Nursery, Greenhouse, and Landscape

Temperature/Humidity Impacts on Greenhouse Mite Predator

Currently greenhouse biological control of twospotted spider mite consists of regular introductions of the predatory mite Phytoseiulus persimilis. Although this is effective most of the time, failures do occur occasionally. Additional natural enemies may be required to successfully manage twospotted spider mite in greenhouses, and the addition of a winged predator that could move rapidly to spider mite "hot spots" would be useful. Stethorus punctillum is a voracious obligate spider mite predator with long-lived adults that are capable of effective dispersal - but most research on this insect has been in orchards.

The predatory behavior of S. punctillum larvae on twospotted spider mite was studied in order to assess how it responded to temperatures and relative humidities typical of greenhouse conditions.  Distance covered, time spent walking, walking speed, angular velocity, and turning rate was recorded at 20, 25 and 30 C and relative humidity levels of 33%, 65% and 90% on leaf disks cut from tomato, pepper, eggplant and cucumber plants.  Movement and predatory activity of S. punctillum significantly increased at higher temperatures, but relative humidity had no significant influence. Host plant species also strongly influenced the performance of the predator, which was most active on pepper and tomato and least active on eggplant.

These preliminary results, which indicate that multi-species predator releases including S. punctillum have potential for improving biocontrol of twospotted spider mite in greenhouses, are being extended by simulated field trials.


Rott,  A. S. and D. J. Ponsonby. 2000. The effects of temperature, relative humidity and host plant on the behaviour of Stethorus punctillum as a predator of the two-spotted spider mite, Tetranychus urticae. Biocontrol 45(2):155-164.

Flowering Plants for Natural Enemies in the West


Many natural enemy adults visit flowering plants to obtain nectar and pollen. Flowers with shallow and exposed nectaries, such as wild carrot and dill, are frequently noted as being utilized by biocontrol species, but plants in the family Polygonaceae, such as domestic and wild buckwheats and common knotweed (Polygonum aviculare) are also reported as providing easily-accessible nectar. Flowering landscape plants that are adapted to culture in the southern Rocky Mountain region and that are visited by arthropods important in biological control of plant pests were identified in surveys at regional botanic gardens in Colorado and Wyoming during 1993 and 1994. 

More than 150 plant species/cultivars in 37 families were assessed for intensity of visitation by various natural enemies of insect pests. A relative rating scle of plant visitation was used: high visitation activity, medium, low or no visitation activity. Several species of beneficials were observed onthe flowers, including lady beetles, green lacewings, syrphid flies, tachinid flies, sphecid wasps and various parasitic wasps. Predatory bugs (Nabis americoferus, minute pirate bugs and twospotted stink bug) were also observed on flowers, but were generally associated with thrips or other prey on the blossoms rather than feeding on the flowers themselves.

Most of the natural enemies did not have specific preferences for a plant species and were frequently seen feeding on flowers of various plants among different families. Visitation to plants varied seasonally, mainly because of differences in flowering times.

Among the plants found to be visited most frequently in the early season (June) were 

Achillea filipendulina 'Coronation Gold' (Asteraceae)
Ajuga reptans 'Bronze Beauty' (Lamiaceae)
Aquilegia x hybrida 'Blue Bird'
Aurinia saxatilis (Brassicaceae)
Lobularia maritima
Penstemon strictus (Scrophulariaceae)
Potentilla recta 'Warrenii'
Potentilla verna
Veronica spicata 'Blue Fox' (Scrophulariaceae)

Midseason (July) floweing plants included

Achillea filipendulina (Asteraceae)
Achillea millefolium 'Moonshine' (Asteraceae)
Ajuga reptans 'Bronze Beauty' (Lamiaceae)
Allium tanguticum
Anthemis tinctoria 'Kelwayi' (Asteraceae)
Aquilegia x hybrida 'Blue Bird'
Aster alpinus (Asteraceae)
Atriplex canescens
Callirhoe involucrata
Chrysanthemum parthenium
Lavendula angustifolia
Linaria vulgaris (Scrophulariaceae)
Lobia erinus
Lobelia maritima
Mentha x piperita
Sedum album (Crassulaceae)
Sedum kamtschaticum (Crassulaceae)
Sedum spurium
'Dragon's Blood (Crassulaceae)
Solidago virgaurea 'Peter Pan' (Asteraceae)
Stachys officinalis (Lamiaceae)
Veronica spicata 'Blue Fox' (Scrophulariaceae)
Veronica spicata 'Red Fox' (Scrophulariaceae)

Late season (August) flowering plants attractive to natural enemies included

Achillea filipendulina (Asteraceae)
Achillea millefolium 'Summer Pastel' (Asteraceae)
Achillea tansliticum (Asteraceae)
Anethum graveolens (Apiaceae)
Anthemis tinctoria 'Kelwayi' (Asteraceae)
Astrantia major 'Margery Fish' (Apiaceae)
Atriplex canescens
Foeniculum vulgare
Limonium latifolium
Mentha x piperita (Lamiaceae)
Monarda fistulosa
Solidago virgaurea 'Peter Pan' (Asteraceae)

It is suggested that these plants may be particularly appropriate selections to be used to increase presence and enhance efficacy of natural enemies in regional gardens and landscape plantings by serving as alternate food sources for adult stages. Selections could also consider time of flowering so a continuous sequence of nectar and pollen producers would be available throughout the season.


Al-Doghairi, M. A. and W. S. Cranshaw. 1999. Surveys on visitation of flowering landscape plants by common biological control agents in Colorado. Journal of the Kansas Entomological Society 72(2):190-196.

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