Management Approaches for Thrips and Garden Symphylans in Lettuce

Transcription

1 REPORT 1: Grden symphyln Project Title Mngement Approches for Thrips nd Grden Symphylns in Lettuce Project Investigtor Dr. Shimt Villnssery Joseph IPM Entomology Advisor University of Cliforni Coopertive Extension Monterey County Abstrct The grden symphyln (Scutigerell immculte) is serious soil pest whose root feeding ffects yield nd survivl of severl high vlued crops in the Cliforni s centrl cost. Lbortory biossys were conducted to determine insecticide efficcy through repellency nd lethlity. To determine indirect repellency (non-contct) of insecticides, choice ssys were conducted where five grden symphylns were introduced into the ren to choose between insecticide-treted nd untreted wells wheres, in direct repellency (contct) ssys, three insecticide-treted 1-cm dimeter discs were psted into the ren nd the number of visits, time spent per visittion nd number of long-durtion (> 10 s) stys of five grden symphylns were quntified. To determine efficcy through direct mortlity, number of grden symphyln died fter 72 h were determined by introducing 10 grden symphylns to insecticide-treted soil ssys. In indirect exposure biossys, seven (Bely, Vydte, Mustng, Lorsbn, Mocp, Az-Direct nd Leverge out of 14 insecticides tested elicited repellency to grden symphyln. Of six insecticides tested in the direct exposure ssys, only Torc elicited contct repellency. In soil ssys, fter 72 h of introduction, Cpture, Vydte, Bely, Mustng nd Torc cused 100, 95, 80, 44, nd 44 % grden symphyln mortlity, respectively, which ws significntly greter thn distilled wter nd four other insecticides. The insecticide tril did not yield ny conclusive informtion. Objective Understnd the efficcy of insecticide chemistries to symphylns through: I. Repellency A). Indirect contct exposure, nd B) Direct contct exposure II. Lethlity III. Field insecticide efficcy tril Procedures The dt from thrips projects were presented in the 2014 nnul report. I (A). Indirect exposure biossy. The biossy rens were constructed using cler, non-venting Petri dishes s shown in the Fig. 1. Two vils were glued to the Petri dishes. The holes on the cp nd Petri dish llow the symphylns to move to the well. A brrier ws creted between the Petri dish nd the inner bottom surfce of the dish ws uniformly roughened using sndpper to fcilitte 1

2 grden symphyln movement. Dried soil ws dded into the vils, nd then 1-mL of insecticide solution or distilled wter ws dded into the vil. In the first set of experiments, soil in both the vil ws treted only with distilled wter. In the lter experiments, one vil ws treted only with distilled wter nd other with insecticide solution. Fourteen insecticides were tested for indirect exposure, nd the detils of ctive ingredients, nd the rtes used re listed in Tble 1 (indicted by symbol*). Once the soil ws dded into the wells, five symphyln were dded to the center of the Petri dish. The Petri dish ws then covered with the lid nd the edges were seled using Prfilm to reduce desicction of symphyln. After 6 hours, those five symphyln were locted nd their loctions inside the ren were documented. For ech insecticide tretment, biossys were replicted 18 times nd totl of 90 symphylns were used for ech insecticide product. I (B). Direct exposure biossy. A cler, non-venting polystyrene Petri dish ws used for the direct exposure biossy. White filter pper ws dipped for 2 seconds in distilled wter nd plced on the bottom of the dish. For this biossy, 1-cm dimeter filter pper discs were mde from 4.7-cm blck qulittive filter pper. These blck discs were dipped into 45-mL insecticide solution in continer for 5 seconds then ir dried for 20 minutes. Three insecticide-treted discs were psted on to the wet white filter pper using wshble glue stick. Blck colored filter pper ws selected for the discs becuse they would be in contrst to white or off-white symphylns nd help with evlution. Five symphylns were introduced to the center of the Petri dish using soft pint brush. The movement of five symphylns ws videotped for 20-min. Nine insecticides were tested using this biossy (Tble 1, indicted by symbol ) nd every insecticide tretment ws videotped nd replicted 6 times per insecticide product. The videos were evluted for number of times symphylns visited the blck discs, time spent per visit on the blck discs, nd number of times symphylns spent > 10 seconds on the blck discs. Stop wtch nd clickers were used to quntify those prmeters. Insecticides belonging to clss pyrethroids were not tested in this biossy becuse they re more likely to trigger hyperctivity fter exposure. II. Soil biossy. Nine insecticides were tested to determine efficcy ginst symphylns. The detils of ctive ingredients nd tested rte re listed in Tble 1 (indicted by symbol ). The soil biossys were performed using 100-mL cups with soil. Twenty five grms of oven-dried soil ws dded to the cup nd 7-mL of insecticide solution or distilled wter per cup ws uniformly pipetted on to the surfce of the soil within the cup. After dding the insecticide solution or distilled wter, the soil ws stirred five times using glss rod to fcilitte movement of symphylns within the gps in soil. Ten symphylns were introduced into ech cup nd the cups were covered with perforted cps to llow ir flow. Ech insecticide tretment ws replicted t lest 15 times (cups) for totl of 150 symphylns per insecticide product. Seventy two hour fter introduction, the biossys were evluted for mortlity. III. Insecticide efficcy tril. This study ws conducted on lettuce field in Slins tht ws reported with grden symphyln incidence nd plnt dmge. All the tretments were ssigned to previously identified hot spot within the field. The lettuce seeds were plnted on 12 Mrch Four replictes of ech tretment were ssigned to 10-feet long 40 beds (two seed lines/bed) ccording to completely rndomized block design. The insecticides used nd theirs rtes were Rdint (spinetorm) t 10 fl oz/cre, Entrust (spinosd) t 10 fl oz/cre, Bely (clothinidin) t 12 fl 2

