Brevicoryne brassicae (cabbage aphid)
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Brevicoryne brassicae Family: Aphididae Common name: cabbage aphid Type: Pest |
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Life cycle: Generations per year: up to 15 during growing season
Description: A minute, soft-bodied, sap-sucking insect; elliptical in shape, becoming more round as it matures through the nymph stages. Has six, long, thin legs; two long, six-segmented antennae which are carried over the body; sucking mouthparts called stylets which are enclosed in a sheath called a rostrum; a pair of very short, upright, backward-pointing tubes called cornicles (or siphunculi) located on the 5th or 6th segment of the abdomen; a shorter projection called cauda located above the anal plate. The cabbage aphid is greyish-green in colour. Aphids have a complicated life cycle. In temperate climates, overwintering eggs hatch in spring. The first generation of wingless females (called stem mothers) are already pregnant…reproducing by parthenogenesis (without fertilization). The offspring are born live, called viviparity…a unique phenomenon in this insect. Stem mothers continue to reproduce throughout the summer, typically giving birth to 5 or 6 nymphs per day. When the host plant becomes overcrowded, or its resources reduced, some of the offspring will develop into adults and grow two pairs of large, clear, membranous wings. Once able to fly, these winged adults, called alates, leave the host plant in search of another, fresh plant. In northern climates, towards the end of the season, the stem mothers produce both male and female offspring. This is timed to dropping temperatures and lowering light levels as the season winds down. After mating, the females lay their eggs in the plant debris of the host plants at soil level, where the eggs will overwinter. (In warmer climates, there is no egg stage in the aphid life cycle. The stem females reproduce continuously throughout the year.) Cabbage aphid eggs are black in colour.
Special Notes: Originally native to Europe, the cabbage aphid is now found worldwide. It is generally thought aphids have been on the planet for roughly 280 million years, placing them in the early Permian period. The oldest aphid fossil was found several years ago in China…an almost complete insect, minus part of the antennae and part of its legs. It has been determined to be a completely new species of aphid and named Dracaphis angustata. The aphid fossil was dated and found to have actually lived during the Middle Triassic Age…after the Permian period. To explain some of the body parts on the aphid…the cornicles, or siphunculi, those slightly elevated, slender protrusions on the back of an aphid, are defensive apparatuses which will exude a fluid that hardens when it comes in contact with air as a deterrent to predators. The substance is also thought to contain alarm pheromones. The shorter cauda tube, located above the anal opening, serves to collect the honeydew excreted from the anus and hold it raised so it does not foul the body.
Host plant list: Cabbage aphids are a particular pest to cabbage, cauliflower, broccoli, Brussels sprouts, rape, radishes, numerous mustards, and kale.
Remedial Actions: There are several predator insects which hunt aphids…lady beetles, ant-lions (green lacewing larvae), yellow jackets, European paper wasps, and others. Organically…usually a strong jet of water from the hose, repeated every few days, will dislodge these pests. If possible, and if there are no beneficial insects feasting on the aphids, grasping the affected area of branch between two fingers and sliding them up the branch will squish many of the offenders. Same goes for rubbing fingers over infested leaves. Another plan of attack is to hit the aphids with a soapy water solution…2 teaspoons (10 ml) of dish soap into 4 cups (1 L) of water, but first check to see if there are any beneficial insects present before you start spraying. Concentrated, repeat forays against this pest are required in order to eradicate them. With the fast turnaround in their reproduction cycle, their numbers can get out of hand very quickly.
Posted on November 8, 2018 |
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Teaser Tuesday
by Leslie Cox; Tuesday; November 6, 2018
A bright spot of colour in the garden on a grey November Day.
Foto Friday
by Leslie Cox; Friday; October 19, 2018
The tenacity of life.
A tree clinging to the very edge of a cliff over the Little Qualicum River.
A new “How To” added
by Leslie Cox; Wednesday; October 17, 2018
Have an excess of leaves? Don’t burn them! They can be turned into black gold for your garden beds with just a minimum of effort on your part.
For directions and a list of helpful ingredients to get those leaves composting, go to How To: Compost an Excess of Leaves in the Hot To menu under In the Garden on the main menu bar. Or follow the quick link here.
How To: Compost an Excess of Leaves
Do not burn those leaves! They are a very necessary part of building soil. Their composition adds rich humus as they break down and the nutrients they contain are released back into the soil to feed plants.
Leaves are composted naturally in all wild and neglected environments. Just look at what happens in a forest.
And we can do the same in our own gardens…even speed up the process a little by shredding the leaves first with a leaf shredder, a mulching lawn mower, or a rotary push mower.
Step 1: Prepare an area to compost your leaves. Lay a tarp or piece of heavy plastic on the ground or in the bottom of one of your compost bins.
Step 2: Add nitrogen. This can be lawn clippings, manure, seaweed, or a nitrogen supplement. (See list below.)
- If using lawn clippings: lay down roughly three inches of leaves first, then sprinkle the clippings evenly over top until this layer measures an inch.
- If using manure: lay down roughly four inches of leaves first, then sprinkle the manure evenly over top until this layer measures an inch.
- If using seaweed: lay down roughly three inches of leaves first, then sprinkle the seaweed evenly over top until this layer measures an inch.
- If using a nitrogen supplement: add a dusting to one wheelbarrow load of leaves. Lay down wheelbarrow load of leaves first, then sprinkle the nitrogen supplement sparingly over top.
Step 3: Build up your heap of leaves in increments following the amounts noted in Step 2. Cover the heap with plastic to keep warmth in and the moisture constant.
Step 4: Remove the plastic and turn the heap every now and then. This will re-generate heat within the pile which aids in composting. How frequently you turn the pile will determine how fast your heap of leaves will compost down into rich humus material.
Nitrogen supplements: use any one of these if you do not have enough grass clippings on hand or easy access to a manure or seaweed source. Follow directions in Step 2.
Plant-based:
- Alfalfa meal
- Coffee grounds
- Cottonseed meal
- Soybean meal
