Timing of spraying in pistachio
In pistachio, “spray timing” depends on the target pest/disease, the tree’s growth stage, and the weather. A fixed calendar is not the right approach: scout first, then decide based on economic thresholds. The schedule below is a practical general framework (shift by 2–3 weeks depending on your region).
Key notes before the calendar
- Weekly scouting: inspect upper and lower leaf surfaces and clusters; look for nymphs of pistachio psyllid and fresh honeydew, mites, thrips, and nut drop.
- Avoid spraying in intense heat or wind; best time is early morning or evening.
- Avoid heavy foliar sprays during pollination wherever possible.
- Rotate modes of action (IRAC/FRAC) and observe pre-harvest intervals and product labels.
- Protect natural enemies (lady beetles, lacewings) and keep the orchard clean.
Suggested seasonal timeline
- Dormant to pre–bud swell (mid- to late winter)
- Goal: reduce overwintering psyllids and scales with a dormant oil spray.
- Notes: choose days without frost or wind, temperatures above about 4–5°C, and ensure thorough canopy coverage.
- Bud swell to leaf-out (early spring)
- Goal: control pistachio psyllid at early nymph stages and fresh honeydew.
- Action: scout closely; if nymphs begin to build, make one spray; reassess 10–14 days later and repeat only if needed.
- Late spring (vigorous vegetative growth)
- Goal: manage thrips and mites.
- Action: treat only if damage signs or high populations appear. Reduce road dust and water stress to limit mite flare-ups.
- Early summer (nut set and growth)
- Goal: continued pest and disease monitoring.
- Diseases: in areas with humid nights, consider protective sprays against Alternaria leaf spot only when weather remains conducive (consult a local advisor).
- Mid-summer, before hull split
- Goal: manage nut-feeding moths (region-specific, e.g., carob/“date” moths).
- Action: use pheromone traps for timing; when thresholds are exceeded, apply targeted sprays or mating disruption; remove infested/fallen nuts.
- Late summer to preharvest (hull split/near harvest)
- Goal: protect fruit at its most vulnerable stage and reduce secondary infections.
- Notes: strictly observe PHIs; spray only if monitoring confirms infestations.
- After harvest (autumn)
- Goal: reduce residual psyllid populations and sanitize the orchard.
- Action: remove mummies and remaining nuts from trees and the orchard floor; if pests are still high, consider a light, targeted spray.
Quick decision guide
- Pistachio psyllid: best timing is when early instar nymphs and fresh honeydew appear (early spring). Delay makes control more difficult.
- Mites: outbreaks are linked to dust and heat (late spring to summer); treat only after thresholds are exceeded.
- Nut-feeding moths: align sprays with trap flight peaks and the hull-split window.
- Foliar diseases: act preventively based on weather forecasts (humidity/rain), not a rigid calendar.
Which methods are used for winter spraying in pistachio?
In winter, the goal is to suppress overwintering pests and sanitize the orchard. Effective methods and how to apply them:
Main winter approaches
1) Dormant oil
- Goal: smother psyllid nymphs/eggs, scales, and mite eggs.
- Timing: after full leaf drop and before bud swell (on frost-free days).
- Application tips:
- Air temperatures above 5°C, no wind, and no rain for 24–48 hours afterward.
- Full canopy coverage to the point of uniform runoff, focusing on bark cracks and undersides of branches.
- Follow the product label for rate (often 1–2%); near bud swell, use the lower end to reduce phytotoxicity risk.
2) Delayed-dormant oil
- Goal: closer to budbreak to hit newly active pests.
- Note: higher burn risk; use conservative rates and apply on mild days.
3) Protective copper after pruning
- Goal: reduce inoculum of canker-causing fungi and sanitize wounds.
- Use: after winter pruning on cut surfaces and a light protective cover over the canopy (in problem-prone areas).
- Caution: do not tank-mix copper with oils; leave 10–14 days between oil and copper. Always follow the label and local recommendations.