3 oz/cre, Wrrior II (lmd-cyhlothrin) t 1.6 fl oz/cre, nd Mustng (zet-cypermethrin) t 4 fl oz/cre. All insecticides were pplied long the seed line (3-inch bnd) on 13 Mrch. Spry ppliction ws done using one-nozzle spryer t 30 PSI. The wter volume used ll pplictions ws 100 gl/cre. No djuvnt ws dded. The potto slice ws used s bit to monitor grden symphylns in the tril. One potto slice ws deployed per plot nd ws retined for 2 dys in the field. The monitoring ws initited on 22 Mrch (weeks fter plnting) nd ws repeted on (weeks fter plnting). Ten plnt smples were rndomly collected from ech plot on 3 April (4 weeks fter plnting) to determine plnt growth. The fresh nd dry weights of these plnts were mesured. Results I (A). Indirect exposure biossy. Of the 1,338 symphylns used for this experiment, 90.5% entered either of the vils in 6-hours. Similr number of grden symphylns were collected from both the vils suggesting tht there were no prticulr preference. More number of symphylns ws found in the well with distilled wter when the other well ws treted with Bely, Lorsbn, Mocp, Mustng, Vydte, Az-Direct nd Leverge. On the other hnd, more symphylns were found in the well with Verimrk thn in the well with distilled wter. When the products, Rdint, Wrrior, Torc, Cpture, Ecotek, nd Tritek were treted to vil, the number of symphylns settled in similr number is both the vils. I (B). Direct exposure biossy. When symphylns were in direct contct with insecticide-treted surfce, symphylns exhibited lesser number of visits nd time spent on the discs treted with Torc thn distilled wter. However, these numbers on the discs treted with Torc were not different from those on discs with Bely, Vydte, nd Ecotek. Similrly, number of times symphylns spent > 10 seconds on distilled wter discs ws higher thn tht on Torc-treted discs. II. Soil biossy. Soil treted with insecticides Vydte, Cpture, Torc, Bely nd Mustng cused greter symphyln mortlity thn distilled wter treted soil (Fig. 2). Mortlity of symphylns ws 100% nd ws greter with Torc-treted soil thn with ll other insecticide tretments expect Cpture. More symphylns died with Vydte thn with Bely nd Mustng treted soil. III. Insecticide efficcy tril. The number of grden symphylns, fresh nd dry weight of lettuce ws not sttisticlly different mong vrious tretments. The number of grden symphylns cptured in potto-slice bit ws numericlly lower in Rdint, Bely, Wrrior II nd Mustng thn in the untreted check (UTC) (Fig. 5). The numericlly lowest numbers of grden symphylns were cptured from Mustng thn UTC or other tretments. The fresh nd dry weight of lettuce ws numericlly greter in the Mustng tretment thn UTC (Figs. 6 nd 7). Conclusion This study estblished reltive efficcy of insecticides ginst symphylns by determining reltive repellency, nd lethlity of insecticides through lbortory biossys. The dt suggest tht certin insecticides, but not ll, re repellent to symphylns before contct. Only tolfenpyrd elicited repellency fter contct. Reduced risk insecticides included in the ssys were neither repellent nor lethl to forging symphylns. More number of symphylns died when insecticides, Vydte, Cpture, 3

