Insect Pest Management on Peppers (Trumble Report)

University of California
UC Riverside

Department of Entomology ̶ 041
College of Natural and Agricultural Sciences

John Trumble
College of Natural and Agricultural Sciences
Department of
Riverside, California 92521
Phone: (951) 827–5264
Email: john.trumble@ucr.edu

California Pepper Commission Research Report 2008-2009

1. Identification
1. California Pepper Commission
2. Insect Pest Management on Peppers
3. Proposal for period beginning March 2008, ending February 2009
4. Principal Investigator:
   Dr. John T. Trumble
   Department of Entomology
   University of California, Riverside
5. Cooperating Personnel:
   William Carson, Greg Kund and Deguang Liu
   Department of Entomology
   Univ. of California, Riverside
6. Locations of Work:
   U.C. Riverside,
   U. C. South Coast Res. & Ext. Center
7. Insects
   Tomato/Potato Psyllid: Bactericera cockerelli (Sulc)
   Beet armyworm (BAW): Spodoptera exigua (H¸bner)
   Tomato Fruitworm(TFW): Helicoverpa zea (Boddie)
   Leafminer: Liriomyza sativae (Blanchard)
   Leafminer: Liriomyza trifoilii (Burgess)
   Lygus bugs: Miridoa spp.
   Stink bugs (SB): Pentatomidae spp.
   Pepper weevil (PW): Anthonomus eugenii Cano
2. Field Screening Trials for Effective Pesticides

Table 1: Pepper Chemical Trial List of Treatments 2008

Treatment #	Compound	Rate-Product	Company
1	Control	-	-
2 a	Voliam Flexi 40 WG	4 oz/Ac	Syngenta
3 a	Voliam Flexi 40WG	6 oz/Ac	Syngenta
4 a	Voliam Flexi 40WG	7 oz/Ac	Syngenta
5 a	Voliam Express ZC	5 oz/Ac	Syngenta
6 a	Voliam Express ZC	7 oz/Ac	Syngenta
7 a	Voliam Express ZC	9 oz/Ac	Syngenta
8 b	Leverage 2.7 SE	5.8 oz/Ac	Bayer
9 b	NNI-0871 + Induce	17.6 oz/Ac	Nichino
10 b	Radiant SC	6 oz/Ac	Dow
11 b	GF-1029 + XR-25 30SG	6.86 oz/Ac 2.85 oz/Ac	Dow
12 b	GF-1029 + XR-25 30SG	6.86 oz/Ac 3.8 oz/Ac	Dow
13 b	GF-1029 + XR-25 30SG	8.57 oz/Ac 2.85 oz/Ac	Dow
14 b	GF-1029 + XR-25 30SG	8.57 oz/Ac 3.8 oz/Ac	Dow
15 b	GF-1029	8.57 oz/Ac	Dow
16 b	XR-25 30SG	3.8 oz/Ac	Dow

^a Treatments 2-7 were sprayed every 14 days on 17and 31 Jul; 14 and 28 Aug.
^b Treatments 8-16 were sprayed weekly starting on 17 July for a total of seven applications.
^c Means in columns followed by the same letter are not significantly different (P<0.05 level, Fisherís Protected LSD Test). Internal damage due primarily to (TFW); external damage due primarily to (BAW). Bugs include Lygus and (SB). Calyx damage can attributed to (TFW), (BAW), and (PW) feeding

Seedlings were transplanted in a sandy loam type soil on 3-4 Jun at the University of Californiaís South Coast Research and Extension Center. Experimental plots were 4 rows wide (5-ft centers) by 40 ft long and separated by a 5-ft buffer. The pepper transplants were drip irrigated (water pH 7.2 - 7.5). Treatments were replicated 4 times in a RCB block design. Weekly applications were initiated at first fruiting for treatments 8-16 (17, 28, and 31 Jul; 7, 14, 21, and 28 Aug). Treatments 2-7 were treated every 14 days starting on 17 Jul as noted in (Table 1) for a total of 4 applications. All applications were made at twilight. A tractor-mounted boom sprayer with 6 nozzles per row incorporated D-3 orifice disks, #25 cores, and 50 mesh screens. Operating pressure was 125 psi delivering 100 gpa. All treatments received a non-ionic surfactant X-77 at 0.125% v/v except treatment 9 which received Induce at 0.25% v/v. Leafminer populations and effects on leafminer parasites were evaluated by weekly counts of leafminer pre-pupae and pupae and dead adult parasites in four 9x11 inch trays/replicate from 12 Aug through 3 Sep, inclusive.

On (16-17 Sep), 100 mature-green to ripe fruit were harvested from the center 2 rows of each replicate (400 per treatment) and examined for Lepidopterous internal damage (TFW) and external damage (BAW). Fruit were also inspected for damage from pepper weevils and hemipterous pests.

