Written by Louis Nottingham, May 2021
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.
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).
Table 1. Conventional Spray Contact Bioassay
|Trt.||Per 100 gallons|
|Malathion 5EC||44.8 fl oz|
|Bexar||27 fl oz|
|Transform WG||2.75 oz|
|TetraCURB conc.||256 fl oz|
|Table 2. Organic Spray Contact Bioassay|
|Trt.||Per 100 gallons|
|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.
Funding: This work is part of a two year grant funded by the Washington Tree Fruit Research Commission and Oregon Sweet Cherry Commission.
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