4 Torc, Bely nd Mustng were pplied to soil reltive to wter treted-soil. The future studies will evlute the efficcy of insecticides when delivered using vrious methods encompssing the properties of insecticide nd soil, nd the behvior nd ecology of symphylns in vegetble production. 4

5 Tble 1. Insecticides evluted ginst symphylns in lbortory biossys. Clss Insecticide Formultion Rte per cre Neonicotinoids Clothinidin* Bely 12 fl oz Pyrethroids Bifenthrin* Cpture 6.8 fl oz Zet-cypermethrin* Mustng 4.2 fl oz Lmbd-cyhlothrin* Wrrior II 1.9 fl oz Neonicotinoids + Imidcloprid + Betcyfluthrin* 6 fl oz Leverge Pyrethroids Orgnophosphtes Ethoprop* Mocp 34 lb Chlorpyrifos* Lorsbn 2.3 pint Crbmtes Oxmyl* c Vydte 32 fl oz Spinosyn Spinetorm* Rdint Rynodine receptor 13.5 fl oz Cyntrniliprole* Verimrk ctivtor Pyridzinone Tolfenpyrd* Torc 21 fl oz Tetrnortriterpenoids Azdirchtin* e Az-Direct 32 fl oz Essentil oils * e, f Ecotek 28 oz Minerl oil * e Tritek 1.5 gl Insecticides included in indirect exposure experiment (*), direct exposure experiment ( ), nd mortlity experiment ( ). Dose determined bsed on 40 gl per cre. 5

6 Tble 2. Grden symphyln response to direct exposure of insecticides. Insecticide Symphyln on treted blck discs No. of visits Time spent (s) > 10-s spent Bely 67.8 ± 9.1b 7.8 ± 1.3b 5.7 ± 1.5bc Rdint ± ± 1.5b 3.3 ± 0.8bc Verimrk ± ± 1.4b 4.1 ± 2.5bc Vydte ± 19.5b 8.3 ± ± 1.2b Ecotek 80.5 ± 20.0b 7.3 ± 1.8b 6.2 ± 1.6b Torc 49.7 ± 13.3b 3.1 ± 0.9b 0.9 ± 0.4b Distilled wter ± ± ± 1.4 Sme letters within ech column re not different. 6

7 Fig. 1. Indirect choice biossy to determine the effect of insecticides on grden symphylns when on vil ws provided with distilled wter nd other with vrious insecticides or distilled wter. Fig. 2. Direct choice biossy to determine the effect of insecticides on grden symphylns when the discs were treted with distilled wter or vrious insecticides. 7

8 Fig. 3. Number of grden symphylns distributed in indirect exposure choice biossy rens with insecticide or distilled wter in one well nd distilled wter in the other well. Pirs of brs with sterisks (*) re different. 8

9 Number of symphylns Fig. 4. Grden symphyln died when exposed to insecticides in the soil biossy for 72 h. Brs with sme letters re not different Rdint Entrust Bely Wrrior II Mustng UTC Fig. 5. Number of grden symphyln cptured using potto-slice bit. 9

10 Lettuce dry weight (g) Lettuce fresh weight (g) Rdint Entrust Bely Wrrior II Mustng UTC Fig.6. Fresh weight of lettuce smpled from vrious tretments Rdint Entrust Bely Wrrior II Mustng UTC Fig.7. Dry weight of lettuce smpled from vrious tretments. 10