Whitefly parasitoids are small wasps. There are two parasitoids that are commonly encountered on cotton farms, Encarsia and Eretmocerus.
The two parasitoids target different nymphal stages of whitefly making them complementary rather than competitive.
Identification: Encarsia is tiny (<1mm long) parasitic wasp which has an orange coloured abdomen and black head and thorax. Whitefly parasitised by Encarsia turn dark brown or black.
Eretmocerus is also tiny, although slightly larger than Encarsia, and completely yellow except for three distinctive red ocelli on the top of the head arranged in a triangle. They are winged and can travel several hundred metres in a day, possibly wind assisted. Males are very rare.
Whitefly parasitised by Eretmocerus turn yellow/brown with red to green eyes visible within the whitefly shell just prior to emergence. The adult Eretmocerus cuts a circular emergence hole in the upper shell.
Lifecycles: Encarsia lays its eggs into the second, third and fourth nymphal stages of the whitefly. The egg hatches inside the immature whitefly (also known as scale) and the wasp larva feeds inside of it. Within two weeks the scale turns black and a wasp emerges soon after.
Eretmocerus lays its egg into the 1st and 2nd stage whitefly nymphs (mostly 2nd) depositing a single egg under but not into the ventral surface of the whitefly nymph. On hatching, after (~4 days), the tiny larva bores into the whitefly nymph over the next 3-4 days and waits until the whitefly pupates. At this stage the whitefly pupae is a cream colour. It then releases digestive enzymes which dissolve the whitefly innards which are used by the wasp larva to complete development. With three larval stages, development from egg to adult takes about 14-28 days, depending on temperature.
Habitat: Eretmocerus are crops specialists, but are also found in grassy margins with broad leaf weeds that harbour Bemisia. Encarsia are found in more habitat types including native remnant vegetation, the edge habitat between remnants and crops and crops.
Targeted prey: Both parasitoid species attack Whitefly Bemisia types in varying proportions through the season.
“Adult Encarsia lays its eggs into the second, third and fourth nymphal stages of the whitefly.” 1-2mm Photo: C. Mares
Parasite_Encarsia in SLW_Zara
“Whitefly parasitised by Encarsia turn dark brown or black.” <1mm Photo: Z. Hall
“Adult Eretmocerus lays its egg into the 1st and 2nd stage whitefly nymphs (mostly 2nd).” 1-2 mm Photo: Z. Hall
“Non-parasitised whitefly nymphs have mycetomes (small yellow bodies) that are symmetrically aligned.” <1mm Photo: T. Smith
“This parasitised whitefly nymph shows displaced mycetomes (small yellow bodies) appearing as a squiggle within its body.” <1mm Photo: Z. Hall