Adam Sisson, Iowa State University, Bugwood.org
Western Flower Thrips (WFT) have shown varying levels of resistance to most of our conventional pesticides. Soil-borne diseases such as fusarium and verticillium cannot be managed with conventional fungicides and must be targeted with fumigants to prevent infection. Biologically-based controls such as released insects and mites along with bio-pesticides comprised of specialized fungi and bacteria provide a new arsenal of weapons for the grower/farmer.
The adoption of biologically-based methods requires that growers change their pest management strategies to a very proactive approach as control happens at a very different speed when compared to conventional insecticides like pyrethroids that have a rapid knockdown. Introducing a parasite or predator into the crop once an insect population has reached severely damaging levels will result in substantial crop losses before the pest is brought under control.
Insect pests such as WFT, which is resistant to many conventional pesticides requires the adoption of a biologically-based program. Often, it is not so much of a question as to whether to adopt biologicals, as it is how to get started.
Most Mid-Atlantic growers know that WFT will find their way into their high tunnels every year. Here are some options that you can employ once you open the page to biocontrols:
Grandevo and Grandevo PTO:
The active ingredient is Chromobacterium substsugae strain PRAA4-1 and spent fermentation media. Grandevo functions primarily as a stomach poison, so it must be ingested by insects and mites to be effective. It does not have systemic activity; therefore, it must be on the feeding surfaces to be effective. Like other stomach poisons, excellent plant coverage is necessary, so use plenty of water and pressure to get complete coverage. Grandevo is more effective on newly hatched larvae and nymph stages of insects and arthropods, so regular scouting and early applications are necessary for good control. We used Grandevo extensively in 2014 at the Penn State Southeast Agriculture Research and Extension Center (SEAREC) in our tunnels and got excellent control of WFT, aphids, spider mites and Broad mites. In discussions with numerous growers at winter meetings the reports have generally been very positive for this novel biopesticide. Grandevo is OMRI approved.
The active ingredient is Metarhizium anisopliae Strain F52. Met52 functions as a contact insecticide. Spores and/or mycelia from the pathogenic fungus M. anisopliae that come in contact with the insect penetrate the insect's exoskeleton and grow within the haemolymph (insect's blood) killing the insect or mite. The spores or mycelia do not need to be ingested, but must come into direct contact with the pests. Upon application, the spores or mycelia attach to the insect or mites cuticle then germinate to form an appressorium which penetrates the pest's cuticle. Blastospores are then formed in the haemolymph which begins a systemic infection that kills the insect in 4-5 days. Like Grandevo, we also used this material extensively at the Penn State SEAREC in 2014 with excellent results. Although a biocontrol, this material is not OMRI approved due to one part of the process under which it is produced. If you tried Met52 when it was first released and were not impressed due its' handling challenges, it is time for another look as it no longer requires refrigeration and goes into solution much easier.
The active ingredient is heat-killed Burkholderia spp. strain 396 cells and spent fermentation media. This material kills insects by enzymatically degrading the exoskeleton and interfering with molting. It is labeled for tomatoes, peppers and cucumbers to control a wide range of 'worms' and for the suppression of aphids, mites, whitefly, WFT, pepper weevil and plant bugs. Venerate XC has just been released to the grower market, so all trials have been on research farms in the U.S. Reports from one researcher in Florida indicated good control of Broad mites in peppers.
Other bioinsecticides include:
- Botaniguard (B. bassiani): manages a wide range of insect pests.
- Gnatrol (B. thuringiensis subsp. Isrealensis): specific to management of fungus gnats.
- PFR 97 (Isaria fumosorosea Apopka Strain 97): manages a wide range of insect pests.
- DiPel (B. thuringiensis subsp. kurstaki): DiPel and the other Bt kurstakis' primarily manage early instar lepidopteran pests.
Insect Predators for WFT management
Neoseiulus cucumeris or Amblyseius cucumeris.
This predatory mite has become the basis for many greenhouses WFT management programs. Since we know that WFT will be an annual problem, growers generally arrange for regular deliveries on a weekly or bi-weekly schedule to prevent the buildup of WFT populations. In the absence of WFT, cucumeris will eat spider mites or pollen.
Orius insidiosus, Minute Pirate Bug, Orius sp.
Orius has become a major component in our managing insects and mites in our high tunnel peppers at the Penn State SEAREC. They were originally identified on Black Pearl pepper plants at the farm from what is apparently a native population. The one downside to Orius is that they are warm to hot weather predators, so other controls must be used early in the high tunnel growing season. They will consumer pollen in the absence of insect prey, so maintaining "Banker Plants" is an important part in using Orius. In 2014, we grew both Black Pearl and Purple Flash peppers as banker plants. While we have a natural population at the farm, Orius can be purchased. Orius does not work well on tomatoes due to the trichoderms (sticky hairs).
Stratiolaelaps scimitus formerly known as Hypoaspis miles.
This predatory mite is a scavenger that lives in the top level of soil and consumes both WFT pupae and fungus gnat larvae. They establish and reproduce quickly and are about the only method to manage WFT pupae.
Storing biocontrols is very different from that of conventional pesticides. Some biocontrols like insect and mite predators and parasites have very limited shelf lives and must be applied very shortly after delivery. As a rule, learn as much as you can about the specific insect or mite you are purchasing, so that you can apply it correctly. In general, biopesticides have longer shelf lives, but do not hold up very well in extreme heat and have defined shelf lives of a year or less even when stored properly. Products vary widely in their storage and handling. For example, Actinovate AG can be stored at room temperature for about a year while RootShield and RootShield Plus have 6 month shelf lives when refrigerated between uses. PFR-97 must be kept frozen between uses and Cease can last for several years when stored at normal room temperatures.
Moving between released insect predators or parasites, biopesticides, and conventional pesticides is possible, but there are many cases where one product will kill or reduce the efficacy of another. Fixed copper fungicides can impact the survival of both bacteria and fungal-based biopesticides. Biopesticides also have the potential to kill released predators. One resource to consider is a free app from Biobest called "Side Effects Manual".
Some of the best websites to get acquainted with predators and parasites of insects and mites are:
Be sure to carefully read the label, all packaging, and when available, technical data sheets and other supporting information from the supplier in order to get the most from any biocontrol.
Pests such as WFT and most soil-borne diseases can best be controlled through biocontrols, so learning which method or material to use and when to use it is rapidly becoming a required skillset for growers. In addition, most of the new pest controls gaining approval from EPA fall into the biocontrol realm, so the shift from conventional pesticides is already well underway. Our challenge as growers, consultants, and researchers is in learning how to adopt these materials in order to grow the highest quality crops.
Prepared by Steve Bogash, retired Horticulture educator.