Depending on the species, whitefly feels particularly comfortable in temperatures between 20 and 30°C. Flying adult insects spread the infestation, but attacks from outside the greenhouse are also a threat.
Whitefly has six development stages: the egg stage, four larvae stages (including pupa), and the adult insect. The greenhouse whitefly tends to spread over the plant vertically, considering that the larvae can only move in the first stage. The adult insects prefer to lay their eggs on young leaves well inside the plant, and this is where you tend to find the eggs and young larvae of greenhouse whitefly.
Whitefly simply blow in
If the population on the infected plant grows too large, the adult insects will fly to another plant in search of somewhere to lay their eggs. There is also a threat of spread due to an attack from outside the greenhouse. In countries like Spain, where polytunnels are still widely used, infestations often just ‘blow’ in. This occurs in countries with high tech greenhouses too, particularly when the windows are open during warmer weather. Another source of contamination is already infested plant material brought in from elsewhere.
Although the greenhouse whitefly does not have any particular overwintering stage, it is capable of surviving for some time on plants with hardy leaves. Eggs can even survive temperatures below freezing (more than fifteen days at -3°C/26.6°F and five days at -6°C/21.2°F). By contrast, the life of the greenhouse whitefly is relatively short in very high temperatures.
Spread over the plant
In contrast to the greenhouse whitefly, which prefers to reside inside the plant, the tobacco whitefly spreads out over the plant in its entirety. The females lay their eggs on the underside of the leaves, just the same. Adult insects can spread by flying or simply on the wind. While the greenhouse whitefly prefers temperatures to be on the more moderate side, the tobacco whitefly is in its element in higher temperatures. An adult female is capable of surviving for ten to fifteen days at temperatures around 30°C/86°F. At the same time, an infestation can also live in and survive winter conditions, even in an empty greenhouse devoid of host plants. However, the tobacco whitefly cannot survive temperatures below freezing.