4) Oil + selective insecticide for severe hot spots
- Only for scale flare-ups/localized hotspots and with local expert advice.
- Benefit: improves efficacy on armored pests.
- Risk: harms beneficials and can drive resistance; rotate modes of action and respect PHIs.
5) Non-chemical complements
- Sanitary pruning of infected wood; remove mummies and leftover nuts; clear dense weeds at the trunk base.
- Whitewash trunks with a lime-based paint to reduce winter sunscald (a protective step, not a spray).
Application methods and equipment
- High-volume coverage: high-pressure lance sprayers or tractor-mounted airblast/mist blowers; move slowly, treat both sides of rows for penetration.
- Semi–low volume with mist blowers: finer droplets and better penetration; avoid winds above ~10–12 km/h.
- Spot spraying: treat only heavily infested trees to reduce pesticide use and preserve beneficials.
Key technical points
- Weather: 5–25°C, with no frost for at least 24–48 h before/after; avoid impending rain.
- Tank-mix compatibility:
- Do not mix oil with sulfur or sulfur-based products, or with captan.
- Leave 2–3 weeks between oils and copper/sulfur products.
- Do a jar test before mixing.
- Water quality: if possible, adjust spray water pH to ~5.5–6.5; very hard water reduces performance.
- Calibration: aim for thorough wetting, not excessive runoff; set travel speed, pressure, and nozzles to achieve uniform coverage.
- Safety and environment: use PPE; keep away from waterways and drains; follow labels and local law.
Common mistakes to avoid
- Spraying at or just before freezing temperatures.
- Poor coverage of inner canopy and bark cracks.
- Repeating sprays by calendar without scouting.
- Ignoring the interval between oils and copper/sulfur or making incompatible mixes.
Sample winter program
- Step 1: After leaf drop → prune and sanitize; remove leftover nuts.
- Step 2: On a mild day → apply a full-coverage dormant oil.
- Step 3: 10–14 days later → recheck; for remaining scale hot spots, consider spot treatment or mechanical removal.
- In orchards with canker history → after pruning, a protective copper spray on wounds (respect oil–copper intervals).
When is the best time to spray pistachio?
The best time depends on: 1) tree growth stage and pest/disease status, and 2) weather and time of day. Calendar-only programs are unreliable; scout first, then act.
Key windows through the year
- Dormancy (mid- to late winter): dormant oil to suppress overwintering pests. Conditions: >5°C, no frost 24–48 h before/after, no wind or rain.
- Bud swell to leaf-out (early spring): control psyllid when early instar nymphs and fresh honeydew appear. Avoid heavy sprays during peak bloom to protect pollinators.
- Late spring: if damage appears, manage thrips and mites; lowering dust and water stress reduces mite pressure.
- Early summer: in areas with humid nights, protective sprays against Alternaria only if weather remains conducive (consult local advice).
- Mid- to late summer (near hull split): time sprays to pheromone-trap flight peaks and onset of hull split for nut-borers.
- Preharvest: only if necessary and always respecting PHIs; prioritize non-chemical measures and removal of infested nuts.
- Postharvest: orchard sanitation and, if needed, targeted measures to reduce residual populations.
Best time of day and operating conditions
- Time of day: early morning or evening (cooler, higher RH) to reduce evaporation and drift.
- Wind: below ~10–12 km/h. Avoid spraying in strong winds.
- Rain: no rain forecast within the product’s rainfast period.
- Temperature: avoid high heat (usually >30–32°C). For oils, 5–25°C is safer.
- Bloom: avoid non-essential sprays during peak pollination to protect pollinators.
Three golden rules
- Weekly scouting: check upper/lower leaf surfaces and clusters for early psyllid nymphs, honeydew, mites, thrips. Best spray timing is when the pest is at its most vulnerable stage (e.g., early psyllid nymphs).
- Thresholds and targeting: spray only when thresholds are exceeded, and focus on hot spots; avoid calendar spraying.
