Red Mite Building in Gala and Red Delicious. June 31st, 2018

Phytoseid mites (T.pyri) feeding on ERM

Phytoseid mites (T.pyri) feeding on ERM

Brief: In a few commercial blocks in Orange and Ulster counties we have begun to see increasing mite populations in apple and stone fruit. As very hot and increasingly dry conditions develop throughout parts of the region its likely mite populations will be on the rise. Rust mite are present and are likely to increase in blocks where predators are few to cause severe infestations, producing ‘silvering’ of the leaves. Two spotted spider mite (TSSM) has also been observed moving up into the tree canopy from block in which newly applied knock down herbicides have been applied to broad leaf weeds. Increasing egg production of European red mite (ERM) has been observed exceeding threshold this past week in a scouted block of Fuji in Ulster county.

Introduction: The rust mite are beneficial in small numbers as a food source for predatory mite T. pyri (Galendromus =Typhlodromus pyri), Amblyseius fallacis and Zetzellia mali. These are our three primary mite predators found in Hudson Valley orchards to maintain low levels of phytophagous, leaf feeding mite..

In years where temperatures exceed 80oF, mite populations, especially European red mite (ERM), can build very quickly. In these situations the time it takes for a mite egg to hatch and mature to the adult stage can occur in about one weeks time (see Chart 1). Thus shortened interval of development, relative to higher average temperature, typically leads to multiple generations and high mite populations that can require season long management. With a greater number of generations during a season, comes the likelihood of increased resistance potential to the miticide management programs you use.

Z. Mali feeding on ERM egg.

Z. Mali feeding on ERM egg.

To maintain the usefulness of new reduced risk materials, managing the build-up of resistance in arthropod populations to insecticides and miticides is essential. Reducing the pressure on a population that selects for the survival of resistant individuals is cited as the primary cause of insecticide resistance. This is often the result of employing a single mode of action pesticide for multiple generations over many seasons. The generally accepted method of reducing selection pressure is to treat each generation of a pest with pesticides of different classes of chemistry. Additionally, the use of oil and non-chemical control strategies such as biological control will contribute to reducing the resistance potential in pest populations.

The recent shift limiting the use of the organophosphate class of insecticides (OP’s) in pome fruit production through legislation, GAP certified market constraints and public perception has prompted fruit producers to use reduced risk pest management tools to control the arthropod pest complex. These include the neonicotinoids such as Actara, Assail, Calypso and Provado; the insect growth regulators (IGR’s) Intrepid and Esteem; the Oxadiazine Avaunt and the spinosyn Delegate. With the advent of reduced risk (RR) pest management programs come insecticides with generally lower levels of toxicity to predacious insects and mite. However, we have observed mite response (flare-ups) through the use of some RR insecticides, and consistently with the use of imidacloprid (Imidacloprid 2F & 4F; Provado, no longer regestered), and Delegate.

Temperature effects on generational development time of ERM.

Temperature effects on generational development time of ERM.

In previous studies it has been demonstrated that the phytoseiid mite, G. (=Typhlodromus) pyri, can be introduced and conserved to achieve biological mite control. The use of RR programs provide a more favorable environment to use biological control organisms to obtain phytophagous mite management while reducing the selection pressure placed on miticides alone. Many of the RR miticides are compatible with the preservation of biological control agents.

From my perspective, the weak link in the biological control of mites is not solely the use of disruptive insecticides. The fungicide mancozeb (Manzate), belonging to the EBDC group, used to manage apple scab (AS) Venturia inaequalis is very disruptive to the mite predator T. pyri. Each application of Manzate made prior to bloom reduces T. pyri populations by roughly 30%, with post bloom applications imposing significantly greater reductions in numbers of phytoseiid predators. Given the importance of achieving AS control, the resistance of AS to sterile inhibitors in the Northeast, rising costs of new fungicides and reduced efficacy of Captan alone compared to Manzate (mancozeb) / Captan combinations, it is unlikely that most producers can avoid using mancozeb strictly to maintain biological control agents. Thus the requirement of AS management in scab susceptible apple varieties will limit optimum biological control measures in tree fruit if mancozeb is employed. However, in blocks of low AS susceptible varieties such as the use of scab resistant varieties developed by PRI, would reduce the need for mancozeb, reducing the negative impact on the phytoseiids.

