Pests in the protected

With the expansion of cultivation in protected environments in Brazil, it was found that some species of insects and mites became serious problems inside greenhouses, causing considerable losses in quantity and quality of production.

The main arthropod pests of protected crops are: tomato moth, whiteflies, aphids, mites, thrips and miners, which occur mainly in tomato, pepper, lettuce, cucumber and melon crops. The high temperature and low humidity, which normally occur inside greenhouses, the absence of mortality factors and small areas with a high density of plants, favor the population increase of these pest species, making their control difficult.

The tomato moth occurs in the crop throughout the cycle, with the critical period being fruit formation. The larvae form mines in the leaves and feed inside them. They also bore the stem, pierce the terminal shoot and attack the fruits.

Whiteflies are pests of great economic importance in greenhouses, occurring in tomato, pepper, lettuce, cucumber and melon crops. They are present throughout the entire crop cycle, with the critical period being from the seedling phase to 30 days after transplanting. They cause damage by directly sucking plant sap and transmitting viruses.

Aphids are mainly associated with tomato, pepper, lettuce, cucumber and melon crops. They can occur throughout the crop cycle, but the critical period goes from the seedling phase to 30 days after transplanting. They cause yellowing and deformation of the foliage, which can reduce yield. They transmit the Y, yellow top and yellow bottom viruses of tomato plants.

Mites occur in tomato, pepper and cucumber crops, mainly at the end of the cycle. They cause yellowing or reddish spots on the side opposite the colonies, which grow until the leaves fall and the plant dies.

Thrips occur on tomatoes, peppers, cucumbers and lettuce. They can attack the crop throughout the cycle, but the most critical phase is up to 60 days after transplanting. They cause direct damage, by scraping the leaves and sucking the sap, and indirect damage, as vectors of viruses.

Leafminers occur in tomatoes, lettuce and cucumbers from germination to harvest. The larvae penetrate the leaflets, digging irregular galleries or mines and destroying the leaf parenchyma, causing the leaves to dry out.

For efficient management of these pests in a protected environment, preventive measures must be adopted at the beginning of the crop, since it is easier to prevent pests from entering greenhouses than to control them. It is therefore recommended:

a) clean the greenhouse before planting again;

b) destroy cultural remains;

c) eliminate external vegetation;

d) use seeds and seedlings free of insects and mites;

e) use mechanical protection against arthropods, such as anti-aphid (aphid) and thrips screens, along the sides;

f) install, inside and outside the greenhouses, yellow traps, covered with glue or burnt oil. These traps aim to retain insects (whiteflies, aphids, thrips and miners) and help monitor pests, alerting the farmer about the species present and the population level. The traps must be hung inside the greenhouses, between the plants, at the height of their upper part.

Even with the adoption of these measures, arthropods can enter greenhouses and, finding favorable conditions for their development, establish themselves as pests. It is recommended to adopt a sampling system, aiming to monitor the presence of pests, so that the infestation is detected at the very beginning, allowing the adequacy of control measures. Sampling must be done randomly, covering the entire internal area of ​​the greenhouse. Plants should be inspected at least once a week to check for the presence of eggs, larvae or adults of insects and mites and for symptoms of damage. To check for the presence of tomato moth, it is recommended to look for eggs and larvae in the leaves and flowers in the upper third of the plant. For whiteflies, aphids and thrips, monitoring must be carried out, looking for the presence of colonies on the underside of the foliage. For thrips, also look inside flowers, flower buds and shoots. For spider mites, watch for symptoms and webbing on the underside of the foliage. For leafminers, observe the number of mines and the percentage of mines with live larvae. Outdoor host plants for pests must also be periodically inspected and, when necessary, sprayed.

Other integrated management tactics are recommended to keep the pest population below the level of economic damage. Among them, we can mention the use of resistant cultivars, chemical control, biological control and the use of sexual pheromones, when commercially available.

The sex pheromone is used in traps distributed in the greenhouse, with the aim of capturing insects, monitoring the presence of the pest, and helping to determine its population growth.

The efficient use of chemical control involves the correct identification of the pest and the phase of its biological cycle of greatest damage; choosing the most appropriate product and form of application, taking into account the mode of action, toxicological class and price; obedience to the manufacturer's recommendations regarding the indicated dosage and withdrawal period.

Biological control using parasitoid eggs

, has shown great potential for controlling tomato moth (

). It presents itself as a promising technique to be used in a protected environment, and is the object of study by Embrapa Hortaliças. This technique, in addition to controlling the pest, is specific and harmless, causing no harm to humans or the environment.

Geni Litvin Villas Boas

Embrapa Vegetables