- Safety and rotation: follow PHI/REI, rotate modes of action, and conserve natural enemies.
How to measure temperature and weather for spraying pistachio
Decisions should be based on the conditions where you spray—inside the canopy at working height, not just a general forecast. Use this practical guide.
Quick summary
- What to measure: temperature, relative humidity (RH), wind (speed/direction), rain likelihood, dew point/thermal inversion.
- Where/how: in the orchard, mid-canopy (about 1.5–2.5 m), multiple spots, then average.
- When: 30–60 minutes before starting, then every 15–30 minutes during spraying.
Simple, useful tools
- Hand anemometer or handheld weather meter: wind speed/direction, temperature, RH.
- Digital thermometer/hygrometer with a radiation shield for accurate readings in sunlit areas.
- Weather apps with local data: for rain/wind/UV and dew point (e.g., Windy, Meteoblue, AccuWeather).
- A simple rain gauge in the orchard to record actual rainfall.
- If available: a “leaf wetness” sensor and a small on-farm weather station.
In-orchard measurement method
1) Measurement points:
- Wind: upwind edge and within the rows.
- Temperature/RH: inside the shaded canopy, mid-height (1.5–2.5 m). Hold the sensor 1–2 minutes at each spot to stabilize.
2) Replicates:
- Take readings from at least 3–5 points in different blocks and average them.
3) Timing:
- Measure 30–60 minutes before spraying; if conditions are marginal, wait 10–15 minutes and recheck.
- During spraying, recheck every 15–30 minutes; pause/adjust if conditions change.
4) Record:
- Log temperature, RH, wind, time, block, and product/nozzle used.
Thresholds and how to read them
- Temperature (°C):
- Dormant oils: 5 to 25 ideal; below 5 or in high heat, risk of burn/reduced efficacy.
- Most insecticides/fungicides: 10 to 28 ideal; above ~30–32 efficacy and safety decline.
- Relative humidity (%RH):
- Better: 60–85. Below 50, droplet evaporation rises; if RH < 40, use larger droplets and anti-drift, or postpone.
- Wind:
- Safer: 3–10 km/h (≈ 0.8–2.8 m/s). Below ~2 km/h there’s inversion risk; above ~12–15 km/h drift rises—stop.
- Know the wind direction and move from upwind to downwind.
- Rain:
- Check the next 6–24 hours. Contact products and oils typically need 12–24 hours dry; many systemics need 6–8 hours (follow the label).
- Delta T (droplet evaporation index):
- Target range: 2 to 8. Below 2 risk of runoff; above 10 fast evaporation and reduced uptake.
- How to get it: with wet/dry bulb readings or any psychrometric/Delta T calculator using temperature and RH.
Spotting hazardous conditions
- Thermal inversion: often at dawn/dusk in calm air, causing horizontal drift.
- Field sign: smoke or dust hangs or moves sideways rather than lifting—stop spraying.
- Simple check: measure temperature at ~0.5 m and at 2–3 m; if higher air is cooler by ~0.5°C or more, inversion is likely.
- Dew/leaf wetness: for many products (especially oils), leaf surfaces should be dry.
- Intense sun/UV: high UV can rapidly degrade certain chemistries; spray early/late in the day.
60-second pre-spray checklist
- Is temperature within the product’s recommended range?
- Is RH above 50%?
- Is wind 3–10 km/h and direction known?
- Any rain likely within the rainfast window? If yes, postpone.
- No thermal inversion (smoke test/two-height temperature check)?
- Leaves dry? UV not extreme? Any nearby beehives? Time accordingly.
What’s the difference between biological, systemic, and contact pesticides in pistachio?
The differences center on mode of action, speed and persistence, coverage needs, impact on beneficials, and resistance risk. Use this practical comparison to choose more precisely.
