Mastrus

Förster, 1869

Species Guides

Mastrus smithii

Mastrus is a of ichneumonid wasps (Hymenoptera: Ichneumonidae) containing that attack lepidopteran , particularly tortricid moths. The genus includes species of significant agricultural importance as agents, notably M. ridens and M. ridibundus, which parasitize the codling moth (Cydia pomonella). Species in this genus are gregarious ectoparasitoids that attack host larvae during the cocooning/prepupal stage. Research has focused on their olfactory host-finding mechanisms, thermal , and integration into programs.

Pronunciation

How to pronounce Mastrus: //ˈmas.trus//

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Identification

Mastrus can be challenging to distinguish from one another; M. ridens was not described as distinct from M. ridibundus until 2010 despite being discovered in Kazakhstan in the 1990s. Accurate identification to species level requires examination of subtle morphological characters and is best confirmed by taxonomic . The is placed in Ichneumonidae based on standard -level characters.

Habitat

in this are associated with where their lepidopteran occur. For M. ridens and M. ridibundus, this primarily includes apple orchards and other environments where codling moth (Cydia pomonella) are present. The genus has been recorded from Central Asia (Kazakhstan) and introduced populations have been established in New Zealand, the western United States, and Argentina for purposes.

Distribution

The has been documented from Denmark, Norway, and Sweden based on GBIF records. within the genus have broader distributions: M. ridens is native to Central Asia (Kazakhstan) and has been introduced to New Zealand, California, and Argentina; M. ridibundus has been studied in Europe and introduced to North America.

Seasonality

M. ridens does not undergo and remains active during winter and early spring when larvae are available in cocoons. initiation in this occurs at ambient field temperatures, with becoming active in spring before codling moth larvae pupate. The extended flowering periods of nectar plants used by adults suggest adult activity spans much of the growing season in agricultural areas.

Diet

feed on nectar from flowering plants; laboratory studies show that access to nectar from such as Teucrium bicolor, Sphaeralcea obtusiloba, and Fagopyrum esculentum increases adult longevity. Larval wasps are ectoparasitoids that feed on the and tissues of lepidopteran larvae.

Host Associations

Cydia pomonella - prepupal gregarious ectoparasitoid of cocooning larvae; primary for programs

Life Cycle

Mastrus are gregarious ectoparasitoids. Females lay on or near larvae inside cocoons. Larvae develop externally on the host, feeding as ectoparasitoids. Multiple larvae may develop on a single host individual. Development occurs on diapausing codling moth larvae in laboratory rearing. occurs within the host cocoon or in adjacent protected locations.

Behavior

Female use olfactory cues to locate . M. ridibundus has been demonstrated to "eavesdrop" on the host's intraspecific , being attracted to 3-day-old cocoons containing larvae or but not to older cocoons with pupae or to excised hosts. This responds to a complex blend of including 3-carene, myrcene, several aldehydes, and geranylacetone. M. ridens is temperature-dependent, with minimum thresholds for flight initiation varying with ambient conditions. Host deprivation and load influence patch-leaving and host-finding .

Ecological Role

As specialized of tortricid moths, Mastrus function as mortality agents for lepidopteran . They are subject to hyperparasitism; hyperparasitoids of M. ridens have been detected in Argentina. The has been deliberately introduced to multiple countries for of codling moth.

Human Relevance

Mastrus are important agents in of apple and other pome fruits. M. ridens was introduced to New Zealand in a classical biocontrol program and is mass-reared in laboratories for release. M. ridibundus was introduced to California for codling moth control. Research has focused on optimizing through selection of nectar-providing plants to enhance longevity and effectiveness. Laboratory colonies are susceptible to bacterial (Serratia marcescens), requiring modified rearing hygiene protocols.

Similar Taxa

AscogasterAlso ichneumonid of codling moth; both have been studied in the same agricultural systems and regions, with hyperparasitoids detected attacking both in Argentina
Mastrus ridibundusCongeneric extremely similar morphologically; M. ridens was not distinguished from M. ridibundus until 2010 despite being discovered in the 1990s, indicating close similarity requiring expert examination

More Details

Taxonomic History

M. ridens was discovered in Kazakhstan in the 1990s but remained undescribed until 2010 due to its close similarity to M. ridibundus, highlighting the need for careful taxonomic work in this .

Conservation Biological Control

Research in Chile and elsewhere has identified native flowering plants that can enhance M. ridens ; Teucrium bicolor and Sphaeralcea obtusiloba have been identified as particularly suitable for increasing longevity.

Rearing Challenges

Laboratory colonies of M. ridens are vulnerable to Serratia marcescens bacterial , which can cause killing both larvae and developing ; control requires sodium hypochlorite sterilization and selection of healthy .