209-Insect Control Guide for Wild Blueberries

Fact Sheet No. 209, UMaine Extension No. 2001


Prepared by David E. Yarborough, Extension Blueberry Specialist, Frank Drummond, Professor of Insect Ecology, School of Biology and Ecology, and Judith A. Collins, School of Biology and Ecology. The University of Maine, Orono, ME 04469. Revised January 2019.

NOTICE: It is unlawful to use any pesticide for other than the registered use. Read and follow the label on the product container. The user assumes all responsibility for a use inconsistent with the label. This fact sheet is to be used only during 2019. Use in subsequent years may lead to improper and illegal use of pesticides. When this guide is outdated, please request an updated version from your Extension office.

For toxicity ratings of wild blueberry insecticides, refer to the 2019 Maine Wild Blueberry Pesticide Chart, Insecticides (PDF).

WARNING! Pesticides are potentially hazardous. Handle carefully! Read and follow all directions and precautions on labels. Store in original labeled containers out of reach of children, pets, and livestock. Dispose of empty containers at once, in a safe manner and place. Do not contaminate forage, streams, ponds or groundwater recharge areas.

Groundwater is a major natural resource. Pesticides have been detected in the groundwater of all states. A sound application program including site-specific selection, adherence to label directions, sprayer calibration mixing accuracy, spill and back-siphon prevention, proper waste disposal, integrated pest management, and judicious pesticide use can prevent groundwater contamination.

Trade names are used for identification. No product endorsement is implied, nor is discrimination intended against similar materials. Cooperative Extension makes no warranty or guarantee of any kind concerning the use of these products.

Blueberry Spanworm

Begin to monitor for spanworm larvae in early spring as the buds break and plants emerge by sweeping with a 12-inch diameter sweep net.  Spray with an insecticide or biocontrol when larval counts on fruit-bearing plants average over 10 per 10 sweeps.  The action threshold should be lowered to 3 or more larvae per 10 sweeps on vegetative year fields.  Repeat treatment, if necessary.  More information may be found in the Wild Blueberry Fact Sheet No. 197 (UMaine Extension No. 2371), Blueberry Spanworm. Burn or fire pruning will also reduce likelihood of damaging populations.

Blueberry Flea Beetle

An action threshold of 50 insects per 10 sweeps has been established for either larvae or adults. Examine fields in early spring for larvae and from mid-June to early July for foliar feeding by adults.  Spray with an insecticide or biocontrol as needed.  More information can be found in Wild Blueberry Fact Sheet No. 200 (UMaine Extension No. 2372), Blueberry Flea Beetle. Burn or fire pruning will also reduce likelihood of damaging populations.

Thrips

When leaf curling occurs in a fruit bearing year, stake out infested area. The following spring, apply insecticide to the staked area before curling reoccurs. Make first application when leaves are 1/4 inch to 1/2 inch long. Repeat when 1/2 inch to 1 inch. These timings are critical. Yellow sticky cards may be used to monitor for blueberry thrips for more efficient timing of applications. A delayed burn in the fruit-bearing year may also be considered; see the cultural techniques section.

Refer to Wild Blueberry Fact Sheet No. 204 (UMaine Extension No. 2275), Integrated Crop Management Field Scouting: Guide for Lowbush Blueberries and Wild Blueberry Fact Sheet No. 202 (UMaine Extension No. 2373), Blueberry Thrips.

Blueberry Maggot

Monitoring for the presence of the blueberry fruit fly will indicate necessity for control based on trap capture threshold and, if needed, to ensure proper timing of insecticide applications. Refer to the blueberry maggot fly factsheet (Cooperative Extension Fact Sheet No. 201 (UMaine Extension No. 5030), Monitoring for the Blueberry Maggot) to learn about field perimeter treatments, spot treatments, and maintaining isolated fields on one production cycle.

Never apply insecticides when less than three to five percent of berries have ripened and turned blue. This is usually early July in most regions of Maine. Repeat applications, if necessary, depending on trap capture results.

Spotted-Wing Drosophila

The Spotted-Wing Drosophila (SWD) is an invasive non-native small vinegar fly with the potential to cause considerable fruit loss of wild blueberries especially at the end of the harvest season.  It was first detected in Maine in 2011. Unlike most other vinegar flies that require damaged fruit to attack, SWD causes damage when the female flies cut a slit and lay eggs in healthy fruit. Monitoring for the presence of the SWD requires a different trap, placement and timing than our native blueberry maggot fly. See Extension Fact Sheet: Spotted-Wing Drosophila Traps at Extension Fact Sheet: Spotted-Wing Drosophila Traps.

