Abstract:
Tomato is one of the most important vegetable crops grown in Ethiopia. Its production is
constrained by arthropod pests and diseases. Fruit borer (Helicoverpa armigera), Whiteflies
(Bemisia tabaci), Aphids (Aphis spp), leafminer (Tuta absoluta), Serpentine leafminer
(Liriomyza sp), Thrips sp and two spotted spidemites (Tetranchus urticae Koch) are the major
economic pests recorded in the study area. The research was initiated to evaluate the potential
of intercropping and plant extract to reduce pests on tomato and their associated natural
enemies using irrigation systems from January to May 2021 at Haramaya University, Rare
research station. The treatments, tomato - onion (Allium cepa L.), tomato - head cabbage
(Brassica Oleracea), tomato - common bean (Phaseolus vulgaris) intercropping and sole
tomato(control), tobacco (Nicotiana tabacum) leaf extract, and Karate 5% EC (Standard
check) were used. The experiment was laid out in a randomized complete block design
(RCBD) with four replications. Tobacco leaf extract was applied weekly for eight times
whereas karate 5%EC was applied at ten days interval for six (6) times until the first fruit
harvest. The data on the population of the insect pests were recorded weekly starting on the
21st day after transplanting for eight (8) weeks. The parasitoids population was recorded from
samples in the laboratory after their emergence from the host. The over all result indicated
that all intercropping systems and tobacco leaf extract significantly (P < 0.05) reduced the
population of these insect pests compared to sole tomato. The highest population reduction
was recorded on tobacco leaf extract followed by tomato – onion. The companion crops
harbored the parasitoids of diverse species in the highest level, but tobacco extract was
comparable to untreated control. Tomato onion intercropping and tobacco leaf extract raised
the best economic performances upon high net benefits and benefit cost ratio. Therefore,
tomato onion intercrops and tobacco leaf extract can be used as the first options in boosting
tomato production as an alternative to karate 5%EC. Further study on the mechanisms of the
effectiveness of botanical extracts with rate and frequency and also intercropping and detailed
morphological and molecular-based parasitoid species identification and their ecological host
ranges are of utmost importance in the sustainable IPM strategies in tomatoes
