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The pest!
Glasshouse spider mite or two-spotted spider mite (Tetranychus urticae) is one of the most common and destructive pests and is found on a wide variety of edible and ornamental crops. Often known to overwinter in the growing structure and equipment, it is critical growers get on top of this pest early.
Why are they such a problem?
Spider mites can inflict severe damage to plants by piercing the plant cells and sucking out the contents. Common symptoms include leaf yellowing and spotting, webbing and stunted growth. They live in colonies, mostly on the underside of leaves, with adult females laying up to 120 eggs in 3 weeks. At high infestation levels, the mites will produce highly visible silk webbing.
How can I control spider mite?
There are various biological control agents and biopesticides that offer an effective and sustainable alternative to chemical pesticides for controlling spider mites. These include Phytoseiulus persimilis and Naturalis-L.
Add biological controls to your toolkit
All growers know that multiple tools and techniques are required to achieve the best results. Growers' first port of call, after cultural and hygiene controls, should be introducing the biological control Phytoseiulus persimilis, a mite which naturally preys upon spider mites across all stages of their life cycle. Much like their prey, these mites have high reproduction rates and a voracious appetite to help tackle infestations.
Other options for biological control can be integrated when environmental conditions are not conducive for Phytoseiulus. These include Amblyseius andersoni, which is an excellent option for early-season establishment in cooler temperatures and Amblyseius californicus*, which is a highly effective control when temperatures start to exceed the optimum range for Phytoseiulus.
*Amblyseius californicus is released only under licence for use on glasshouse-grown crops, please contact Fargro for further details.
Fargro technical specialists also find Feltiella acarisuga an extremely useful control, particularly in cucumber crops. Feltiella is a tiny parasitic wasp that lays its eggs inside the spider mites’ eggs, which hatch and devour them from inside.
How to control spider mite using Beauveria bassiana?
Beauveria bassiana is a highly effective entomopathogenic fungus included in such products as Naturalis-L . Naturalis-L is a biopesticide that has an on-label approval for all edible crops and ornamental plant production (protected).
Unlike chemical pesticides, Beauveria bassiana leaves no chemical residues and can be used with confidence right up until the day of harvest, giving you flexibility and peace of mind. Beauveria bassiana also offers an excellent resistance management tool, enabling the conventional chemistry that remains to be as effective as possible.
How does it work?
Once Beauveria bassiana is in contact with the spider mites, the fungus produces a series of enzymes and penetration pegs. The fungus then germinates within the insect and feeds upon the nutrients inside the host and multiplies until the host is dead.
The solution is highly effective across the entire lifecycle of spider mites, making Naturalis-L an effective partner in an IPM programme.
An integrated pest management approach
To achieve maximum effectiveness in pest control, it is recommended to adopt an integrated pest management approach that utilises multiple control methods and to take a more preventative, rather than reactive approach to control. Combining Naturalis-L with macrobiological solutions such as Phytoseiulus persimilis will achieve greater control.
Research conducted at the University of Padua, Italy found that the use of Naturalis-L had no impact on Phytoseiulus persimilis egg hatch, leaving them with a near 100% survival rate, whereas spider mite eggs only had a 4% survival rate after the treatment.
Phytoseiulus persimilis should be introduced initially to target early infestations and then followed up with a treatment of Naturalis-L. The synergy between the two solutions will create a more cost-effective strategy, enabling you to produce a high-quality sustainable end product.
If you would like to better understand how to integrate preventive biopesticides into your IPM programme, please contact the Fargro Technical Team on 01903 256856 or email technical@fargro.co.uk
Article written by Fargro Technical