# Nasturtiums — Blackfly & Caterpillar Control (bee-safe)

Steve's nasturtiums get wiped out every August by two pests. This page captures the diagnosis
and the annual control plan. Context: nasturtiums grown in pots, soil reused yearly, watered via
drip irrigation only in dry spells. Growth/flowering is fine — pests are the problem.

## The two attackers

### 1. Blackfly (black bean aphid, *Aphis fabae*)
Tiny black insects clustered on stems, flower buds and undersides of leaves. **Not butterfly
eggs** — butterfly eggs are laid singly or in pale/yellow clusters and don't crawl. Blackfly
suck sap and coat the plant in honeydew → sooty mould, smothering and killing it.

**Overwintering:** black bean aphids lay eggs on **spindle (*Euonymus europaeus*)** and
**viburnum** shrubs — NOT on nasturtiums and NOT in soil. Winged females fly in every spring.
Steve has a **viburnum (laurustinus, *V. tinus*)** on the property — blue-black berry clusters,
opposite evergreen leaves, reddish stems. That is the egg factory.

### 2. Caterpillars (cabbage white, *Pieris brassicae*/small white)
Nasturtiums are a trap crop for cabbage whites too. Larvae peak in August. Eggs are **clusters of
tiny yellow eggs on leaf undersides**.

## Annual control loop (all bee-safe)

| Enemy | Weapon | When |
|-------|--------|------|
| Blackfly eggs on viburnum | Horticultural/plant-oil **winter wash** (Bug Clear Winter Wash / Vitax) | Jan–Feb |
| Blackfly founders | Squash first cluster + soap spray + ant barrier | June |
| Cabbage white eggs | Squash yellow clusters under leaves | July (weekly) |
| Caterpillars | **Bt spray (XenTari)** — repeat after rain / every 7–10 days | July–Aug |
| End of season | Rip out + bin infested growth (not compost), scrub pots | October |

### Key notes
- **Winter wash** kills blackfly eggs on the viburnum twigs before hatch. Bee-safe (no bees in winter).
- **Ant barrier** (grease band/sticky ring on pot rim or stem base) stops ants farming/protecting
  blackfly — big lever everyone misses.
- **Early colony squashing** is the biggest single lever — stop the first generation in June and
  the year collapses.
- **Herbicide is the wrong tool** for aphids — kills plants not insects, leaves residue. Don't use.
- **Soil reuse is fine** — blackfly don't overwinter in soil. Tip out old roots, check for
  vine weevil grubs (creamy-white C-shaped, brown head), top up but **don't fertilise**
  (nasturtiums flower best in poor soil).

## Bee-safe soap spray (recipe)

- **1 tsp (5 ml) pure liquid soap** — castile (Dr Bronner's) or horticultural soap (Safers).
  NOT Fairy/washing-up liquid (detergents strip leaf wax).
- **1 litre water** (warm helps mixing).
- Optional: **1 tsp vegetable oil** for knockdown/sticking.

**Use:** spray at **dusk** (bees gone; dry+harmless by morning, no residual). Soak undersides,
growing tips, flower buds. Repeat **every 3–5 days for two weeks**, then weekly while colonies
active. Avoid open flowers (petal spotting, not bee harm).

## Soap vs XenTari — don't mix, alternate
- **Soap** = blackfly (aphids), every few days while colonies active.
- **XenTari (Bt)** = caterpillars only, every 7–10 days, after rain. Harmless to bees/adult
  butterflies/birds.
- **Avoid "Bug Clear Ultra"** — acetamiprid (neonic), harms bees.