Abstract:
Cabbage aphid, (Brevicoryne brassicae L.)is one of the most serious insect pests and its damage
potentially affects the quality and market value of cabbage. The Field experiments were carried
out at Gondar Zuria district in 2017 under irrigation to determine the effective rates and type of
insecticide against cabbage aphid. The aim of the study,the experiment was composed of two
chemical insecticides (Diazinon 60% EC and Dimethoate 40% EC) with two different rates
(0.5and 0.25) and untreated check (control). A total of nine treatments were arranged in RCBD
with three replications. The head cabbage variety Copenhagen was used for this experiment. All
agronomic practices were carried out as per the recommendation. Data werecollected on
incidence of aphid, severity, aphid mortality and other related agronomic data. Random
sampling methods were used to collect data for the above mentioned parameters before and after
application of treatments. For the laboratory experiment, insecticides (Diazinon 60% EC and
Dimethoate 40% EC) with two different rates (0.5and 0.25) and untreated check (control) were
factorially combined and laid on Completely Randomized Design with three replications. Data were
analyzed by using SAS computer software (version 9.2) and LSD was used to separate treatments
means. There was significant (P<0.05) differences among treatments on aphid incidence. Among
the treatments the maximum aphid incidence (50%) was recorded after the first spray on
untreated plots .While, the minimum aphid incidence (12.5%) was counted from Dimethoate plus
Diazinon at rate of 0.5% and 0.25% treated plot. Minimum incidences 4.17% of aphid was
recorded from plots treated with Dimethoate 0.5 plus Diazinon 0.25 after 3
rd
sprays, while the
maximum percent incidence (58.33%) was recorded from the control plot. In case of final aphid
severity, maximum (3%) was recorded on unsprayed plots, while much lower level (0%) was
observed on plots treated with Diazinon 0.25 plus Dimathote 0.5. In case of aphid mortalities
evaluated 96 hours after application of treatments, the maximum (90%) of aphid mortalities was
recorded in Dimethoate 0.5 plus Diazinon 0.25 treatment, while the lowest (14.33%) was
recorded in control treatment. The highestmarketable (111.9 ton ha-1) yield was obtained from
plots treated with Diazinon 0.25 plus Dimethoate 0.5 whereas, the lowest (23.37ton ha-1) in
untreated plot. Generally, plots treated with Diazinon 0.25 plus Dimethoate 0.5 resulted in the
lowest aphid infestation percentage, minimum severity level and effective as well as recorded
maximum yield. Combinedapplication of Diazinon plus Dimethoate with the rates of 0.25 and 0.5
respectively, recommended as the best control method against cabbage aphid and it is useful to
develop sustainable management methods against this pest via combined with others tactics.
