Browsing by Author "Dwomoh, Emmanuel Agyemang"

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    Biology of xanthodes graellsii (Feisth) (Lepidoptera: Noctuidae)
    (1996) Dwomoh, Emmanuel Agyemang
    The biology of Xanthodes graellsii (Feisth) was studied in the laboratory and the field. The number of larval instars varied from 5 to 6 but developmental period of X. graellsii (from egg to adult stage) reared in the laboratory was longer than those reared in the field. The sex of the pupa of X. graellsli can be determined by the position of genital pore on the abdomen. In the female the genital pore occurs ventrally on the 8th abdominal segment whilst in the male it is located between 8th and 9th segments. Studies carried out on the nocturnal activities of X. graellsii revealed that adult emergence generally occurs between 1800 and 0600 and it is unimodal in distribution. The major peak for both sexes occurred after midnight. Feeding activity of the moth began at 2000 hr and ceased at 0500 hr; two peaks of feeding activity were observed. The major peak for both sexes occurred before midnight. Copulation occurred between 1900 and 0400 hr. Oviposition in female X. graellsii started at 1900 hr with a major peak between 1900 and 2000 hr. Two smaller peaks were observed between 2100 and 0300; 0400 and 0500. The flight activity was determined with an insect suction trap. The combined catch for both sexes demonstrated a bimodal distribution with the major peak occurring after midnight. Female moths were more active around midnight while male predominated in the post-midnight periods. Using the presence of spermatophore in the female bursa copulatrix as a sign of successful mating, it was observed that 2-day old male and 3-day- old female copulated successfully. Maximum mating occurred when one-day-old male was allowed to mate 3-day-old female moths. Both male and female moths copulated once per night, however repeated matings occurred in both sexes during their life time. Three insecticides were screened for their effectiveness in controlling X. graellsii attacking okro. Chlorpyrifos (48% EC) at 500 ml per acre applied at fortnightly interval gave the most effective protection to okro leaves than the other insecticides. Chlorpyrifos sprayed plants also provided the highest fruit yield followed by B. thuringiensis. Residual effectiveness of the three insecticides to the 3rd, 4th and 5th instar larvae of X. graellsii was evaluated by comparing percent mortality of larvae fed on treated leaves 1, 4, 9 and 14 days after insecticide application. Chlorpyrifos was found to have the highest residual effect against the three larval instars of X. graellsii. It was followed by B. thuringiensis. Irrespective of the insecticide used, it was observed that larval mortality decreased with increase in interval after insecticide application in the field. Preliminary studies carried on the effect of planting date on the incidence of x. graensii showed that egg and Larval infestation of okro plants started as early as 4 weeks after emergence for different planting dates. It was also observed that adjusting planting dates could contribute to the reduction of egg and larval population of X. graellsii
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    Studies on the biology, ecology and management of sap sucking bugs of cashew with particular reference to helopeltis schoutedenireuter (hemiptera: miridae) in Ghana
    (2007) Dwomoh, Emmanuel Agyemang
    Knowledge of the insect complex associated with any crop is essential for developing control strategies for the crop. Literature on cashew insects in Ghana is scanty and few known pest species include Anoplocnemis curvipes (F) and Helopeltis schoutedeni Reut. Although fruit yield increases may be obtained with the use of » chemical insecticides, complete reliance on them for crop production does not appear to the answer to increased and sustainable production. It was therefore necessary to relop more efficient, sustainable and environmentally acceptable management tegies against important insect pests of the crop in anticipation for extensive ivation country-wide. Field surveys were conducted from July 2003 to October 2005 in 13 major cashew growing areas within 10 districts of the Northern, Upper West, Brong-Ahafo and Eastern Regions of Ghana to collect and identify the insect fauna on hew. Helopeltis schoutedeni Reuter (Hemiptera: Miridae) was selected for detailed "dies on the basis of its prevalence and devastating effect on cashew. Its biology was died in the laboratory at 24.9 0 C to 33 ° C and 72.4% to 88.5% Relative humidity H.). Petri dish laboratory bioassay and field experiments were also conducted to ^ermine the efficacy and persistence of lambda-cyhalothrin, imidacloprid and a cock- of cypermethrin and dimethoate on H. schoutedeni The relationships between O. ginoda and flushing shoots damage by sap sucking bugs, as well as the effectiveness O. longinoda as a bio-control agent in the protection of cashew were investigated. The ijor sap sucking insect species were Helopeltis schoutedeni (Reut.), Anoplocnemis rvipes (F.) and Pseudotheraptus devastans (Dist.). Investigations were also conducted methods by which O. longinoda can be successfully established on cashew trees already inhabited by some competing ant species. A total of 170 insect taxa were collected and 57 were identified to at least the generic level. The life cycle of the most lent pest, H. schoutedeni, from egg to adult emergence lasted 24.0 days. Both the )h and adult fed on the plant by sucking sap from flushing shoots, panicles and fruits they caused serious tree damage in all the localities throughout the year even though population sizes in the localities differed significantly OP=0.05). The H. schoutedeni ations showed a mono-modal distribution that peaked from December to February gradually declined from April to August. The pattern of dispersion of the bug in the tations was clumped (S2IM> 1) throughout the study period. In the laboratory ssay, lambda-cyhalothrin and a cock-tail of cypermethrin and dimethoate were found effective. The persistence tests indicated that, one day after application, both insecticides gave100% kill but only the cock-tail killed more than 95% after seven days. There was a negative correlation between numbers of O. longinoda nest and percentage pest damage flushing shoots. Plots treated with both insecticides recorded the smallest H. /lOHtedera-infested trees followed by O. longinoda-tieated plots. O. longinoda monstrated potency as a natural control agent for most of the insect pests. Of the 210 s that were examined in a 1.5 hectare plantation, 89 (42.4%) were colonized by ant cies. Methods used to overcome antagonism from resident ants are reported. Both bda-cyhalothrin and a cock-tail of cypermethrin and dimethoate may be used to ntrol H. schoutedeni should there be its massive invasion of a cashew farm, but the ~k-tail is a better choice for prophylactic use as it showed longer persistence. .longinoda is as effective as the insecticides in suppressing populations of H. houtedeni, A. curvipes and P. devastans on cashew trees.