Colorado potato beetle
Leptinotarsa decemlineata
Role in the garden
A yellow-and-black-striped beetle whose adults and larvae devour the leaves of the potato.
Practical guide
Prevention
A long rotation. A straw mulch favours the beetle's predators and markedly reduced damage to potatoes in a trial (Brust, 1994). In the field, companion plants (flax, tansy, horseradish, French marigold, bush bean) did not reduce Colorado beetles, some even attracted them (Moreau et al., 2006); tansy repels them in scent tests (Panasiuk, 1984), an effect not confirmed in that trial.
Early signs
Small clusters of yellow-orange eggs under the leaves, hairless red larvae grazing on the leaves, foliage nibbled to lace.
Action / control
Daily hand-picking of adults, larvae and eggs.
Sources
- Hare, J.D. (1990). Ecology and management of the Colorado potato beetle. Annual Review of Entomology, 35, 81-100.
- Brust, G.E. (1994). Natural enemies in straw-mulch reduce Colorado potato beetle populations and damage in potato. Biological Control, 4(2), 163-169.
- Moreau, T.L., Warman, P.R. & Hoyle, J. (2006). An evaluation of companion planting and botanical extracts as alternative pest controls for the Colorado potato beetle. Biological Agriculture & Horticulture, 23(4), 351-370.
- Panasiuk, O. (1984). Response of Colorado potato beetles, Leptinotarsa decemlineata (Say), to volatile components of tansy, Tanacetum vulgare. Journal of Chemical Ecology, 10(9), 1325-1333.
Favourite plants / resources
Related plant entries
Tomato
Central plant of the tomato guild. The neighbouring basil is reputed to hinder aphids through its volatile compounds.
Potato
A nightshade with traditional planting (April) or grown under mulch (Charles Dowding) requiring zero earthing-up. Demanding in manure, it readily heads the rotation on an enriched bed (GAB/FRAB Bretagne). Not to follow or precede a tomato on the same bed (shared blight, Phytophthora infestans).
Aubergine (eggplant)
A tropical nightshade that needs a lot of warmth (>20 °C at night), often grown in a cold greenhouse in northern France. Vibration-pollinated (buzz) by bumblebees, hence the value of attracting them. High demand for water and nutrients. Against Meloidogyne nematodes, the French marigold (Tagetes patula) only works as a dedicated, dense crop over a whole season, not as a mere border (see its fact sheet).