Eretmocerus eremicus
A lemon-yellow parasitoid wasp, 0.75–1 mm long, with green eyes, native to the desert Southwest, that lays its eggs under the scale-like nymphs of whiteflies. It is the parasitoid growers use for silverleaf whitefly (also called tobacco or sweetpotato whitefly), which Encarsia formosa handles poorly, and it also attacks greenhouse whitefly. Koppert rates it effective at higher temperatures than Encarsia, and a parasitised scale turns yellow to beige rather than black.
At a glance
- Mode
- Parasitoid, plus host feeding
- Rate
- 1–10 /m² (about 1 per 1–10 sq ft) weekly
- Ships as
- Pupae on cards, in blisters or loose
- Temp
- 77–84 °F (25–29 °C) best
- Parasitised scale
- Turns yellow to beige, not black
- Setting
- Greenhouse and protected crops
How it works
The female lays her egg underneath a whitefly nymph, not inside it, and prefers second and early third instars. The larva hatches, attaches to the underside of the host and burrows in once the whitefly reaches its last stage, then eats it from within. Females also kill nymphs by host feeding, and Biobest says they do more of it when whitefly numbers are high. Cornell records 3–5 eggs a day over an adult life of 6–12 days at 27 °C (81 °F), and the UK supplier LS Systems puts one female's total at around 150 whitefly larvae.
The whole cycle takes 17–20 days according to Biobest, and about 22 days according to Arbico. About two weeks after the egg is laid the scale turns yellow, or beige to light brown on silverleaf whitefly, and the new wasp leaves through a small round hole. A healthy whitefly leaves through a T-shaped split. Koppert rates it effective at a higher temperature range than Encarsia formosa, and Biobest says it lives longer than Encarsia in the heat and is more resistant to pesticides, which is why it is used in hot crops and for silverleaf whitefly. Sources differ on the top end: Koppert and Biobest say it is still active above 86 °F (30 °C), while UMass says it is inactive above that.
Is it established?
Count yellow and beige scales against pale ones on the older leaves near the release points. There is nothing to see in the first week.
- DAYS 1–7Adults start emerging from the card pupae within a day or two and spread into the crop; Beneficial Insectary says leave cards up 21 days for full emergence
- DAYS 10–14First parasitised scales, yellow on greenhouse whitefly and beige to light brown on silverleaf whitefly
- WEEKS 3–4Round exit holes in the coloured scales — the first home-bred wasps are out
- AFTERKeep releasing weekly until most scales are parasitised or the crop is sold
Release & handling
Pupae come glued to cards (60 per card in Koppert's Ercal, 100 per card in Biobest's and Buglogical's), in blister packs, or loose in sawdust. Hang or scatter them the day they arrive. Holding advice varies: Koppert allows one to two days at 47–50 °F (8–10 °C) in the dark, Arbico says no more than one night at 40 °F, and Beneficial Insectary says do not cold-store, or keep at 45–50 °F for no more than 18 hours.
Release the same day
Adults usually start emerging within one to two days of delivery (Arbico), so get the cards or pupae into the crop before then.
47–50 °F (8–10 °C), dark
One to two days at most (Koppert). US suppliers allow less: one night (Arbico) or 18 hours (Beneficial Insectary).
Shade, dry, low in the crop
Koppert hangs cards about 30 in (75 cm) below the plant heads, out of direct sun. Loose pupae go on a dry surface, never where irrigation will wet them.
Take yellow cards down
Remove them before release and put them back four days later (UConn), or they catch the wasps.
Pesticide sensitivity
More tolerant of pesticides than Encarsia (Biobest), but still a small wasp. UMass says to wait 3–4 days after applying an insect growth regulator or other pest control product before releasing it. Check each product against a side-effects database such as Koppert One before spraying. Check a product →
When to choose something else
Eretmocerus is the parasitoid for Bemisia and for hot houses. Choose something else, or add to it, when:
- The whitefly is greenhouse whitefly in a long, moderate-temperature crop — Encarsia formosa is the standard there, and mixes of the two are sold
- Numbers are already high — a predator can go on the hot spots: the whitefly ladybird Delphastus catalinae, which UMass says needs more whitefly than most growers will accept, or the predatory mite Amblyseius swirskii, which UConn reports suppressed whitefly better alongside Eretmocerus than either alone in poinsettia
- The tomato crop is heavily deleafed — the UK supplier LS Systems warns that intensive deleafing removes the parasitised scales and stops the population building
- You are outdoors in a garden — like Encarsia, it is sold for greenhouses and protected crops, and conserving wild natural enemies is the practical route outside
Where to buy
Suppliers listed alphabetically, not ranked. helpfulbugs takes no commission and does not sell insects.
- Arbico Organics5,000 (20 × 250 blisters)US
- Beneficial Insectary (ERETforce)5,000 / 7,500 / 10,000 / 15,000US
- Biobest (Eretmocerus-System)5,000 / 10,000EU / UK
- Buglogical5,000 / 10,000US
- Koppert (Ercal)3,000 / 15,000GLOBAL
Eretmocerus eremicus by target
Rate and timing differ by what you are releasing it against. Each page below is the program for one pest.