Apply insecticides using action thresholds. A threshold of an average of 0.5 cumulative male fly / trap is a very conservative threshold where the following week the expected probability of fruit infestation is expected to be 0.5%. A threshold of an average of 3.5 cumulative male flies / trap is a moderate risk threshold where the following week the expected probability of fruit infestation is expected to be 10%. A Threshold of an average of 7 cumulative male flies / trap is a higher risk threshold where the following week the expected probability of fruit infestation is expected to be 25%. These thresholds are based upon the use of 3 SWD traps along a blueberry field edge baited with sugar syrup and yeast (see recommendation table for SWD monitoring and for insecticide class).

All publications may be found on the Fact Sheets page of the Cooperative Extension: Maine Wild Blueberries website. Or by request from Cooperative Extension by calling 1.800.897.0757 x 1.

Cultural Techniques to Reduce Insect Infestation
More information may be found in Wild Blueberry Fact Sheet No. 253,
Cultural Management for Insects and Diseases in Wild Blueberries.
Insects Method Comments
Blueberry Maggot Harvesting Harvesting techniques that reduce fruit loss can minimize the number of infected fruit left on the plants and on the ground.
Management Keep isolated fields in the same cycle.
Winnower cleanup Compost, burn or dispose of winnower refuse.
Flea Beetle, Sawfly, Spanworm Fire pruning Blueberry litter must be ignited.
Thrips Fire pruning Burn curled stems as soon as extensive curling occurs in early spring, but not later than July 1 in a nonbearing crop or reduction in next year’s fruit buds will occur.
Spotted wing drosophila Early harvest Monitor adult and larval populations; Refer to Cooperative Extension Bulletin No. 210, Spotted Wing Drosophila: Pest Biology and IPM Recommendations for Wild Blueberries for additional information

 

Chemical Insect Control Methods for Wild Blueberries

Apply insecticides when monitoring indicates insect populations have reached threshold levels. See Wild Blueberry Fact Sheet No. 204 Integrated Crop Management Field Scouting Guide for Wild Blueberries for details.

Insect Material Rate
(Amount of product/acre)
Comments
Blueberry Maggot Malathion (malathion)

 

 

several formulations registered Maximum number of applications per year is three, and the minimum retreatment interval is five days. Reentry 12 hours, apply up to one day to harvest. Potential for phytotoxicity at lower gallons/acre.
Imidan 70-W (phosmet) 1.3 lb. Limit 5 applications/acre/year
Aerial ULV 2 gal/acre water.
Reentry 3 days, 3 days to harvest. Limit 5 lbs ai/acre/year.
Admire Prosystemic Protectant 4.6F (imidacloprid) 2.1 to 2.8 oz. 3 days to harvest; min. 7 days between applications. Max. 0.5 lbs ai/acre/year.

NOTE: Current research in the field suggests that there is little direct effect on bee survival at the colony level, but there is laboratory evidence that imidacloprid can enhance bee mortality due to interactions with other insecticides and fungicides.

Montana 2F; 4F (imidacloprid) 2F – 4.8 to 6.4 oz;
4F – 2.4 to 3.2 oz
3 days to harvest; min. 7 days between applications. Max. 0.5 lb ai/acre/year.

NOTE: see above

GF-120 NF Naturalyte Fruit Fly Bait (spinosad) ORGANIC 10 to 20 oz in a
1:1.5 (GF-120 NF:
water) dilution ratio
Use a large spray droplet size of 4000 to 6000 μm (4 to 6 mm) to optimize length of bait attractiveness and longevity in the field.
Asana XL 0.66EC (esfenvalerate) 4.8 to 9.6 oz. Reentry 12 hours; 14 days to harvest. Can act as a bee repellent, do not apply within 7 days of pollination. Max. 0.2 lb ai/acre per season.
Sevin 4 (carbaryl) 1.5 to 2 qts. Repeat as necessary up to 5 times but do not apply more than once every 7 days. 7 days to harvest. Max.10 qts/acre/year

OBSERVE BEE CAUTION.

Sivanto 200 SL (flupyradifurone) 10.5 to 14 oz. 3 days to harvest. Reentry 4 hrs. Max.0.365 lbs ai/acre/year. Apply at least 7 days apart.
Delegate WG (spinetoram) 3 to 6 oz. No more than 6 applications/yr. Minimum 6 day interval between applications. 3 days to harvest. Reentry 4 hours. Max. 0.305 lbs ai/acre/year.

OBSERVE BEE CAUTION.

Assail 30SG; 70WP (acetamiprid) 30SG – 4.5 to 5.3 oz.
70WP – 1.9 to 2.3 oz.
No more than 5 applications/yr not less than 7 days apart. 1 day to harvest. Reentry 12 hrs. Max. 0.5 lbs ai/acre/year.
Exirel (cyantraniliprole) 13.5 to 20.5 oz.

