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Statement




© 2008 Plant Management Network.
Accepted for publication 25 October 2007. Published 18 January 2008.


Spinetoram Is Compatible with the Key Natural Enemy of Frankliniella Species Thrips in Pepper


Mrittunjai Srivastava, Department of Entomology and Nematology, North Florida Research and Education Center, University of Florida, Quincy 32351; Lara Bosco, Di.Va.P.R.A. Entomologia applicata all’Ambiente, University of Torino, Grugliasco, Italy; Joe Funderburk, Department of Entomology and Nematology, and Steve Olson, Department of Horticultural Sciences, North Florida Research and Education Center, University of Florida, Quincy 32351; and Anthony Weiss, Dow AgroSciences, 804 River Hammock Boulevard, Brandon, FL 33511


Corresponding author: Joe Funderburk. jef@ufl.edu


Srivastava, M., Bosco, L., Funderburk, J., Olson, S., and Weiss, A. 2008. Spinetoram is compatible with the key natural enemy of Frankliniella species thrips in pepper. Online. Plant Health Progress doi:10.1094/PHP-2008-0118-02-RS.


Abstract

Feeding by the western flower thrips, Frankliniella occidentalis, causes damage to the fruits of pepper, and the species is the key vector of Tomato spotted wilt virus. Effective management integrates conservation of populations of the natural predator, Orius insidiosus, with the use of reduced-risk insecticides, namely spinosad. We conducted field experiments in northern Florida in 2005 and 2006 and in central Florida in 2006 to evaluate the new reduced-risk insecticide spinetoram for control of thrips and to determine the impact on natural populations of O. insidiosus. Spinetoram at 61 g ai/ha was as effective as spinosad at 140 g ai/ha against the western flower thrips and the other common thrips in Florida, Frankliniella tritici and Frankliniella bispinosa. The mean numbers of the predator were very high in all treatments in each experiment, and their numbers relative to the numbers of thrips indicated that predation was sufficient to suppress thrips populations in all treatments. Broad-spectrum insecticides when included in the experiments provided little or no control; sometimes, they flared thrips numbers compared to untreated pepper.


Introduction

Thrips (Thysanoptera) are tiny insects with fringed wings. There are over 5000 described species with about 87 species of thrips that are pests of commercial crops due to their feeding on leaves, fruits, and flowers causing discoloration, deformity, and reduced marketability (8). Figure 1 shows flecking damage to a pepper fruit caused by the feeding of the adults and larvae of the western flower thrips, Frankliniella occidentalis. The western flower thrips of worldwide distribution is considered the primary vector of Tomato spotted wilt virus (14). Symptoms of the disease include retarded growth, chlorosis, necrosis, and the characteristic ring spots on the leaves and fruits. Peppers display a range of symptoms, and the ring spots are not always present on the leaves (Fig. 2). Other vectors in the southeastern US include F. bispinosa and F. fusca (1). Another common thrips species in crops in the southeastern US is the non-vector species F. tritici (13). Chellemi et al. (5) noted that populations of each of the above-mentioned species peaked during the peak flowering of wild host plants in northern Florida between March and June. Large populations of F. occidentalis, F. tritici, and F. bispinosa migrate into the spring crop of flowering peppers, causing reduced-marketability from thrips feeding damage and from their vectoring of Tomato spotted wilt virus (6,11).


     
 

Fig. 1. Flecking damage on pepper fruit caused by the feeding of adult and larval Frankliniella occidentalis.

 

Fig. 2. A pepper plant infected with Tomato spotted wilt virus with retarded growth and other symptoms.

