Inside View: April 2011

March 14, 2011
Written by Gary Jones
New” crop pests and diseases regularly cause concern to greenhouse growers. Those listed here represent a selection of pests identified in recent years with potential for crop harm, but not all have been reported yet in commercial Canadian greenhouses.

Paratrioza cockerelli (syn. Bactericera cockerelli, Tomato-Potato psyllid). This has appeared spasmodically in British Columbia since around 2000. In 2007, it was present in 88 per cent of B.C. greenhouses surveyed, causing economic concern in tomato and pepper crops. Good cleanup between crops has prevented it from becoming a serious pest.

Myzus persicae ssp. nicotianae (tobacco peach aphid) and Myzus antirrhinii (snapdragon aphid). Both are considered by some as subspecies of Myzus persicae. It was fairly widespread in B.C. tomato and peppers in 2002-03, and M. nicotianae is fairly common in ornamentals in Ontario.

Chrysodeixis chalcites (Tomato looper or Golden twin spot looper). New in Canada in 2004, this is a regulated pest with eradication status.

Duponchelia fovealis (Pyralid moth). First found in Ontario glasshouse ornamentals in 2005, larvae of this moth feed on leaves, causing crop losses. It has potential to damage greenhouse tomatoes and peppers and has a large host range including flowers and corn. It has multiple generations a year without a diapause stage. Recently Duponchelia has been found in floriculture operations in Ontario and B.C. It prefers lower leaves (most often found near soil level), so it can be difficult to detect.

Tuta absoluta (Tomato leafminer moth, South American tomato moth.) Native to Central and South America and first seen in Europe in 2009, it is capable of causing 50-100 per cent losses in tomatoes. No sighting in Canada as yet. Larvae penetrate fruit, leaves and stems, creating mines and galleries. Adult moths are about 7 mm long, with larvae about 6 mm. Although tomato is a preferred host, it enjoys other Solanaceae.

Control is only achieved with chemicals and then with difficulty. It is a regulated pest in Canada; CFIA should be notified of any sightings.

Drosophila suzukii (Spotted wing drosophila). Found primarily on soft-berried fruits, it has been reported on one case of cherry tomatoes in a private garden in Oregon. No true diapause stage. While it is a major talking point with berry fruit growers, greenhouse vegetable growers also should keep an eye on this one.

Other insects that have been mentioned as possible greenhouse pests but have not necessarily been high on the radar include:
  • Bagrada hilaris (Bagrada Bug). Sometimes called the “Harlequin Bug” or Painted Bug, this potential pest is from Africa. It is not clear if it will survive this far north or on our typical crop species. A pest of crucifer/cole crops mostly, it has been exploding in southern California and Arizona, both commercially and in urban areas.
  • Halyomorpha halys (Brown Marmorated Stink Bug). Present in the U.S. (including in Oregon), it is a “hitchhiker” with a very broad host range. The primary damage is caused by its feeding on leaves and fruits (causing distortion, corkiness and cat-facing). It has been reported on both tomatoes and green peppers.
  • Scirtothrips dorsalis (Chili Thrips). Damage often looks more like that of broadmite (i.e., distorted growing points) than of other thrips species but feeding scars on leaves are also often seen. Damage occurs at lower pest numbers and is more severe than for other thrips.

DISEASES
■ Pospiviroids
Columnea Latent viroid (CLVd). First reported on tomatoes in the U.K. in 2007, describing leaf distortion, stunting, leaf bronzing and necrosis. Not yet reported in B.C. One isolated case of another important pospirviroid, Tomato Chlorotic Dwarf viroid, was reported (and successfully eradicated) in Manitoba in 1996, and another, Mexican Pepita viroid, has been identified recently causing severe problems in U.S. greenhouse tomatoes. While seedborne, these viroids are also easily transmitted mechanically.

Tomato yellow leaf curl virus. First detected in the Netherlands in 2007, although present in other European countries for several years prior to that, symptoms include curly leaves in plant heads, leaf margin chlorosis and complete stop to plant growth. Transmitted by tobacco whitefly, it’s not yet reported in Canada.

NOTE: Pest information from Tracy Hueppelsheuser, BCMAL, at Lower Mainland Horticulture Improvement Association Short Course, Jan. 2011. Additional comments from Graeme Murphy and Gillian Ferguson, OMAFRA greenhouse IPM specialists.

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