 

Do not apply prior to or during bloom, do not apply when bees are foraging. Rotate with products with different modes of action; minimum interval between treatments is 5 days. Reentry 12 hrs. 3 days to harvest. Do not exceed 0.4 lbs ai/acre/year.
Spanworm Larvae Imidan 70-W (phosmet) 1.3 lb. Organophosphate. Should be used on larger instar larvae. Apply at 7-10 day intervals. Aerial ULV 2 gal/acre water. Reentry 3 days, 3 days to harvest. Limit 5 applications/acre/year. Max. 5 lbs ai/acre/year.

OBSERVE BEE CAUTION.

Intrepid 2F (methoxyfenozide) 10-16 oz. Do not apply more than 0.75 lb ai/acre/year or make more than 3 applications per calendar year. Drift and runoff from applications of this product may be hazardous to sensitive aquatic invertebrates in water bodies adjacent to the treatment area.

Reentry 4 hrs. 7 days to harvest.  Minimum 7 day interval between applications.

Asana XL 0.66EC (esfenvalerate) 4.8 to 9.6 oz. Reentry 12 hours; 14 days to harvest. Can act as a bee repellent. Do not apply within 7 days of pollination. Max. 0.2 lb ai/acre per season.
Assail 30SG; 70WP (acetamiprid) 30SG – 4.5 to 5.3 oz.
70WP – 1.9 to 2.3 oz.
See notes on Assail under blueberry maggot.
Spanworn Larvae BIOCONTROL Entrust SC (spinosad) ORGANIC 4 to 6 oz. Reentry 4 hrs. 3 days to harvest.  Max. 0.45 lbs ai/acre/year.  Max. 6 applications/year. Minimum 6 day interval between applications.

TOXIC TO BEES UP TO 3 HOURS FOLLOWING TREATMENT.

(Bacillus thuringiensis) Several products and formulations registered Apply to small early instar larvae for best control. Larval death not immediate, but feeding quickly inhibited.

May use when bees are present.

Flea Beetle Imidan 70-W (phosmet) 1.3 lb. Organophosphate. Apply at 7-10 day intervals. Aerial ULV 2 gal/acre water. Reentry 3 days, 3 days to harvest. Limit 5 applications/ acre/year. Max. 5 lbs ai/acre/year.

OBSERVE BEE CAUTION.

Delegate WG (spinetoram) 3 to 6 oz. See Delegate comments under blueberry maggot.
Assail 30SG; 70WP (acetamiprid) 30SG – 4.5 to 5.3 oz.
70WP – 1.9 to 2.3 oz.
See Assail comments under blueberry maggot.
Flea Beetle BIOCONTROL BotaniGard
ES (Beauveria bassiana)
1/2 to 1 qt. Apply at 5-10 day intervals in evening. Flea beetle larvae only. Be sure no fungicide residues are in spray tank. May apply up to day of harvest. Best results occur when applications are made in the evening since sunlight kills the Beauveria spores over time.

May use when bees are present.

Entrust SC (spinosad)
ORGANIC
4 to 6 oz. Reentry 4 hrs. 3 days to harvest.  Max. 0.45 lbs ai/acre/year.  Max. 6 applications/year. Minimum 6 day interval between applications

TOXIC TO BEES UP TO 3 HOURS FOLLOWING TREATMENT.
Strawberry Rootworm Adults Imidan 70-W (phosmet) 1.3 lb. Organophosphate. Apply at 7-10 day intervals. Aerial ULV 2 gal/acre water. Reentry 3 days, 3 days to harvest. Limit 5 applications/ acre/year. Max. 5 lbs ai/acre/year.

OBSERVE BEE CAUTION.

Delegate WG (spinetoram) 3 to 6 oz. See Delegate comments under blueberry maggot.
Assail 30SG; 70WP (acetamiprid) 30SG – 4.5 to 5.3 oz.
70WP – 1.9 to 2.3 oz.
See Assail comments under blueberry maggot.
Strawberry Rootworm Adults BIOCONTROL Entrust SC (spinosad)
ORGANIC
4 to 6 oz. Reentry 4 hrs. 3 days to harvest.  Max. 0.45 lbs ai/acre/year.  Max. 6 applications/year. Minimum 6 day interval between applications

 

TOXIC TO BEES UP TO 3 HOURS FOLLOWING TREATMENT.

