Integrated control of thrips in vegetables in eastern Africa - icipe

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• Thrips Identification software was provided to the partner institutes and quarantine organizations. NaCRRI, Uganda contributes to the output 1; While KARI contributes to output 2 and 4. 9. Achievements and Constraints 9.1. Output 1: Identity, importance and distribution of major plant infesting thrips studied in Kenya and Uganda. Information on the thrips fauna and their importance in East Africa is very scarce. This information is very important to prioritize the key pest thrips and target vegetable crops for formulation of region specific and species specific management strategies. In this regard a nationwide survey on thrips fauna associated with key vegetables and their associated plants were initiated in August, 2008 in Kenya. Over 60 locations covering 12 districts distributed within five provinces (Nairobi, Central, Eastern, Rift Valley and Western Provinces) in Kenya and in Kampala, Uganda were surveyed. More than 2100 thrips specimens have been collected, slide mounted, identified and a database established. The important thrips species in terms of abundance, encountered in the survey were onion thrips, Western flower thrips, tomato thrips, Ceratothripoides sp. and Bean flower thrips. Apart from the important species listed above more than 20 terebrantian and many tubelliferan thrips were observed. Onion thrips (Thrips tabaci, Lindeman 1988) was abundant both in the highlands (Gilgil, Naivasha and Lari) and in upper midlands (Kajiado and Nairobi), and less abundant in lowlands of Yatta in Kenya and Namulonge in Uganda. T. tabaci was a key pest of onion and cruciferous vegetables. This species was collected from more than 44 host plant species belonging to 15 families. Western Flower thrips (Frankliniella occidentalis, Pergande, 1895) was distributed in most of the locations surveyed however they were quiet abundant in the highlands of Gilgil, Naivasha and Lari divisions as compared to the lowlands (Yatta and Namulonge). The western flower thrips was a key pest in French beans and tomato. This species was collected from more than 47 host plant species belonging to 18 families. Tomato thrips (Frankliniella schultezi, Trybom, 1910) is native to this region and it was distributed in most of the locations surveyed it was more abundant in the lowlands of Yatta and Namulonge as compared to the highlands. This species is widely found on French bean, potato and cucurbits. It was observed in more that 52 plant species belonging to 21 families. Ceratothripoides sp. was widely distributed in Embu, Kenya and in lowlands such as Athi River in Kenya and Namulonge in Uganda. However it was significantly absent in the highlands of Naivasha, Gilgil and Lari. This species was predominantly observed in solanaceous crops like tomato, potato and eggplant, African nightshade etc. It was observed in 23 plant species belonging to 15 families. Incidentally this native species has been intercepted by UK plant health Inspection service from Karela exported from Kenya and notified in the EPPO in 2005. The Bean Flower thrips (Megalurothrips sjostedti, Trybom, 1908) was widely distributed in lowlands as compared to the highlands. The BFT was observed in more than 32 plant species belonging to 14 plant families. This species as reported earlier was predominantly observed in fabaceous crops such as French bean, common bean, broad bean, lablab etc. Among the other species observed in the survey, the chilli thrips, Scirtothrips dorsalis was found to be distributed in the lowlands on chillies, capsicum and bitter gourd. Specimens have been sent to Dr. Moritz for confirmation of identity. Incidentally this species again is an invasive species with South Asia as the centre of origin. This pest again was intercepted in 2003 by the UK plant quarantine from bitter gourd exported to UK from Kenya. However no information on the distribution of this pest exists in Kenya. More detailed survey on host plants and distribution of this species is needed. Predatory thrips (Aeolothrips sp.), parasitoids and pirate bugs were the commonly encountered natural enemies however less abundant. Surveys in the next 6-10 months will cover the Coast, Nyanza, Western, Rift valley and Eastern provinces in Kenya and more locations in Uganda.
9.2. Output 2: Field ecology and dispersion of Frankliniella occidentalis studied on French beans in Kenya Western flower thrips probably invades fields from infested plants in neighboring fields and field margins. However, detailed knowledge on the spatial pattern of the invasion as well as on the secondary spread in the field and influence of abiotic and biotic factors is not available. Experiments within this output will address some the above research gaps and it will form a part of a Ph. D student thesis jointly supervised by partners in University of Hannover. A Ph. D student identified from Hannover participated in the planning meeting organized July 2008. However the student subsequently declined to take up the offer. In this regard, prospective students from Kenya and Uganda were screened and a student from Kenya has been selected in consensus with partners in Hannover. The student joined the program in January 2009. The second draft of the research proposal has been submitted for review by the supervisors in Hannover and icipe. Large –scale and small scale farm fields have been identified in Thika and Embu to evaluate the population dynamics of thrips in French bean over seasons. Surveys on the thrips diversity in Kenya have revealed regional differences in distribution of key pest thrips. Evaluation of the population dynamics over different seasons will provide us information on the seasonal variations. It will also enable us to understand the influence of large-scale, high intensive and less diverse farming system as compared to small-scale, low intensive and diverse farming system. Field experiments to evaluate the population ecology and dispersion of WFT have been initiated in the KARI, Embu in December, 2009. The influence of intercrops such as baby corn, sunflower and potato on dynamics of thrips population on French bean will be simultaneously evaluated. 9.3. Output 3: Metarhizium-based control product developed. Beauveria bassiana and Metarhizium anisopliae are potential microbial control agents that can be utilized for management of thrips. Previous studies at icipe have led to the identification of a virulent isolate of Metarhizium anisopliae (icipe69) against the bean flower thrips. Its efficacy has been proven in the field against flower thrips, the onion thrips, the western flower thrips in cut flower and runner bean, and at less extent against the western flower thrips on French bean. A Ph.D student joined the ARPPIS programme in October 2008 to undertake activities pertaining to this output. The student has submitted the first draft of the proposal for review by the icipe’s supervisors. The student has already started culturing fungal isolates from the icipe’s Arthropod Germplasm Centre and initiated bioassays against the WFT. Eight isolates of M. anisopliae and 7 isolates of B. bassiana are ready so far for screening. Virulent B. bassiana isolates will be further screened for their endophytic properties in selected host plants. 9.4. Output 4: Additional environmentally friendly control options tested in the greenhouse and field and IPM strategy developed. Green house experiments have been initiated in December 2009 for evaluation of botanical pesticides such as neem, pyrethrum and garlic extracts for the management of WFT. Both soil and foliar application of the above botanicals are evaluated. Further laboratory bioassays will be conducted to screen for effective botanical pesticides. Effectiveness of plastic mulches and live mulches for management of thrips will be evaluated in small scale field trials to be established by Feb 2009. Based on the outcome of the above experiments, field trials with French bean to evaluate the best treatments will be initated by June 2009. Role of intercropping French bean with babycorn, sunflower and potato for the management of western flower thrips will be evaluated, simultaneously with the field ecology experiments.
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Integrated control of thrips in vegetables in eastern Africa - icipe

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