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Evaluations of Conventional and Organic Insecticides Against Leafhoppers: First Year Results

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Written by Louis Nottingham, May 2021

Introduction:

Prior to this project, there was no available experimental information on insecticide toxicity against X-disease vectors Colladonus Reductus and C. geminatus (Fig 1). In 2020 we performed lab bioassays to screen various insecticide products against the most abundant of these two species in Washington cherries, C. reductus. Below are summaries of the most reliable results for organic and conventional insecticides. We will continue these screenings in 2021, with added focus on residue degradation and strategic spray timings.

leafhoppers
Fig 1. Primary leafhoppers vectoring of X-disease in Washington and Oregon cherries, A) Colladonus reductus and B) Colladonus geminatus.

2020 Contact Spray Bioassay Methods. C. reductus were collected in commercial cherry and apple orchards and returned to the lab. Arenas were constructed using 8 oz plastic deli cups with slightly moistened soil and excised cherry leaves (Fig. 2). Five to nine C. reductus were moved into each arena, then sealed with a plastic lid with a mesh cutout. Once leafhoppers were in all arenas, insecticides were applied using hand-pump aluminum spray bottles, sprayed through mesh lids to contact the leafhopper, leaf, and soil. Containers were then stored in a greenhouse prior to evaluation. After 24 hours, leafhoppers were rated as either alive, dead, or moribund (sick).

Fig. 2. Leafhopper bioassay arena (lid not shown).

 

Table 1. Conventional Spray Contact Bioassay

Trt. Per 100 gallons
UTC
Malathion 5EC 44.8 fl oz
Bexar 27 fl oz
Actara 2.75 oz
Transform WG 2.75 oz
TetraCURB conc. 256 fl oz

 

Table 2. Organic Spray Contact Bioassay
Trt. Per 100 gallons
UTC
TetraCURB organic 2%
Cinnerate 60 fl oz
Entrust SC 8 oz
Neemix 4.5 16 fl oz
Azera 56 fl oz/acre
Pyganic 1.4 EC 64 fl oz

 

Results and Discussion:

Five insecticide materials achieved 100% mortality of C. reductus: 3 conventional, Asana (esfenvalerate), Actara (thiamethoxam), and malathion; and 2 organic, Pyganic (pyrethrins) and Azera (pyrethrins and azadirachtin). For the premix product Azera, the pyrethrins component is likely “pulling the weight”, because azadirachtin alone (Neemix) resulted in average mortality. Transform also resulted in high mortality at ca. 90%. Although these data are preliminary, they will help guide future research and provide initial information to growers for decisions making. Our future research will continue to identify effective and ineffective products, while looking deeper into residue decline and strategic spray timings. Additionally, it will be useful to develop assay methods for longer-running experiments testing selective insecticides such as IGRs against eggs and nymphs.

Fig. 3. Conventional Insecticides. Bars show average leafhopper mortality resulting from each insecticide. Bars not sharing a letter are significantly different according to Tukey’s HSD (P < 0.05)

 

Fig. 4. Organic Insecticides. Bars show average leafhopper mortality resulting from each insecticide. Bars not sharing a letter are significantly different according to Tukey’s HSD (P < 0.05)

 

Funding: This work is part of a two year grant funded by the Washington Tree Fruit Research Commission and Oregon Sweet Cherry Commission.

Use pesticides with care. Apply them only to plants, animals, or sites listed on the labels. When mixing and applying pesticides, follow all label precautions to protect yourself and others around you. It is a violation of the law to disregard label directions. If pesticides are spilled on skin or clothing, remove clothing and wash skin thoroughly. Store pesticides in their original containers and keep them out of the reach of children, pets, and livestock.

YOU ARE REQUIRED BY LAW TO FOLLOW THE LABEL. It is a legal document. Always read the label before using any pesticide. You, the grower, are responsible for safe pesticide use. Trade (brand) names are provided for your reference only. No discrimination is intended, and other pesticides with the same active ingredient may be suitable. No endorsement is implied.

For more information including efficacy charts

X-disease phytoplasma (Western X)

Contact


Louis B. Nottingham, Ph.D.

Research Assistant Professor
WSU – TFREC
louis.nottingham@wsu.edu

 

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