Lepidopteran pressure was high in the categories of External damage by (BAW) (Table 2). Most treatments provided good control of the Lepidopterous insects. Internal damage by (PW) was significant this year, and the Voliam-Flexi, Leverage, and XR-25 treatments provided the best control. Leafminer populations were low, and no statistical separation was possible on any sample dates. The results of dead adult parasites were not included this year due to low numbers recorded from the tray counts. No phytotoxicity was observed in any of the treatments.

All data were analyzed with ANOVA and a Fisherís Protected LSD test (P<0.05). No phytotoxicity was observed in any of the treatments. Psyllid populations were low this year.

Figure 1. Calyx feeding damage by the pepper weevil and worm larvae.



Figure 2. Calyx feeding damage by treatment. Several materials performed better than the control and the pepper weevil pressure was high this season. The untreated control is treatment #1.



Figure 3. Damage by beet armyworm, tomato fruitworm, and cutworms. All materials provided significantly better suppression as compared to the control treatment (#1) except treatment (#10).



Figure 4. Internal fruit damage by pepper weevil. Pepper weevil pressure was very high.



Table 2. Chemical trial mean number of Damaged Fruit

		Mean Number of Fruit Damaged/Replicate c
Treatment/ Formulation	Rate Amt/acre	Internal	External	All Leps	Pepper Weevil Internal	Calyx Damage	Bugs
1) Control	-	0.75	18.25 de	19.00 ef	48.75 bc	9.25 bcde	5.50 ab
2) a Voliam Flexi 40 WG	4.0 oz/Ac	0.25	4.75 ab	5.00 abc	5.00 a	5.00 ab	8.25 abc
3) a Voliam Flexi 40WG	6.0 oz/Ac	0.25	3.25 a	3.50 ab	3.25 a	3.00 a	8.25 abc
4) a Voliam Flexi 40WG	7.0 oz/Ac	0.00	2.50 a	2.50 a	2.25 a	4.25 ab	4.75 ab
5) a Voliam Express ZC	5.0 oz/Ac	1.50	9.00 abc	10.50 bcd	60.75 c	12.25 de	5.00 ab
6) a Voliam Express ZC	7.0 oz/Ac	2.50	7.00 abc	9.50 abcd	59.25 c	7.00 abcd	8.50 abc
7) a Voliam Express ZC	9.0 oz/Ac	0.75	6.00 abc	6.75 abcd	77.50 cd	4.75 ab	2.25 a
8) b Leverage 2.7 SE	5.8 oz/Ac	0.50	6.75 abc	7.25 abcd	21.00 ab	9.50 bcde	4.50 a
9) b NNI-0871 + Induce	17.6 oz/Ac 0.25% v/v	0.50	10.75 bc	11.25 cd	99.25 d	13.75 e	4.25 a
10) b Radiant SC	6.0 oz/Ac	0.75	20.25 e	21.00 f	65.25 c	10.75 cde	2.75 a
11) b GF-1029 + XR-25 30SG	6.86 oz/Ac 2.85 oz/Ac	0.00	7.25 abc	7.25 abcd	16.75 ab	9.00 bcde	8.00 abc
12) b GF-1029 + XR-25 30SG	6.86 oz/Ac 3.8 oz/Ac	1.00	7.50 abc	8.50 abcd	18.00 ab	5.75abc	11.25 bcd
13) b GF-1029 + XR-25 30SG	8.57 oz/Ac 2.82 oz/Ac	0.25	8.25 abc	8.50 abcd	19.25 ab	6.00 abc	12.25 cd
14) b GF-1029 + XR-25 30SG	8.57 oz/Ac 3.8 oz/Ac	0.00	4.75 ab	4.75 abc	10.75 a	6.75 abc	16.75 d
15) b GF-1029	8.57 oz/Ac	2.50	8.00 abc	10.50 bcd	71.75 cd	7.00 abcd	4.50 a
16) b XR-25 30SG	3.8 oz/Ac	1.25	12.25 cd	13.50 de	15.25 a	5.00 ab	7.25 abc
ANOVA F value (by column)		1.736	3.746	3.788	7.474	2.504	2.753
ANOVA P value (by column)		0.075	0.001	0.001	0.001	0.008	0.004

^a Treatments 2-7 were sprayed every 14 days on 17and 31 Jul; 14 and 28 Aug.
^b Treatments 8-16 were sprayed weekly starting on 17 July for a total of seven applications.
^c Means in columns followed by the same letter are not significantly different (P<0.05 level, Fisherís Protected LSD Test). Internal damage due primarily to (TFW); external damage due primarily to (BAW). Bugs include Lygus and (SB). Calyx damage can attributed to (TFW), (BAW), and (PW) feeding.