 

Growers in the southeastern US responded in the late 1980s and early 1990s to the invasion of F. occidentalis by the application of broad-spectrum, highly toxic insecticides. These insecticides were sprayed on a frequent calendar schedule in unsuccessful attempts to control thrips. Funderburk et al. (6) showed that applications of fenpropathrin and acephate suppressed thrips populations initially, but their numbers increased rapidly a few days after application in numbers that were eventually many-fold greater than untreated pepper. Successful management approaches were achieved through the conservation of natural enemy populations. Minute pirate bugs (Anthocoridae) are effective biological agents against thrips in greenhouses (12). Under field conditions it was thought that the characteristics of rapid colonization and population growth of thrips surpassed the capacities of natural enemies to control them (9). However, Funderburk et al. (6) and Reitz et al. (11) showed that natural infestations of the native anthocorid species, Orius insidiosus (Say), were effective in suppressing populations of thrips, even under these conditions. Tavella et al. (12) reported that over 96% of the immature and adult stages of F. occidentalis and Orius spp. were aggregated in the flowers of greenhouse peppers. Hansen et al. (7) reported similar patterns of aggregation of Frankliniella spp. and O. insidiosus in field pepper.

In much of the southeastern US, F. occidentalis and Tomato spotted wilt virus are the key pest problems in pepper and other crops (3). An effective integrated pest management program that employs reduced-risk insecticides, natural infestations of O. insidiosus, and cultural control tactics including ultraviolet-reflective mulch are widely implemented for pepper (11). Spinosad (Dow AgroSciences, Indianapolis, IN) is the most effective insecticide able to suppress populations of F. occidentalis, and it is a reduced-risk insecticide that does not suppress populations of O. insidiosus at labeled rates (6,11). Spinosad also is effective in suppressing populations of numerous other occasional pests of pepper.

Spinetoram (Dow AgroSciences) is a new spinosyn insecticide that, like spinosad, is derived from the fermentation of Sacchanopolyspora spinosa. Spinetoram is a reduced-risk insecticide because of its low toxicity to many beneficial insects and because of its low human and environmental toxicity.

Our purpose was to evaluate the compatibility of spinetoram for control of thrips with biological control in field pepper. We tested a range of rates of spinetoram for suppression of F. occidentalis, F. bispinosa, and F. tritici in field pepper against the standard rate of spinosad. The effects of these rates on natural populations of O. insidiosus were determined.


Evaluation of Spinetoram on Thrips and Thrips Predator Populations

Field experiments were conducted in 2005 and 2006 at the University of Florida North Florida Research and Education Center in Quincy, Gadsden Co. Another experiment was conducted in 2006 at the University of Florida Plant Science Research and Education Unit in Citra, Marion Co. Six-week-old transplants of ‘Camelot X3R’ (Quincy experiments) and ‘Aristotle’ (Citra experiment) sweet pepper were transplanted into raised plastic beds spaced 90 cm apart. Each bed consisted of two linear rows with 30-cm spacing between and within rows. Beds were fumigated with methyl bromide at 339 kg/ha about one week prior to transplanting. Plants were irrigated based on the plant needs through a trickle tube at the center of each bed. Experimental design was a randomized complete block with four replicates in each experiment. Plot size was one two-row bed by 9 m. Foliar-applied treatments of spinosad 2SC and spinetoram 1SC were included in each experiment. Foliar-applied treatments of esfenvalerate 0.66 (E. I. DuPont de Nemours and Co., Wilmington, DE), novaluron 0.83EC (Chemtura Corp., Middlebury, CT), and spiromesifen 2SC (Bayer CropScience LP, Research Triangle Park, NC) were included in some experiments. Imidicloprid (Bayer CropScience LP) was applied through the trickle tube at transplanting to selected treatments in the Quincy experiment in 2006. Foliar-applied insecticides were applied with a backpack sprayer that was powered by pressurized carbon dioxide and that was equipped with 4 D7 nozzles per double-row bed. The amount of spray was 316 liters/ha. Application dates were 18 and 25 May in the 2005 Quincy experiment. Application dates were 5, 10, and 19 May in the 2006 Quincy experiment and 3, 11, and 18 May in the 2006 Citra experiment. Treatments were evaluated for effects on insect populations two and six days following the foliar insecticide application dates unless prohibited by rainfall. The densities of adult thrips of each species, total larval thrips, and adult and nymphal O. insidiosus were estimated in each plot on each evaluation date by collecting 10 flowers per plot and placing them in vials containing 70% alcohol. Thrips and O. insidiosus were extracted from the flowers and identified using 7 to 80× magnification. Tests of data revealed no serious departures from normality, and data analyses are reported for untransformed data. Significant treatment differences for adult thrips of each species, for total larval thrips, and for total adult and nymphal Orius insidiosus on each sample date were determined using analysis of variance for a randomized complete block and subsequent Duncan’s Multiple Range Test (P < 0.05). Significant treatment differences for the number of thrips of all species and stages and for the number of O. insidiosus for data pooled over all sample dates were determined for each experiment using analysis of variance for a randomized complete block and subsequent Duncan’s Multiple Range Test (P < 0.05).