Quick overview
- Biological (biopesticides): natural origin (microbes, botanicals, oils). Mostly contact/ingested, slower but safer for the environment and beneficials, shorter persistence, sensitive to temperature/RH/UV.
- Systemic: absorbed and moved in the plant’s vascular system; effective on sap-feeders like psyllids, longer protection, less need for 100% coverage, but higher resistance risk and stricter PHI/pollinator considerations.
- Contact: act only where they touch the pest; often faster knockdown, depend on thorough coverage, shorter persistence, potentially harsher on beneficials.
Definitions and traits
1) Biologicals
- How they work: microbial (Beauveria, Metarhizium, Bacillus spp.), oils/soaps, or plant-based (e.g., azadirachtin from neem). Usually act by contact/ingestion.
- Speed and persistence: slower (several days) with shorter residual; require repeats and suitable environmental conditions.
- Conditions: insect-pathogenic fungi perform best in higher RH and moderate temperatures; strong UV reduces efficacy.
- Pros: safer for pollinators and natural enemies; short PHI; suitable near harvest and within IPM.
- Cons: sensitive to environment; need good coverage; often less effective at very high pest densities or on older stages.
2) Systemics
- How they work: absorbed through leaves/stems/roots and moved in xylem/phloem; some move one-way, others two-way.
- Speed and persistence: may start slower than some contact products but persist longer with protective effect.
- Pros: good for hidden sap-feeders (e.g., psyllid nymphs on undersides of leaves); less dependent on perfect coverage.
- Cons: higher resistance risk (rotate IRAC/FRAC codes), PHI constraints, pollinator cautions, and avoid use during bloom. For nut-borers with larvae that enter nuts quickly, timing is critical and systemics are not always the main solution.
3) Contacts
- How they work: kill by direct contact with the pest or eggs/nymphs; includes many insecticides, miticides, and copper fungicides.
- Speed and persistence: often faster knockdown but shorter residual; require uniform canopy coverage (including leaf undersides and interior).
- Pros: rapid control of hot spots; good for sensitive stages (early psyllid nymphs, active mites).
- Cons: coverage- and timing-dependent; higher risk to beneficials; often need repeats if reinfestation occurs.
Note: some products are “translaminar” (move across the leaf blade and persist within the leaf) without being fully systemic. These are useful against mites and thrips in pistachio, but still need good coverage.
Practical use in pistachio
- Pistachio psyllid:
- Biologicals/bi-rationals (oils, soaps, microbials, botanicals) are useful on early nymphs in early season and better conserve natural enemies.
- Systemics can work early (pre-bloom) on building populations; rotate modes of action, avoid bloom, and follow PHI/pollinator guidance.
- Selective contacts for sudden, localized outbreaks—only with excellent coverage.
- Mites and thrips:
- Most miticides are contact or translaminar; coverage quality and dust reduction are key.
- Biologicals (e.g., oils) can reduce pressure but are often insufficient during severe flare-ups.
- Foliar diseases (e.g., Alternaria):
- Copper is contact/protectant; systemics/penetrants offer preventive/curative roles; rotate FRAC groups to avoid resistance.
- Nut-borers:
- Time sprays with pheromone-trap peaks and the short window before larvae enter nuts; targeted contacts are often more effective then. Emphasize prevention, mating disruption, and orchard hygiene.
When to prefer which?
- Near harvest or within IPM to preserve beneficials: biologicals and non-chemical methods.
- Early season on hidden sap-feeders: selective systemics, outside bloom, with MOA rotation.
- Fast knockdown of hot spots: selective contacts with excellent coverage.
- Winter (dormancy): dormant oils (biological/physical) to reduce overwintering pests.
Key decision points
- Coverage and timing matter more than product type; target the pest at its susceptible stage.
- Always rotate IRAC/FRAC codes to manage resistance.
- Follow labels for rate, PHI, and REI exactly, and heed local guidance.
- Avoid incompatible mixes (e.g., oils with sulfur/some coppers) and respect intervals between applications.