In reviewing the many options for mite management one should be aware of the stage of development that is present in the field. If eggs are high in number, the use of materials with ovicidal efficacy should be selected (Esteem, Zeal, Apollo, Savey/Onager, Nealta and to some extent Acramite); applications against newly emerging mite larvae (Savey, Zeal, Nealta) or against motile mites (Nexter, Nealta and AgriMek) should be made at lower than economic threshold levels when recommended by the label. Considering the impact insecticides and miticides can have on the phytoseiid populations may provide increased levels of phytoseiid presence and enhanced biological mite control. In the table below are pest management tools grouped according to their toxicity against the phytoseiid Amblyseius fallacis.

Toxicity of Insecticides and Miticides to Predatory Phytoseiid Mite

Toxicity of Insecticides and Miticides to Predatory Phytoseiid Mite

Below is a list of miticides with a brief description of their use, relative to their class or mode of action.

Keep in mind when choosing a miticide that many of the newer materials are contact materials requiring complete coverage to be effective. A number of agrichemical companies have added to their miticide label a minimum use rate of 100 gallons per acre to aid in improving coverage. For legal (and efficacious) applications to be made this requirement must be met.

Scouting each block to determine mite presence and threshold as we move through the season is critical for effective management.

Review Cornell Guidelines for miticide efficacy recommendations based on your management needs.

Classes of Reduced Risk Miticides & Labels (Cornell Tree Fruit Guidelines)

Class 6:
AgriMek Abamectin (*Agri-Mek, *Agri-Flex, *Abba) is a natural fermentation product containing a macrocyclic glycoside, used on apples and pears as an acaricide/insecticide. When used as currently recommended, it controls European red mite and pear psylla, and aids in the control of spotted tentiform leafminer. Abamectin is toxic to bees and predator mites on contact, but the foliar residue dissipates quickly, making it essentially non-toxic to these species after a few hours (low bee-poisoning hazard).

Proclaim (Emamectin benzoate) is similar to Agri-Mek (abamectin), with activity against the Lepidopteran complex, primarily the obliquebanded leafroller leafminer and mite. Residual activity is shorter than AgriMek with motile mite being the primary target stage. The use of a penetrant is required for mite management and complete coverage is required for mite control with higher sprayer volume recommended. Do not use sticker/binder type adjuvants as they may reduce translaminar movement of the active ingredient into the plant.

Class 10 A&B:
Apollo, containing Clofentezine, is a tetrazine compound used as a contact acaricide that acts primarily as an ovicide/larvicide; it is particularly effective against winter eggs of European red mite. Following early season applications, it gives excellent residual control. Its use in apples is restricted to no later than 45 days before harvest, but in pears, cherries, peaches and apricots it may be used up until 21 days before harvest. It is safe to bees (low bee-poisoning hazard), beneficial insects, and predatory mites. It is not an effective adulticide.

Savey and Onager, with the active ingredient Hexythiazox, is a carboxamide compound used as a contact and stomach-poison acaricide. It is effective against eggs and larvae of European red mite; it will not kill adults. It is registered for a single application in all pome and stone fruits, and may be used up to 28 days before harvest. It provides excellent residual control, and is safe to bees (low bee-poisoning hazard), beneficial insects, and predatory mites.

Zeal (extoxazole) – derived from diphenyloxazoline, this miticide acts as an ovicide and has molt inhibiting activity against immature mite. Zeal is a contact miticide with translaminar movement, performs much like Acramite against twospotted spider mites, but is more effective on European red mite. It acts slowly with results in mortality taking several days. Labeling requires a minimum gallonage of 100 GPA. Zeal is considered by the EPA to be a reduced risk miticide.

Class 20:Kanemite Kanemite (acequinocyl) in the quinoline class of insecticides, is as a mitochondrial electron transport inhibitor (METI), blocking cellular respiration. It should also be limited to one application/year. Kanemite provides quick knockdown and long residual control. labeling requires minimum gallonage of 100 GPA. Kanemite is considered by the EPA to be a reduced risk miticide.