Efficacy of Insecticides Against F. occidentalis and F. tritici

Populations of F. occidentalis were common in the Quincy experiments, but not in the Citra experiment. Unlike northern Florida, populations of F. occidentalis typically are only a small proportion of the total thrips population in central Florida (7). Numbers in the 2005 experiment conducted in Quincy were greatest on the 24 May sample date, and this is the only date in which there were significant treatment differences (F = 5.0; df = 5, 15; P = 0.06). The standard rate of spinosad and the highest rate of spinetoram provided significant control as compared to the untreated pepper (Table 1). Populations of F. occidentalis were much greater in the experiment conducted in Quincy in 2006, especially on the 6, 9, 10, and 13 May sample dates when there were significant treatment differences (F = 2.0, 3.5, 2.3, and 2.8, respectively; df = 8, 28; P < 0.08, 0.01, 0.05, and 0.05, respectively). Treatments that included novaluron and spiromesifen had numerically, but not statistically, higher numbers of adults than untreated pepper on each of these sample dates (Table 2). The treatment of esfenvalerate had significantly more adults than untreated pepper on the 10 May sample date. This result is consistent with previous reports of pyrethroid insecticides such as esfenvalerate flaring populations of F. occidentalis in pepper (6,7,10,11). Treatments that included spinosad or spinetoram usually had numerically lower numbers of adult F. occidentalis than untreated pepper but the only significant difference was the highest rate of spinetoram compared to untreated pepper on 13 May (Table 2).


Table 1. The mean number of adult Frankliniella occidentalis per ten flowers on four dates according to treatment in the field experiment conducted in Quincy, FL in 2005.

Treatment and active ingredient per hectare Mean Frankliniella occidentalis adults
per 10 flowers
*
20 May 24 May 27 May 31 May
untreated 2.3a      3.3a 0.0a 0.0a
spinosad 140 g 0.3a      0.7b 0.3a 0.0a
spinetoram 18 g 0.0a      2.0ab 0.8a 0.0a
spinetoram 26 g 0.8a      2.3ab 0.5a 0.0a
spinetoram 44 g 1.0a      1.3ab 0.0a 0.0a
spinetoram 61 g 1.3a      0.0b 0.5a 0.5a

 * Means in the same column followed by the same letter are not significantly different according to ANOVA and subsequent DMRT (P > 0.05).


Table 2. The mean number of adult Frankliniella occidentalis per ten flowers on six dates according to treatment in the field experiment conducted in Quincy, FL in 2006.

Treatment and active ingredient per hectare Mean Frankliniella occidentalis adults
per 10 flowers*
6 May 9 May 10 May 13 May 20 May 23 May
untreated 12.0abc  29.8abcd 12.0b 17.4a    4.6a 1.6a
esfenvalerate 56 g 6.0c     24.0bcd 28.8a  9.8ab 3.0a 0.5a
spinosad 140 g 20.5ab    23.3bcd 15.0b  8.8ab 5.5a 1.3a
spinetoram 26 g  11.0abc  10.8d 12.8b  8.8ab 3.0a 1.5a
spinetoram 44 g  10.8abc  10.5d   18.0ab  8.5ab 4.5a 1.3a
spinetoram 61 g  8.8bc  15.2cd 11.8b 5.3b 3.5a 0.5a
novaluron 87 g 22.3a     32.8abc 13.3b 14.0ab 3.5a 2.5a
imidicloprid 285 g
& novaluron 87 g
 17.3abc  45.8a   24.3ab 17.5a    4.3a 0.8a
imidicloprid 285 g &
spiromesifen 145 g
 15.0abc  42.5ab 15.8b 17.3a    6.3a 1.8a

