The whitefly, Bemisia tabaci, an insect of the order Hemiptera which attacks more than 600 species of plants, is one of the most important agricultural pests around the world. The insecticidal Cry proteins from Bacillus thuringiensis (Bt) are useful biological pesticides, and some are toxic to Hemipteran insects. In this study, Colombian native isolates of Bt were functionally characterized at molecular and biological levels. The strains contained between one and five different crystal shapes: round, triangular, amorphous, bipyramidal and squared. The strains presented between three to seven bands of proteins in their electrophoretic pattern that were organized into six groups according to their possible biological activity on insect pests. Cry1Aa, cry1Ab, cry1Ac, cry1B and cry1C genes were identified for PCR in the different Bt isolates. Bioassays were performed on tomato leaves whose surface was spread with 3 μg · ml−1 crude extract of Bt toxins. Second instar larvae of whitefly, which were placed on top of leaves and exposed to the toxins for 7 days, exhibited mortalities from 18 to 69%. The lethal concentration 50 (LC50) of ZBUJTL39, Bt kurstaki HD1 and ZCUJTL9 strains were 1.83, 1.85 and 2.16 μg · ml−1, respectively (p < 0.05). These results show that the native Bt strain ZBUJTL39, which contained the genes cry1Aa, cry1Ab, cryCa and cryBa could eventually be used for the development of an integrated management program together with other tools for the control of B. tabaci.
The use of suitable mass rearing methods is crucial to establish successful inundative or
inoculative biological control programs. The development of an artificial diet considerably
reduces costs of mass rearing. In this study, the efficacy of a new meridic artificial
diet for rearing the predatory bug, Orius albidipennis (Het., Anthocoridae), was studied.
The artificial diet was composed of some natural materials including lamb liver, hen yolk,
whey protein, honey, royal jelly and some specific vitamins. To determine the artificial diet
efficacy life table parameters of the bugs, using the two-sex life table method, fed artificial
and factitious diets, Ephestia kuehniella egg + date palm pollen, were compared. Results
showed that O. albidipennis could complete its life stages and reproduce when reared on the
recommended artificial diet. However, its fecundity and survival rate when fed the artificial
diet was lower than the controls. Overall, due to lower production costs the artificial diet
can be recommended for mass rearing of O. albidipennis despite the lower fecundity and
survival rate.
Biological parameters of the larval parasitoid Cephalonomia tarsalis (Ashmead) (Hymenoptera : Bethylidae) and its host the saw-toothed beetle Oryzapehilus surinamensis (L.) (Coleoptera : Silvanidae) were studied in the laboratory. The duration of the immature period, survival during development, as well as adult longevity and the number of progeny of both insects were recorded. Our data were used for the estimation of several demographic parameters and life table construction of both the host and the parasitoid. The wasp managed to complete its development (egg – adult) in 19.8 days at 25oC, whereas the adult female lived for 24.3 days. The host O. surinamensis demonstrated a longer developmental period (30.5 days) and adult female longevity (103.0 days). Female wasps laid an average of 66.4 eggs throughout their lifetime whereas their beetle hosts laid five times more eggs (313.9). Life table parameters of C. tarsalis were estimated for the first time. The intrinsic rate of natural increase (rm) was 0.124 which was almost double that of its host (0.056). Our results are discussed on the basis of evaluating and improving the performance of C. tarsalis as a biocontrol agent against O. surinamensis in storage facilities.
The aim of this review is to describe ecological and physiological features of Andrallus spinidens Fabricius and to discuss various possibilities of using it as an appropriate biocontrol agent in different agroecosystems. This hemipteran is a cosmopolitan predator of caterpillar pests of rice, wheat, soybean, moong, pigeon pea, maize, sugarcane and cowpea with special feeding on Chilo suppressalis Walker, Naranga aenescnes Moore, Helicoverpa armigera Hübner and Spodoptera litura Fabricius. Climate, spatial distribution of prey and type of agricultural crop are among the factors influencing the biology and spatial-temporal distribution of A. spinidens. Studies have shown random or aggregated distribution of the predatory bug with population peaks in April, July and October. The 1st instar nymphs have no feeding, the 2nd and 3rd (the first 2 days) instars are seedling feeders while they are voracious predators of caterpillars from the middle of 3rd instar to adulthood. The salivary gland consisted of two anterior-, two lateral- and two posterior lobes with major secretion of trypsin, chymotrypsin, amino- and carboxypeptidases. The alimentary canal has a four-sectioned midgut in which the third section seems to be the main place for digestive enzymes including α-amylase, trypsin, chymotrypsin, elastase cathepsins B, L and D as well as carboxy- and aminopetidases. Andrallus spinidens have shown compatibility with some insecticides and the entomopathogenic fungus, Beauveria bassiana. The predatory bug may be successfully reared in a laboratory using Galleria mellonella larvae as prey and both conservation and augmentation should be considered as biological control strategies against insect pests.