- Match weather to product type: biologicals are more sensitive to RH/UV; oils need ~5–25°C.
Key post-spray care for pistachio
After spraying, the goals are to secure full efficacy, minimize risks to trees/workers/environment, and plan the next step based on measured results. Use this checklist.
Safety and legal requirements
- Restricted-entry interval (REI): no one enters blocks without PPE until REI ends; post warning signs.
- Pre-harvest interval (PHI): near harvest, align harvest dates with PHI.
- Personal hygiene: wash hands and clothing after work; clean/store PPE separately.
- Notifications: inform beekeepers/neighbors if present about REI timing.
Protecting deposit and environmental conditions
- Rain/irrigation: observe the product’s rainfast interval.
- General guide: penetrants/systemics 2–6 hours; many contacts and oils 12–24 hours; dormant oils 24–48 hours without rain/overhead irrigation.
- Wind/dust: avoid dust-generating activities for several hours after spraying.
- Heat/strong sun: on very hot days after spraying, monitor leaves for burn symptoms.
Evaluating efficacy
- When to assess:
- Contacts: 24–48 hours later;
- Systemics/IGRs/biologicals: 3–7 days (slower).
- How to check:
- Psyllid: count early nymphs, honeydew levels, and ant activity on 20–30 clusters/tree across several blocks.
- Mites/thrips: use a hand lens to check upper and lower leaf surfaces at multiple canopy heights.
- Diseases: note new lesions and progression versus pre-spray.
- If control is inadequate: don’t rush to repeat within 24–48 hours; after the expected effect window, if thresholds are still exceeded, switch MOA (IRAC/FRAC), improve coverage, and act.
Checking for phytotoxicity
- Watch for: scorched leaf margins, water-soaked/bronzed spotting, leaf cupping, leaf/nut drop, blemishes on green hulls.
- Aggravating factors: high temperatures, incompatible tank mixes, insufficient interval between oil and sulfur/copper.
- Corrective action: if seen, avoid repeating the same mix/rate; review spray-water pH/quality and adjuvants; next time, do a small patch test.
Planning the next application
- MOA rotation: avoid back-to-back use of the same group; respect seasonal max applications.
- Intervals and conflicts:
- Leave at least 14 days between oils and sulfur;
- Leave 10–14 days between oils and copper (follow the specific label).
- Improve coverage: if coverage was poor, recalibrate water volume, nozzles, pressure, and travel speed; use water-sensitive paper to evaluate uniformity.
- Timing: align the next spray with sensitive stages (e.g., early psyllid nymphs) and trap/scouting data.
Equipment and waste
- Leftover tank mix: use or dispose per label; never discharge into waterways/wells.
- Rinsing tank and nozzles: triple-rinse and reuse the rinse water in the next spray; clean filters/clogged nozzles and check for wear.
- Storage: empty, dry tank; check hoses for leaks; verify pressure gauge function.
Record-keeping
- Record: date/time; temperature/RH/wind; product/rate/water volume; adjuvants; nozzle/pressure/speed; treated blocks; growth stage; pest level before/after; any phytotoxicity.
- Why: to optimize future sprays, comply with rules, and manage resistance.
Notes by product type
- Biologicals: slower action; wait 2–3 days before assessing. If microbes were used, avoid immediate copper/sulfur sprays thereafter and plan around high UV.
- Systemics/penetrants: look for reduced honeydew/young nymphs within 3–7 days; avoid washing foliage in the first hours.
- Contacts: if populations rebound, investigate coverage and timing first, not just chemistry changes; repeat spot treatments as needed.
Quick 24–72 hour post-spray checklist
- Did early rain/irrigation occur? If yes, check the label for possible re-spray guidance.
- Has the REI ended and signage been removed?
- Was coverage and efficacy assessed on 20–30 sample trees?
- Any signs of phytotoxicity?
- Is the next spray’s timing and MOA rotation set and on the calendar?
