APRIL–JUNE
Rose aphid
Coats buds and shoot tips in spring. Low to moderate numbers do little damage, and heat and predators usually end it.
Crop hub · Garden · Home garden
Roses
Aphids are the commonest insects on roses. UC IPM names three, the rose aphid, the potato aphid and the cotton or melon aphid, and handles them all the same way. In most of California they are a problem for about six weeks in spring and early summer. The lady beetles, lacewings, hoverflies and parasitic wasps that arrive on their own do most of the work, and in many gardens a strong jet of water early in the day is all that is needed on top. UC IPM says broadly toxic insecticides are not warranted in most gardens.
If the problem is holes in rose leaves, the shape of the hole names the culprit. See-through windows grazed between the veins in late spring are rose sawfly larvae, which Bt cannot kill because they are not caterpillars. Leaves eaten to a lace of veins in July are Japanese beetle. Ragged holes in the open blooms in June are rose chafer. Neat semicircles cut from the leaf edge are leafcutter bees, native pollinators that UC IPM says have no effective control, and need none.
In Florida and Texas, chilli thrips are the exception to the cosmetic rule. They bronze and curl the newest leaves and buds, and in a Florida field study on Knock Out roses and buttonwood they made up 95% of the thrips collected from the plants. On the roses, heavier damage went with fewer and smaller flowers.
crop context · shrub rose, early summer
What eats roses, in the order it arrives
MAY–JUNE
Rose sawfly
Grazes leaves into see-through windows. The RHS says plants usually recover with no effect on flowering.
ReleaseNothing to releaseHose or hand-pick; Bt does not work
LATE MAY–JUNE
Rose chafer
Tan, long-legged beetles chew holes in open blooms for three to four weeks. Worst near sandy soil.
ReleaseNothing to releaseHand-pick, or net the bushes
JULY–AUGUST
Japanese beetle
Skeletonises leaves and eats the flowers in midsummer. Pheromone traps draw in more beetles than they catch.
ReleaseNothing to release for the adultsShake into soapy water early in the morning
MAY–SEPTEMBER
Rose leafhopper
Pale yellow hoppers under the leaves leave a pale stippling. The RHS finds roses are often able to withstand large numbers.
ReleaseNone neededTolerate — no control needed
SPRING TO AUTUMN · FL & TX
Chilli thrips
Bronzes and curls new growth and buds. Heavier damage goes with fewer, smaller flowers.
Season calendar
US GARDENS · QUALITATIVE READING OF EXTENSION SOURCES| J | F | M | A | M | J | J | A | S | O | N | D | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rose aphid | Jan: Quiet | Feb: Quiet | Mar: Building | Apr: Pest pressure high | May: Pest pressure high | Jun: Pest pressure high | Jul: Building | Aug: Quiet | Sep: Quiet | Oct: Quiet | Nov: Quiet | Dec: Quiet |
| Rose sawfly | Jan: Quiet | Feb: Quiet | Mar: Quiet | Apr: Quiet | May: Pest pressure high | Jun: Pest pressure high | Jul: Building | Aug: Building | Sep: Quiet | Oct: Quiet | Nov: Quiet | Dec: Quiet |
| Rose chafer | Jan: Quiet | Feb: Quiet | Mar: Quiet | Apr: Quiet | May: Building | Jun: Pest pressure high | Jul: Building | Aug: Quiet | Sep: Quiet | Oct: Quiet | Nov: Quiet | Dec: Quiet |
| Japanese beetle | Jan: Quiet | Feb: Quiet | Mar: Quiet | Apr: Quiet | May: Quiet | Jun: Building | Jul: Pest pressure high | Aug: Pest pressure high | Sep: Building | Oct: Quiet | Nov: Quiet | Dec: Quiet |
| Leafhoppers | Jan: Quiet | Feb: Quiet | Mar: Quiet | Apr: Quiet | May: Quiet | Jun: Building | Jul: Pest pressure high | Aug: Pest pressure high | Sep: Building | Oct: Quiet | Nov: Quiet | Dec: Quiet |
| Chilli thrips (FL, TX) | Jan: Quiet | Feb: Quiet | Mar: Quiet | Apr: Building | May: Pest pressure high | Jun: Pest pressure high | Jul: Pest pressure high | Aug: Pest pressure high | Sep: Pest pressure high | Oct: Pest pressure high | Nov: Building | Dec: Quiet |
- Pest pressure high
- Building
- Release window
- Quiet
- Rose aphid · high pressure Apr–Jun
- Rose sawfly · high pressure May–Jun
- Rose chafer · high pressure Jun
- Japanese beetle · high pressure Jul–Aug
- Leafhoppers · high pressure Jul–Aug
- Chilli thrips (FL, TX) · high pressure May–Oct
Starter program
Garden roses need no release program. This is the order of jobs through a season, for a garden that has had no broad-spectrum sprays this year.
- SPRINGHose the aphids offA forceful spray of water early in the day, repeated as needed, is often all that natural control needs as a supplement
- SPRINGKeep ants off the canesAnts guard aphids from their enemies; sticky barriers or baits may improve biological control
- ALL SEASONHoverfliesGrow open flowers near the roses to feed the adults whose larvae eat aphids
- MAY–JUNECheck the leaves for rose slugsPick or hose them off, or spray young larvae with insecticidal soap. Bt will not work
- JUNE–AUGUSTShake beetles into soapy waterRose chafers from late May, Japanese beetles a few weeks later; skip the pheromone traps
Setting up the garden
Most rose damage is cosmetic, so the choices that matter most are what not to spray.
Skip broad-spectrum sprays
UC IPM says broadly toxic insecticides are not warranted in most gardens, and spider mites often build up after carbaryl or pyrethroid sprays.
Leave the systemic out
Soil-applied imidacloprid controls aphids but is not usually necessary, and UC IPM warns it may harm pollinators and natural enemies.
Soap or oil, if anything
Insecticidal soap, horticultural oil and neem oil suppress aphids with only a moderate impact on natural enemies.
Leave the leafcutter bees alone
Neat semicircles cut from the leaf edge are nest material for a native pollinator. There is no effective control and no need for one.