Assessing the potential impact of biological control of Plutella xylostella (diamondback moth) in cabbage production in Kenya

Abstract

This study assessed the potential economic impact of the introduction of Diadegma semiclausum, an exotic parasitoid of the diamondback moth (Plutella xylostella, DBM), on cabbage production in Kenya. The study first established yield losses caused by DBM through two methods: measurements from farmer-managed fields and through farmers' interviews. Crop losses were calculated at 31% from farmer-managed fields, and at 36% from farmer interviews. With a crop loss of 31%, yield loss was estimated at 6.8 tons/ha or US$ 452.9/ha, and at US$ 7.9 million per year for the whole country. Control costs as provided from the interviews, amounted to US$ 118.9/ha. The project costs amount to a net present value of US$ 1.2 million. Based on an annual cabbage production of 256,524 tons, a cabbage price of US$ 66.3/ton, a 30% abatement of yield losses, a 7.9% reduction in cost of production, a supply and a demand elasticity of 0.9 and −1.4 respectively, and an annual increase of consumption of 2.6%, the economic surplus produced by the release of the parasitoid was estimated at US$ 28.3 million for 25 years. Consumers were estimated to get 58% of the benefit and producers 42%. The benefit-cost ratio was estimated at 24:1, with an internal rate of return of 86%, indicating a high return to the investment.

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

“…The use of synthetic organic insecticides is the main method of control against this pest (Furlong et al, 2013). These insecticides can cause several consequences such as the elimination of natural enemies, the increased cost of production, emergence of resistant strains, environmental and health problems (Hooks and Johnson, 2003;Macharia et al, 2005;.…”

Efficacy of Cymbopogon Schoenanthus L. Spreng (Poaceae) Extracts on Diamondback Moth Damaging Cabbage

“…DBM larvae are very difficult pests to control [15] and therefore, are the greatest threat to crucifer production in many parts of the world. The losses can reach the 90% [13,16]. This explains the large use of insecticides in crucifer production.…”

“…Owing to its polyvoltine characteristics and serious overlap of generations, this pest can easily develop resistance to various kinds of insecticides [17][18][19], including biological one such as Bacillus thuringiensis [20][21][22], and particularly in sub-tropical and tropical countries [23]. To overcome resistance, farmers resort to increasing frequency and rates of pesticide applications and to mixed cocktails of pesticides [16]. In addition, the information about the chemical composition of these pesticides is not always publicly available [24].…”

Spatiotemporal distribution and impact of diamondback moth parasitoids in the Dakar Niayes in Senegal

“…Additionally, pesticides may have a negative impact on insect biodiversity with a reduction of natural enemies (Furlong et al, 2012), an impact on the healf of users and consumers an increase of production costs (Chilcutt and Tabashnik, 1997) and a risk of appearance of resistant strains (Hooks and Johnson, 2003;Macharia et al, 2005;Shelton et al, 2007;Huang et al, 2010). Because of the negative aspects, alternative methods are needed.…”