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Apple Bloom: Supporting Pollinators & Managing Pests. May 11th, 2020

Overview: After a number of recent cold events, during and prior to the onset of bloom, we are now challenged to evaluate the health of our crop and provide support for strong pollination of the remaining viable flowers. Evaluations of flowers by Dana Acimovic, Department of Horticulture at the Hudson Valley Research Laboratory, has found a wide range of flower survival in regional varieties.

Similar observations of flower browning have also been observed throughout the Hudson Valley region and reported by Dan Donahue, ENYCHP-Tree Fruit Specialist, and south through New Jersey and Eastern PA by Win Cowgill, Rutgers Emeritus/ Win Enterprises International, LLC. during our recent conversations on the topic Monday mornings (Morning Brew).

Given reduced flower viability, this is now a critical time to support pollinators for optimum pollination of viable flowers during bloom. At the same time, increasing temperatures and sunlight this week will undoubtably provide ideal conditions for insect pest emergence. Scouting for feeding by the lepidopteran complex, Mullein and Tarnish Plant Bug, European apple sawfly and Rosy apple aphid of foliage and developing fruitlets may begin in earnest later in the week.

As honey bees do not fly on days with temperatures below 50F, or during low sunlight conditions, optimizing insecticide applications during these conditions will help conserve bee health. Ideally, constraints placed on applications should strongly consider spraying if temperature is below 50°F all day, waiting to spray until after 7 p.m. and to stop spraying by 7 a.m.

Understanding bee activity and insecticide constraints will provide best practices this week for both pollinator support and insect pest management.

If insecticide applications are necessary during the week, selecting materials that are allowed during bloom to manage insects should be used judicially.

• Tarnish plant bug can be managed using Beleaf (flonicamid)
• The lepidopteran leafroller complex, specifically obliquebanded leafroller, can be managed using product containing Bacillus thuringiensis (BioBit, DiPel DF, Javelin, Thuricide, Xentari).
• Codling moth adults are not flying yet, allowing a very short window of employing mating disruption tools (Isomate-CM/OFM TT @ 200 ties/ acre, sprayable Checkmate CM 2.0 @ 2.4-4.8 fl oz/acre, Madex HP @ 0.5-3 fl oz/acre)
• Mullein Plant Bug can be managed using Assail (acetamiprid) with strong consideration of its application in late evening or early morning, except during high temperatures.
• Additional constraints should include: Apply only if temperature is below 50°F all day, then it is safe to spray at any time of day. And if temperature is above 50°F, do not spray until after 7 p.m., and stop spraying at 7 a.m.
• Avaunt (indoxacarb) would fall under the same constraints for management of plum curculio.

In Depth: Bullet points on honey bee biology provide some basic understanding on how to best manage our orchard and bee colonies during the bloom window.

Foraging Behavior of Honey Bees
• At any given time approximately one-third of the honeybees in a colony are searching, or foraging, for nectar or pollen.
• Foraging bees rarely collect both nectar and pollen during the same flight.
• About 50% of the honeybees foraging in Red Delicious apples are pollen collectors
• Higher percentage of pollen collectors are available in larger colonies with large amounts of brood (immatures).
• Honeybees don’t forage in full force until temperatures are above 65°F and winds are less than 10 miles per hour and light intensity is above 60,000 lux.
• Winds greater than 15 miles per hour will slow or altogether stop foraging behavior.

Number of Colonies per Acre
• Colonies should be placed in apple orchards just as the first king bloom opens.
• Experiments have shown that the best results are obtained with hives placed in groups of 4-6 at 150-yard intervals. This may be impractical in large orchards, where colonies should be placed in groups of 8-16 at 200- to 300-yard intervals throughout the orchard, starting about 100 yard from the edges.
• A general rule is that a colony having 6 frames of brood with “bees to cover” will have a population of 20,000 adult bees. This is the minimum size an orchardist should accept for apple pollination.
• A two-story colony with at least 20,000 bees will normally provide adequate pollination for an acre of tree fruit.
• Although one colony per acre may be sufficient during most years, it may not provide enough bees during a cold, wet spring when weather conditions provide for only a limited amount of bee foraging.
• The use of two colonies per acre to be sure that adequate numbers of pollinators are present even during poor weather.

