Aphid control strategies in the spring
Published in the Davis Enterprise April 24, 2003
At this time of year winged female aphids are landing on your roses and fruit trees. These are pregnant and give birth to 50 or more babies each day. Each baby is a pregnant female! These do not have wings. These are not the same as the black aphids that you find later in the season, which tend to be on the undersides of the leaves, are harder-bodied and more difficult to kill.
Do nothing at first! Watch the aphid population for a few days, and leave your porch light on at night. Leatherwing beetles and ladybird beetles may show up and start eating them (they'll also be attracted to your porch light, so you can tell if they're in your yard). If the population seems to be stable or decreasing your problem may simply go away. If you want to help diminish the population, you can try the following strategies:
- Blast them off daily with water. This knocks the pregnant adults off and kills them. More vigorous spraying may be needed to knock off the babies, which are more securely attached to the plant.
Spray with any of the following pesticides:
- Insecticidal Soap. Quick kill of those that are present; will need to be repeated daily. Our hard water reduces the effectiveness of soap sprays. You can make your own spray out of soap that you buy at the store, but it can't be a detergent and we don't have a rate of application to recommend. There is a risk of burning foliage if you make it too strong, so it's better to buy a product which has been tested and labeled for this purpose.
Pyrethrum. Quick kill of those that are present; will need to be repeated daily. Material breaks down immediately. Toxic to beneficials, but only for a short period.
Synthetic pyrethroid (several different ones are available). Quick kill of those that are present, lasting for a day or so. Material breaks down in a couple of days. Toxic to beneficials for a couple of days.
Neem products. Somewhat effective at smothering those that are present. Repels new winged aphids that are landing. Material breaks down fairly quickly. Moderately toxic to beneficials for a short period. Provide some fungus prevention as well. Very effective on whiteflies.
Paraffin oils. Very effective at smothering those that are present and any that land within the next few hours after applying. Material breaks down fairly quickly. Toxic to beneficials for a few hours. This is what we use in the nursery yard.
Systemic spray combined with a synthetic pyrethroid. Provides quick knockdown, then the systemic part provides continued kill for up to 30 days. Aphids have to feed on the plant for it to kill them. Material breaks down very slowly. Toxic to beneficials for a couple of days.
Apply a fertilizer/systemic insecticide combination. Provides slow kill. Aphids have to feed on the plant for it to kill them. Material breaks down very slowly. Not directly toxic to beneficials.
Spray an "old-fashioned" insecticide such as Malathion or Orthene. Provide quick kill and continue to do so for a few days. Materials break down fairly slowly. Somewhat to very toxic to beneficials.
© 2008 Don Shor, Redwood Barn Nursery, Inc., 1607 Fifth Street, Davis, Ca 95616
Feel free to copy and distribute this article with attribution to this author.
Click here for Don's other Davis Enterprise articles