Introduction:

Severe infestations by a sawfly species of the genus Zadiprion (Hymenoptera: Diprionidae), previously considered as Zadiprion howdeni, were detected in the forests of the Sierra Juárez of Oaxaca from 2018 to 2021.

Objective:

The objective was to corroborate the identity and generate information on biological and ecological aspects of the defoliator Zadiprion sp. affecting Pinus trees in the Sierra Norte of Oaxaca.

Materials and methods:

The biological development of the defoliator Zadiprion sp. was studied by field sampling in forests of Santa Catarina Ixtepeji. The species was identified by observing the external and internal morphological characteristics of the adult stage, based on taxonomic keys of diprionids. The number of instars was estimated by measuring the width of the larval head using digitized images and fitting a mathematical model.

Results and discussion:

The species infesting the study area is not Z. howdeni but a new species named Zadiprion llanderalae nov. sp. The larvae fed on needles of Pinus oaxacana Mirov., Pinus patula Schiede ex Schltdl. & Cham. and Pinus leiophylla Schiede ex Schltdl. & Cham., with the first being the main host. The species has one generation per year. In the field, an average density of 39.2 ± 9.69 sawfly cocoons∙m-2 was reported; 50.1 % of these were attacked by parasitoids, including wasps of the genus Exenterus (Hymenoptera: Ichneumonidae).

Conclusions:

We describe the species Z. llanderalae nov. sp. and provide data on its life cycle. This information is important for the planning of its management.

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