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Entomology Research

Selected Highlights of the 2020 Entomology Program

Dr. Anne L. Averill and Martha M. Sylvia

Management Options for Resistant Cranberry Weevil:

This is one of the most pressing pest challenges for the industry. Cranberry weevil populations have sequentially become resistant to each insecticide class. We have not discovered an effective non-insecticidal management strategy, but have had made some progress towards a  behavioral control option with Rutgers.

Refereed publication: C. Rodriguez-Saona, … M.M. Sylvia and A.L. Averill. 2020. Fine-tuning the composition of the cranberry weevil (Coleoptera: Curculionidae) aggregation pheromone. J. Applied Entomology 00:1-5.

Insecticide screening trial for cranberry weevil control: Actara (a neonicotinoid), is currently used throughout the cranberry industry. Resistance is anticipated, so in 2020, we tested a new class of insecticides, the pyrethroids, which are used widely in other crops.

Large field plots (4 reps/treatment) on State Bog were treated with either Danitol (pyrethroid), Fanfare (pyrethroid), or Actara (current industry standard). After 5 days, weevil counts were compared to untreated Control plots.

In sum, control was excellent in Fanfare plots. Danitol was not effective, showing no difference from the untreated plots.

Residue analysis: To have Danitol registered and available for growers, we are working with ADAMA, the registrant. We are cooperating with Ocean Spray to collect residue data.

Bumble Bee Colony Health at Managed Bogs:

Bumble bees are the most important wild pollinators in cranberry. We worked to identify pesticide use that may impact these wild bees by deploying sentinel commercially-available bumble bee colonies at 7 commercial cranberry bogs (4 colonies/site).  Colonies performed poorly at 4/7 of the sites. Chemical analysis of pesticides in pollen is pending. Initial analysis suggests that at least four different spring insecticides applied pre-bloom are being taken up by the cranberry plant and may be at toxic/sublethal levels in pollen weeks later.

Spatial Analysis of Landscape Composition for Bumble Bee Species Diversity and Pathogen Load:

Michael Nelson’s group in the UMASS Environmental Conservation Dept is utilizing our data sets to investigate if surrounding land-use and land cover (e.g. cranberry farms vs other landscapes) affect bumble bee community diversity and health.

Emerging Insect Pests: Sampling and Management

Scale Insects:

Scale insects continue to form outbreak populations across the industry and are difficult to assess and manage. Putnam scale (Diaspidiotus ancylus) is the causal agent for many vine die-off areas.

Outreach to growers: We microscopically inspected vines that we collected (18 samples) or were provided by growers (23 samples). A broad-spectrum conventional insecticide or late-water management were successfully recommended.

Crop oil screening trial for scale control. We evaluated an environmentally-sound spray option. While the vines were dormant, replicated field plots were treated with 1 gal/acre crop oil or 5 gal/acre crop oil. In June, immature scale abundance, adult female mortality and percent of scales parasitized by a black wasp were compared to control plot populations. The 5 gal/acre treatment showed strong promise. Parasitism rates were surprisingly high.

To have crop oil registered and available for growers, work continues with Drexel to develop a Special Local Needs label for use on cranberry

A new Leaf beetle – triachus vacuus

This tiny beetle (1-2 mm) has been building up in numbers, with the first infestation identified in 2015. Now there are many sites, ranging across Carver, Plympton, Taunton to RI. Infestations cause substantial vine injury owing to impressive localized outbreaks.

Outreach to growers: We confirmed infestations at 10 sites. A fact sheet was sent to growers;  M.M. Sylvia and A.L. Averill. Pest alert - July 2020. New leaf beetle “The Golden Casebearer”

Identification: We sent the beetles to the USDA for identification. It is Triachus vacuus, with a range across the eastern US. It is a native species but is poorly studied. It is not identified as a pest elsewhere. Interestingly, specimens had been submitted to USDA for MA cranberry in the 1960s. It is in the ‘casebearer’ beetle group, which has an odd biology - females encase eggs with excrement. The developing larva then carries around a fecal case that it adds to as it grows.

Winter moth – green cranberry spanworm

These spring species are very hard to tell apart, but proper ID is required since anticipated damage, assessment, and management are different. We observed that green spanworm is increasing while winter moth has sharply declined. Many green spanworm moth flights were observed in June.

Outreach to growers: 12 sites were visited and growers made aware of evolving pest status