Introduction

Biology

Damage

Cultural Control

Biological Control

Chemical Control

References

Links

Acknowledgments

Your turn

CHEMICAL CONTROL

FOR COMMERCIAL NURSERIES

In order to reduce the movement of bamboo mites in commerce and to reduce the potential for aesthetic and economic damage, chemical treatment may be warranted.

Some factors to consider with chemical control are
· mode of action,
· residual,
· potential for phytotoxicity,
· selectivity,
· application efficiency,
· re-entry interval, and
· toxicity.

Few miticides have been registered specifically for bamboo with the exception of Floramite. Although most miticides will be efficacious, it is incumbent on the grower to test each new pesticide on a few plants and wait 7 to 10 days to check for phytotoxicity. Miticide activity varies and it is useful to know the mode of action of a chosen pesticide to kill mites.

Some miticides kill immature and adult mites, some kill eggs and immatures only, some kill practically all stages.
For example
· Hexagon targets eggs and immature mites only but has a very long residual and also sterilizes the female mites.
· Oxythioquinox (Joust or Morestan) have ovicidal activity but the products are no longer manufactured (growers can use up existing labeled stock until September 30, 2002).
· Floramite has some ovicidal activity but targets immature and adults mites.

When using miticides without ovicidal activity, two applications against mites 7-10 days apart are recommended. Several of the newer miticides have restrictions on the number of applications per season to reduce development of mite resistance. Rotations between products with different modes of action will help reduce selection for resistance. It is very important to read all labels completely.

Contact is one of the most important issues for applicators trying to eliminate bamboo mites. Thorough coverage of the bamboo leaves, particularly the leaf underside housing the mites, is required for good activity. This is particularly important with bamboo mite, as this mite produces thick webbing, which may reduce pesticide penetration. High pressure and electrostatic sprayers may increase coverage. Some miticides, such as Avid, have systemic activity (translaminar movement of the pesticide) and can increase mite suppression particularly where thorough coverage is difficult. The natural waxiness and near vertical growth of bamboo leaves often cause pesticides to bead up and roll off of the leaves. The addition of a surfactant can reduce this occurrence, ideally spreading the chemical evenly over the leaf for good contact. Don Emenegger of Uniroyal Chemical Company has evaluated the use of surfactants alone and with Floramite for control of bamboo spider mite. His findings show that the surfactant rate used is much more important than the particular surfactant itself (Emenegger, pers. comm.). As many surfactant labels give a range of rates, it was important to adjust the surfactant rate on any given plant variety until spray droplets spread instead of beading up on the leaf surface. Additionally, although not registered pesticides, many of the surfactants themselves had direct activity on the mites. Mite eggs, however, were not affected and the mite population eventually rebounded. Silicon-based surfactants (Silwet and Silgard) are recommended for Floramite. Latron is recommended for Kelthane. Oil may enhance Avid activity. Oil, itself, has miticidal activity upon direct contact, including the ability to smother mite eggs. There is no residual activity in oil and insecticidal soap products, however, and frequent applications may be necessary.

Selectivity of the pesticide targeting mites is also an issue. Where multiples pests are present (for example, bamboo aphid and bamboo mite) some growers choose a pesticide with broad-spectrum activity such as Talstar. More selective miticides may be indicated for sites using biological control or interested in conserving natural enemies. Floramite has been used in conjunction with predatory mite releases in Oregon with no apparent impact on the predatory mite, Neosieulus fallacis. Oils and soaps, though they can kill on contact, have no residual, leaving immigrating natural enemies unharmed. Although homemade concoctions of oil and soap applications may very well have an effect on the mites, the base products are not formulated for plant use and may cause phytotoxicity. It is also important for applicators at commercial nurseries to use pesticides legally registered by the EPA and licensed in their state.

Toxicity and re-entry levels vary tremendously. The chart provided of specific products, gives this information for several of the most commonly used miticides. Additional information on chemical control of bamboo might may be found on the web at http://www.ent.orst.edu/urban/home.html.