Vol. 1, Issue 2 (March 2001)

This page is brought to you with the co-operation of the Alberta Research Council and Alberta Agriculture, Food & Rural Development.


Reports on trap catches indicates that thrips populations are the same as last week. The number of thrips caught per trap ranged between 0 and 37. As we said before Tomato spotted wilt tospovirus (TSWV) has been observed on begonias and impatiens. Therefore, continue to check for thrips in your crops. Plant foliage showing damage symptoms due to thrips feeding are normally distorted or new growth is stunted. Once the populations are increasing it is time to use chemical or biological controls. Keep good records of type of pesticides applied, rates and time and date of application.

Fungus Gnats

Fungus gnats population increased. Populations are expected to increase with plant growth. Good sanitation is important to control fungus gnats. For example, avoid wet floors and clean up spilled media. This is the time to apply biological controls as well. Hypoaspis sp is a predatory mite for fungus gnat and naturally inhabits the top layer of soil. The females lay their eggs in the soil and the nymphs and adults feed on soil-dwelling insects, including fungus gnat larvae, springtails and thrips pupeae. Their entire life cycle takes about 10 days. We will talk about Nemasys in the next issue.


The population of whiteflies is at the same levels as last week. Continue monitoring and remember to act quickly when they are detected, especially if you are using Encarsia formosa for control. Whitefly predatory beetle should also be considered for release. Remember if you have trapped one whitefly there are several more which escaped the traps.

Shore fly

Shore fly numbers has jumped from less than 1 per trap last week to about 7 per trap this week. They prefer damp areas and algae.

Spider mites

Spider mites may not be trapped on yellow traps because they do not fly. During a greenhouse visit spider mites were seen on dahlia leaves. Look for small pin head type of injury on the upper surface of leaves and young spider mites on the underside of the leaves. You may see two spots on the sides of these young spider mites. They were also noted on older leaves of marigolds. Spider mites attack plants which are under stress. This stress may be due to water logging, drying out, transplant shock over fertilization. Several spider mite predators are available.


Aphids have been observed on peppers. They may not be seen on traps at this stage. They may look green and may hide easily in the new buds of peppers. The leaves my appear as if have been chewed and small irregular holes on young leaves may be present.