Darussalam, Singapore, Thailand, and other AMS, whereby results were available from Thailand by the time of writing of this document. A brief summary is given in Box 2. 35 Box 2: Field trial on management of flea beetle with biocontrol agents A replicated field trial to evaluate the effectiveness of two BCA against flea beetles, namely the nematode Steinernema carpocapsae (produced by DOA, Thailand) and the beetle-specific microbial Bacillus thuringiensis var tenebrionis (Valent BioSciences), was conducted during the dry season in a Chinese cabbage field of about 0.2 ha in a vegetable growing area of Chiang Rai, Thailand. This area was under the management of the Royal Project Foundation, and the field trial was implemented as cooperation between the Royal Project, the DOA, and the project ‘ASEAN Sustainable Agrifood Systems (ASEAN Biocontrol)’. Farmers had reported that his area shows heavy infestations with flea beetles: this was confirmed as high numbers of flea beetles (here: Phyllotetra striolata) were already present when the cabbage seedlings were planted in the field. The main purpose of the trial was to compare larvicidal treatments (both BCA target the larvae of the flea beetle and are applied to the soil) with farmers’ practice, which consisted of the application of broad-spectrum synthetic pesticides that targeted the adult beetles only. While synthetic pesticides were applied six times (and as a mix of various active ingredients) during the 1.5 month-long growing period, nematode and Bt var tenebrionis applications were restricted to four and three applications, respectively. Untreated plots served as true negative controls. The results of the trial showed that both BCA significantly improved root development (weight) of Chinese cabbages during the early weeks of growth, while total plant weight was similar in all treatments. However, once the plants’ biomass extended beyond 600 g, development of the negative control plants significantly lagged behind when compared to the other treatments. Damage to cabbage leaves was high across all treatments due to the fact that adult beetles were highly mobile and able to fly to neighbouring plots. At harvest, Chinese cabbages grown on the negative control plots showed a significantly higher proportion of undeveloped heads (loss) and a significantly lower mean total weight of marketable cabbages when compared with plants treated with BCA or synthetic pesticides. Furthermore, in the two marketable cabbage categories 1 and 2 BCA-treated plots produced significantly more heads than those treated with synthetic pesticides. Cost-benefit analysis revealed that application of Bt var tenebrionis was economical in comparison to synthetic pesticides. In the case of the latter total input costs (including fertiliser) were too high, which generated a loss of income during that season. The trial was replicated in the wet season. Because flea beetle numbers and the associated damage were much lower than in the dry season, insect management was generally uneconomic. Profits at harvest could only be realised under the conditions of the negative control, i.e. by avoiding inputs for insect management (and reducing fertiliser inputs). In conclusion, both BCA applications helped farmers to achieve better harvesting results when compared to no pest control and synthetic insecticides in the dry season. These experiences also underline the necessity to keep an eye on the economic aspects of farming. Because farmers in that area plant cabbage in a row most of the time, they maintain high levels of the insect pest, particularly in the dry season. Better crop rotation would certainly improve the situation while further reducing input costs.
Implementing Biological Control Agents in the ASEAN Region
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