 

Spotted-Wing Drosophila Very Effective
Delegate WG (spinetoram) 3 to 6 oz. Spinosyn. No more than 6 applications/yr, Minimum 6 day interval between applications. Reentry 4 hours. 3 days to harvest. Max. 0.305 lbs ai/acre/year.
Imidan 70-W (phosmet) 1.3 lbs. Organophosphate. Apply at 7-10 day intervals. Aerial ULV 2 gal/acre water. Reentry 3 days, 3 days to harvest. Limit 5 applications/ acre/year. Max. 5 lbs ai/acre/year.
Mustang Maxx  (zeta-cypermethrin) 4 oz. Pyrethroid.  Reentry 12 hours. 1 day to harvest. Max 0.15 lbs ai/acre/year.  Min. 7 day interval between applications.
Effective
Malathion 8F
Malathion 8 Aquamul
(Malathion)
Up to 40 oz Organophosphate. Maximum of 2 applications and 5 lbs ai/acre/year. 1 day to harvest.

 

Entrust SC (spinosad)
ORGANIC
4 to 6 oz. Reentry 4 hrs. 3 days to harvest (1 day SWD; see supplemental label).  Max. 0.45 lbs ai/acre/year.  Max. 6 applications/year. Minimum retreatment interval is 6 days.
Exirel (cyantraniliprole) 13.5 to 20.5 oz. Reentry 12 hrs. 3 days to harvest. Do not apply prior to or during bloom; do not apply when bees are foraging. Rotate with products with different modes of action; minimum interval between treatments is 5 days. Do not exceed 0.4 lbs ai/acre/year.
Fair Effectiveness
Sevin 4 (carbaryl) 1.5 to 2 qts. Carbamate. Repeat as necessary up to 5 times but do not apply more than once every 7 days. Reentry 12 hrs. 7 days to harvest. Max.10 qts/acre/year.
Assail 30SG
(acetamiprid)
4.5 to 5.3 oz Neonicotinoid.  No more than 5 applications/yr. Min 7 days between applications. Reentry 12 hrs. 1 day to harvest. Max. 0.5 lbs ai/acre/year. Add 1 lb. sugar/acre in spray tank to enhance performance.
Montana 2F, 4F (imidacloprid) 2F – 4.8 to 6.4 oz

4F – 2.4 to 3.2 oz

Neonicotinoid. 3 days to harvest. Min 7 days between applications. Max. 0.5 lb ai/acre/year.

Add 1 lb. sugar/acre in spray tank to enhance performance.

Limited Effectiveness
AzaGuard, AzaSol (azadirachtinneem) Use label rates Effective under low to moderate SWD pressure. Once the SWD numbers build up, change to another compound.
Thrips Diazinon
(diazinon)
Several formulations registered Make 1st application when new emergent sprouts are 0.25 to 0.5 inch high, second application when sprouts are 0.5 to 1 inch high.
Malathion
(malathion)
Several formulations registered
Admire Prosystemic Protectant 4.6F
(imidacloprid)
2.1 to 2.8 oz. for sprout application during emergence  See comments under blueberry maggot.
Montana 2F; 4F (imidacloprid)

 

2F-4.8 to 6.4 oz; or

4F-2.4 to 3.2 oz for sprout application during emergence (see Diazinon application timing)

Sivanto 200 SL (flupyradifurone)  10.5 to 14 oz. 3 days to harvest. Reentry 4 hrs. Max.0.365 lbs ai/acre/year. Apply at least 7 days apart.

Follow ALL label directions.

  • Accurate identification of pests and monitoring to determine the best times to spray are critical for achieving effective, economical control.
  • Apply pesticides only when economic thresholds are exceeded, based on the monitoring.
  • Use caution while loading spraying equipment with pesticides. Follow all safety precautions.
  • Use common sense when applying pesticides. DO NOT contaminate nearby lands, buildings, water bodies, and roadsides. Keep domestic animals and children away from fields.
  • For detailed information on safe spray use, please refer to the Wild Blueberry Growers Guide.
  • Avoid aerial application of pesticides near buildings, public roads or water supplies or on windy days.
  • Reentry restrictions: never enter a sprayed area without protective clothing or until stated on the label.
  • Be sure your sprayer is well cleaned and does not have any fungicide residue when using Botanigard since fungicide will kill the living spores.

Protecting Honey Bees from Insecticides

  • Refer to Cooperative Extension Bulletin No. 2009, IPM Tactics to Reduce Pesticide Exposure to Honey and Native Bees for additional information.
  • All pesticides are not equally hazardous to bees. Select the one that is least hazardous. Commonly used insecticides are listed in the chart according to their relative hazards.
  • Do not apply insecticides near honey bee hives.
  • Treat plants ONLY before (check persistence for each insecticide, for instance, Phosmet is 7-10 day persistence) or after bloom, or when bees are not actively foraging in the crop (before or after bloom) and pruned fields.

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.

© 2019

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