 * Means in the same column followed by the same letter are not significantly different according to ANOVA and subsequent DMRT (P > 0.05).


The adults of F. tritici were more common in both of the Quincy experiments than the adults of F. occidentalis. This species was rare in the samples in the Citra experiment in 2006. The mean numbers of adults by treatment in the 2005 and 2006 Quincy experiments are shown in Tables 3 and 4, respectively. The adults of F. tritici are highly vagile, and their ability to re-colonize treated crops frequently results in an apparent rather than real lack of control by short-residual insecticides (10). This was reflected in the results in our experiments in that there were significant treatment differences on only the 31 May sample date in 2005 (F = 4.3; df = 5, 14; P = 0.05) and on the 6 and 9 May sample dates in 2006 (F = 2.9 and 3.9, respectively; df = 8, 28; P < 0.01). On the 31 May sample date in 2005, each insecticide treatment of spinosad and spinetoram resulted in significant suppression compared to the untreated control. In the 2006 experiment, the application of novaluron resulted in significantly increased numbers compared to untreated pepper on 6 May and the treatment of imidicloprid and novaluron resulted in significantly increased numbers compared to untreated pepper on 9 May.


Table 3. The mean number of adult Frankliniella tritici per ten flowers on four sample dates according to treatment in the field experiment conducted in Quincy, FL 2005.

Treatment and
active ingredient
per hectare
Mean Frankliniella tritici per 10 flowers*
20 May 24 May 27 May 31 May
untreated 4.5a 26.7a 84.0a 72.8a
spinosad 140 g 4.0a 34.7a 94.5a 32.5b
spinetoram 18 g 3.0a 29.7a 68.8a 27.0b
spinetoram 26 g 1.3a 32.7a 51.8a 31.0b
spinetoram 44 g 2.5a 30.3a 52.3a 27.0b
spinetoram 61 g 4.0a 63.3a 37.8a 29.8b

 * Means in the same column followed by the same letter are not significantly different according to ANOVA and subsequent DMRT (P > 0.05).


Table 4. The mean number of adult Frankliniella tritici per ten flowers on six sample dates according to treatment in the field experiment conducted in Quincy, FL in 2006.

Treatment and active ingredient per hectare Mean Frankliniella tritici per 10 flowers*
6 May 9 May 10 May 13 May 20 May 23 May
untreated   9.4bcd 6.1bc 2.4a 9.9a 10.0a   9.0a
esfenvalerate 56 g 5.0d   4.0bc 7.3a 2.3a  8.3a   4.5a
spinosad 140 g 12.8bcd 5.3bc 3.5a 3.5a 12.3a   8.3a
spinetoram 26 g 17.3ab   2.0c    3.3a 3.8a   6.3a   7.5a
spinetoram 44 g 12.5bcd 2.0c    4.5a 3.3a   6.3a   9.5a
spinetoram 61 g 5.8cd 4.8bc 2.8a 1.8a   5.8a   5.8a
novaluron 87 g 23.8a     4.3bc 3.3a 6.5a   8.0a 13.3a
imidicloprid 285 g
& novaluron 87 g
16.5abc 10.3a     5.0a 8.8a 12.3a 10.5a
imidicloprid 285 g
& spiromesifen 145 g
11.8bcd  8.3ab 5.3a 8.0a   9.5a 13.0a

 * Means in the same column followed by the same letter are not significantly different according to ANOVA and subsequent DMRT (P > 0.05).


