Montdorensis is an Australian predatory mite that feeds on thrips, whitefly, other small insects and mites. It also feeds on pollen and honeydew. It is proving to be a very effective biological control agent for thrips and whitefly in protected crops. Montdorensis is a small, pale, pear-shaped mite about the same size as twospotted mite.
The gut contents take on a yellowish tinge when it feeds on thrips larvae, pinkish when it feeds on tomato russet mite, and greenish-black or brown when it feeds on spider mite. The eggs are clear and oval, and are laid on the undersurface of leaves (often on hairs), under the calyx of fruit and sepals of flowers, or other protected areas. At 25°C montdorensis takes 6 or 7 days to go through its life cycle from egg to mature adult. A young adult female can lay three or four eggs a day, to a total of more than 50 during her lifetime (about 4 weeks). A female mite kills an average of 14 thrips larvae per day.
The video below shows an adult Montdorensis predatory mite consuming an immature western flower thrips. After impaling the thrips with its mouthparts the voracious predatory mites sucks out the contents before moving on to hunt down other unfortunate thrips in the neighbourhood.
- Onion thrips Thrips tabaci
- Plague thrips Thrips imaginis
- Tomato thrips Frankliniella schultzei
- Western flower thrips Frankliniella occidentalis
- Melon thrips Thrips palmi
- Greenhouse whitefly Trialeurodes vaporariorum
- Silverleaf whitefly Bemisia tabaci
Montdorensis feeds on a wide range of thrips larvae, but will not control greenhouse thrips Heliothrips haemorrhoidalis. Thrips and whitefly appear to be its preferred food, but it also feeds on spider mites, broad mites and tomato russet mites, and scavenges on other invertebrates and pollen when thrips are absent. Montdorensis is being trialled on tomatoes for tomato russet mite. It is one of the few predatory mite species that appear able to survive well on tomatoes, with their sticky glandular hairs, and it consumes russet mite rapidly enough to keep ahead of its fast multiplication. As with other thrips-eating phytoseiid mites, montdorensis is too small to consume adult thrips or large larvae. Screening and weed management should be used to prevent large numbers of adult thrips from entering the greenhouse. Control options need to be at hand to reduce damaging levels of adult thrips if they do become established. Hypoaspis (Stratiolaelaps) soil-inhabiting predatory mites can also help by killing thrips pupae at ground level.
Montdorensis prefers warm temperatures. It moves, develops and reproduces slowly in cool conditions, with no activity below 11°C. Adults can tolerate 45°C in greenhouses but eggs and younger stages perish at this extreme. The optimum temperature range is 20 to 30°C. Short winter days and cool nights will not induce hibernation. As long as the mean daily temperature is warm, the predator will keep working all year round. Montdorensis is best used as part of an IPM program that covers all pests and diseases in the crop; otherwise, pesticide residues are likely to prevent the predator from performing at its best. Montdorensis has been used successfully in commercial crops of gerbera, strawberry, chrysanthemum, and cucumber. The number of pesticide applications needed to control thrips has been much reduced.
Chemical residues toxic to montdorensis must have had time to degrade before the predators are released. Synthetic pyrethroids and some organophosphates may need up to 8 weeks to break down in protected environments. There is a range of less hazardous chemicals which are preferred if spraying is necessary.The chemical toxicity table provides a guideline for chemical use, and more detailed information can be obtained from the supplier.
Introduction rates and frequency of introduction are likely to be crop-specific. Recommendations are evolving as more experience is gained. Check suppliers for current recommendations. A suggested starting point is to release montdorensis mites weekly or fortnightly at 10-20 per m2 until they are well established and thrips are under control.They are most effective as a preventive treatment, rather than as a cure for an already damaging pest population. The predators are supplied in a vermiculite carrier through Express Post.They can then be easily sprinkled on the leaves to distribute them evenly through the crop.
A note on release rates: Unlike chemicals which generally exhibit a clearly defined dose response curve, with beneficial insects, more is always better. However, they are costly to produce and the goal should be to achieve the best results at minimal cost. We are constantly trying to strike a balance between cost and efficacy. There are many factors that should be considered including the value of the crop, the magnitude of the pest population and the activity (or otherwise) of naturally occurring beneficial species. Also unlike chemicals, where it is common to respond to pest populations that have already exceeded some ‘economic threshold’, we recommend establishing beneficials early in the life of the crop before pest populations reach threatening levels. In most cases our releases are inoculative and we anticipate that our beneficials will establish and breed up within the crop to give long term control. As a general principle, 2-3 releases of modest numbers is better than a single large release – this reduces risk, improves establishment and accelerates the development of multiple overlapping generations of the beneficial species.
Cultural practices to aid establishment
Relative humidity is critical for egg hatching, and 70% humidity is needed for a high hatch rate. In a crop with a full canopy this is not a problem. When plants are small, or conditions exceptionally dry, watering down paths and under benches, or misting, will result in better establishment.
Many commonly used chemicals have been tested for toxicity to montdorensis. Pesticides vary widely in their impact on beneficials. Synthetic pyrethroid and organophosphate sprays are generally very toxic and should be avoided. More information is available at Australasian Biological Control. Fungicides are generally safe, but some have severe adverse effects on egg-laying. In protected crops the residual effect of pestcides may last much longer than for the same material when used in the field.
This Syngenta press release shows just how excited they are about the release of monties in Europe. Australian growers already have access to this exciting new biological control agent.