Helicoverpa armigera Hubner (Lepidoptera: Noctuidae) is one of the most damaging insect pests globally, causing estimated global economic losses of over 3 billion US dollars annually. Crops most affected include cotton, tomato, soybean, grain crops such as corn and sorghum, chickpea and other pulses. Adults of this species possess strong migratory abilities (>2000 km), high fecundity and rapid reproductive rates; completing 4–6 generations per year in most cropping regions. Furthermore, the larvae are polyphagous, with a wide and diverse host range and possess the ability to enter diapause in order to survive adverse climatic conditions. At present, it is distributed across most of Oceania, Asia, Africa and southern Europe and has recently spread to South America. Various control measures have been trialled or proposed for the treatment of this pest, including synthetic insecticides, phytopesticides, microbial pesticides, macro‐biocontrol agents (both parasitoids and predators) and the development of genetically modified crops (e.g. Bt cotton). Successful control necessitates the use of an integrated pest management (IPM) approach, wherein biological, chemical and physical control measures are combined for the greatest control efficacy.

A review on biological interactions and management of the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

Three insect groups, known from the literature, were confirmed to make up a seed pest complex in cowpea fields in Benin Republic (West Africa) Several species of heteropteran pod‐sucking bugs (PSBs), two lepidopteran species, namely Maruca testulalis (Geyer) and Cydia ptyehora (Meyrick) and the weevil Apion varium Wagner occurred throughout southern Benin Field infestations of PSBs and M testulalis were always present, whereas A varium and C ptyehora occurrence was sporadic Seed damage assessment at harvest time showed that in 80% of 25 fields, planted between 1990 and 1992, PSBs were the most important pests PSB damage to seed usually ranged between 40 and 85% Seed damage from M testulalis was low, despite occasional high flower infestations C ptyehora was a minor pest in all locations Significant correlations between seed damage and cumulative number of insect days (CD) during pod formation was found for all three groups For PSBs alone, the CD values were significantly correlated w

Seed-damaging field pests of cowpea (Vigna unguiculata L. Walp.) in Benin: occurrence and pest status

In field trials conducted at the Experiment Station and in a farmer’s field at Mbita near the shores of Lake Victoria, Kenya, applications of 2% or 3% neem seed extract (NSE) @ 200 l/ha with a knapsack sprayer at 38, 47 and 51 days after emergence (DE) of the cowpea crop or 5%, 10% or 20% NSE sprayed @ 10 l/ha with an ultra-low-volume applicator at 31, 39 and 49 DE often significantly reduced the number of larvae of the flower thrips,Megalumthrips sjostedti (Trybom), in cowpea flowers recorded 2 days after each treatment. Also fewer adults occurred in flowers at 51 DE in plots sprayed with 5%, 10% or 20% NSE. Cowpea grain yield was significantly higher in plots sprayed with 20% NSE than in untreated control plots and was comparable to the grain yield obtained in plots sprayed thrice with cypermethrin. Because of the low cost of NSE treatment, the net gain was often more when the crop was sprayed with NSE than with cypermethin. Also, grain quality was superior in neem-treated plots than in untreated or cypermethrin-treated plots.

Neem seed extract spray applications as low-cost inputs for management of the flower thrips in the cowpea crop

The influence of post-flowering pests on cowpea seed yield with particular reference to damage by Heteroptera in southern Benin

