Strawberry Research: Mites

     Strawberry, Fragaria ananassa Duchesne, is a high value crop commercially produced in several states including California, Florida, Michigan, North Carolina, New York, Ohio, Oregon, Pennsylvania, Washington, and Wisconsin. Florida is second after California in terms of production, harvested area, and total yield in US strawberry production. Acreage production and strawberry value have increased over the past 10 years. During 2010, strawberries were produced on approximately 8,800 acres valued at $362 million dollars. Because of mild winters in Florida, the strawberry industry has benefitted from high prices in early winter markets making the crop the most profitable small fruit grown in Florida.
     Strawberries are attacked by several insects and mites both in field and greenhouse production. For the past 10 years, our Small Fruit and Vegetable IPM (SFVIPM) laboratory has conducted various research investigating the ecology and management of the twospotted spider mite (TSSM), Tetranychus urticae Koch; a key pest of strawberries in Florida.  
     The twospotted spider mite is recognized as the most important arthropod pest that could potentially affect marketable yield of strawberries in Florida. This mite feeds on strawberry leaves resulting in chlorosis, which leads to a decrease in photosynthetic activity and a subsequent reduction in yield. In addition, they degrade the quality of fruits rendering them unmarketable. In the past, T. urticae has been controlled with several applications of acaricides. However, due to the high fecundity and problems associated with resistance to acaricides, other alternative control measures need to be explored. Our lab has focused on management of T. urticae with predatory mites primarily Neoseiulus californicus McGregor and Phytoseiulus persimilis Athias-Henriot. In elucidating our understanding of predatory mites in the strawberry system, we studied the environmental conditions that support T. urticae as well as the predator. We also explored the potential of using reduced-risk miticides with predatory mites.

Effects of Environmental Conditions on reproduction and development of Twospotted Spider Mites in strawberries (White and Liburd 2005)

     Low moisture levels and temperatures >27OC promoted twospotted spider mite (TSSM) development both in field and greenhouse experiments. Overhead irrigation tends to support higher incidences of angular leaf spot, Xanthomonas fragaria Kennedy & King disease as compared with drip irrigation.

Management of twospotted spider mites using predatory mites and Acramite (Rhodes and Liburd 2006a and Rhodes et al. 2006b)

     Our laboratory compared two predatory mites: Phytoseiulus persimilis and Neoseiulus californicus alongside Acramite, a reduced-risk miticide commonly used to control TSSM. The findings indicate that N. californicus releases and properly timed Acramite applications are excellent options to control TSSM in north Florida.

Biological control of twospotted spider mites with Neoseiulus californicus (Fraulo and Liburd 2007 and Fraulo et al. 2008)

     Studies were conducted to evaluate the most effective time to release N. californicus for controlling TSSM in strawberry plantings. One- time early release (4 wks after planting [WAP]) when TSSM population is not high proved to be best option compared with mid (8 WAP) and late (12-16 WAP) releases to control TSSM. We also find that releasing the predatory mites had no effect on arthropod community structure when comparisons were made between communities with and without N. californicus releases.

Current studies include:

  1. Movement of TSSM and N. californicus within the strawberry plantings
  2. Site specific management of TSSM
  3. Ecology of N. californicus

Additional Strawberry Research:

Strawberry sap beetle

     There are several species including Lobiopa insularis (Castelnau), and Carpophilus sp. (Coleoptera:  Nitidulidae). Sap beetles can be problematic in fields with ripe fruit that has had heavy rains or a delayed harvest.  However, acceptable control of sap beetles can be achieved culturally by simply picking the fruit before it over-ripens.

Alternatives to Methyl Bromide

     Besides plant-pathogens, weeds and twospotted spider mites (TSSM), nematodes are a serious problem affecting Florida strawberry production areas. No nematode resistant strawberry varieties exist, and there are no post-plant remediation strategies available. Strawberries are susceptible to multiple nematode species, with sting nematodes Belonomymus longicaudatus being the most severe. Therefore, methyl bromide is traditionally applied as a biocide approximately two weeks prior to planting. Since the United States are participating in the Montreal Protocol which requires a gradual phase-out of methyl bromide, manufacturers have begun this phase-out by adding higher percentages of chloropicrin into the methyl bromide formulations. During the phase-out period, research and registration efforts have been ongoing to find suitable replacements for methyl bromide in strawberry production. 1,3-dichloropropene (TeloneŽ EC and InLineŽ ) and sodium azide (SEP 100), another soil fumigant that has been previously tested in several high value cash crops, is currently being evaluated in strawberries.      
     The treatments are methyl bromide + chloropicrin (57:43), 1, 3-dichloropropene + chloropicrin (InLine 83:17), sodium azide (SEP 100) at different concentrations, and an untreated control. InLine and SEP 100 were applied through the drip irrigation system under virtually impermeable film. The predator Neoseulus californicus was released at different times in the season for TSSM control.

Strawberry Publications

  • Fraulo, A.B., and O.E. Liburd. 2007. Biological control of twospotted spider mite, Tetranychus urticae Koch, with predatory mite, Neoseiulus californicus, in strawberries. Expermental and Applied Acarology 43: 109-119.

  • Liburd, O.E., J.C. White, E.M. Rhodes, and A.A. Browdy. 2007. The residual and direct effects of reduced-risk and conventional miticides on twospotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae) and predatory mites (Acari: Phytoseiidae). Florida Entomologist 90: 249-257.

  • Rhodes, E.M., and O.E. Liburd. 2006. Evaluation of predatory mites and acramite for control of twospotted spider mites in strawberries in north-central Florida. Journal of Economic Entomology 99: 1291-1298.

  • Rhodes, E.M., O.E. Liburd, C. Kelts, A.I. Rondon, and R.R. Francis. 2006. Comparison of single and combination treatments of Phytoseiulus persimilis, Neoseiulus californicus, and Acramite (bifenazate) for control of twospotted spider mites in strawberries. Experimental and Applied Acarology 39: 213-225.

  • White, J.C., and O.E. Liburd. 2005. Effects of soil moisture and temperature on reproduction and development of twospotted spider mites Tetranychus urticae Koch (Acari: Tetranychidae) in strawberries. Journal of Economic Entomology 98: 154-158.

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