Populations of larvae in both of the Quincy experiments were F. occidentalis and F. tritici. The mean numbers of larvae by treatment in the 2005 experiment are shown in Table 5. There were significant treatment differences on 20, 27, and 31 May (F = 7.4, 3.0, and 6.5, respectively; df = 5, 15; P < 0.001, 0.05, and 0.01, respectively). Each of the treatments of spinetoram provided significant control compared to untreated pepper on these sample dates with no significant differences between the rates of spinetoram. The standard treatment of spinosad provided significant control compared to untreated pepper on 20 and 31 May. There were no significant treatment differences on 24 May despite a many-fold greater number of larvae estimated in untreated pepper compared to insecticide-treated pepper. The lack of significant difference was due to poor precision of the sample estimates combined with the fewer error degrees of freedom resulting from the loss of some of the samples before processing. The mean numbers of larvae by treatment in the 2006 experiment conducted at Quincy are shown in Table 6. There were significant treatment differences on 6 and 9 May (F = 8.0 and 4.8, respectively; df = 8, 28; P < 0.001). There were significantly greater numbers of larvae in the esfenvalerate treatment compared to untreated pepper on 6 May. There were significantly greater numbers of larvae in the imidicloprid and spiromesifen treatment compared to untreated pepper on 9 May. There were numerically, but not statistically, fewer larvae in the spinosad treatment and each of the spinetoram treatments compared to untreated pepper on both dates.


Table 5. The mean number of Frankliniella larvae per ten flowers on four sample dates according to treatment in the field experiment conducted in Quincy, FL in 2005.

Treatment and active ingredient per hectare Mean Frankliniella larvae per 10 flowers*
20 May 24 May 27 May 31 May
untreated 8.8a 34.3a 10.8a 44.8a
spinosad 140 g 2.3b  2.7a 7.5ab  4.5b
spinetoram 18 g 2.0b  6.7a  3.5b  5.0b
spinetoram 26 g 1.5b  6.0a  3.0b  2.3b
spinetoram 44 g 2.0b  4.8a  1.3b  3.3b
spinetoram 61 g 1.8b  3.7a  1.5b  0.8b

 * Means in the same column followed by the same letter are not significantly different according to ANOVA and subsequent DMRT (P > 0.05).


Table 6. The mean number of Frankliniella larvae per ten flowers on six sample dates according to treatment in the field experiment conducted in Quincy, FL in 2006.

Treatment and active ingredient per hectare Mean Frankliniella larvae per 10 flowers*
6 May 9 May 10 May 13 May 20 May 23 May
untreated 4.8b 14.4bc 20.4a 7.8a 4.5a 2.9a
esfenvalerate 56 g 16.5a   18.0ab 22.3a 12.8a   3.5a 1.8a
spinosad 140 g 1.5b 13.5bc 12.5a 9.0a 5.5a 2.8a
spinetoram 26 g 2.3b 4.8c 16.0a 7.0a 3.0a 2.5a
spinetoram 44 g 0.5b 4.8c 10.8a 8.0a 5.8a 2.5a
spinetoram 61 g 1.3b 3.5c   8.8a 3.5a 3.0a 2.8a
novaluron 87 g 2.3b 20.3ab 16.0a 8.8a 5.8a 3.8a
imidicloprid 285 g
& novaluron 87 g
4.5b 20.8ab 23.0a 12.3a 4.8a 2.8a
imidicloprid 285 g
& spiromesifen 145 g
4.3b 27.3a 23.8a 12.3a 4.8a 3.0a

 * Means in the same column followed by the same letter are not significantly different according to ANOVA and subsequent DMRT (P > 0.05).


