Preventative action is key for cabbage maggot control in leafy brassicas
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Cabbage maggots can wreak havoc on transplanted brassica seedlings – they bore into the stems of new transplants, creating a tunnel that ultimately leads to stunted, yellowed or, in the worst case, dead plants. Even if plants don’t die, their roots are full of wounds that are prime entry points for other harmful pathogens. To reduce yield loss potential, it's important that growers take preventive measures to control cabbage maggots.
Multiple generations per season
Cabbage maggots are the larval form of cabbage root flies – small grey-black flies that emerge from the soil in early spring. Adult females immediately lay small, white, torpedo-shaped eggs below the soil line and these hatch in as little as three to seven days. The larvae start feeding on seedling roots right away and continue feeding for up to four weeks before they pupate and start the cycle again.
While this lifecycle allows for two to three generations of cabbage maggots per season, it’s the first generation in the spring that causes the most significant economic damage to brassica transplants, such as broccoli, cabbage and cauliflower*.
Scouting for cabbage maggot
To check for eggs, gently disturb the soil around and near seedling stems – a small knife, chopstick, paint brush or similar tool will be helpful. Look for clumps of two to twelve eggs laid alongside the stem or near to it, noting that occasionally, eggs are laid singly. Cabbage root fly eggs are very small – about one-eighth of an inch – oblong and white.
According to the Ontario Ministry of Agriculture and Rural Affairs (OMAFRA) there are no economic thresholds for cabbage maggot, and the presence of eggs on or near seedling stems is enough to consider the plant infested and likely to experience feeding damage.1 This is why taking preventative control measures is absolutely critical when it comes to managing cabbage maggot in leafy brassicas.
Success™ insecticide offers a solution
Getting cabbage maggots under control is tough. There are few insecticide options since timing is a challenge given how quickly larvae hatch and start feeding, and they are difficult to reach because they live and feed below ground.
But there is a solution for growers that can be applied at the time of transplanting: Success™ insecticide with Qalcova™ active (spinosad). Qalcova active is a unique class of insecticide that is derived from naturally occurring soil bacteria species called Saccharpolyspora spinosa.
Success insecticide is an important tool for integrated pest management (IPM) plans. Success offers growers a unique Group 5 mode-of-action that can be safely rotated with any other insecticidal group, is very active at low rates, is very effective against cabbage root maggot in brassica transplants and is safe for beneficial insects when used according to label directions.
Drench before transplanting
Brassica seedlings are most vulnerable right after transplantation. Success insecticide, applied as a drench 24 hours prior to field transplantation, offers seedlings effective protection against cabbage maggot as plants establish.
Specifically, Success is applied at a rate of 12.5 mL to 2 L of water per 1,000 plants, followed by another 2 L of water to rinse the product off the plants and into the growth medium. This process neatly positions the active ingredient in the transplant so that when seedlings are planted in the field, the larvicide is already in the plant tissue ready to be ingested by cabbage maggot larvae when they feed.
As with many below ground insect pests, once you see damage caused by cabbage maggot, it’s too late to do anything to recover those plants. Preventative strategies, like applying Success insecticide with Qalcova active prior to transplant, are the best defence against this voracious pest.
To learn more about how Success can fit on your farm, contact your local Corteva Horticulture Expert.
*Except for rutabaga, which is negatively affected by all generations of cabbage maggot.
1Ontario Ministry of Agriculture and Rural Affairs, Cabbage Maggot page: https://www.ontario.ca/page/cabbage-maggot
