Vol. 1, Issue 5 (April 2001)

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

 Thrips

Thrips population is on the increase. Their numbers went up from 12 to 18 thrips per trap. Thrips were identified on marigolds and petunias. Keep in mind that thrips are difficult to control with insecticides. They prefer confined spaces. Generally adults are found deep in flowers, larvae in growing points, and pupae in soil. To ensure that all stages of the lifecycle are targeted, apply any particular insecticide three times at 5-day intervals. Rotate insecticide classes after each 3-spray cycle to avoid the development of resistance. Effective insecticides include Trumpet® (bendiocarb), Malathion, and Nicotine Sulphate.

Fungus Gnats

Fungus gnat populations are still high. The fungus gnat life cycle, from egg to adult, may be completed in three to four weeks. Females lay up to 200 eggs. Most of the insects' life is spent as larvae and pupae in organic matter or soil. Therefore most insecticides, especially those in the class of "insect growth regulators" (IGR), control only the young developing larvae and will have no direct activity against adults. Commercially available IGRs include Dimilin®, Citation® and Neem. Neem at this stage is an experimental insecticide that we are testing in our greenhouses. Dimilin® (diflubenzuron) is registered for the control of fungus gnats. Do not exceed label rates, volumes or number of applications.

Whitefly

Whitefly numbers were low. Whiteflies were seen on mandervilla plants in one greenhouse. Only adults were seen but soon they will lay eggs to start the next cycle of multiplication. The whitefly life cycle, from egg to adult, may be completed in three to five weeks. Females lay up to 175 eggs. Impower® (imidcaloprid) and Enstar II® are registered for control of whiteflies and aphids in greenhouses on ornamental plants.

Shore fly

Shore fly numbers are still low in areas where Citation has been used. Then again, we have noted a gradual increase in areas where no insecticides have been used. Dimilin® is also registered for shorefly control.

Spider mites

Watch for spider mites in dracaenas, impatiens and roses. Inspect foliage closely using a hand lens of 10X magnification. Commercially registered miticides for spider mite control include Vendex®, Kelthane, Dynomite®, and Avid®.

Aphids

Aphids have been observed on peppers, tomatoes, periwinkle and ipomea. Don't let them get out of hand. Good coverage of insecticides is needed to destroy them.