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The efficacy of spot spray and cover spray applications of Metarhizium anisopliae (Metsch.) Sorok. in combination with the thrips attractant Lurem-TR (methyl-isonicotinate) was compared in field experiments for the management of bean flower thrips (BFT), Megalurothrips sjostedti (Trybom), on a cowpea crop in two seasons (June-December 2014). Treatments were applied five days after the placement of Lurem-TR in the field. During the first season, BFT densities per plant 5 days post-application were lower in spot spray (10.1 ± 4.3) and cover spray (11.5 ± 4.8) treatments than in the control treatment (41.8 ± 15.2). In the second season, 5 days post-application, the spot spray treatment recorded the lowest BFT density of 32.5 ± 6.0, followed by cover spray with 40.9 ± 7.0 thrips. The control treatment recorded the highest BFT density of 67.4 ± 10.3 5 days post-application. Conidial viability and thrips conidial acquisition did not differ between the two application methods. Grain yields of 1430.7 ± 114.2 kg and 1312.1 ± 87.7 kg were obtained in the cover and spot spray treatments, respectively, while 976.8 ± 105.2 kg in the control during the second season. The cost benefit analysis indicated profits with the spot spray than cover spray application due to the reduction in labor and the quantity of inoculum used. Spot spray application of biopesticides could therefore be a viable option for small-scale farmers for the management of BFT on cowpea.

The effect of host plant resistance on growth and developmental parameters of the bean flower thrips Megalurothrips sjostedti Trybom was determined on nine cowpea ( Vigna unguiculata {L.}Walp.) cultivars under laboratory conditions. Newly emerged adults M. sjostedti were confined on peduncles with floral buds of the different cowpea cultivars. M. sjostedti suffered 100% pre-imaginal mortality on cowpea lines Moussa local, TVu1509, TVx3236, Sewe and Sanzibanili. Antibiosis is believed to be the mechanism of resistance operating in these cultivars. On KVx404-8-1, M. sjostedti had a prolonged developmental period though not significantly different from Vita 7, the susceptible check at P M. sjostedti with the suitability index (growth index) not significantly different from the susceptible check (Vita 7) at P

Studies were carried out in eastern Uganda to assess the effect of legume flower thrips ( Megalurothrips sjostedti ) injury on cowpea grain yields and to establish economic injury levels (EILs) and action thresholds for thrips on cowpea. The studies relied on various insecticide spray regimes to obtain different thrips densities per experimental unit and use of exclusion cages in the field to confine defined numbers of thrips populations. A significant negative relationship ( y =−0.011 x +1.77; r =0.87; P =0.003) was observed in the field studies between thrips densities and cowpea grain yields. The EIL was established at seven thrips per inflorescence. The study also revealed that three well timed (i.e., applied after bud initiation to minimize flower bud abortion) insecticide sprays are effective in the control of thrips. The three sprays are regarded effective in that thrips densities were kept below the established thresholds. More than three sprays also reduced thrips populations to less than seven per inflorescence but these were not economical.