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insect PEST CONTROL


Advice on Pest Control from Harry Niemi, Edmonton Alberta

Lily Leaf Beetles

New to Edmonton over the past couple of years, lily leaf beetles decimate and kill several lily species.


Lily Leaf Beetles are excellent flyers that spread from yard to yard.

The best control is to look for adults on the first warm days of spring as they need to mate. They chew small holes into the leaves from underneath. If you find one adult, there are more hiding out of view or on the verge of emerging as adults from under the surface of the soil. They always go to the top of the lily to attract mates after hatching and once fertilized live and lay eggs under the leaves.

I tried to squish the adults and their larva during the first year with limited success. There were two separate hatches during the summer with hundreds of beetles per hatch. Several lilies did not recover from the attack.

Last year I sprayed my lilies twice early in the year with Raid House and Garden from above and under the leaves as soon as I saw an adult. I also sprayed the soil surface around the plants. I applied this on two occasions. This slowed down the problem, but harms other beneficial insects. 

This year I squished over 35 so far to the end of May. Hard to tell what awaits us for the rest of this season.
Update June 14, 2020. The squished beetle count is now at 74.
Update August 10, 2020, the count is now 107.
Update August 31, 2020, the count is now 127.

My daughter researched this some more and found studies on the lily beetle's pheromones which are released from squished beetles. Apparently, adults are attracted to the pheromone from a great distance. I am now dropping the live beetles into oil which kills them quickly and keeps neighbourhood beetles from finding our lilies.

CONTROL whiteflies

When you get a few in your greenhouse, they multiply rapidly and destroy several different varieties of plants.

Whiteflies rest under leaves making them difficult to spray. Eggs are not affected by insecticides and will hatch.

Removal of the infected leaf is a good control (if you catch them quick enough). The normal cycle from egg to adult is 30 days in a warm environment. Adults lay hundreds of eggs on the underside of leaves. Eggs look like fine white dust. Once hatched, whiteflies attach themselves to the underside of the leaf and remain stationary through several instar stages until they emerge as winged adults.

There are males and females but mating is not necessary for reproduction.

Maintaining a temperature below 62°F will slow the lifecycle.  Whiteflies die when the temperature drops below freezing. Biological control can be obtained with a couple of species of mites that feed exclusively on them.

Spider Mites

Spider Mites are a greenhouse pest reproducing at alarming rates once the temperature is over 80 degrees.

It only took 2 weeks from the first time I spotted minor damage on one of my overwintering plants to total decimation. Every leaf has fallen off the first plant and the two-spotted spider mites spread to several other plants before I realized what was happening. 

I introduced predatory mites (Spidex) as a biological control to the greenhouse in mid-April, but maybe it was too late. This is what can happen when you overwinter plants from the previous season.

It worked, no spider mites anywhere by end of April. Sadly, the infected plants dropped most of their leaves and did not come back properly until the end of June.

aphid CONTROL

Aphids are born in the adult and emerge as live miniature versions of their parent.

Aphids do not lay eggs. They lay living miniature versions of themselves. Some aphids are born already pregnant. They will grow wings to create new colonies on other plants over time. The key to controlling aphids is eliminating the adults. Obvious infestations should be plucked from plants.

*Regular feeding of plants with 20-20-20 reduces the aphid population. Aphids prefer unhealthy or injured specimens.

Biological control is obtained with tiny parasitic wasps (Aphipar). They lay their eggs in the aphid and when they hatch, the new wasps lay eggs until there are no more aphids.

black vine weevils

Tough to control without biological solutions. The beetle larva girdles the roots of certain plants.

Feeding marks from adults are narrow irregular rectangles extending from the edge of a leaf inwards. Adults only feed at night and hide during daylight. They prefer to feed on specific plants including ivy, kiwi, passion fruit, berganzea, rhododendron, etc. 

Black Vine Wevils are not native to Alberta and have arrived with bedding plants from Eastern Canada and the US. The larva survive winter underground.

All black vine weevils are female and lay 5 to 6 eggs per day for several months 60 days after emergence as an adult. Their eggs are perfectly round and cream coloured and laid on top of the soil. The grubs hatch and burrow into the soil. They feed on the roots of certain plants and will girdle roots until the plant dies.

The best control I have found are nematodes that invade the larva. This is a biological control that must be applied before freeze-up. I have been using biological controls for over a decade. Visit Koppert for more info. 
Koppert.ca

LEAF HOPPERs

The leaf hoppers I had for almost 20 years would hatch twice every year on my Engelman Ivy and Virginia Creeper.

When we planted the Virginia Creeper and Engleman Ivy,  they would turn bright red in the fall and look spectacular. A few years later, leaf hoppers invaded our yard. They eat the leaves from underneath and destroy the leaves before fall arrives. There are two hatches every year with clouds of adults in the evening. When these hatches occur, eggs are layed on the underside of new leaves. In the fall, leaf hoppers lay eggs in the stems of the plants as well as under leaves. Adults overwinter in dead refuse.

I learned this method 3 years ago. Watch for adults on the first warm days of spring when they become airborn and begin to mate. A single liberal application of Raid House and Garden to the flying insects during the spring hatch has eliminated the pest completely from hundreds of feet of 6 foot tall fencing. They appear to be gone altogether.