Microbial insecticide model and homoclinic bifurcation of impulsive control system

A new microbial insecticide mathematical model with density dependent for pest is proposed in this paper. First, the system without impulsive state feedback control is considered. The existence and stability of equilibria are investigated and the properties of equilibria under different conditions are verified by using numerical simulation. Since the system without pulse has two positive equilibria under some additional assumptions, the system is not globally asymptotically stable. Based on the stability analysis of equilibria, limit cycle, outer boundary line and Sotomayor’s theorem, the existence of saddle-node bifurcation and global dynamics of the system are obtained. Second, we consider homoclinic bifurcation of the system with impulsive state feedback control. The existence of order-1 homoclinic orbit of the system is studied. When the impulsive function is slightly disturbed, the homoclinic orbit breaks and bifurcates order-1 periodic solution. The existence and stability of order-1 periodic solution are obtained by means of theory of semi-continuous dynamic system.

POTENSI CENDAWAN Synnematium sp. SEBAGAI AGENS PENGENDALI Lawana sp. (FLATIDAE; HOMOPTERA)

<p><strong>Potency of Synnematium sp. as biocontrol agent of Lawana sp. (Flatidae; Homoptera)</strong></p><p>Research on potency of Synnematium sp. as biocontrol agent of Lawana sp. was carried out from May to June 2001 with a scries of pathogenicity tests in ield laboratory Narmada (Mataram) and Insect Laboratory Balittro, Bogor. The research consisted of two pats ie: (I) inoculation of the fungi on egg cluster of Lawana sp. of different ages, and (2) inoculation of the fungi with various application methods to the imagoes of Lawana sp.. Results showed that Synnematium sp. could infect 0-4 days old of eggs. Eggs more Uian 4 days old could be also infected, however 3-5% could still hatch to be nymphs. Application to parasitized eggs did not affect the parasitoid to hatch. Tests on the adults showed that 3 days ater inoculation with the fungi, adults of Lawana sp. became weak, while the motality occurred ater 5 days inoculation. Colony of Synnematium sp. on PDA media, primarily was white, then dark small balls sclcrotium, and formed synnemata on the top. The presence of sclerotia and synnemata seemed that the fungi is potential to be developed as microbial insecticide material ("micoinsectiside").</p>

Insecticidal Activity of Bacillus thuringiensis Proteins against Coleopteran Pests

Bacillus thuringiensis is the most successful microbial insecticide agent and its proteins have been studied for many years due to its toxicity against insects mainly belonging to the orders Lepidoptera, Diptera and Coleoptera, which are pests of agro-forestry and medical-veterinary interest. However, studies on the interactions between this bacterium and the insect species classified in the order Coleoptera are more limited when compared to other insect orders. To date, 45 Cry proteins, 2 Cyt proteins, 11 Vip proteins, and 2 Sip proteins have been reported with activity against coleopteran species. A number of these proteins have been successfully used in some insecticidal formulations and in the construction of transgenic crops to provide protection against main beetle pests. In this review, we provide an update on the activity of Bt toxins against coleopteran insects, as well as specific information about the structure and mode of action of coleopteran Bt proteins.