ABSTRACT
Pseudoligosita yasumatsui and Anagrus nilaparvatae are both egg parasitoids of the brown planthopper, Nilaparvata lugens (Stål) (BPH). In this study, we obtained a stable strain of P. yasumatsui reproduced via thelytoky through indoor rearing and screening. We assessed the parasitism capacity of this strain on eggs of N. lugens by comparing the parasitism preference and circadian rhythm of this strain to that of A. nilaparvatae, which is proved as the dominant egg parasitoid species of BPH in rice fields. The findings indicated that both egg parasitoids could parasitize fertilized and unfertilized BPH eggs, however, with a significant preference for fertilized eggs. The daily parasitization volume of P. yasumatsui was slightly higher than that of A. nilaparvatae. Both egg parasitoids preferred parasitizing 1-3-day-old BPH eggs, but the parasitism amount of 5-6-day-old BPH eggs by P. yasumatsui is higher than that by A. nilaparvatae. The parasitism events of both species of egg parasitoid wasps occurred primarily from 7:00-15:00 and the parasitism amount at night accounted for less than 15% of the total amount. The results indicate that this strain of P. yasumatsui reproduced via thelytoky could be valuable for rice planthopper control.
ABSTRACT
The Dubas bug (Ommatissus lybicus de Bergevin) is a pest species whose entire life cycle occurs on date palms, Phoenix dactylifera L, causing serious damage and reducing date palm growth and yield. Pseudoligosita babylonica Viggiani, Aprostocetus nr. Beatus, and Bocchus hyalinus Olmi are very important parasitic natural enemies of Ommatissus lybicus in northern Oman. In this study, random farms were selected to (a) model the link between occurrences of the Pseudoligosita babylonica, Aprostocetus nr beatus, and Bocchus hyalinus (dependent variables) with environmental, climatological, and Dubas bug infestation levels (the independent variables), and (b) produce distribution and predictive maps of these natural enemies in northern Oman. The multiple R2 values showed the model explained 63%, 89%, and 94% of the presence of P. babylonica, A. nr beatus, and Bocchus hyalinus, respectively. However, the distribution of each species appears to be influenced by distinct and geographically associated climatological and environmental factors, as well as habitat characteristics. This study reveals that spatial analysis and modeling can be highly useful for studying the distribution, the presence or absence of Dubas bugs, and their natural enemies. It is anticipated to help contribute to the reduction in the extent and costs of aerial and ground insecticidal spraying needed in date palm plantations.
ABSTRACT
The tritrophic interaction Argia insipida Hagen in Selys, the Trichogrammatidae egg parasitoid Pseudoligosita longifrangiata (Viggiani) and the host plant Tonina fluviatilis (Eriocaulacea), which is a substrate for egg deposition of A.insipid, was investigated. The study locality was a stream with rapids where macrophytes such as T. fluviatilis grow. Information on aquatic egg parasitoids is scarce. This is the first record of egg parasitism of A. insipida by P. longifrangiata in Brazil, and the first record of occurrence of P. longifrangiata in the country. Parasitized and unparasitized eggs of A. insipida were observed only on leaves 0-5 cm below the water surface. The maximum number of pairs of A. insipida laying eggs in the study area was observed between 13:00h and 14:00h. Leaves of T. fluviatilis become yellowish and dry out when large numbers of eggs of A. insipida are laid on them.
Foi estudada a interação entre Argia insipida Hagen in Selys, o parasitóide de ovos Pseudoligosita longifrangiata (Viggiani) (Hymenoptera: Trichogrammatidae) e a planta Tonina fluviatilis (Eriocaulacea), utilizada como substrato de oviposição de A. insipida. O local de estudo foi um curso de água com intensa correnteza, contendo macrófitas como T. fluviatilis. As informações sobre parasitóide de ovos aquáticos são escarsas. Este é o primeiro registro do parasitismo de ovos de A. insipida por P. longifrangiata no Brazil e o primeiro registro da ocorrência de P. longifrangiata no país. Ovos de A. insipida parasitados e não-parasitados foram observados somente 0-5 cm abaixo da superfície da água. O período de maior incidência de casais de A. insipida realizando posturas foi entre 13:00h e 14:00h. As folhas de T. fluviatilis tornam-se amareladas e secam quando um grande número de ovos é inserido nas folhas.
