Category Archives: Insecticides

Scouting for onion thrips

Onion thrips (Thrips tabaci) feed on more than just onions; they also feed on cabbage, leaf lettuce, a variety of other vegetables and fruits, field crops, and many weed species. Thrips are unique from other insects as they have rasping-sucking mouthparts that allow them to scratch the cell walls of leaves, suck up the cell contents including the chlorophyll, and leave behind a shiny, translucent trail on the leaf. A single female can produce Continue reading Scouting for onion thrips

Time to Scout for Asparagus Beetles

Asparagus beetle activity is on the rise. The adult beetles hide in soil cracks or underneath residue during the heat of the day.  Egg laying is often the most obvious sign of their activity. The presence of eggs on the harvest spears, may affect marketability. On young fern, heavy amounts of larval feeding has a negative impact on growth and development.

As harvest concludes, scout plantings regularly as the spears begin to elongate and develop a full canopy of fern. Spray thresholds are as follows:

Eggs:   2 /10 spears with eggs
Larvae:   50% of plants with   larvae OR 10% Defoliation
Adults:   5-10% of   plants infested

If controls are required during the harvest season, play close attention to the pre-harvest intervals.  Products with a 24-hr pre-harvest interval include: malathion (Malathion 85E), cypermethrin (Mako, Upside 2.5 EC), and acetamiprid (Assail 70WP).

Spotted Asparagus Beetle (Hannah Stevens, retired MSU)
Common asparagus beetle (Hannah Stevens, retired MSU)

Cabbage Maggot; An old pest with limited options

The cabbage maggot (Delia radicum) is the larvae stage of the cabbage root fly which can cause severe damage to all Brassica crops. The adult cabbage maggot is a fly that is about half the size of a house fly and is grey in colour.

In the early spring, cabbage maggot flies emerge from the soil and the females lay small, white eggs ~2-10 cm below the soil line. Depending upon the temperature, eggs hatch 3-7 days later as larvae that immediately start boring Continue reading Cabbage Maggot; An old pest with limited options

Potato Insects – Insecticide Activity Table

Here is a quick reference guide for insecticides registered on potatoes in Ontario. Use it as a guide only, always refer back to the label. Remember to rotate insecticide groups for resistance management.

Potato Insecticide Activity Table Final

Printable Potato Insecticide Activity Table

Continue reading Potato Insects – Insecticide Activity Table

Carrot Weevil Control Update

Carrot weevil remains the most important insect pest to many Ontario carrot growers, and the amount of damage seems to be increasing in recent years. Carrot weevil females overwinter in the soil and plant debris and lay their eggs in cavities in the crown of the carrots. These eggs develop and hatch into larvae and begin to feed on the carrot root. Feeding damage from the carrot weevil larvae causes unmarketable tunneling near the crown of the carrot and can account for significant losses to commercial growers.

Continue reading Carrot Weevil Control Update

Preventing Yield Loss from Flea Beetles

Flea beetles are a common crop pest of crucifers in Ontario and overwinter as adults near the soil surface in debris and stubble from the previous crop. They typically become active with the first extended period of warm weather in the early spring as the leaf litter begins to thaw. The beetles feed on weeds throughout the field and have the ability to fly on calm days and will attack brassica seedlings as they emerge or transplants as they are planted.

Females will begin laying eggs in soil for about 30 days. Flea beetle larvae will hatch from eggs 12 days later and feed on the root hairs and taproots of seedlings. Left unchecked, adults will feed on leaves of transplants and the larvae will burrowing into the plant near the juncture of the root and stem. Continue reading Preventing Yield Loss from Flea Beetles