The most common and destructive pests of glasshouses include Whitefly, Aphids and Thrips. These pests result in significant economic losses to fruit and vegetables each year. Globally, losses are estimated in the hundreds of millions of dollars. For example, Western Flower Thrips cause extensive financial losses of at least £3,000 per ha per season to soft fruit growers. The market is large and with 4,969 hectares of strawberries grown in Britain, the cost of damage in that area alone is estimated to run to £15,000,000 each year. The temperate conditions of the greenhouse in conjunction with the plentiful supply of food are ideal for these pests which can result in irreversible crop damage. Prevention is the best way to avoid potential devastation therefore early detection is key to achieving proper control.
Monitoring for pests should be at the forefront of your pest management programme. Early diagnosis will increase the likelihood of minimising damage and gaining maximum control. Russell IPM offer IMPACT sticky boards for glasshouse pest monitoring. The IMPACT range is available in yellow for Whitefly and Aphids and blue for Thrips. They should be placed throughout the crop as a monitoring device.
Blue sticky cards, placed throughout the crop, are a useful monitoring tool to help trap and detect pest problems before they become a problem.
Russell IPM has recently launched a new range of patterned traps that are proven to significantly increase insect catch. The improved products include Optiroll Super sticky roller traps and Impact Super sticky boards. The range has been optimised in colour and pattern following extensive research carried out by Dr Clare Sampson of the University of Keele.
Trials were conducted in commercial tomato crop grown in glasshouses. During the trials, the yellow sticky traps were hung throughout the crop, with and without black oval patterns printed on one side (Fig.1). After 24 hours the traps were examined and the number of Whiteflies (Trialeurodes vaporariorum) were counted on patterned and plain yellow traps.
The patterned traps were found to catch approximately double the number of whitefly when compared to the plain rolls (Fig 2.). This effect was observed at different whitefly densities and seasons, demonstrating that the pattern remains effective at luring pests irrespective of external conditions. Following the success of the trial, Russell IPM has patented the use of patterns on sticky traps to secure the future of the product and potential for development in the agricultural and horticultural industry.
Dr Clare Sampson explained the results further, ‘The increase in whitefly catch was strongest on the back of the patterned traps, with more whitefly concentrated on the edge of the pattern.’
Russell IPM recommend that the sticky boards be positioned just above the plants and readjusted throughout plant growth (see Fig. 3). In low-growing crops, the sticky boards should be placed no higher than 30 cm above the crop and positioned throughout the glasshouse. The rolls can be hung between crop rows just above the plant or parallel to it. Both traps should be monitored regularly.
Patterned trap is available from Russell IPM in both the sticky board and roll format. The Impact boards are available in a variety of sizes whilst the Optiroll sticky roller trap is available in a 30cm and 15cm size. The Impact boards are recommended as a monitoring device whilst Optiroll is suitable for mass trapping due to its larger surface area.
Safe & Sustainable Trapping
Greenhouse pests are often found all over the world due to the favourable warm conditions found within these glass buildings. Due to the lack of natural predators and abundance of food, greenhouse pests can exponentially increase in population size and cause significant damage to produce and plants.
Pest Identification and Specific Treatments
Regular monitoring for pests will allow early identification of an infestation and subsequent treatment before the situation becomes serious. As mentioned earlier, installation of sticky boards such as IMPACT yellow for Whitefly and Aphids or IMPACT blue for thrips, will detect the presence of the insects before infestations become serious.
Following detection of a pest problem, a suitable pest control programme should be selected. The most successful solutions utilise integrated pest management programmes such as the implementation of predatory mites with sticky roller traps.
Integrated Pest Management Programmes Trials
Four years of large scale trials combining the application of natural enemies (mainly the predatory mite Neoseiulus cucumeris) and Optiroll special blue sticky rolls have proved highly effective in bringing Western Flower Thrips under control.
The integration of Optiroll Blue into an existing management programme increased the marketed Class 1 strawberry from 67% to 92% while reducing Class 2 from 33% to 8%.
The combined use provides a robust control system, consistently giving better thrips control than either method alone. The predatory mites feed on thrips larvae, while the traps catch adult thrips, giving growers a holistic solution that is proven to deliver results and increase financial return with the added benefit of reducing pesticide use.
Sampson C, Kirk WDJ (2013) PLOS ONE 8(11): 80787. Figures and statements are based on the application of Optiroll blue, between all tunnels from first flowering, in integration with programmed releases of predatory mites in strawberry grown in semi-protected tunnels and careful selection of a pesticide programme that was compatible with the predatory mites.
What do the growers say?
“Combining predators with traps has been very successful in controlling thrips. We have had no crop loss due to thrips in newly planted fields and minimal loss at the end of the season on a replanted 2nd year field. The cost of the programme is less than one weeks’ loss of production”.
“After taking part in farm trials testing the blue Optiroll from Russell IPM in 2012, I have used the traps routinely on everbearer strawberries. Using the rolls, in conjunction with programmed applications of N. cucumeris throughout the season, has resulted in no fruit being lost to WFT damage.”
Farmers were pleased to find that the Optiroll blue traps, which are selectively attractive to western flower thrips, integrated well with the natural enemies being released in strawberries and that bumblebee pollination was not affected by the traps.
Strawberry fruit bronzing (numbers of seeds surrounded by bronzing*) in plots with and without Russell IPM blue Optiroll traps.
