Abstract
Chrysodeixis chalcites, an important pest of banana crops on the Canary Islands, is usually controlled by chemical insecticides. The present study aimed to evaluate the efficacy of the most prevalent isolate of the Chrysodeixis chalcites nucleopolyhedrovirus (ChchNPV, Baculoviridae) as a biological insecticide. Overall the prevalence of ChchNPV infection in C. chalcites populations was 2.3% (103 infected larvae out of 4,438 sampled), but varied from 0–4.8% on Tenerife and was usually low (0–2%) on the other islands. On Tenerife, infected larvae were present at 11 out of 17 plantations sampled. The prevalence of infection in larvae on bananas grown under greenhouse structures was significantly higher (3%) than in open-field sites (1.4%). The ChchNPV-TF1 isolate was the most abundant and widespread of four genetic variants of the virus. Application of 1.0x109 viral occlusion bodies (OBs)/l of ChchNPV-TF1 significantly reduced C. chalcites foliar damage in young banana plants as did commonly used pesticides, both in greenhouse and open-field sites. The insecticidal efficacy of ChchNPV-TF1 was similar to that of indoxacarb and a Bacillus thuringiensis (Bt)-based insecticide in one year of trials and similar to Bt in the following year of trails in greenhouse and field crops. However, larvae collected at different time intervals following virus treatments and reared in the laboratory experienced 2–7 fold more mortality than insects from conventional insecticide treatments. This suggests that the acquisition of lethal dose occurred over an extended period (up to 7 days) compared to a brief peak in larvae on plants treated with conventional insecticides. These results should prove useful for the registration of a ChchNPV-based insecticide for integrated management of this pest in banana crops on the Canary Islands.
Highlights
Banana is the main crop on the Canary Island archipelago, covering an area of about 9,000 hectares and a total production of 381,983 tonnes in 2015 [1]
A total of 4,438 larvae were collected from greenhouse and open-field banana crops, across 30 different sites on the islands (Table 1)
The present study aimed to evaluate the natural diversity of ChchNPV on the Canary Islands and the efficacy of this virus to control C. chalcites populations on young banana plants both in greenhouses and open-field trials
Summary
Banana is the main crop on the Canary Island archipelago, covering an area of about 9,000 hectares and a total production of 381,983 tonnes in 2015 [1]. The tomato looper, Chysodeixis chalcites is a noctuid pest of bananas in the Canary Islands [2, 3]. Larvae often feed on banana fruit, causing damage to the epidermis that greatly reduces the market value of damaged fruit [3]. Control of this pest mainly involves the use of pesticides [2,3,4]. IPM is an ecologically based pest control strategy that favors natural mechanisms of pest control with minimal disruption from broadspectrum pesticides [7, 8]
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