Efficacy of Insecticides Against F. bispinosa

The predominate species of flower thrips in pepper in central Florida is F. bispinosa (7), and it was the predominate species in the Citra experiment conducted in 2006. Populations of F. occidentalis and F. fusca occurred in very low numbers. The thrips larvae were predominately F. bispinosa. The mean numbers of the adults of F. bispinosa are shown in Table 7. The adults of this species are highly vagile, and re-colonization of insecticide-treated plots obviously affected the results. There were significant treatment differences on 4 May when all of the insecticide treatments resulted in suppression of adults compared to the untreated control (F = 7.7; df = 5, 15; P < 0.001). The mean numbers of larvae by insecticide treatment are shown in Table 8. There were significant treatment differences on 4 and 23 May (F = 2.2 and 3.9; df = 5, 15; P < 0.10 and 0.01, respectively), with each insecticide treatment resulting in significant suppression compared to the untreated control.


Table 7. The mean number of adult Frankliniella bispinosa per ten flowers on six sample dates according to treatment in the field experiment conducted in Citra, FL in 2006.

Treatment and active ingredient per hectare Mean Frankliniella bispinosa per 10 flowers*
4 May 9 May 12 May 16 May 19 May 23 May
untreated 21.3a 21.0a 19.3a 6.6a 7.5a 40.3a
esfenvalerate 56 g 4.3b 11.8a 10.5a 7.3a 2.0a 13.5a
spinosad 140 g 7.0b 18.0a 11.8a 6.5a 2.8a 18.0a
spinetoram 26 g 4.5b 19.3a 18.3a 8.8a 3.3a 21.3a
spinetoram 44 g 4.3b 14.8a 12.8a 4.8a 2.5a 17.0a
spinetoram 61 g 4.0b 18.5a 8.3a 8.0a 3.3a 11.3a

 * Means in the same column followed by the same letter are not significantly different according to ANOVA and subsequent DMRT (P > 0.05).


Table 8. The mean number of Frankliniella larvae per ten flowers on six sample dates according to treatment in the field experiment conducted in Citra, FL in 2006.

Treatment and active ingredient per hectare Mean Frankliniella larvae per 10 flowers*
4 May 9 May 12 May 16 May 19 May 23 May
untreated 15.3a 3.5a 3.5a 1.3a 0.0a 3.3a
esfenvalerate 56 g 6.3b 1.0a 2.3a 3.8a 0.5a 1.0b
spinosad 140 g 6.5b 2.5a 0.3a 0.8a 0.0a 1.0b
spinetoram 26 g 6.8b 1.5a 1.5a 1.5a 0.3a 1.3b
spinetoram 44 g 8.0b 0.3a 0.0a 1.3a 0.3a 1.3b
spinetoram 61 g 6.0b 0.5a 0.8a 1.8a 0.5a 0.0b

 * Means in the same column followed by the same letter are not significantly different according to ANOVA and subsequent DMRT (P > 0.05).


Effects of Insecticides on Predator Populations

There were no significant treatment differences in the number of O. insidiosus on any sample date in the 2005 and 2006 experiments in Quincy. The mean number of Orius insidiosus per ten flowers for each treatment for data averaged over all sample dates each year is shown in Table 9. The mean numbers of the predator in relation to the mean numbers of total thrips (i.e., combined numbers of adults and larvae of all species) were sufficient in all treatments to suppress and usually to control populations of thrips. The ratio of the mean number of thrips to the mean number of O. insidiosus ranged between 18.1 and 75.0 for treatments in the 2005 experiment and between 9.8 and 24.0 for treatments in the 2006 Quincy experiment. Funderburk et al. (6) showed that a ratio less than about 180 was sufficient for predation to result in suppression of thrips while control of thrips occurred rapidly when ratios were below about 50. Baez et al. (2) showed that O. insidiosus will prey more heavily on the less mobile thrips larvae than on adults, but as abundance of larvae declines predation on adults increases. This explains why the numbers of thrips larvae (Tables 5 and 6) were much less on all sample dates in both experiments than the number of thrips adults (Tables 1, 2, 3, and 4). Consequently, predation prevented the buildup of thrips populations in the peppers, even though there obviously was much immigration of adult thrips into the pepper plots. Rapid movement of thrips from numerous plant sources to pepper is typical in May in northern Florida (6,10,11).


