Whitefly on Aubergine Moneymaker Cleared with Encarsia Formosa Cards Under Glass

Greenhouse whitefly, Trialeurodes vaporariorum, moves onto the undersides of Solanum melongena leaves within days of the first honeydew flecks showing on lower foliage. On Moneymaker aubergines under glass, the fastest rise comes at 22 to 25 degrees Celsius, with numbers roughly doubling every 10 days when the pest is left unchecked. Encarsia formosa, the chalcid wasp sold on hanging cards by suppliers including Ladybird Plantcare and Dragonfli, attacks the scale stage. Pupae taken by the parasitoid turn black, giving a visible measure that adult trap catches alone cannot supply. Each card release point carries parasitised scales that emerge over 7 to 10 days, so wasp emergence is spread across a whitefly population with overlapping generations.

Release before honeydew takes over

Late releases fail often. Hang a yellow sticky trap at canopy height, one per 10 square metres, and use the first weekly catch as the trigger: put in the first Encarsia card when the trap shows one to three adults across the week, before honeydew and sooty mould reach the third leaf tier.

At that early density, roughly one card per 5 to 10 plants keeps pace with the pest. Two to three introductions at fortnightly intervals cover the build-up period. By the fourth week, the black-scale count on lower leaves shows whether the wasp is established or whether a hot, dry corner has slowed emergence and searching.

Read the black scale before buying more

Blackened scales show successful parasitism; pale, flat scales still contain live whitefly. Count both on three lower leaves per plant before ordering repeat Encarsia cards, because a rising black fraction shows the current wasps are gaining and another batch would waste money.

Temperature, humidity and vent settings under glass

Encarsia formosa searches poorly below 18 degrees Celsius, and its flight drops away on bright, cold spring mornings. A lean-to glasshouse against a north wall can stay cool at plant height even when the ridge feels warm. The wasp needs sustained daytime warmth of 20 to 25 degrees to parasitise at a rate that outpaces Trialeurodes egg-laying. Clip a maximum-minimum thermometer at mid-canopy for the useful reading; ridge-level warmth can disguise cold around the crop. A run that dips to 14 degrees overnight in April will establish slowly, however many cards are added.

Dry, still air suits whitefly and also dries the parasitised scales on the card before adult wasps emerge. Damping down the path and staging in the morning helps hold relative humidity above 50 percent, supporting emergence without soaking the foliage. Wet aubergine flowers invite Botrytis, so leaf wetting should stay limited.

Aubergine has its own humidity demand. Below 60 percent humidity, pollen clumps and flowers may drop. The same damping-down routine that helps Encarsia also supports fruit set.

Root watering should stay separate from leaf wetting. A Hozelock drip irrigation kit set to two short pulses a day keeps compost moisture even and leaves dry. Splashing the undersides of leaves can dislodge young wasp scales, so overhead watering works against the biological control.

Vent settings decide how long the house stays in the wasp’s working range. Opening the ridge vent hard at 26 degrees removes heat, while adult whitefly can disperse to neighbouring tomato plants and spread the problem across the house. A vent cracked at 24 and fully open by 28, paired with a lower-level louvre, smooths the swing and keeps the internal temperature usable for more of the day.

Getting Moneymaker big enough by April

Moneymaker aubergine needs a long season. Sow from late January to mid-February in a heated propagator held at 21 to 27 degrees Celsius, because seed germinates erratically below 20 degrees and can take three weeks on a cool windowsill. A Vitopod or similar thermostatically controlled propagator set to 25 degrees usually brings emergence down to 8 to 12 days. Prick out at the first true leaf into 9 cm pots, then move plants into 3 or 5 litre containers, or into a border, once roots fill the pot and night temperatures under glass hold above 15 degrees.

Early sowing feeds back into whitefly control through plant vigour. A Moneymaker plant that reaches 40 cm with a strong stem by mid-April has enough leaf area to tolerate a low-level infestation while Encarsia catches up. A stunted March-sown plant loses a larger share of its photosynthetic area to the same colony. Feeding starts once the first flowers set: a high-potash tomato feed at half strength twice a week supports fruiting without pushing the soft, sappy growth that whitefly prefer. Nitrogen-heavy feeding produces tender foliage that lets a colony expand quickly, so the potash bias is part of pest management as well as fruit production.

Calcium symptoms that get blamed on insects

Greenhouse tomato calcium feed advice transfers directly to aubergine, and it belongs in whitefly planning because calcium-related fruit disorders are often blamed on pests. Blossom-end rot on aubergine appears as a sunken brown patch at the flower end. It develops when calcium fails to reach the fruit tip during rapid swelling, almost always after a drip schedule allows compost to dry and then floods it. In peat-free multipurpose compost that already carries adequate calcium, erratic watering is the usual cause.

A Hozelock or Blumat drip kit should deliver water little and often: four to six short cycles across a hot day gives steadier moisture than one heavy soak. Where water is soft, calcium nitrate feed at 150 to 200 parts per million calcium once a week during heavy fruiting can close the gap. It also adds nitrogen, which pulls against the potash bias, so reduce it once the disorder stops appearing. The practical check is simple: the compost surface should never crust dry between cycles, and a moisture meter probe pushed 5 cm into a 5 litre pot should sit consistently in the mid range.

Raised bed spacing and the Solanum rotation

In a raised bed under a polytunnel or cold frame, Moneymaker aubergines need 45 to 60 cm between plants and 60 cm between rows. That is wider than many kitchen garden charts suggest for the crop. The extra air movement supports pest control because dense planting traps still, humid air that whitefly favour and blocks the light and access Encarsia needs to patrol leaf undersides. A single 1.2 metre wide raised bed holds two staggered rows at most; three rows crowd the crop.

The rotation point follows from the family. Aubergine, tomato and potato all sit in the Solanaceae, sharing pests and soilborne disease. A bed that grew blight-susceptible maincrop potatoes last season carries risk for this season’s aubergines. Blight resistant potato varieties such as Sarpo Mira and Carolus reduce airborne Phytophthora pressure in the potato crop itself, although they do not sterilise the ground for the following Solanum crop. Keeping aubergines out of any bed that held potatoes within the last two years, and placing them where alliums or legumes grew, reduces carryover of eelworm and overwintering whitefly sheltering on volunteer Solanaceae.

Wide spacing and a clean rotation slot give biological control a house where it can work.

Worked count for a 10-plant tunnel run

Take ten Moneymaker aubergines in a border, two yellow sticky traps, and a first catch of two adults per trap in the second week of May. That trip point calls for the first Encarsia release. At one card per five plants, use two cards, each seeding roughly 60 to 100 scales. Split them between plants three and eight so emerging wasps spread from the centre outward. A second identical release two weeks later covers the next whitefly generation.

By early June, count black parasitised scales against pale live ones on three lower leaves per plant. A black fraction climbing past half across most plants means the two releases established and a third batch is unnecessary. A fraction stuck below a quarter, paired with rising trap catches, points to a cool corner or dry-air problem, with another card and a humidity correction needed.

Those counts show the difference between an Encarsia population that is catching up and one that is failing to establish.

The black-scale count also leaves one blind spot: it records parasitism on aubergine leaves, while mobile adults may still drift through vents onto nearby tomatoes where traps have yet to be hung. The awkward part is that adult movement between crops is easier to suspect than to prove from black scales on aubergine leaves.