Topic: 2020 Cranberry Growers Twilight Meeting
Host: Cesar Rodriguez-Saona <CRodriguez@RCE.Rutgers.edu>
Webex Host: Patricia D. Hastings
Date: Tuesday, June 23, 2020
Time: 5:45 pm, Eastern Daylight Time (New York, GMT-04:00)
Session number: Not Available
Registration password: Please obtain your session password from your host.

Agenda

5:45-6:00 PM Verification ID for registrants getting pesticide credits

6:00-6:20 PM “2020 Weed Management Updates for New Jersey Cranberries”
Dr. Thierry Besancon, Assistant Extension Specialist, Weed Science

6:20-6:35 PM “Cranberry Hybrids: their Nutrition and Crop Potential”
Dr. Nicholi Vorsa, Professor and Director, Rutgers P.E, Marucci Center
Dr. Jennifer Johnson-Cicalese, Research Associate

6:35-6:55 PM “Scouting and Managing Summer Diseases in Cranberry”
Dr. Peter Oudemans, Professor Blueberry/Cranberry Pathology

6:55-7:10 PM “Non-fungal Diseases of Cranberry”
Dr. James Polashock, Research Plant Pathologist, USDA-ARS

7:10-7:30 PM “2020 Cranberry Insect Pest Management – An Update”
Dr. Cesar Rodriguez-Saona, Extension Specialist, Entomology

7:30-8:00 PM “2020 Revisions to the New Jersey Pesticide Regulations”
Patricia Hastings, Pesticide Safety Education Program Coordinator, Rutgers NJAES

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To register for this session
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Go to https://rutgers.webex.com/rutgers/k2/j.php?MTID=t30838a4d3eac637397cb4b8b935d6418 and register.

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For assistance
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You can contact Patricia D. Hastings at:
hastings@njaes.rutgers.edu
1-848-932-0176

https://www.webex.com

Blunt-nosed leafhoppers (BNLH) continue to be an increasing threat to cranberries in NJ. This insect pest has also the potential to affect other cranberry-producing states. Here I put together some guidelines to consider when managing BNLH in cranberries:

1. 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 don’t 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.

2. As an IPM practice, we recommend to monitor BNLH populations before bloom using a sweep net.

3. 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.

4. 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 have increased.

5. 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.

6. 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). Ocean Spray growers need to check restrictions on use of these insecticides prior to application.

7. Last year, we (in collaboration with James Polashock, USDA-ARS) tested whether we could increase the cranberry’s own immune defenses to combat disease infection. In greenhouse studies (Fig. 1), we treated phytoplasma-infected cranberries with commercial products that elicit defenses in plants against diseases. Unfortunately, these treatments were unsuccessful at reducing the phytoplasma and, even worse, they made the cranberries more susceptible to BNLH and caterpillars.

Fig. 1. Greenhouse study on the effects of elicitors of plant defenses on cranberry-phytoplasma-insect interactions

8. We have observed that phytoplasma infection makes the cranberry root system weaker. Thus, applying stresses to infected cranberries such as sanding or herbicides could prevent them from growing and potentially cause their death. Greenhouse and field studies in collaboration with Thierry Besancon (Rutgers U.), James Polashock (USDA-ARS), Dan Schiffhauer and Lindsay Wells-Hansen (Ocean Spray) are underway to test this concept.

Cranberries are starting to 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.

Degree-day model for Sparganothis fruitworm

Figure 1 shows life history benchmarks of interest for Sparganothis fruitworm and associated degree-day (DD) estimates from March 1(Shawn Steffan, USDA-ARS/University of Wisconsin-Madison). Flight initiation is predicted around 595 DD, at a lower temperature threshold of 50°F. Based on this model, Sparganothis has accumulated (starting April 15) 521 DD, meaning that flight should start in about 3 days in our region.

Fig. 1. Sparganothis fruitworm degree-day model

As we approach bloom, Sparganothis fruitworm, spotted fireworm, and blackheaded fireworm adults will start to emerge. Growers need to start monitoring for Sparganothis adults using pheromone traps. As in previous years, I will be tracking the activity of Sparganothis adults using a degree-day model we developed in collaboration with Dr. Shawn Steffan from University of Wisconsin-Madison/USDA-ARS. Based on our degree-day model for Sparganothis, flight initiation is expected at around 596 DD (using March 1 as biofix; see chart). As of June 01, Sparganothis has accumulated 345 DD (using April 15 as biofix). Last year, at around this time, Sparganothis had already accumulated 529 DD. This means we are about one week behind from last year. This indicates that flight activity has not started and will not start until about 10-11 days from now. Growers are advised to place pheromone traps for monitoring this pest by the end of this week or, at the latest, by early next week.

