Laboratory evaluation of toxicity of <i>Bacillus thuringiensis</i>, neem oil and methamidophos against <i>Plutella xylostella</i> L. (Lepidoptera: Plutellidae) larvae

Abstract

Diamondback moth (DBM), Plutella xylostella (L.), remains a major pest of brassica crops worldwide. Chemical control of this pest remains difficult due to the rapid development of resistance to insecticides and to their effect on natural enemies. The objective of this study was to assess the toxicity of Bacillus thuringiensis (Bt), neem oil and methamidophos on larvae of P. xylostella under laboratory conditions. Leaf-dip bioassay for DBM larvae was used to assess mortality. For each treatment, three doses (low, medium and high) were applied on cabbage leaves and presented to third instar larvae. Larval mortality was performed every 24 hours for a period of eight days. The application of the three dosages of Biobit was more effective against P. xylostella larvae when compared to the other treatments. However, there was no significant difference in larval mortality when all three doses of Biobit were tested compared to the control. Methamidophos was the least toxic treatments with high dosage recording the lowest mortality rate of 52.5%. These results showed that Btbased biopesticides and neem extracts could be of help, but their deployment should be part of an integrated pest management package, which recognizes the constraints of farmers while addressing the requirement to control of P. xylostella populations.

Evaluation of some microbial agents, natural and chemical compounds for controlling tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

“…Effects of different natural control agents (A-B) against tomato leaf miner, Tuta absoluta humidity (Khidr et al 2013). Sow and Diarra (2013) reported that Bt alone is not highly effective as a control measure of lepidopterous pests but it can help and complement integrated control measures.…”

Effects of the BioArt product on the dynamics and incidence of major cabbage pests

“…This population decline may be related to the formation of mature cabbages that would not be preferred as laying substrates by females. Indeed, the evolution of cabbage is inversely proportional to the glucosinolates content of the plant and this could be a factor limiting egg laying (Sow et al, 2013). These observations show that the abundance of P. xylostella depends not only on the treatment of the plots but also on the development stage of plants (Ngom et al, 2020).…”

“…The possibility of growing it all year round, both in dry and rainy seasons, makes it possible to fund other activities and/or other crops (AUMN, 2009). Unfortunately, this crop is very susceptible to attacks from several insects and pathogens (Sow et al, 2013;Labou et al, 2016;Labou et al, 2017).…”

“…Different active substances are used alone or in mixture to control cabbage pests (Sow et al, 2013).…”

“…Pesticides used in excessive or unsuitable amounts, including broad-spectrum insecticides, are the source of contamination of vegetable products, particularly cabbage (Sow and Diarra, 2013;Tendeng et al, 2017).…”