ABSTRACT

The African sweetpotato weevil (Cylas puncticollis Boheman) is one of the most important insect pests of sweetpotato in Africa. It ranks the number one constraint to sweetpotato production in Nigeria. A field study was conducted at the National Root Crop Research Institute Umudike, Abia state during 2015 and 2016 cropping seasons to evaluate the effect of intercropping three varieties of sweetpotato (UMUSPO-1, UMUSPO-3 and BUTTERMILK), with hot pepper (Capsicum frutescens Linn) on the management of sweetpotato weevil (C. puncticollis).The experiment consisted of three different intercropping patterns (i) sweetpotato intercropped with pepper using  earthing up at 0 level, 2 levels and 3 levels, (ii) sweetpotato intercropped with pepper using three different pepper population densities (1m x 1m, 1m x 0.5 m and 1m x 0.25m) and (iii) sweetpotato intercropped with pepper using different times of introducing pepper i.e planting same time with sweetpotato, 2 weeks and 4 WAP, 2 weeks and 4 weeks before planting sweetpotato. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replicates. The plot size was 18m². Parameters evaluated were weevil population density, marketable and unmarketable weight of crop, crop yield, root damage, root weight, yield loss, percentage colonization and number of roots produced. Result from the studies indicated that lower insect pest populations were recorded in the intercrop plots (0.22,0.70, 0.80, 0.88, 0.99, 1.05, 1.22 ) than sole crop plots (1.64, 1.77, 1.95, 2.03, 2.09,  2.17, 2.31, ) in both cropping seasons. Results showed that intercropping with earthing up at 2 and 3 levels, using higher pepper population densities of 20,000 and 40,000 plants per hectare and introduction of  pepper 2 and 4 weeks before planting sweetpotato were significant (P ≤ 0.05) in lowering the weevil population (0.22, 0.99, 0.70, 0.80, 0.88, 0.07, 1.05 ) and also gave lower unmarketable yields of sweetpotato roots (0.00, 0.02, 0.03, 0.09, 0.16, 0.,0.08, 0.11) lower colonization (5.50, 6.20, 7.70, 8.20, 15.40,16.20, 10.20,)  and lower yield loss (1.00, 6.30, 0.70, 3.20, 3.60, 4.30, 7.80,) of sweetpotato roots than the sole crops  (2.05, 0.77, 57.0, 41.8, 66.10, 25.4). Higher unmarketable roots, higher root damage, higher colonization and higher yield losses were recorded in the sole crop plots and also when intercropped with no earthing up, when pepper was planted using a lower population density of 10,000 plants per hectare (1m x1m) and when sweetpotato was planted 2 and 4 weeks before pepper. Generally, higher marketable yields were recorded in the intercrops than the sole crop plots. Result from the study also indicated that intercropping did not affect the yield of sweetpotato hence some of the intercrop plots recorded higher root number (61.00, 57.00, 84.00, 50.30, 40.30) and root weight (5.85, 3.22, 5.78, 9.71, 7.81, 4.05) similar to the sole crops. Results from the studies revealed the potential of sweepotato and pepper intercrop with earthing up at 2 and 3 levels, using higher pepper population densities (20,000 and 40,000 plants per hectare) and introducing pepper 2 and 4 weeks before sweetpotato in the management of sweepotato weevil. Hence, the recommendation to resource poor farmers for effective control of sweetpotato weevil especially during dry seasons when the insect pest infestations are more prevalent in addition to reducing the cost of production of sweetpotato and increase food production in Nigeria.