Investigations on population dynamics and management of lepidopteran insect pests viz., Spodoprea litura Fabricius, Helicoverpa armigera (Hubner) Hardwick, Maruca testulalis Geyer and Plusia orichalcea Fabricius infesting blackgram [Phaseolus mungo (L.) Hepper] were carried out at B. A. College of Agriculture, Anand Agricultural University, Anand during kharif 2006. The population abundance of lepidopteran insect pests (S. litura, H. armigera, M. testulalis and P. orichalcea) on blackgram were found from 38 (3 week of September) to 48 standard week (4 week of November). The higher activity of these pests were noticed during 40 th to 45 standard week (October to 1 week of November). The pod borers M. testulalis and H. armigera reached to a maximum level during 43 standard week (4 week of October), whereas S. litura and P. orichalcea reached at peak level on 41 standard week (2 week of October) and 44 standard week (5 week of October), respectively. Abstract The blackgram crop suffered less by lepidopteran insect pests (S. litura, H. armigera, M. testulalis and P. orichalcea) and produced higher yield when crop sown in the months of June and July. However, the maximum yield was harvested from 1 week of July sown crop with low pest incidence. August and September sown crop were damaged more by lepidopteran insect pests affecting the potentiality of crop and produced lower yield. The neem based formulations Neemazal–F (0.1%) and neem seed kernel extract (NSKE 5%) were found more effective in checking the lepidopteran insect pests of blackgram. Vanguard (0.4%) highly effective against H. armigera, S. litura and M. testulalis, whereas Gronim (0.4%) effective against H. armigera, M. testulalis and P. orichalcea. Neem oil (0.3%) and Econeem (0.2%) was effectively checked P. orichalcea incidence on blackgram. Among the evaluated insecticides, emamectin (0.002%) was found to be highly effective against all lepidopteran insect pests of blackgram. Fenvalerate (0.02%) and quinalphos (0.05%) were found to be superior in reducing the S. litura, M. testulalis and P. orichalcea. Thiodicarb (0.075%) was effective in checking the H. armigera and S. litura, whereas cypermethrin (0.01%) was effective against H. armigera and M. testulalis. Endosulfan (0.07%) suppressed the H. armigera population in blackgram crop. Maximum yield was harvested from the Neemazal-F treated plots followed by NSKE (10.73 q/ha), Azadex (9.91 q/ha), Econeem (9.66 q/ha), Vanguard (9.43 q/ha) and Gronim (9.06 q/ha). In the said treatments, increase yield over control ranged from 21.42 to 47.32% and avoidable losses were upto 17.57%. The NICBR of effective neem based treatments NSKE, Neemazal – F, Azadex, Vanguard and Gronim were 1 : 24.56, 1 : 7.22, 1 : 5.61, 1 : 4.13 and 1 : 2.98, respectively.The blackgram crop suffered less by lepidopteran insect pests (S. litura, H. armigera, M. testulalis and P. orichalcea) and produced higher yield when crop sown in the months of June and July. However, the maximum yield was harvested from 1 week of July sown crop with low pest incidence. August and September sown crop were damaged more by lepidopteran insect pests affecting the potentiality of crop and produced lower yield. The neem based formulations Neemazal–F (0.1%) and neem seed kernel extract (NSKE 5%) were found more effective in checking the lepidopteran insect pests of blackgram. Vanguard (0.4%) highly effective against H. armigera, S. litura and M. testulalis, whereas Gronim (0.4%) effective against H. armigera, M. testulalis and P. orichalcea. Neem oil (0.3%) and Econeem (0.2%) was effectively checked P. orichalcea incidence on blackgram. Among the evaluated insecticides, emamectin (0.002%) was found to be highly effective against all lepidopteran insect pests of blackgram. Fenvalerate (0.02%) and quinalphos (0.05%) were found to be superior in reducing the S. litura, M. testulalis and P. orichalcea. Thiodicarb (0.075%) was effective in checking the H. armigera and S. litura, whereas cypermethrin (0.01%) was effective against H. armigera and M. testulalis. Endosulfan (0.07%) suppressed the H. armigera population in blackgram crop. Maximum yield was harvested from the Neemazal-F treated plots followed by NSKE (10.73 q/ha), Azadex (9.91 q/ha), Econeem (9.66 q/ha), Vanguard (9.43 q/ha) and Gronim (9.06 q/ha). In the said treatments, increase yield over control ranged from 21.42 to 47.32% and avoidable losses were upto 17.57%. The NICBR of effective neem based treatments NSKE, Neemazal – F, Azadex, Vanguard and Gronim were 1 : 24.56, 1 : 7.22, 1 : 5.61, 1 : 4.13 and 1 : 2.98, respectively.

Population dyanamics and management of lepidopteran insect pests of blackgram

Field trials were carried out for two seasons on the effect of insecticides on insect pests, damage and yield of three cowpea cultivars.During the first season, the preflowering stage of crop growth was found to be infested by Aphis spp, Empoasca spp, Ootheca spp and Epilachna spp, the flowering stage by Megalurothrips sjostedti, Heliothis armigera, Astylus atromaculatus, Coryna kersteni and Mylabris amplectens and the postflowering stage by H. armigera and a number of coreid and pentatomid bugs. Fenthion gave the least protection against pod damage by H. armigera. There were significant increases in the number of harvestable pods per plant with insecticides. There were no significant differences in hull weight and shelling percentage. Grain yield was increased by 96.2 and 109.4% after treatment with dichlorvos and cypermethrin, respectively.In the second season, cypermethrin and monocrotophos were most effective. Cypermethrin reduced the number of pod-sucking bugs by 58%, H. armigera by 93%, while monocrotophos reduced Empoasca spp by 39% and M. sjostedti by 79%. Cypermethrin reduced damage by pod-sucking bugs by 28%, and by H. armigera by 95%. Monocrotophos reduced damage by pod-sucking bugs by 14%, and by H. armigera by 80%. Significant increases in the number of harvestable pods per plant were obtained with monocrotophos and cypermethrin treatments. There were no significant differences between the number of seeds per pod, and the weight of 1000 seed-grains. Grain yield was increased by 55.4% after both cypermethrin and monocrotophos treatment. The application of these insecticides were financially beneficial but the gain was reduced when six sprays were applied. Cypermethrin and monocrotophos are promising insecticides for controlling insect pests on cowpeas.

Relative effectiveness of insecticide sprays on insect damage and yield of three cowpea cultivars in Swaziland.

Laboratory studies were conducted to assess the infestation potential of Callosobruchus maculatus (Fab.) on 12 elite and one local cowpea cultivars which were stored under subtropical conditions. Index of susceptibility, loss in grain quality and the number of adult progeny that emerged from previously infested grain were the criteria used to assess the vulnerability of the cowpeas to post-harvest infestation. Cultivars TV × 309-1C and TV × 1193-10F showed some degree of resistance to post-harvest infestation by C. maculatus and could therefore be stored safely for a relatively long time. TV × 1192-01D and TV × 1999-ID were the most susceptible cultivars to post-harvest attack by C. maculatus. Length of storage adversely affected the ability of the cultivars to resist the insect attack. Crop resistance, adequately supplemented with good sanitation, can be profitably applied to control insect infestations in grains during storage.

G. W. K. Mensah

Papers

Relative effectiveness of insecticide sprays on insect damage and yield of three cowpea cultivars in Swaziland.

Infestation Potential of Callosobruchus maculatus (Fab.) (Coleoptera:Bruchidae) on Cowpea Cultivars Stored Under Subtropical Conditions