Biological Features and Molecular Genetic Structure of Habrobracon hebetor Populations

One of the promising entomophages capable of controlling the abundance of the codling moth is Habrobracon hebetor Say. Natural populations of the gabrobragon can reduce the number of caterpillars of the corn moth to 22%, the garden moth to 35%, the cotton moth to 45%, and the gamma moth to 30%. This work aims to assess the parasitic activity of the gabrobragon as a regulator of the codling moth abundance in various geographic populations, to select a host insect for its mass breeding in laboratory conditions, and to assess the molecular genetic variability of the structure of H. hebetor populations. The capture of natural populations of the gabrobragon H. hebetor was carried out in apple orchards in Krasnodar Krai and Stavropol Krai of Russia using cassettes in which caterpillars of the codling moth were placed. As a result of the research, the natural starting population of the gabrobragon H. hebetor was captured, and a method for their maintenance and breeding was developed. The most effective host insect is the wax moth (Galleria mellonela L.), which resulted in 195 adults, compared to 98 of the mill moth (Ephestia kuhniella Zell.). The gabrobragon population introduced into the apple tree cenosis continued its reproduction in natural conditions and largely suppressed the number and harmfulness of the codling moth. The RAPD analysis of the Krasnodar and Stavropol populations of Habrobracon hebetor Say revealed a high level of DNA polymorphism and genetic diversity in the studied geographic populations of the gabrobragon. At the same time, intrapopulation variability was 87.1%, while interpopulation variability accounted for 12.9% of the total indicator. The limited gene flow (Nm = 3.298) results in relatively low identity (GI = 0.906) between populations and significant interpopulation variability. This indicates that the analyzed insect samples probably represent different geographic populations of the H. hebetor ectoparasite.

Influence of Temperature and Photoperiod on the Fecundity of Habrobracon hebetor Say (Hymenoptera: Braconidae) and on the Paralysis of Host Larvae, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

Studies were carried out in the laboratory to understand the optimum environmental conditions at which the ectoparasitoid, Habrobracon hebetor Say (Hymenoptera: Braconidae), can paralyze and lay eggs when reared on the larvae of the stored product pest, Plodia interpunctella Hübner (Lepidoptera: Pyralidae). At the four temperatures investigated (20, 25, 30, and 35 °C), optimum temperatures for oviposition were found to be 25 and 30 °C, while 35 °C was the least favorable temperature. No significant differences were found between the percentages of diapausing and non-diapausing larvae paralyzed by the wasp at the temperatures of 20, 25, 30, 35 °C within 5 days. However, in another experiment that investigated the effect of photoperiods at different temperatures that included 15, 19 and 28 °C, the number of paralyzed larvae was highly reduced at low temperatures (15 °C) but photoperiods had no significant impact on the number of host larvae paralyzed. In addition, observations at short time intervals also showed that lower temperatures slowed down host larvae paralysis. The results suggest that H. hebetor can paralyze host larvae of P. interpunctella more efficiently and deposit more eggs at temperatures within the range of 20–30 °C.

Ovipositor of the braconid wasp Habrobracon hebetor: structural and functional aspects

The Braconidae are a megadiverse and ecologically highly important group of insects. The vast majority of braconid wasps are parasitoids of other insects, usually attacking the egg or larval stages of their hosts. The ovipositor plays a crucial role in the assessment of the potential host and precise egg laying. We used light- and electron-microscopic techniques to investigate all inherent cuticular elements of the ovipositor (the female 9th abdominal tergum, two pairs of valvifers, and three pairs of valvulae) of the braconid Habrobracon hebetor (Say, 1836) in detail with respect to their morphological structure and microsculpture. Based on serial sections, we reconstructed the terebra in 3D with all its inherent structures and the ligaments connecting it to the 2nd valvifers. We examined the exact position of the paired valvilli, which are bilateral concave structures that protrude into the egg canal. In H. hebetor, these structures putatively divert the egg ventrally between the 1st valvulae for oviposition. We discuss further mechanical and functional aspects of the ovipositor in order to increase the understanding of this putative key feature in the evolution of braconids and of parasitoid wasps in general.

Ectoparasite Habrobracon Hebetor Say Is an Efficient Biological Control Agent of Lepidopteran Pests

Ectoparasite Habrobracon hebetor Say is one of the most widely used biological controllers in biological plant protection against a number of harmful lepidopterans, including especially dangerous pests of corn, soy, fruit and vegetable crops. As a result of research conducted in 2017, food specialization and parasitic activity of three different populations of H.hebetor were studied. Two races have been identified for mass rearing and application: pyralid and leaf roller (against corn moth, bean pod borer, apple and plum moths), and pyralid owl-moth (against cotton moth, corn borer, bean pod borer and boxwood moth). As a result of studies of biological features and trophic needs, it has been determined that caterpillars of mill moth (Ephestia cuhniellia Zella) should be used as a host insect for laboratory cultivation of the stock population of the Habrobracon pyralid and leaf roller race (race No. 1). For the introduced from South Kazakhstan the H.hebetor pyralid and noctuid race the most productive rearing is on the caterpillars of large bee moth (Galleria mellonela L.). Optimal temperature for rearing of both races is 26-28 ° C, relative air humidity is 70% and photoperiod is not less than 16 hours. It has been noticed that before laying eggs on the host’s caterpillars, the Habrobracon female preliminarily paralyzes the victim, piercing the sheath with ovipositor. As a result, the caterpillar stops eating and is immobilized. In 3-4 days larvae hatch out of the laid on the caterpillar eggs. The larvae feed on the contents of the caterpillars for 4-5 days, then pupate and after 6-8 days an adult insect leaves the cocoon. The development of one generation lasts 13-16 days, one cocoon includes one parasite. 1,000 large bee moth caterpillars used for infection provide on average 5.8-6.0 thousand cocoons, of which an average of 4.5-4.7 thousand parasites fly out.