The vegetable
leafminers (Agromyzidae: Diptera) are important economic pests of agricultural
crops and ornamental plants in many countries around the world. They are small
(2-6mm) insects whose larvae feed entirely in living plant tissues, primarily
as leafminers, but also in stems, roots and seeds. The mining larvae feed
actually more on sap than on solid tissues of the leaf. The mined leaves turn
pale, get distorted and may dry up. The larval feeding can severely
reduce yield and kill the plants at high fly density. Consequently, almost 100
percent of damage to the affected plant. The Agromyzidae is divided into
two subfamilies which have been largely supported by recent analyses both of
morphological characters and of DNA sequence data. The Agromyzidae is one of
the largest dipteran families, with more than 3000 species belonging to 30
genera worldwide. The species of vegetable leafminers are distributed
throughout the world from the north of Greenland to Patagonia and the
subantarctic islands south of New Zealand.
 |
| Image: Leaf miner |
The management of
agromyzid leafminers continue to be a topic of extensive reset rich and
scientific debate. Synthetic and natural insecticides for leafminers control
have been extensively researched and are commonly used by farmers and producers
regardless of production scale and crops. The effectiveness of these
insecticides have been reduced by their indiscriminate use, which has adversely
impacted natural enemies and resulted in the development of resistance to
several groups of insecticides. Discriminate use of chemicals has to lead to
problems like pest resurgence, pest outbreak, and development of resistance by
pest species to insecticides, elimination of natural enemies, and risks to
human and animal health besides environmental pollution.
 |
Image: Vegetable leafminer Liriomyza sativae |
Integrated pest
management (IPM) seeks to provide an effective and economical control strategy
that minimizes the disturbance of anthropogenic control measures on the natural
components of the agro-ecosystems. As a result, biological control is often
emphasized as an important remediation strategy to combat pest outbreaks. A
total of 163 agromyzids and 98 parasitic wasps were reared from the Canberra
region from plant samples with agromyzid mines, larva and pupae.
In Bangladesh, around 7
species of agromyzid flies were so far recorded from 53 host plants.
A sound taxonomic framework is needed in order
to determine, what information would be most helpful in the selection and the
use of suitable species of parasitoids for use of biological control.