Pollinizer Distribution
• Suitable pollinizer varieties must be planted throughout the orchard in adequate numbers to provide pollen for all main-variety trees.
• Most bees (98%) tend to work down tree rows in intensive plantings rather than cross the aisle spaces, and may only work 2 or 3 adjacent trees on a single foraging trip.

Pesticides : Insecticides, Fungicides, Herbicides and Inert Ingredients, that are applied during the bloom period can poison honeybees, causing death, lack of foraging, abnormal behavior, poor brood development or dead broods, queenless hives and will likely lead to reduced pollination of tree fruit.

Very cold temperatures over the past few weeks have reduced insect feeding activity on foliage. However, this will quickly change this week as temperatures climb into the upper 60’s to upper 70’s beginning Wednesday. Scouting for the pest complex will be important as we begin making insect pest management decisions with late varieties still in bloom.

An important aspect of protecting bees during pollination and beyond is not simply understanding the toxicity of bees to insecticides, but includes the understanding of direct fungicide toxicity, toxicity from the inert ingredients such as adjuvants and synergy of the ingredients we add to the tank mix found in the formulations we employ. The importance of chemical interaction or synergy between chemicals has recently been brought to light in a publication titled: A Pesticide Decision-Making Guide To Protect Pollinators In Tree Fruit Orchards. Utilizing this guide will provide you with practical tools for choosing materials to best conserve our pollinators this season.

Primary pests of concern during bloom include tarnish plant bug, mullein plant bug, lepidopteran complex including leaf roller and green fruit worm complex, rosy apple aphid and European red mite.

As some insecticides can be applied without constraint to protect our crop, as per EPA product labeling, employing them with discretion is essential. In Class IV this group have been found to be ‘non-toxic’ or to be more precise, not directly toxic to foraging bees when freshly applied. Yet, some may have long term effects on developing brood and as such should be use with prudence.

Insecticides found in Class IV (below) have undergone long term studies and a broad scope testing of the active ingredients across replicated sites. These active ingredients were not found to be hazardous to honey bees at any time on blooming crops and as such carry no application constraints during bloom. TAs stated earlier, the interaction and synergy of adjuvants and fungicides should be taken into consideration during the selection process to reduce risk to pollinators.

• Altacor (chlorantraniliprole)
• Apollo (clofentezine)
• Bacillus thuringiensis
• Beleaf (flonicamid)
• Centaur (buprofezin)
• Cyd-X (CM granulosis virus)
• Dimilin (diflubenzuron)
• Esteem (pyriproxyfen)
• Ethrel (ethephon)
• Fruitone
• FujiMite, Portal (fenpyroximate)
• Intrepid (methoxyfenozide)
• K-Salt Fruit Fix (NAA)
• Kanemite (acequinocyl)
• M-Pede (potassium salts of fatty acids)
• Monterey Sucker Stopper Concentrate (NAA)
• Onager / Savey (hexythiazox)
• Rex Lime Sulfur (lime sulfur/calcium polysulfide)
• Sulforix (lime sulfur/calcium polysulfide) sulfur
• Surround (kaolin clay)
• Thiolux (flowable/micronized sulfur)
• Vendex (fenbutatin oxide)
• Zeal (etoxazole)

The Class III group are not hazardous if applied in late evening or early morning except during high temperatures. Constraints include that the application be made only if temperature is below 50°F all day, and that temperature is above 50°F, do not spray until after 7 p.m., and stop spraying at 7 a.m.

• Acramite (bifenazate)
• Assail (acetamiprid)
• Avaunt (indoxacarb)
• Aza-Direct (azadirachtin)
• Battalion (deltamethrin)
• Calypso (thiacloprid)
• Delegate (spinetoram)
• Entrust (spinosad)
• GF-120 (spinosad)
• Lannate (methomyl)
• Neemix (azadirachtin)
• Nexter (pyridaben)
• petroleum oil
• Proclaim (emamectin benzoate)
• PyGanic (pyrethrins)
• Pyramite (pyridaben)
• Success (spinosad)
• TriStar (acetamiprid)

In closing, this season, as challenging as it has been, requires us to make every effort to conserve and support our native pollinators and honey bees. Our crop depends on their success.

References:
A pesticide decision-making guide to protect pollinators in tree fruit orchards
• Original web article: Orchard Pest Management Online – Honeybee (Online Video)
Pollination and Protecting Bees, WSU CAHNRS Video Production (Everything about bees, pollination, and protecting bees)