Impact of precipitation on the performance of insecticides in blueberries
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Impact of Precipitation on the Performance of Insecticides in Blueberries. John Wise, PhD MSU Department of Entomology Trevor Nichols Research Center. Factors that Influence Pesticide Wash-off. Rainfall Characteristics Penetrative & Translocative Properties of the Compound

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Impact of precipitation on the performance of insecticides in blueberries
Impact of Precipitation on the Performance of Insecticides in Blueberries

John Wise, PhD

MSU Department of Entomology

Trevor Nichols Research Center


Factors that influence pesticide wash off
Factors that Influence Pesticide Wash-off in Blueberries

  • Rainfall Characteristics

    • Penetrative & Translocative Properties of the Compound

    • Insecticide Inherent Toxicity and Application Rate

    • Drying time, Persistence, and Additives

(image by Marlene Cameron)


Translocation and systemic mobility: in Blueberries

Translaminar -penetration of a foliar applied pesticide from the adaxial cuticular surface of the leaf, through the epidermis layer and distributing into the mesophyll on the abaxial side.

Acropetal - horizontal mobility in the plant xylem from central leaf tissue to the marginal ends.

Basipetal - movement of the insecticide within the phloem from the site of application in the downward direction.


Insecticide Penetration in Fruits in Blueberries

Penetration of the fruit cuticle follows the same process as described for leaves, but desorption into the epidermal cells of the hypanthium follows a simple diffusion process.



Insecticides tested
Insecticides tested in Blueberries









Insecticide comparison effect of rain
Insecticide comparison – effect of rain in Blueberries

Bushes were protected from rain or had 0.81 inches of rain 24 hours after application.

Protected from all other rainfall over 7 days.

Isaacs et al. 2012


Rainfastness rating chart general characteristics for insecticide chemical classes
Rainfastness Rating Chart in BlueberriesGeneral Characteristics for Insecticide Chemical Classes

  • H – highly rainfast (≤30% loss), M – moderate (≤50% loss), L – low (≤70% loss), S-systemic residues

  • Michigan Fruit Management Guide E154 http://bookstore.msue.msu.edu/


Blueberry Insecticide Precipitation Wash-off in BlueberriesRe-application Decision Chart:Expected cranberry fruitworm control in blueberries, based on each compound’s inherent toxicity to CBFW larvae, maximum residual, and wash-off potential from rainfall.

* Number of days after insecticide application that the precipitation event occurred.

X – Insufficient insecticide residue remains, thus re-application is recommended.


Blueberry Insecticide Precipitation Wash-off in BlueberriesRe-application Decision Chart:Expected Japanese beetle control in blueberries, based on each compound’s inherent toxicity to JB adults, maximum residual, and wash-off potential from rainfall.

* Number of days after insecticide application that the precipitation event occurred.

X – Insufficient insecticide residue remains, thus re-application is recommended.


Residue wash off profiles for imidan

(2 h drying) in Blueberries

(24 h drying)

Residue Wash-off Profiles for Imidan


Residue wash off profiles for assail
Residue Wash-off Profiles for Assail in Blueberries

(2 h drying)

(24 h drying)



Implications for insecticide performance
Implications for Insecticide Performance in Blueberries

  • Most compounds maintain good activity with up to 0.5 inch simulated rainfall (24 h drying), showing little need to immediately re-apply. Short-lived materials may require re-application when 0.5 in of rain occurs after 7 days of field aging.

  • Organophosphate insecticides appear to be most susceptible to wash-off, but high toxicity to the pest may compensate for residue loss.

  • Carbamate and pyrethroid insecticides are low-moderately susceptible to wash-off, and are generally short-lived, but in some cases inherent toxicity compensates for loss.

  • Neonicotinoid surface residues are susceptible to wash-off, but sub-surface residues remain stable. Longer drying periods before rainfall will allow maximum plant penetration and improve rainfastness.

  • IGR compound rainfastness is moderate to high up to 1 in rain.

  • The performance of Spinosyn and Diamide compounds appear to be the least affected by precipitation, with rainfastness ranging from moderate to high up to 1 inch of rainfall.

  • Adjuvants can improve pesticide deposition and rainfastness.