Biological Control Methods for Citrus Rust Mites and Spider Mites on Florida Citrus Utilizing Predaceous Arthropods as Part of IPM

Biological Control Methods for Citrus Rust Mites and Spider Mites on Florida Citrus Utilizing Predaceous Arthropods as Part of IPM

Summary

Objectives
1.) Determine the seasonal occurrence and distribution of Agistemus floridanus (Acari: Stigmaeidae) and other predaceous arthropods within individual trees in seven selected commercial citrus grove sites located in central and south Florida for one year.

2.) Identify important weed (ground cover and vine) plants within the citrus groves that contain A. floridanus or other prevalent species of predaceous arthropods during the year. Determine when specific ground cover plants are flowering within each selected grove site. Determine if there is seasonal or vertical movement of predaceous mites or insects between citrus and ground cover vegetation or vines within the groves.

3.) Determine the life table parameters of A. floridanus and other selected prevalent predators including developmental rates, reproductive potentials, and number of female progeny produced per adult female in the laboratory when provided with citrus rust mite as the food source.

4.) Determine comparative toxicities of all registered pesticides (including insecticides, miticides, fungicides and herbicides) used in the Florida citrus industry at recommended and reduced field rates against A. floridanus populations and one or more other selected prevalent species of predaceous mites or insects based on results from Objective 1.

5.) Establish experimental citrus grove sites with other farmers previously on chemical mite control programs and implement augmentative infestations of selected predaceous arthropod species and ground cover plants (if appropriate) and modify spray programs to minimize toxicity to the selected predators. Continued monitoring of these sites will be completed during years two and three of the project to establish successful biological control of the targeted mite species and fine tune the methods.

Approach
Two important groups of pests on Florida citrus include the rust and spider mites. Sole reliance on chemical control has resulted in significant economic production costs to growers. Florida citrus has a highly diverse complex of phytophagous, predacious, saprophytic and fungivorous mites within the tree canopies and on various cover crop plants. This project identified 29 species of Phytoseiidae, 10 Cheyletidae, 10 Tydeidae, 1 or more Tarsonemidae, 2 Cunaxidae, 4 Ascidae, 1 Histiostomatidae, 2 Macrochelidae, 1 Parasitidae, 3 Laelapidae, 6 Acaridae, 1 Bdellidae, 1 Anystidae, 2 Eupalopsellidae, and 5 predacious thrips species (Insecta: Thysanoptera). Prevalent species of Phytoseiidae from high to low frequencies were: Euseius mesembrinus (47%), Typhlodromalus peregrinus (33%), Iphiseiodes quadripilis (7%), Typhlodromips dentilis (3%), Typhlodromina subtropica (1%), and Galendromus helveolus (<1%). All other phytoseiid species were less than 1% of the total 27,805 slide-mounted specimens identified from subsamples. Agistemus floridanus (Stigmaeidae) was the third most abundant predacious mite (2,428 slide-mounted specimens) following the first two phytoseiids. Ground cover plants were identified and 59 of 77 had one or more species of Phytoseiidae present. Euseius mesembrinus, T. peregrinus, I. quadripilis and T. dentilis were found in abundance on one or more ground plants. Vertical movement of predators was documented. Stigmaeid mites were not recovered from ground cover plants. Herbicide programs of cooperators did not create phytophagous mite problems although stigmaeid/phytoseiid ratio differences were indicated between herbicided and non-herbicided groves. Feeding and life table studies with stigmaeid predators continue. Several phytoseiid mites and two species of stigmaeids (A. floridanus [native] and A. industani [exotic]) were shown to feed on citrus rust mites. Pesticides (24) were sprayed in the field in 250 gallons of water per acre using conventional tractor-drawn airblast equipment to compare toxicities against two phytoseiid mites (i.e. E. mesembrinus [native] and E. stipulatus [exotic]) and two stigmaeid mites (i.e. A. floridanus [native] and A. industani [exotic]). Pesticides were rated as either highly toxic, toxic or slightly to non-toxic based on their overall effect on gravid females, subsequent egg production and surviving immatures. Results
Pesticides considered highly toxic to gravid female phytoseiids were: Nexter 75WP at 6.6 oz, Guthion 50WP at 4 lbs, Carzol 92SP at 1 lb, Dicofol 4 EC at 6 pints and Comite 6.55 EC at 3 pints. Toxic pesticides to gravid female phytoseiids were: Nexter 75WP at 5.2 oz, Agri-mek 0.15 EC at 10 oz + 5 gallons petroleum oil, Ferbam 76WP at 15 lbs, and Benlate 50WP at 1.5 lbs + Ferbam 76WP at 5 lbs, Sevin 80S at 10 lbs, Sevin XLR at 2 gallons + 1 gallon petroleum oil, Benlate 50WP at 3 lbs, Ethion 4EC at 6 pints + 5 gallons petroleum oil, and Alert 2SC at 20 oz. Pesticides resulting in significant egg reduction or immatures were: Agri-mek 0.15 EC at 10 oz + 5 gallons petroleum oil, Nexter 75WP at 6.6 oz, petroleum oil at 5 or 10 gallons (reduced immatures of both Euseius species), Ferbam 76WP at 15 lbs, Benlate 50WP at 1.5 lbs + Ferbam 76WP at 5 lbs, or Benlate 50WP at 3 lbs (reduction in eggs), and Nexter 75WP at 6.6 oz + 5 gallons petroleum oil (reduced eggs and immatures). For A. industani, highly toxic pesticides to gravid females were: Dicofol MF at 6 pints, Fenbutatin-oxide 50WP at 2 lbs, Chlorenapyr 2SC at 0.3 lbs + 5 gallons petroleum oil, Sulfur (Kumulus 80DF) at 15 lbs, Ethion 4EC at 6 pints + 5 gallons petroleum oil, Propargite 6.55 EC at 3 pints, Pyridaben 75WP at 6.7 oz, and Chlorfenapyr 2SC at 0.3 lbs. Highly toxic pesticides that reduced oviposition were:

Propargite 6.55EC at 3 pints, Ethion 4EC at 6 pints + 5 gallons petroleum oil, Ferbam 76WP at 10 lbs, Dicofol MF at 6 pints, Pyridaben 75WP at 6.7 oz, Fenbutatin oxide 50WP at 2 lbs, Benomyl 50WP at 1.5 lbs + Ferbam 76WP at 5 lbs, Sulfur (Kumulus 80DF) at 15 lbs, and petroleum oil at 2.5 gallons. Highly to moderately repellent or irritating pesticides to gravid female A. industani were: Trilogy 90EC at gallons, Benomyl 50WP at 2 lbs, Benomyl 50WP at 1.5 lbs + Ferbam 76WP at 5 lbs, and Ferbam 76WP at 10 lbs.

In two completed field evaluations during 1997, all treatments that included copper resulted in significantly higher citrus rust mite and spider mite densities during the growing season. There was significantly greater rind blemish injury from citrus rust mites at one site during 1997. The 1997 tests, indicated that tydeid mites had significant reductions mid to late season at both grove sites while no effects on the phytoseiid mite complex were recorded.

December 1998.