 instars to complete their development. Because the first instars feed during the day (and at night), scouting can be done during the daytime using sweep nets to estimate larval abundance. Larvae turn nocturnal during the later instars and thus night sweeping (9 pm – 1 am) is recommended for sampling. Larvae complete their development by June-July. Older instars are very voracious and capable of destroying 100 blossoms within a 3-week period. There is a pre-pupal stage that lasts until the end of August and a pupal stage that lasts until October. Adults emerge from the end of August to the end of October.

Lepidopteran Pests Monitoring and Control – Use sweep netting for monitoring early lepidopteran pests (pre-bloom). A sweep set consists of 25 sweeps and 1 sweep set is recommended per acre (this may vary depending on the size of bogs). The action threshold for false armyworm, blossomworm, other cutworms, and spongy moth (we use a combined threshold from adding all these caterpillars per sweep set) is an average of 4.5 caterpillars in sets of 25 sweeps. For brown and green spanworms is an average of 18 per sweep set. The action threshold for blackheaded fireworm and Sparganothis fruitworm is an average of 1.5 per sweep set. We recommend the use of reduced-risk materials such as the insect growth regulator (IGR) Intrepid, the spinosyn insecticide Delegate, or any of the diamide insecticides Altacor, Exirel or Verdepryn if populations exceed action thresholds. These are reduced-risk, softer insecticides that are very effective against lepidopteran pests. Remember to rotate insecticides with different modes of action to prevent onset of insecticide-resistant pest populations.

Leafhoppers –There is continuing concern among New Jersey cranberry growers of a potential increase in leafhopper populations because of changes in pest management strategies (e.g., adoption of new reduced-risk products and decreased applications of broad-spectrum insecticides). The blunt-nosed leafhopper is of particular concern because this insect can transmit cranberry false blossom disease. This leafhopper has one generation a year. The adults are found in the highest numbers during July, although nymphs or adults may be found from the end of May until October. The eggs are laid in August-September and the overwintered eggs hatch in May or June. The nymphs go through 5 instars to complete their development.

Leafhopper Monitoring and Control: Leafhopper nymphs can be sampled using sweep nets (as described above for lepidopteran pests). 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. There is no established threshold based on sweep net counts because it varies depending on the age of beds, the variety, and/or with false blossom incidence. These decisions should be made by comparing current numbers with prior infestation history.

In cases of high numbers of blunt-nosed leafhopper nymphs, we recommend application of a broad-spectrum insecticide, such as Sevin, Diazinon (no aerial applications allowed), Fanfare, or Danitol. Broad-spectrum insecticides will disrupt biological control particularly the natural enemies (predators and parasitoids) of Sparganothis fruitworm, so their use should be restricted only to areas of high leafhopper populations.