Common Greenhouse Pest Insects
Aphids, including Macrosiphum euphorbiae and Aphis gossypii, are common pests found in glasshouses across the globe. The biggest threat posed by the small greenfly is its ability to transmit plant viruses that affect a range of economically important crops. Secondly, the aphids have a rapid reproductive rate which can lead to heavy and severe infestations. The host range of the common glasshouse aphid is extremely broad and includes fruit, vegetable and fibre crops, ornamentals and flowers.
Damage by aphids is caused by feeding whereby the sap extraction can drain plant nutritional resources quite rapidly. The aphids release secretions during sap extraction from the phloem that can contain pathogenic plant viruses that cause severe damage to the crop. Damage often manifests as curled, dried leaves with occasional yellow spots. Secretions can foster mould development resulting in crop soiling.
Reproduction in Aphids is mainly asexual and is affected by external factors such as nutritional availability, temperature and overcrowding. In glasshouses the females most often produce offspring vivaparously which will then immediately begin feeding from plant sap. Maturity occurs rapidly and winged aphids can occur when infestation levels are extremely high, enabling mobility of the pest to find new plant hosts. Aphids prefer to feed on the underside of young leaves but the entire plant can be used as a feeding point if space is at a minimum.
Control of this pest has proved difficult owing to its rapid reproductive potential, large host range and potential for pesticide resistance. Pesticide resistance occurs rapidly in aphids and in a number of reported cases, the use of chemicals has resulted in further destruction than would have occurred without the treatment. Integrated pest management programmes are becoming the most promising strategies for aphid control. Using aphid predators or parasites in collaboration with yellow sticky roller traps can provide unrivalled control.
Each glasshouse has a diverse range of crops, microclimates and other ecological conditions that result in a unique ecosystem. As insects are living organisms they are very susceptible to slight environmental changes and so control strategies that work in one greenhouse may not work so well in another. In collaboration with various growers in different climates and industries, Russell IPM has developed 3 core products in the Optiroll range that are each suited to the array of environments most commonly found to host aphid species. Not all aphids develop wings and thus, sticky roller traps work most effectively in areas where infestations levels are high.
As a major pest of greenhouse environments, the common whitefly Trialeurodes vaporariorum can cause significant damage in many fruit, vegetable and ornamental crops. The feeding action and secretions produced by the whitefly can transmit viruses and fungi into the plant that prevent it from proper functioning.
Whiteflies feed by inserting a proboscis into the leaf and piercing the plant phloem. The feeding and associated diseases can result in growth stunting or discolouration of the plant due to the physiological stress caused by the pest.
Whiteflies will mature through six life stages which begins with the egg, first, second, third and fourth larval stage, pupae and adult. The eggs are deposited by the female into the epidermal cells on the lower leaf surface, often in a circular formation. The final nymph stage will begin feeding through insertion of the proboscis into the leaf phloem. Once they have located a suitable feeding location, the pest will remain immobile until they reach adulthood.
Due to the possibility of insecticide resistance and the fact that many insecticides are not certified for use inside glasshouses, chemical control methods are not recommended for whitefly control. Furthermore, pesticides can hinder biological control methods and leave unwanted residues on produce. Since the emergence of insecticide-resistant whitefly, biological control methods such as mass trapping in conjunction with predatory mites has proven to be an excellent integrated pest management programme that achieves a good level of control. Each glasshouse has a diverse range of crops, microclimates and other ecological conditions that result in a unique ecosystem. As insects are living organisms they are very susceptible to slight environmental changes and so control strategies that work in one greenhouse may not work so well in another. In collaboration with various growers in different climates and industries, Russell IPM has developed 3 core products in the Optiroll range that are each suited to the array of environments most commonly found to host whitefly species.
Thrips such as Frankliniella occidentalis, can be hard to detect due to their small size and tendency for hiding in small and concealed parts of the plant. Symptoms of plant damage by thrips include: deformation of buds, shape distortion of fruits or vegetables during growth and a range of leaf spots and scars from thrips feeding. The larvae feed throughout the plant and leave the crop susceptible to secondary infection resulting in moulding and wilting.
Despite their small size of approximately 1mm in length the repercussions of Thrips infestations can be huge.
Thrips have six main life stages which includes the egg, two larval, prepupal, pupal and adult stages. Eggs are laid on the underside of leaves, flower structures or fruit. In some cases this can result in wart-like growths but in others it is undetectable.
Larvae mature through two instars in concealed and well-protected plant parts such as within flower petals or under the calyx of fruits. In heavy infestations the larval will become mobile as they attempt to nourish upon all parts of the plant that are above ground. Most thrips, including western flower thrips, fall to the ground in order to pupate.
Finally, the adult thrips will emerge with slender and fringed wings in order to take flight and seek a partner for reproduction.
An integrated pest management programme is required to control thrips because they live a portion of their life cycle on the plant and the other portion is lived in the soil or medium. The best way to eradicate a thrips infestation is to combine OPTIROLL blue sticky traps to control the flying adults and predatory mites such as Neoseiulus cucumeris to control the thrips larvae. The use of pesticides is no longer recommended due to the increasing resistance and the concealed locations thrips most commonly inhabit within the plant making pesticide reach difficult.
Beneficial Insect Control
Predatory mites, Neoseiulus cucumeris