Daane Black widow spiders CTGC 2007

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San Joaquin Valley Table Grape Seminar Using Black Widow Spider Biology to Improve Control Kent Daane, Glenn Yokota, Pedro Hernandez California Table Grape Commission & University of California

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Why is there a concern? 1. Public fear

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Why is there a concern? 3. BWS is an Invasive

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Outline How to sample BWS where are they in the vineyard what is their seasonal development sampling program How to kill BWS which pesticides work best when to treat

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Where are BWS in the vineyard? Sampled 2003-05 4-5 vineyard blocks collected every 2-4 weeks BWS number, age, sex BWS location

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Berm Base- trunk Mid- trunk Cordon Arms Canopy Cluster Spiders (%) per vine section Where are BWS in the vineyard?

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5% - On ground w/o apparent “vine support”

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40-60% - Base of trunk/trellis (look for webs)

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Peeling bark & old leaves often form nest structure

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20-25% - Mid-trunk - between stake and trunk

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In vine crevices (no trellis / ground support)

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Where are BWS in the vineyard?

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Where are BWS in the vineyard – Hiding Leaves (2%) Mid-Trunk (15-25%) Upper Cordon (15-20%) Base-Trunk (40-60%) Berm, leaf-litter (5%) In Stake (4%) Arms (5%) Canopy (1%)

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Black widow spider vineyard

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Wood stake- 4 inch Wood stake- 1 inch Metal stake- 4 inch Metal stake- 1 inch Black widow spider vineyards Wood stakes – far/close C-Metal stakes – far/close T-Metal stakes – far/close Milk cartons for replants Cement valves/leaves Where are BWS in the vineyard?

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Aug Sept Oct Nov Dec Jan ‘07 Feb Spiders per vine (sum ±SEM) 0 2 4 6 Overhead trellis Standard T-trellis Where are BWS in the vineyard?

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Cement Valve Milk carton No stake Leaves 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Habitat preferences Spiders per vine ±SEM) Metal “C” 1-in Wood 1-in Metal “C” 4-in Metal “T” 4-in Metal “T” 1-in Where are BWS in the vineyard?

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Recognizing black widows & busting myths Female BWS & Egg sac Egg sac & Spiderlings

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Recognizing black widows & busting myths BWS “spiderling” (1/64th inch)

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Nearly mature females have beautiful color pattern on top! Recognizing black widows & busting myths immature female (3/4 inch) BWS adult male (top) (bottom)

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How does the BWS age structure change? Winter / Fall Spring & Summer: 2-3 generations April-October: egg sac

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0 10 20 30 40 50 60 70 80 90 100 Aug/21/03 Sep/19/03 Oct/23/03 Nov/21/03 Dec/22/03 Jan/22/04 Feb/20/04 Mar/22/04 Apr/21/04 May/20/04 Jun/21/04 Jul/20/04 Aug/19/04 Sep/22/04 Oct/22/04 Nov/22/04 Dec/17/04 Jan/19/05 Feb/23/05 Mar/24/05 Apr/22/05 Black widow spiders per 200 vines How does the BWS age structure change? Egg Sac Spiderling Immature Adult Empty Nest

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0 5 10 15 20 25 30 35 Sep/12/03 Oct/10/03 Nov/10/03 Dec/12/03 Jan/13/04 Feb/13/04 Mar/12/04 Apr/13/04 May/11/04 Jun /11/04 Jul/15/04 Aug/10/04 Sep/8/04 Oct/6/04 Nov/10/04 Dec/6/04 Jan/12/05 Feb/9/05 Mar/8/05 Apr/6/05 Black widow spiders per 200 vines How does the BWS age structure change? Egg Sac Spiderling Immature Adult Empty Nest

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0 10 20 30 40 50 60 70 80 90 Aug/27/03 Sep/26/03 Oct/31/03 Nov/26/03 Dec/26/03 Jan /27/04 Feb/27/04 Mar/29/04 Apr/29/04 May/27/04 Jun/29/04 Jul/27/04 Aug/27/04 Sep/29/04 Oct/29/04 Nov/29/04 Dec/29/04 Jan/31/05 Feb/28/05 Mar/29/05 Apr/26/05 Black widow spiders per 200 vines Egg Sac Spiderling Immature Adult Empty Nest How does the BWS age structure change?

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Population increase from a point source 255.8  22.5 spiderling / egg

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Population increase from a point source finish start

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24 – hr sampling

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Black widow exposure rating: 0 = hidden, 2 = exposed 7am 5pm 0.0 0.5 1.0 1.5 2.0 September 0.0 0.5 1.0 1.5 2.0 January 7pm 9pm 11pm 1am 3am 5am Midnight 1pm 3pm 7am 9am 11am Noon

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How to sample BWS Look in “hot” spots Record webs on 1000 vines / block (fast, walk 5-10 rows) Mark 50-100 vines with webs (visit webs after dark) Destroy webs before pesticides (visit 3-7 days post spray)

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Outline How to sample BWS where are they in the vineyard what is their seasonal development sampling program How to kill BWS which pesticides work best when to treat

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Lorsban, Lannate Applaud, Omite, Abermectin Provado Danitol Contact sprays for adult BWS

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Survival (%) 0 1 2 3 5 7 10 0 50 100 Days after application Contact sprays for adult BWS Danitol, Lannate, Lorsban (100%) Applaud, Provado Agrimek (10%) Omite (25%)

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Lorsban Danitol Control Lannate Residual activity on bark for adult BWS

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So…which insecticides are best for BWS? Delayed dormant Lorsban Lorsban kills adult BWS, but had little impact on immatures Dead adult BWS Live immatures

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Summary, Conclusions and Questions……. Recognize BWS stages….. Look for webs in popular hiding spots

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Summary, Conclusions and Questions……. Consider spot treatments … Delayed-dormant Lorsban kills adults, not immatures In-season Danitol In-season Lannate

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Summary, Conclusions and Questions…….

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Summary, Conclusions and Questions…….

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Spiderlings’ main predator – other spiders!

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Label rate of Danitol, Lorsban & Lannate 0.1 10 100 0.01 0.1 1 10 30 50 70 90 99 ~ 100 Dose insecticide application (as % label rate) Mortality (%) 99.9 1 LD 50 = 2.5% of label rate LD 99 = 9.1% of label rate Lannate for adult females