Hot Choices: Summer Mite Management Tools & Biological Control.

Brief: Mite numbers are approaching and in some orchards, exceeding economic threshold levels. Scouting for mite populations and the onset of bronzing should be underway and should act as the basis for management.

European red mite thresholds of 5 mite per leaf in July and 7.5 ERM / leaf in August should be used as management thresholds.(Table for assessing threshold)

Two-spotted spider mite (TSSM) cause more economic injury to apple foliage then does European red mite (ERM) at lower population levels. That said, TSSM thresholds should be adjusted lower then ERM thresholds as these mite can build quickly after herbicide applications occurring in July.

Miticides (ERM) (TSSM) (ARM) should be applied as thresholds are approached for most effective control as many active ingredients act slowly. For contact activity, excellent coverage is essential to reach the interior of larger trees by mid-summer.

Introduction: In some Mid-Hudson Valley orchard blocks we’ve begun to see increasing mite populations in apple and stone fruit. Two-spotted spider mite often migrate up from burned out herbicide treated weeds and European red mite (ERM) that have overwintered in low numbers begin to spike as this warming trend and drier conditions increase throughout parts of the region. Rust mite are present and in severe infestations will cause ‘silvering’ of the leaves.

These microscopic 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.

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.

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 continued shift in 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, 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 non-target, predacious insects and mite. However, this is not true for all materials. We have observed dramatic mite response (flare-ups) through the use of some RR insecticides, and consistently with the use of imidacloprid (Admire Pro, Imidacloprid 2F & 4F; Provado, no longer registered), and Delegate.

The pyrethroids (IRAC 3A) are user friendly compared to the carbamates and OP’s but produce a detrimental effect on mite predators. A single application producing a significant reduction of the phytoseiid mite complex and coccinellid beetles.

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 Reduced Risk (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. 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 (Envidor, 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.

Below is a list of miticides with a brief description of their use, relative to their class or mode of action. At the bottom of the page is included an efficacy chart based on mite species. 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.

Classes of Reduced Risk Miticides & Labels

Class 6: AgriMek
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.
Gladiator EC (3A/6)
Minecto Pro (6/28)

Class 10: Apollo, Savey & Onager & Zeal
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 & Portal
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 23: Envidor
*Envidor (spirodiclofen) is from a tetronic acid which disrupts the endocrine system, affecting energy production. Envidor is an IGR- insecticide with slow activity compared to quick knock down activity, requiring early intervention. Envidor is not acutely toxic to adults and may affect some insect pests as well as mites. Envidor should not be used with oil. Labeling requires a minimum gallonage of 100 GPA.

Class 25: Nealta
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. The same active ingredient, Bifenazate, if the AI in Banter SC and WDG formulations.