Small Bugs and Stink Bugs on Pistachios

Kent Daane, UC Berkeley [email protected]

Houston Wilson, UC Riverside [email protected]

Judith Stahl, Glenn Yokota, Paul DaSilva, Walt Bentley, Bob Beede

Outline Bug Species Small bugs Stink bugs Damage Seasonal Biology Economic Injury Controls Monitoring Insecticides & timing (bio-controls, trap crops)

Bug Species: Small Bug Pests

Calif. buckeye bug (Neurocolpus Phytocoris relativus longirostrus)

Calocoris norvegicus Lygus hesperus

Photo: web

1 Bug Species: Large Bug Pests

Photo: web

Green Stink Bug (Chinavia (=Acrosternum) hilaris)

Stink bugs (Pentatomidae)

Red Shouldered Stink Bug (Thyanta pallidoverins) Uhler’s stink bug

Say’s Stink Bug Uhler’s Stink Bug (Chlorochroa sayi) (Chlorochroa uhleri)

2 Stink bugs (Pentatomidae)

Red Shouldered Stink Bug (Thyanta pallidoverins)

Green Stink Bug (Chinavia (Acrosternum) hilare)

Green Stink Bug (Chinavia (=Acrosternum) hilaris)

3 Green Stink Bug (Chinavia (=Acrosternum) hilaris)

Green Stink Bug (Chinavia (=Acrosternum) hilaris)

4 Green Stink Bug (Chinavia (=Acrosternum) hilaris)

Green Stink Bug (Chinavia (=Acrosternum) hilaris)

5 Green Stink Bug (Chinavia (=Acrosternum) hilaris)

Whitish bands on antenna Blunt face

Margin pattern

Brown marmorated stink bug

Whitish bands on antenna rough Blunt shoulders face (scutellum)

Margin Whitish bands pattern on back legs (tibia) Brown marmorated Brochymena sp. stink bug “Rough stink bug

6 Outline Bug Species Small bugs Stink bugs Damage Seasonal Biology Economic Injury Controls Monitoring Insecticides & timing (bio-controls, trap crops)

Pistachio Small Bug Pests

Lygus hesperus

For Lygus (and other small bugs) the orchard’s proximity to their preferred host plants is important (overwinter as an adult); they can 3-5 generations / yr depending on host plant, but it is the early-season pistachio damage (dropped nuts)

Pistachio Small Bug Pests

Potato mirid (Calocoris norvegicus)

Again, early-season damage; one from Purcell & Welter 1990 JEE generation per year; overwinters as an egg in weedy host plants

7 Pistachio Small Bug Pests

Phytocoris (Phytocoris relativus and Phytocoris californicus)

Pistachio Small Bug Pests Phytocoris preys on NOW eggs

and European fruit lecanium Phytocoris (Phytocoris relativus and Phytocoris californicus); overwinter as egg in young tree branches (e.g., on pistachio); four generations per year.

Pistachio Large Bug Pests typically have 2 generations

50 100 DD 500 1000 1500

40 (A) 2015 - Sacramento

0 Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec BMSB BMSB per trap per (average week ± SEM)

8 Strong fliers – and can migrate – but some (Green SB) overwinter in the orchard

Hemiptera “half-wing” actually two wings with the half-wing covering the second fly-like wing

Bug Damage - Mouthparts general seed feeders

needle-like mouthparts strong mouthparts = deep probing

stink bug’s mouthpart

April-May “Dropped nuts”

9 “Damage signal” from insects – probably large bug at this stage

Almond damage (RE Rice)

10 Kernel necrosis and “Stigmatomycosis”

Kernel necrosis and “Stigmatomycosis”

Damage amount & Seasonal development

1) Bug density 3) Crop load

2) Bug size 4) Shell hardness

11 2) Bug size – Pistachio cage study with RSSB

12 b

9 A ab 6 ab 3 a

Dropped nuts nuts Dropped / cluster 0

b 20 b 15 B

5 ab a 0

Epicarp lesions / lesions Epicarp cluster Control RSSB RSSB RSSB small large adult nymph nymph

3) Crop load & compensation 10 100

8 80 Nuts per cluster Nuts per

6 60 Plant 4 compensation 40 Epicarp lesions 2 20

0 0 Mar 1 Apr 1 May 1 Jun 1 Jul 1 Aug 1Sept 1 Oct 1

Brown marmorated stink bug

Pistachio damage for (a) different insect treatments, (b) the pistachio phenology and (c) different pistachio varieties: ‘el exp’ = epicarp lesions recorded immediately after insect exposure, ‘el harv’ = epicarp lesions recorded during harvest, ‘dropped’ = dropped nuts, ‘kn’ = kernel necrosis, ‘stigma’ = fungal symptoms indicating stigmatomycosis, ‘aborted’ = aborted nuts.

12 Brown marmorated stink bug

Outline Bug Species Small bugs Stink bugs Damage Seasonal Biology Economic Injury Controls Monitoring Insecticides & timing (bio-controls, trap crops)

Monitoring for Small & Large Bugs Sweep samples for small bugs Beat samples for large bugs easy, species in canopy & immediate response Monitor damaged nuts indicates bug presence shows “%” crop damage Critical sampling period April-June (pistachios) March- May (almonds)

13 Compared different sampling methods (beating tray, sweep net, D-Vac, visual sampling) to a ‘complete’ insect collection with Bob Beede spraying the pistachio trees and collecting the insects that dropped onto a plastic sheet

Phytocoris & Calocoris Stink Bugs Leaffooted Bugs Relative No. Bugs Collected / Hour Bugs Collected No. Relative

Insecticide Sweep D-Vac Visual Beating Spray Net Tray (ground cover)

14 Monitoring for Small & Large Bugs Sweep samples for small bugs Beat samples for large bugs easy, species in canopy & immediate response Monitor damaged nuts indicates bug presence shows “%” crop damage Critical sampling period April-June (pistachios) March- May (almonds)

Monitoring for Small & Large Bugs Sweep samples for small bugs Beat samples for large bugs easy, species in canopy & immediate response Monitor damaged nuts - indicates bug presence shows “%” crop damage Critical sampling period April-June (pistachios) March- May (almonds)

15 Cover crop trial in 2018 and 2019 with Nichols Farms (Pistachio Board funded project)

Cover crop Control mixed seeds resident weeds

Trend: Towards the end of the season most stink bugs in the cover crop without increase in canopy

4 control canopy b 3 control ground a

a 2 a ab a

[mean ± SE] a a a a a a a 1 a a a a Stink bugs per sample sample per bugs Stink a a a a a a a 0 31-May31. Mai 14-Jun 24-Jun 17-Jul 30-Jul 23-Aug

Conclusion: Lots of small bugs (early-season) or some large bugs (early, mid-season), insecticides are the most reliable option. But remember (1) crop load compensation, (2) bug size, and (3) mid- to late-season shell- hardening, Pyrethroids (April-May) are often used for bugs. Materials are broad- spectrum, and may be connected to Gill’s mealybug problems & NOW resistance

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