Cassava Poison Bait Development to Control German Cockroach

Abstract

Recently, the application of plant extracts has drawn much attention as effective
alternatives to synthetic insecticides. These plant extracts are more biodegradable and safe
for humans and the environment than chemical insecticides. This experiment’s research
objectives were to (1) determine the acute toxicity of cassava (Manihot esculenta Crantz)
extract against adult German cockroach (Blattella germanica (L.)) (in terms of 24 hour-
Median Lethal Concentration, oral 24 hr-LC50), (2) determine the hydrogen cyanide (HCN)
concentration from four parts of cassava (stem, peel (periderm and cortex), starchy flesh
(parenchyma), and leaf), and (3) evaluate the food preference of German cockroach on
cassava bait formulations using Rodgers’s index.
The results showed that (1) in the oral toxicity tests, the LC50 values of the
extracts of the stem, peel (periderm and cortex), starchy flesh (parenchyma), and leaf of
cassava, 24 hr after the test, were 49.287, 126.224, 129.625 and 137.645 ppm, respectively.
(2) The hydrogen cyanide values of the extracts of the stem, peel (periderm and cortex),
starchy flesh (parenchyma), and leaf of cassava were 305.34, 156.19, 110.94, and 32.83
mgHCN/L, respectively. (3) Both sexes of German cockroach preferred the A4 cassava bait
formulation composed of 500 grams of ripe cassava, 125 grams of granulated sugar, and 30
ml of cassava’s starchy flesh extract following by the A3 cassava bait formulation
composed of 500 grams of ripe cassava, 125 grams of granulated sugar, and 30 ml of
cassava’s peel extract. Moreover, the male German cockroaches significantly preferred the
A4 and A3 formulations more than other formulations (p-value<0.05). Female German
cockroaches significantly preferred the A4 formulation more than the other formulations
(p-value<0.05). Male German cockroaches significantly preferred the A4 formulation more
than the females did (p-value<0.05); on the other hand, female German cockroaches
significantly preferred the B4 cassava bait formulation composed of 500 grams of ripe
cassava, 125 grams of beef extract powder, and 30 ml of cassava’s starchy flesh extract
more than the males did (p-value<0.05).
The results suggest that the highest toxicity and highest HCN values of the
cassava extracts were found in the stem and acted as a stomach poison for cockroaches.
Cassava bait attracted both sexes of German cockroach; therefore, cassava may prove to
be a candidate ingredient for the development of a safer bioinsecticide to control German
cockroaches as an environmental friendly method.