Effect of Deltamethrin on the Leaf Miner (Liriomyza cicerina) of Chickpea and its Parasitoids

The objective of this work was to investigate the effects of chemical treatments on larvae and adults of the chickpea leaf miner (Liriomyza cicerina) and its parasitoids. The study was conducted according to the split-plot design with three replicates, during the cropping seasons 2016 and 2017 in the northwestern Tunisia. Deltamethrin treatments were applied on winter and spring chickpea varieties (Nour and Amdoun, respectively) when the pest density reached a level of 2-3 larvae/leaf in 50% of plants in the field. The number of emerged parasitoids and pest adults were recorded, and parasitism rates were investigated after treatments. Results revealed that the number of captured pest adults has been reduced in treated plots compared to control ones. Respective reduction rates attained 64.15% and 60.17% for Nour and Amdoun varieties during 2017. Additionally, the highest and the lowest parasitism rates were recorded respectively for Opius monilicornis 26.09% on control samples and for Diaulinopsis arenaria 2.88% on treated samples of Nour variety. In all experiments, L. cicerina larvae adults and parasitoids mortalities were higher for the spring variety. Hence, the use of more selective insecticides should be recommended to reduce the negative side-effects on the chickpea leafminer natural enemies.

Combining Host Plant Resistance, Selective Insecticides, and Biological Control Agents for Integrated Management of Tuta absoluta

Combination of pest management strategies that minimize pesticide use and conserve natural enemies is important for a sustainable environment. Overreliance on synthetic insecticides in the management of Tuta absoluta has led to pesticide resistance leading to difficulties in managing the pest. In this regard, alternative measures need to be put in place to reduce the effects of this pest. The objective of this study was, therefore, to assess the effectiveness of host plant resistance, biological control, and selective insecticides when used in combination, in the management of T. absoluta in tomato production. The study was set up in a greenhouse in a completely randomized design involving two tomato varieties, an insecticide (chlorantraniliprole), and a biological control agent(Macrolophus pygmaeus), applied singly or in combination. Data were collected on T. absoluta damage from the lower, intermediate, and upper leaves. The results from this study show that a combination of insecticide with a moderately resistant variety had a significantly lower T. absoluta damage as compared with a susceptible variety combined with an insecticide. However, the moderately resistant variety when combined with insecticide showed no effect when the biological control agent was added. The susceptible variety significantly reduced T. absoluta damage when combined with the biological control agent. These results indicate that treatment combinations in insect pest management can be utilized. The present study results indicate that using a moderately resistant variety (Riogrande VF) in combination with the insecticide chlorantraniliprole (Coragen®) and a susceptible variety (Pesa F1) in combination with the biological control agent (M. pygmaeus) can improve T. absoluta management. Under good habitat management, the susceptible variety will perform equally as the moderately resistant variety due to suppression of the T. absoluta populations by natural enemies. These findings show the importance of environmental conservation both by enhancing natural enemy abundance and use of selective insecticide in the management of T. absoluta in tomato production. Combinations in this present study are likely to reduce insecticide doses, thereby reducing the cost of production and enhancing environmental compatibility with natural enemies.

Do Ready-Mix Insecticides Cause Lethal and Sublethal Effects on Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) Pupa?

The use of selective insecticides aids farmers in maintaining pest populations below the economic threshold level. The integrated use of biological and chemical control is only possible if the effects of insecticides on natural enemies are studied. Although the IOBC/WPRS standards allow us to compare these studies worldwide, the methods used are sometimes inconsistent. This study determined the effects of ready-mix insecticides applied on pupae of Trichogramma pretiosum (Riley, 1879) (Hymenoptera: Trichogrammatidae) and compared the effects on emergence of two different methods of exposing T. pretiosum pupae to insecticides: immersed or sprayed using a Potter tower. Both methods gave the same results, indicating that they can be compared. Moreover, it is important to go beyond IOBC/WPRS classification and study the effects of pesticides on different biological parameters of natural enemies. This additional step may increase the likelihood of successful integration of biological and chemical control. Based on the emergence reduction, Chlorantraniliprole + lambda-cyhalothrin, abamectin + chlorantraniliprole, and alpha-cypermethrin + teflubenzuron were classified as innocuous (class 1). Cypermethrin + profenofos and cyproconazole + thiamethoxam were classified as slightly harmful (class 2). Methanol + methomyl and lufenuron + profenofos were classified as harmful (class 4). Abamectin + chlorantraniliprole, although classified as innocuous, reduced the parasitism, longevity, and flight capability of the adult parasitoids. None of these insecticides altered the emergence and sex ratio of the second generation.

Pemodelan Homologi Komparatif FABP Belalang Kembara (Locusta migratoria) Dengan PHYRE2 dan Skrining Virtual Inhibitor Potensial

The outbreak of locusta migratoria has caused a local crisis in production and cultivation of agricultural crops in East Nusa Tenggara Province. FABP (Fatty Acid-Binding Protein) plays an important role in transporting fatty acids from cytoplasm into mitochondria to generate ATP energy for locusta to fly and migrate. FABP inhibition is an attractive strategy to be exploited for novel insecticide development. Comparative homology modeling using Phyre2 had been used to generate two FABP models built from desert locusta (Schistocerca gregaria, 98% percent identity) and mice (Mus musculus, 40% percent identity) FABP protein as templates. Both FABP models showed an acceptable quality of stereochemistry and structural energy with lower atomic clash scores after refinement. Virtual screening identified potent inhibitor candidates with highest affinity energies which are (i) a heterocyclic compound C00628966 (-10.2 kcal/mol) and (iii) an imidazole derivative C15721579 (-8.5 kcal/mol) that were stabilized through a hydrogen bond with Ser53 also (iii) a pyrimidine derivative C73698912 (-8.1 kcal/mol) stabilized through hydrogen bonds with Thr57, Thr62 and Ser55. Their interactions resemble inhibitors that have been known to inhibit homologous FABP in humans. Therefore, these compounds warrant further in vitro validation and assay for development of selective insecticides to control locusta population.