Trichogramma chilonis, an effective egg parasitoid for control of white stem borer Scirpophaga innotata (Walker), (Lepidoptera: Pyralidae) in rice

Rice an important staple food crop of the world, which is attacked by the various insect pests, among them the stem borers are the most destructive pests, distributed in all rice growing areas of the world and cause the severe losses. This research investigated the efficacy of the parasitoid Trichogramma chilonis (Ishii) to control the white stem borer (Scirpophaga innotata) in rice. In this respect the field studies were conducted in lower Sindh, Pakistan for the year, Kharif - 2017 and 2018. Trichogramma egg parasitoid over 230 species are reported to have been remained in biological control of insect pests of over 200 insect species belonging to 70 different families, mainly the order Lepidoptera, Hemiptera, Orthroptera and Thysnoptera, in order to manage the white stem borer of rice the Trichogramma chilonis (Ishii) was used as a bio-control agent. The Studies revealed that T. chilonis proved an effective biocontrol strategy against white stem borer of rice. The result of this study could be useful in an integrated pest management program for the management of white stem borer of rice the Trichogramma chilonis. Keywords: Stem borer, Biocontrol, Parasitoid, Population suppression.

Stability of May’s Host–Parasitoid model with variable stocking upon parasitoids

Using the Kolmogorov–Arnold–Mozer (KAM) theory, we investigate the stability of May’s host–parasitoid model’s solutions with proportional stocking upon the parasitoid population. We show the existence of the extinction, boundary, and interior equilibrium points. When the host population’s intrinsic growth rate and the releasement coefficient are less than one, both populations are extinct. There are an infinite number of boundary equilibrium points, which are nonhyperbolic and stable. Under certain conditions, there appear 1:1 nonisolated resonance fixed points for which we thoroughly described dynamics. Regarding the interior equilibrium point, we use the KAM theory to prove its stability. We give a biological meaning of obtained results. Using the software package Mathematica, we produce numerical simulations to support our findings.

The abundance and diversity of fruit flies and their parasitoids change with elevation in guava orchards in a tropical Andean forest of Peru, independent of seasonality

Lower elevations are generally thought to contain a greater abundance and diversity of insect communities and their natural enemies than higher elevations. It is less clear, however, how changes in seasons influence this pattern. We conducted a 2-year study (2013‒2014) in guava orchards located in a tropical Andean forest of Peru to investigate differences in fruit flies (Diptera: Tephritidae) and their parasitoid communities at two elevations and over two seasons. Fruit fly traps were installed, monitored, and guava fruits were sampled from eight orchards at low (800–950 m above sea level) and high (1,700–1,900 m above sea level) elevations and during the dry and rainy seasons. At each orchard, adult fruit fly trap captures and emergence of fruit flies and their parasitoids from guava fruit were quantified to determine their abundance and species composition. There was a greater abundance and species richness of fruit flies captured in traps at lower elevations, as well as higher abundance and species evenness of fruit flies that emerged from fruit, indicating that lower elevations are associated with larger fruit fly populations. The abundance, species richness and diversity of parasitoids were also greater at lower elevations. Consequently, guava fruit infestation and fruit fly parasitism rates were also greater at lower elevations. Seasonality also influenced fruit fly populations with a greater number of flies emerging from guava fruit and more fruit infested in the rainy season. However, seasonality had no effect on parasitoid population parameters or rate of parasitism, nor did it interact with elevation as an influence of populations of fruit flies or their parasitoids in guava orchards. This study highlights the importance of examining both elevation and seasonality for a better understanding of the population dynamics of fruit flies and their parasitoids in tropical agroecosystems.

Dynamics of a class of host–parasitoid models with external stocking upon parasitoids

This paper is motivated by the series of research papers that consider parasitoids’ external input upon the host–parasitoid interactions. We explore a class of host–parasitoid models with variable release and constant release of parasitoids. We assume that the host population has a constant rate of increase, but we do not assume any density dependence regulation other than parasitism acting on the host population. We compare the obtained results for constant stocking with the results for proportional stocking. We observe that under a specific condition, the release of a constant number of parasitoids can eventually drive the host population (pests) to extinction. There is always a boundary equilibrium where the host population extinct occurs, and the parasitoid population is stabilized at the constant stocking level. The constant and variable stocking can decrease the host population level in the unique interior equilibrium point; on the other hand, the parasitoid population level stays constant and does not depend on stocking. We prove the existence of Neimark–Sacker bifurcation and compute the approximation of the closed invariant curve. Then we consider a few host–parasitoid models with proportional and constant stocking, where we choose well-known probability functions of parasitism. By using the software package Mathematica we provide numerical simulations to support our study.

Karakteristik Morfologi dan Kelimpahan Populasi Parasitoid (Hymenoptera) pada Hama Invasif Kutu Putih Ubi Kayu, Phenacoccus manihoti Matile-Fererro (Hemiptera: Pseudococcidae) di Bali

Morphological Characteristics and Populations Abundance of Parasitoid (Hymenoptera) on Invasive Pests Cassava Mealybug, Phenacoccus manihoti Matile-Fererro (Hemiptera: Pseudococcidae) in Bali. This study aims to know the morphological characteristics of parasitoid, population abundance and distribution patterns of parasitoid associated with P. manihoti on cassava crop in Bali. The study was conducted on all cassava crop in Bali with a field observation method that was determined by taking shoots of cassava plants attacked by cassava mealybug P. manihoti, then cassava mealybug P. manihoti were nurtured, then observation was carried out every day until parasitoid appeared and being identified. The results of the study showed that there were three dominant types of parsitoid that were found to be associated with invasive pest P. manihoti, namely Anagyrus lopezi, Acerophagus papayae and Blepyrus insularis. The abundance of parasitoid populations was dominated by parasitoid A. lopezi with a range of values 48.6–81.8%. Then followed by parasitoid A. papayae 7.7 - 37.1%, and B. insularis 3.4 - 14.3%. The distribution pattern of parasitoid varies in each species, parasitoid A. lopezi spreads in groups categories, Parasitoid A. papayae and B. insularis spread random-regulary on cassava crop throughout on each of the Regencies in Bali.