Training
on ocular identification of Leafminer flies and
its natural enemies in farmers' fields
Module
3
Identification
Of Leafminers And Their Natural Enemies
Objective: The participants should be able to learn ways on how to conserve natural enemies in the field for leafminer management.
The vegetable leafminers are generally difficult to control. The selective action of natural enemies provides accurate free of cost control of leafminers. Natural enemies play an important role in the reduction of leafminer population. Therefore, the conservation of the natural enemies is a vital keep leafminers below economically damaging levels.
A. Maintenance of grasses along vegetable refuge harbors parasitic wasps' population. These serve as alternate hosts when the primary host is not available. Augmentation can be achieved by allowing the growth of certain grass or Poaceae species, which provides pollen for the adult wasps after emergence.
B. The removal of broad-leaved weeds minimizes the continuous multiplication of leafminers on such alternate hosts. Parasitism normally increases its level on the first attack on leafminers and reduces the number of reproductive flies on the succeeding generation. The production of natural enemies at 50-60% significantly reduces leafminer population.
C. The reduction in the use of broad-spectrum insecticides of pesticide use will eventually increase the number of parasitic wasps. Also keeping-off insecticides early in the crop growth will encourage rapid build-up of natural enemies. With proper application, timing, and selection of insecticide to be used, the natural enemies will be spared and thus will regulate leafminer populations from becoming pest.
D. Though commercial production of parasitic wasps is already available in markets of many advanced countries with leafminer outbreaks. The use of natural enemies of leafminers is generally restricted for greenhouse releases only. Normally, the parasitic wasp adults mass-produced in the laboratory do not readily adapt to environmental stresses and therefore have low survival. Moreover, this augmentation is quite expensive for resource-poor-farmers. Hence, an alternative augmentation technique is to collect parasitized leafminers for rearing and upon emergence release them in the field. This would help increase parasitic wasp
population and also reduce leafminer population.
Activities:
- Place field collected leaves with mines in plastic containers for parasitic wasps' emergence.
- Label
- Get percentage parasitism using the following formula:
|
Emerged number of wasps
|
|
%
parasitism = |
------------------------- |
X 100 |
|
Emerged number of wasps + Emerged number of flies
|
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Module
1
Module
2
Module
3
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