Class 21:
Nexter (formerly known as Pyramite) (pyridaben) belongs to the pyridazinone class of miticides. Nexter’s mode of action as a mitochondrial electron transport inhibitor (METI) blocks cellular respiration. Conservative resistance management would recommend the use of METI miticides (Nexter, Portal or Kanemite) to be limited to one application/year. Nexter is an effective miticide against European red mites with less activity against the two-spotted spider mite. Nexter is also effective against the apple rust mites. Boron prevents water-soluble bags (WSB) from dissolving. Care must be taken not to add soluble bag packets of Nexter to tank mixes with Boron and also to rinse tanks thoroughly after Boron applications prior to using WSB. Labeling requires a minimum gallonage of 100 GPA.

Portal (fenpyroximate) a phenoxypyrazole class of insecticide, is as a mitochondrial electron transport inhibitor (METI), blocking cellular respiration. It should also be limited to one application/year. Portal acts as a contact miticide, requiring complete coverage. Labels state that the miticide rapidly stops feeding and egg laying with 3-7 day mortality observed in the field. Portal is considered by the EPA to be a reduced risk miticide.

Class 25:
Envidor® 2 SC Miticide requires a 24(c) label for use in Ney York State. Envidor (Spirodiclofen) is a member of the tetronic acid family, is labeled for use against mites, including European red mite, twospotted spider mite, and apple and pear rust mites, on pome fruits, under a FIFRA 24(c) Special Local Need label. The label must be in possession of the user at the time of application. A maximum of 1 application per season is allowed, with a PHI of 7 days; this product is not for sale, distribution or use in Nassau and Suffolk Counties. It is relatively harmless to beneficial species and has a low bee-poisoning hazard.

Nealta miticide is a suspension concentrate formulation containing the active ingredient cyflumetofen, a member of the beta-ketonitrile class of chemistry. When used as directed, Nealta provides knockdown and residual control. of tetranychid mites on the crops listed on this label. Nealta is a highly active contact miticide on egg, nymph, and adult stage tetranychid mites (ERM & TSSM). Because Nealta is not systemic and has no translaminar activity, thorough coverage of plant surfaces is necessary for effective control. Nealta is not effective on non-tetranychid mites such as rust mite.

Unknown Mode of Action: Acramite
Acramite (bifenazate)- is a hydrazine compound derived from carboxylic acid ester. Its mode of action is a GABA (gamma-aminobutryric acid) agonist in insects. Acramite has quick knockdown, is primarily used against the motile stages of mite, and has some ovicidal activity. Acramite is a specific, selective miticide, with good activity against spider mites but little to no rust mite activity. Labeling requires a minimum gallonage of 50 GPA. Acramite is considered by the EPA to be a reduced risk miticides.

Pre-Mix Formulations:
Minecto Pro is a pre-mix formulation containing a combination of cyantraniliprole, a 2nd-generation member of the anthranilic diamide group (which activates the insect’s ryanodine receptors, stimulating release of calcium from muscle tissues, causing paralysis and death), and abamectin, a natural fermentation product in the avermectin class with an agonist mode of action on the neurotransmitter gamma-aminobutyric acid (GABA), found in several products labeled to control mites and pear psylla. This product is labeled for pome fruit and stone fruit use in NY, to control Lepidoptera species as well as mites and pear psylla. It is a restricted use pesticide with a high bee-poisoning hazard; not registered for use in Nassau or Suffolk counties.

Gladiator is labeled in NY against a wide range of pests of pome fruit and stone fruit. It is a combined formulation of the pyrethroid zeta-cypermethrin, plus the macrocyclic glycoside avermectin B1, which is the major component of the insecticide/miticide abamectin, the a.i. found in *Agri-Mek and related products. The pome fruit label includes internal worms and leafrollers, apple maggot, European apple sawfly, plum curculio, pear psylla, rosy apple aphid, spirea aphid, leafminers and leafhoppers, tarnished plant bug, stink bugs, and Japanese beetle. The stone fruit label lists American plum borer, leafrollers, leafhoppers, peachtree borers, plum curculio, oriental fruit moth, stink bugs, tarnished plant bugs. It is also labeled for European red mite and twospotted spider mite in all tree fruit crops. It has a high bee poisoning hazard.