Table 9. The mean number of Orius insidiosus and total thrips of all species per ten flowers averaged over all sample dates according to treatment in the field experiments conducted in 2005 and 2006 in Quincy, FL and in 2006 in Citra, FL.

Treatment and active ingredient per hectare Quincy, FL
2005
Quincy, FL
2006
Citra, FL
2006

Orius* Thrips* Orius* Thrips* Orius* Thrips*
untreated 1.0a 75.0a 1.9a 30.0ab   9.4a 24.3a
esfenvalerate 56 g 1.9a 30.0ab   4.6b 11.0b
spinosad 140 g 1.0a   46.7ab 1.8a  27.6abc 4.3b 12.8b
spinetoram 18 g 0.5a 36.5b
spinetoram 26 g 1.1a 33.0b 1.4a 20.9bc 4.6b 14.9b
spinetoram 44 g 0.8a 31.4b 2.1a 20.6bc 4.5b 11.3b
spinetoram 61 g 1.9a 34.3b 0.8a 15.8c    4.0b 10.7b
novaluron 87 g 1.9a 34.2a  
imidicloprid 285 g
& novaluron 87 g
1.8a 40.3a  
imidicloprid 285 g &
spiromesifin 145 g
1.6a 38.4a  

 * Means in the same column followed by the same letter are not significantly different according to ANOVA and subsequent DMRT (P > 0.05).


There were significant treatment differences for O. insidiosus on the 12, 19, and 23 May sample dates in the 2006 Citra experiment (F = 11.3, 4.9, and 4.6, respectively; df = 5, 15; P < 0.001, 0.001, and 0.01, respectively). The numbers O. insidiosus in the 2006 Citra experiment were significantly less in each insecticide treatment including esfenvalerate, spinosad, and each rate of spinetoram compared to untreated pepper when the data was averaged over all sample dates (F = 5.4; df = 5, 15; P < 0.001) (Table 9). Spinosad was not reported in previous publications to suppress O. insidiosus, although pyrethroid insecticides including esfenvalerate were reported to suppress populations of the predator (6,10,11). Ramachandran et al. (10) showed that the predator moves rapidly between pepper plants in search of thrips prey. It is possible that the predator was tracking populations of thrips; that is, they were moving to and staying in greater numbers in the untreated plots with higher numbers of thrips. The mean numbers of the predator in untreated pepper and in all insecticide treatments were very high, and the number of thrips was very low relative to the number of the predator (the ratio of the mean number of thrips to the mean number of O. insidiosus ranged between 2.4 to 3.2 for all treatments). These ratios indicated that predation had a great impact on populations of thrips in untreated pepper and in all of the insecticide treatments. Butler and O’Neil (4) showed that increasing thrips availability has positive effects on the life history of O. insidiosus and that predation rates of at least 20 thrips per day are necessary for optimal survival, longevity, and egg production. Numbers of the predator were sufficient relative to the number of thrips to prevent population buildup in all treatments (Table  9), and numbers of thrips larvae were less on all sample dates than the number of adult F. bispinosa (Tables 7 and 8, respectively).


Spinetoram and Conservation Biological Control of Thrips

The combination of control of the invasive thrips species, F. occidentalis, with spinosad and conservation of natural populations of O. insidiosus is an effective integrated pest management program that is widely adopted in the southern US (6,10,11). In these studies spinetoram at less than half the rate was as effective as spinosad against F. occidentalis while conserving populations of O. insidiosus. Lower rates of spinetoram provided inconsistent efficacy against the adults and larvae. Spinetoram in these studies was as efficacious as spinosad in controlling F. tritici and F. bispinosa. Overall, spinetoram was as effective as spinosad in suppressing the total number of thrips in the 2005 Quincy experiment, the 2006 Quincy experiment, and the 2006 Citra experiment (F = 2.7, 5.0, and 5.2, respectively; df = 5, 15; 8, 24; and 5, 15, respectively; P < 0.05, 0.001, and 0.001; respectively) (Table 9). Very few broad-spectrum insecticides are available with efficacy against F. occidentalis, and populations in pepper typically outstrip the toxic effects of broad-spectrum insecticides that suppress populations of O. insidiosus (6,10,11). Flaring of the populations of F. occidentalis by insecticides were rare in these experiments (though see Tables 2 and 4), apparently because predation was great in all treatments.

