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Research Projects
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Fruit Fly
We are studying biological control of twospotted spider mites
to determine how plant stress and environmental factors affect pest and predator
efficiency in strawberries.
Effects of Environmental Conditions on Twospotted Spider Mites and its Associated Predators
In Florida, strawberries are
produced on approximately 7,000 acres with a farm gate value at an estimated170 million dollars annually. This value makes strawberries the most
profitable small fruit to produce in Florida. Despite these facts
strawberries are attacked by several insect and mite pests in the greenhouse,
but only two are recognized as significant problems in the field. One group
of these pests is the 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.
The two-spotted spider mite Tetranychus urticae Koch, has been recognized as the most significant
arthropod pest in strawberries in Florida. T. urticae feeds on
strawberry leaves resulting in chlorosis, which leads to a decrease in
photosynthetic activity and a subsequent reduction in yield. 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, the management of T. urticae has become a major problem for
growers. As an alternative to chemical control, researchers have focused on inoculative releases of many species of predator mites. Phytoseiulus
persimilis Athias-Henriot has been the main species released in Florida
but its establishment in suppressing populations of T. urticae has only
been successful in southern areas of the state. Neoseiulus californicus McGregor has also been released sporadically throughout Florida but
information regarding its potential, especially in northern Florida, is
unavailable. Our goals are to investigate environmental conditions, including
ambient temperature and soil moisture, to determine their impact on
reproduction of T. urticae and its associated predators. In addition,
we wanted to evaluate other IPM strategies for suppressing populations of
two-spotted spider mite.
Alternatives to Methyl Bromide in Strawberries grown in north-central Florida
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 (Telone® EC and InLine® ) 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.
At the end of the season, we are hoping to identify a working alternative for methyl bromide in north-central Florida strawberry production that would also allow for successful management of TSSM with Neoseulus californicus.
Objectives
- To conduct laboratory
controlled studies to evaluate the effects of soil moisture and temperature on two-spotted spider mite and its associated predators in strawberries.
- To determine how irrigation techniques and watering
regimes affect two-spotted spider mite as well as the predatory mites P.
persimilis and N. californicus.
- To evaluate combination tactics using predators as
well as reduced-risk miticides for suppressing two-spotted
spider mite populations.
Papers and Presentations
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