Sparganothis fruitworm degree-day model

Four insecticides have recently been registered in cranberries. There are:
Cormoran. This insecticide from ADAMA is a mix of Rimon (novaluron) and Assail (acetamiprid). The cranberry use rate is 9-12 fl oz/acre and the label lists several insect pests including leafhoppers, blackheaded fireworm, cranberry blossomworm, Sparganothis fruitworm, and spotted fireworm. This insecticide has provided good control on leafhopper nymphs in our research trials (Table 1). This toxicity against leafhoppers is most likely due to Assail since Rimon has no toxic effects on leafhoppers. Rimon is an insect growth regulator (chitin inhibitor) that has potential toxicity on honeybee brood when foraging bees pick up residues from the field and take them back to the hive. Thus, care needs to be taken when using this product pre-bloom.

Exirel (cyantraniliprole). This insecticide from FMC has a use rate of 10-20.5 fl oz/acre and the label lists Sparganothis fruitworm, blackheaded fireworm, and cranberry fruitworm as target pests. In our insecticide trials, this product has provided excellent control of caterpillars (“worms”) (Table 1). Exirel belongs to the same class of insecticide as Altacor (diamides). I recommend using these insecticides in rotation with Intrepid and Delegate for the control of lepidopteran pests.

Table 1. Efficacy of Registered Cranberry Insecticides (New Insecticides in Bold)

+++ Excellent control, ++ Moderate-to-Good control, + Poor control, – No control; x = bee toxicity

Movento (spirotetramat). This insecticide from Bayer Crop Sciences has a use rate of 8-10 fl oz/acre in cranberries. The label lists cranberry tipworm and leafhoppers as targets. In our insecticide trials, this product has provided excellent control against cranberry tipworm. However, cranberry tipworm has not been a pest problem of cranberries in New Jersey. It provides some control against leafhopper nymphs (Movento inhibits lipid metabolism so it works best against immature insects); however, the label says to not apply until after petal fall. Because Movento has limited use in New Jersey cranberries, I did not include it in Table 1.

Closer (sulfoxaflor). This insecticide from Corteva (former DowAgrosciences) has a use rate of 2.75-5.75 fl oz/acre in cranberries. The label lists leafhoppers as target pests. In our insecticide trials, Closer has shown good-to-excellent leafhopper control (Table 1). This product cannot be used when bees are active (between 3 days prior to bloom and until after petal fall).

There is continued concern among New Jersey cranberry growers of increases in blunt-nosed leafhopper populations due to changes in pest management strategies (e.g., adoption of new reduced-risk products and decreased applications of broad-spectrum insecticides). Blunt-nosed leafhopper is of particular concern because they are vectors of false blossom disease.

Blunt-nosed leafhopper nymphs. Photo credit: Lindsay Wells-Hansen.

Life Cycle – The blunt-nosed leafhopper has one generation a year. Blunt-nosed leafhopper eggs overwinter and begin to hatch in early May. The nymphs (see Picture; small yellow-colored insects) will go through five instars in about a month. The adults begin to appear early in July and are most abundant in late July. Numbers of this species start to diminish by the first week in August. The adults have a characteristic blunt head and vary from light yellowish-gray to dark brown. Eggs are laid in August-September.

Damage – Nymphs and adults get their food by sucking the plant juices of the cranberry with their piercing-sucking mouthparts. This direct injury is, however, not noticeable. They are most important as vectors of false blossom disease.

Scouting and Control – The most important point in leafhopper control is locating the infestation. Monitoring for this insect is accomplished best with an insect sweep net. Nymphs can be monitored before bloom using sweep nets. 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. 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. In cases of high blunt-nosed leafhopper numbers, we recommend application of a broad-spectrum insecticide, such as Lorsban. This time of the year (May 20-30) would be the period for pre-bloom applications. The neonicotinoids Actara and Assail are very effective against blunt-nosed leafhoppers and can be used to target the adults after bloom. There is no threshold so decisions should be made based on current numbers and prior infestation history. Broad-spectrum insecticides will disrupt biological control particularly the natural enemies (predators and parasitoids) of Sparganothis fruitworm, so their use should be minimized to areas of high blunt-nosed leafhopper populations.