Literature Cited

1. Avila, Y., Stavisky, J., Hague, S., Funderburk, J. E., Reitz, S. R., and Momol, T. 2006. Evaluation of Frankliniella bispinosa (Thysanoptera: Thripidae) as a vector of Tomato spotted wilt virus in pepper. Florida Entomol. 89:204-207.

2. Baez, I., Reitz, S. R., and Funderburk, J. E. 2004. Predation by Orius insidiosus (Heteroptera: Anthocoridae) on species and life stages of Frankliniella flower thrips (Thysanoptera: Thripidae) in pepper flowers. Environ. Entomol. 33:662-670.

3. Bauske, E. M. 1998. Southeastern tomato growers adopt integrated pest management. HortTechnology 8:40-44.

4. Butler, C. D., and O’Neil, R. J. 2007. Life history characteristics of Orius insidiosus (Say) fed diets of soybean aphid, Aphis glycines Matsumura and soybean thrips, Neohydatothrips variabilis (Beach). Biol. Control 40:339-346.

5. Chellemi, D. O., Funderburk, J. E., and Hall, D. W. 1994. Seasonal abundance of flower-inhabiting Frankliniella species (Thysanoptera: Thripidae) on wild plant species. Environ. Entomol. 23:337-342.

6. Funderburk, J. E., Stavisky, J., and Olson, S. 2000. Predation of Frankliniella occidentalis (Thysanoptera: Thripidae) in field peppers by Orius insidiosus (Hemiptera: Anthocoridae). Environ. Entomol. 29:376-382.

7. Hansen, E. A., Funderburk, J. E., Reitz, S. R., Ramachandran, S., Eger, J. E., and McAuslane, H. 2003. Within-plant distribution of Frankliniella species (Thysanoptera: Thripidae) and Orius insidiosus (Heteroptera: Anthocoridae) in field pepper. Environ. Entomol. 32:1035-1044.

8. Mound, L. A. 1997. Biological diversity. Pages 197-216 in: Thrips As Crop Pests. T. Lewis, ed. CAB International, Wallingford, UK.

9. Mound, L. A., and Teulon, D. A. J. 1995. Thysanoptera as phytophagous opportunists. Pages 3-19 in: Thrips Biology and Management. B. L. Parker, M. Skinner, and T. Lewis, eds. Plenum Press, NY.

10. Ramachandran, S., Funderburk, J. E., Stavisky, J., and Olson, S. 2001. Population abundance and movement of Frankliniella species and Orius insidiosus in field pepper. Agr. Forest Entomol. 3:129-137.

11. Reitz, S. R., Yearby, E. L., Funderburk, J. E., Stavisky, J., Olson, S. M., and Momol, M. T. 2003. Integrated management tactics for Frankliniella thrips (Thysanoptera: Thripidae) in field-grown pepper. J. Econ. Entomol. 96:1201-1214.

12. Tavella, L., Alma, A., Conti, A., and Arzone. A. 1996. Evaluation of the effectiveness of Orius spp. in controlling Frankliniella occidentalis. Acta Hortic. 431:499-506.

13. Toapanta, M., Funderburk, J., Webb, S., Chellemi, D., and Tsai, J.1996. Abundance of Frankliniella spp. (Thysanoptera: Thripidae) on winter and spring plant hosts. Environ. Entomol. 25:793-800.

14. Ullman, D. E., Sherwood, J. L., and German, T. L. 1997. Thrips as vectors of plant pathogens. Pages 539-565 in: Thrips as Crop Pests. T. Lewis, ed. CAB International, Wallingford, UK.