Assessment of Diversity Indices and DNA Barcoding of Parasitic Fauna Associated with Groundnut Leafminer (GLM), Aproaerema modicella Deventer (Lepidoptera: Gelechiidae)

Background: Parasitoid wasps have received a great share of heed in the biological control of pests. However, they are often difficult to identify because of their small body size and profound diversity. In this view, biodiversity indices of parasitic fauna was reckoned and proper identification of those biocontrol agents were done through morphological and molecular technique such as DNA barcoding.Methods: Biodiversity indices of parasitoid of Groundnut Leafminer (GLM), Aproaerema modicella Deventer were reckoned for three agroclimatic zones viz., Irrigated Eastern zone (IE), Rainfed zone (R) and Irrigated Western zone (IW) of Tamil Nadu. Biodiversity indices viz., Relative density, Simpson’s Index, Shannon-Wiener Index, Pielou’s Evenness Index, Margalef Index and Beta diversity were assessed for the parasitic fauna associated with GLM. Apart from this, morphological characterization of prominent parasitoids were done with the help of available literatures and taxonomic experts. The molecular characterization of parasitoids were done using mitochondrial Cytochrome Oxidase I (mtCOI).Result: The relative density of parasitoid families and species indicated the dominance of braconidae and Chelonus blackburni Cameron. Among the agroclimatic zones, rainfed zone had higher species diversity, richness and evenness. In addition, the morphological and molecular confirmation revealed that the parasitoids associated with A. modicella as Temelucha spp., Stenomesius japonicus, Bracon hebetor, Sympiesis dolichogaster, Chelonus blackburni and Avga choaspes. The amplified sequences were submitted to NCBI database and accession numbers were obtained.

Impact of volatile cues on foraging response of egg larval parasitoid, Chelonus blackburni Cameron

Y-tube olfactometer study was carried out to observe the orientation response of egg-larval parasitoid Chelonus blackburni Cameron towards various concentrations of volatile cues emitted from three potato varieties and Phthorimaea operculella Zeller. Volatile cues were subjected to Gas Chromatography-Mass Spectrometry (GC-MS) profiling to identify the signaling molecules present in the pool of volatile cues. Out of 16 selected volatile cues concentrations obtained from plant and host insect sources, 10 cues acted as significant attractant for C. blackburni. Volatile cues emitted from Kufri Surya in vegetative stage were able to generate highest stimulation in C. blackburni. Among volatiles obtained from larval and adult stage of P. operculella, adult cues were found to be more efficient in the alteration of foraging behaviour of targeted parasitoid. GC-MS of targeted cues revealed the presence of fifteen saturated hydrocarbons ranging from C12 to C54; varying in concentrations. Study specified that C. blackburni preferred cues could be exploited to enhance the host searching efficacy during Integrated Pest Management releases.

Selective toxicity of diafenthiuron to non-target organisms: honey bees, coccinellids, chelonus, earthworms, silkworms and fish

Diafenthiuron, an insecticide widely used in the management of pests of cardamom and cotton, was assessed for its toxicity-effect on beneficials commonly found in these ecosystems. Diafenthiuron was found to be toxic to honey bees, the prime pollinators of crop plants. Diafenthiuron at the highest tested dose caused 40% mortality to the coccinelid grubs at 48 h after treatment so, diafenthiuron was found to be slightly harmful. Monocrotophos, on the other hand has been found to be a highly toxic pesticide. Diafenthiuron is moderately harmful to the adults of Chelonus blackburni L. The testing was done using the insecticide diafenthiuron. An insecticidecoated vial (scintillation) bioassay was performed. It was found that there was 86.67% mortality in 48 h, at the recommended dose. Diafenthiuron is highly toxic to the silkworm, killing more than 80% of the caterpillars in 24 h, at all the doses tested. Diafenthiuron, even in the highest dose tested, is non-toxic to the earthworm, Perionyx excavatus, which was found to have a 3.33% mortality. As far as fish are concerned, the common carp, Cyprinus carpio L., is found to be highly susceptible to diafenthiuron and even doses 10 times lower than the field dose can kill the fish within 6 h.

AN IMPROVEMENT OF THE HOLLING TYPE III FUNCTIONAL RESPONSE IN ENTOMOPHAGOUS SPECIES MODEL

In this study, we analyze the functional response for a parasitoid-host and a predator-prey system, as a tool of biological control of pests to evaluate the potential of bio-control agents. A possible biological interpretation was given to the adjustment coefficients of type I and II functional response by Hassell.1 Based on this, we propose new expressions for type III in terms of a new parameter that we call entomophagous potential (parasitoid or predator), providing examples using actual data from trials carried out previously for parasitoid species Chelonus blackburni Cameron (Hym.: Braconidae) and predator species Joppeicus paradoxus Puton (Het.: Joppeicidae). The novelty of the paper consists in the fact that these new expressions for Holling type III functional response have a biological interpretation, and result in a better fit to data than Hassel's model.

Contact toxicity of synthetic pyrethroids, organophosphorus and carbamate insecticides to adults of the parasite Chelonus blackburni Cameron

SUMMARYFour synthetic pyrethroids: fenvalerate, deltamethrin, cypermethrin and permethrin were evaluated as spray deposits on cotton leaves for their contact toxicity to adults of the parasite Chelonus blackburni Cameron (Braconidae). Fenvalerate was found to be the least toxic of the four pyrethroids. In another study five organophosphorus insecticides (profenofos, bromophos ethyl, chlorpyrifos, quinalphos, monocrotophos), three carbamates (U.C.51762, carbosulfan, bendiocarb) and diflubenzuron were evaluated for their contact toxicity to the same parasite. U.C.51762 (carbamate group experimental insecticide) and diflubenzuron were less toxic while the five organophosphorus insecticides, carbosulfan and bendiocarb were highly toxic to the parasite.Contact toxicity of spray deposits of four synthetic pyrethroids were studied against parasitization and subsequent development of the parasite C. blackburni on thin strips of egg cards Corcyra cephlonica Stainton. It was observed that fenvalerate was not reducing oviposition or affecting subsequent development of the parasite and emergence from the parasitized eggs while the other pyrethroids, permethrin, cypermethrin and deltamethrin, were toxic.