Balochistan is an introverted province of Pakistan where most of the farmers are illiterate and rely on insecticides alone for controlling insect pests. Onion is a major cash crop in Balochistan Pakistan. Thrips are the main problem on onions. Pollution and health hazards can be avoided by the minimal use of insecticides. Other control measures like cultural and botanical insecticides should be tested in the region against onion thrips. Work of this aspect has not been reported
Six different experiments were conducted in this research project in onion ecosystem to get the details of onion cultivation and pest management with emphasis on thrips control other than insecticides
A survey was conducted to evaluate the importance, agronomic practices, irrigation, plant protection activities and economic status of onions in Balochistan. One hundred and eighty onion growers / professionals from all six divisions (counties) of the province (State) were interviewed through a formatted questionnaire, at their doorsteps. The survey revealed that the crop plays an important role the economy of the province and that 100% of the respondents of the region cultivate onions because of its economic importance. Kalat and Quetta are the two main divisions in the province for the production of onions. An average of 0.49 ha is under onion cultivation by each farmer in the province. The maximum average onion cultivated area and yield was reported from the Kalat division as 3.09 ha and 17758 kg ha-1 respectively. The Kalat and Nasirabad divisions have the youngest farmers (<35 years). Farmers are generally between 36-50 years of age in Quetta and Zhob divisions. Sibi and Makran have the oldest farmers () 50 years old). Commonly Sariab Surkh Local and Chiltan-89 onoin cultivars are gowin w=th a broadcast method a seed rate range of 12-16 kg ha-1. Fertilizer is applied in the Kalat Quetta and Zhob divisions while pesticides are used in the Kalat Quetta Nisarabad and Zhob divisions. The crop is irrigated 16-30 (minimum to maximum) times. Irrigation water thrips (Thrips spp.) attack and the presence of weeds are the major reported problems associated with onions in the province. Control of weeds is done by hand weeding in all divisions. The best cost/benefit ratio (1:4-49) is reported from Nisarabad and the least (1:2.60) from the Makran division.
Six onion cultivars (Red Creole Chiltan-89, Local Sariab Surkh, White Globe and Local Kandhari) were evaluated against thrips infestations to determine varietal resistance. The results of the trial showed infestations that thrips tabaci Lindeman (thysanoptera: Thripidae) is the species attacking onions in the region. T. tabaci infested more or less all varieties. The local Kandhari follwed by Sariab Surkh was the most susceptible variety to thrips infestation and showed maximum succulency (95.37 & 92.17% respectively). Chiltan089 was the least succulent variety with 92.02% Red Creole and White Globe varieties were discarded due to their poor growth and yield performance. Both are Short day varieties not suited to the region. The maximum yield (11130 kg ha-1) was obtained by Chiltan-89 and the minimum by Sariab Surkh and Local Kandhari (3537 & 3812 kg ha-1 respectively). The thrips population got its peak (15.42 thrips desities per plant) at 27.94 C and 36.33% relative humidity (RH) in the month of August.
Five row spacing (20,25,30,35 and 40 cm) with a constant (20cm) plant-to-plant distance were tested to evaluate the effect of inter row spacing of onion plants against thrips populations. An inverse relation was found between increased row spacing and thrips density. The maximum mean number of thrips (8.25 per plant) was recorded on the plants cultivated in rows 20cm apart, these plants had a minimum yield of 19090 kg ha-1. The minimum mean number of thrips (4.66 and 5.78 per plant) was recorded from T5 (40 cm RxR distance) and T4 (35 cm RxR distance) with 21130 and 21340 kg ha-1 yield respectively. The optimum number of thrips(6.02 per plant) was recorded on plants cultivated in rows 30 cm apart with a maximum yield of 26160 kg ha-1.
A synthetic insecticide (Monocrotophos 40 WSL) and three botanical treatments (Datura alba Seed Extract infusion FEI) were used against onion thrips on onions. All of these insecticides caused mortality of onion thrips at various degress of significance over the untreated control. C. procera Li, was the best botanical insecticide giving 43.88% thrips control, Monocrotophos gave 77.65% mortality of onion thrips. D. Alba SEI and C. colocynthus FEI gave minimal (21.33 and 6.43%) control respectively. The results encourage the idea of pollution free methods of pest control.
Besides onion T. tabaci was also discovered from 35 cultivated and 21wild plant species from the onion-ecosystem of the region.
This research concludes that Chiltan-89 should be recommended for commercial cultivation in rows 30 cm apart with a 20cm plant-to-plant distance. The application of 150-100-100 kg ha-1 NPK is the best fertilizer rate for the crop. Calotropis procera Latex Infusion, LI is currently the best botanical insecticide for use in onion thrips Integrated Pest Management (IPM) programmes.