Feltiella acarisuga
Predatory gall midge used against spider mites
Overview
Feltiella acarisuga is a predatory gall midge whose larvae feed on spider mites.
It is naturally associated with spider-mite colonies and can be useful as part of an integrated biological-control programme, particularly where mite infestations are spread through a crop rather than concentrated in a few isolated hotspots.
The adult midge does not feed on spider mites. It is the orange larval stage that actively searches within mite colonies and consumes eggs, young mites and adults.
Identification
Adults
Adults are small, delicate, mosquito-like midges.
They are rarely noticed during crop inspection because they are short-lived, active in low light and do not directly attack the pest.
Larvae
The predatory larvae are:
- small and elongated;
- orange to reddish-orange;
- found close to spider-mite colonies;
- often visible amongst mite webbing and eggs.
The larvae should not be confused with pest gall-midge larvae, which may look similar but occur in different plant tissues or feeding situations.
Target pests
Feltiella acarisuga primarily attacks:
- two-spotted spider mite;
- carmine spider mite;
- other accessible spider mites within the family Tetranychidae.
It is not normally used against broad mites, tarsonemid mites or eriophyid mites.
How it works
Adult females locate spider-mite colonies and lay eggs close to suitable prey.
After hatching, the larvae move through the colony and feed on several mite life stages.
The larvae pierce the mite and consume its contents.
Once fully developed, the larvae pupate on the leaf, often forming a small white cocoon close to the leaf veins.
Environmental conditions
Feltiella acarisuga generally performs best where:
- spider-mite colonies are already present;
- humidity is moderate to high;
- temperatures are suitable for active midge development;
- pesticide residues are not disrupting adults or larvae.
Very dry conditions can reduce egg and larval survival.
The predator is therefore often better suited to protected crops or crop canopies with reasonable humidity than very dry, exposed environments.
Monitoring establishment
Look for:
- orange larvae within spider-mite colonies;
- dead or emptied spider mites;
- white pupal cocoons attached to leaves;
- reduced expansion of mite hotspots.
Because adults are difficult to see, larvae and pupae are usually the best evidence of establishment.
Role in biological control
Feltiella acarisuga is usually used as a supporting predator rather than the sole control agent.
It can complement predatory mites such as:
It can be particularly useful where spider mites occur across a large crop area and flying adults can locate colonies independently.
Limitations
Control may be reduced when:
- spider-mite populations are extremely low;
- humidity is consistently low;
- colonies are heavily treated with incompatible pesticides;
- crop temperatures are outside the useful activity range;
- spider-mite webbing or crop structure restricts access.
It should be used as part of a wider integrated programme including monitoring, hotspot removal, crop hygiene and compatible predatory mites.
Related BioWiki pages
Biological-control performance depends on crop, temperature, humidity, pest density and pesticide compatibility.