3. IPM strategies in Peppers

Seedlings were transplanted in a sandy loam type soil on 3-4 June at the University of Californiaís South Coast Research and Extension Center. Experimental plots were 3 rows wide (5-ft centers) by 40 ft long and separated by a 5-ft buffer. The pepper transplants were drip irrigated (water pH 7.2 - 7.5). Treatments were replicated 4 times in a RCB block design. Applications were made using a rotation of materials specified in (Table 3). All applications were made at twilight. A tractor-mounted boom sprayer with 6 nozzles per row incorporated D-3 orifice disks, #25 cores, and 50 mesh screens. Operating pressure was 125 psi delivering 100 gpa. All treatments received a non-ionic surfactant X-77 at 0.125% v/v. Leafminer populations and effects on leafminer parasites were evaluated by weekly counts of leafminer pre-pupae and pupae and dead adult parasites in four 9x11 inch trays/replicate from 12 August through 3 September, inclusive. Psyllid populations were monitored by counting the total number of eggs, nymphs, and adults from five plants per replicate (20 plants per treatment). On (16-17 September), all of the mature-green to ripe fruit were harvested from the center row of each replicate. The number and weight of the fruit were recorded for harvest yield data. From each replicate 100 fruit were sub-sampled (400 per treatment) and examined for Lepidopterous internal damage (tomato fruitworm) and external damage (beet armyworm)(Figure 5). Fruit were also inspected for damage to the Calyx, and from pepper weevils and hemipterous pests. The results for insect damage are summarized in (Table 4).

Lepidopteran pressure was high in the categories of External damage by beet armyworm. Internal damage from tomato fruitworm was not significant this year. The low input and chemical standard treatments performed well for Lepidopteran control. Internal damage by pepper weevil was significant this year and the chemical standard performed the best. Leafminer populations were low, and no statistical separation was possible on any sample dates. The results of dead adult parasites were not included this year due to low numbers recorded from the tray counts. No phytotoxicity was observed in any of the treatments.

Table 3. Pepper IPM Trial Treatments 2008

Treatment #	Compound	Rate-Product	Company
1	Control	-	-
2 a	Low Input: Actara (8-7-08) Xentari DF (7-28-08) (8-21-08)	4.0 oz/Ac 16.0 oz/Ac	Syngenta Valent
3 a	Lannate 2.4 LV + Pounce 3.2 EC (7-17-08) (7-28-08) (8-7-08) (8-14-08) (8-21-08)	48.0 oz/Ac 8.0 oz/Ac	Dupont FMC

 ^a The treatments were sprayed as listed in the table.
All data was analyzed with ANOVA and a Fisherís Protected LSD test with (P<0.05).

Table 4. Pepper IPM trial mean number of damaged fruit.

		Mean Number of Fruit Damaged/Replicate  a
Treatment/ Formulation	Rate Amt/acre	Internal	External	All Leps	Pepper Weevil Internal	Calyx Damage	Bugs
1) Control *		0.75	18.25 b	19.00 b	*	*	*
2)Low Input: Actara 25 WG Xentari DF	4.0 oz 16.0 oz	0.75	7.00 a	7.75 a	80.75	13.75 b	4.75
3)Chemical Standard Lannate 2.4 LV + Pounce 3.2 EC	48.0 oz 8.0 oz	0.75	8.00 a	8.75 a	27.25	2.75 a	5.75
ANOVA F value (by column)		0.000	6.266	6.082	18.931	10.171	0.156
ANOVA P value (by column)		1.000	0.020	0.021	0.001	0.005	0.868

 ^a Means in columns followed by the same letter are not significantly different (P<0.05 level, Fisherís Protected LSD Test). Internal damage due primarily to tomato fruitworm; external damage due primarily to beet armyworm. Bugs include Lygus and stink but. Calyx damage can be attributed to tomato fruitworm, beet armyworm, and pepper weevil feeding.
* Control plots were affected by disease and the results are not representative of the actual insect pressure in the field.

Figure 5.


4. Pepper variety trials
Experimental Design:

We evaluated at 5 commercially-available pepper varieties. We specifically included the top four varieties performing well in the earlier bell pepper variety trials conducted by UC ANR (ëMercadoí, ëDouble Upí, and ëBaroní(Fouche & Mullen 2005), along with one variety that is commonly used by home gardeners ëSweet Pepper Orange Belleí and another that is commonly grown in the desert areas (ëValiantí). Potato psyllids have been identified as a key pest of concern for peppers in the Ventura County area.

Behavior tests were started utilizing the Noldus Observer software program (Noldus, Wageningen, The Netherlands). Leaves remained attached to the plant while the assays were conducted. All assays were conducted in arenas made by layering the following: a Plexiglas rectangle (9 by 12 cm) serving as a base, the test leaflet, a foam (1 by 3 by 6 cm) with a hole (2 by 2 cm) cut in it, and an additional piece of glass that covered the arena to prevent psyllids from escaping during observation. A newly emerged adult was introduced into the arena and allowed to adjust to the microenvironment for 5 min before initiating the behavioral recording. An observation period lasted for 15 min. The observations were recorded using the Noldus Observer, which provides data on the cumulative duration of each behavior as well as the number of occurrences of each behavior. Sixteen replicates of each plant line were tested. Specific behaviors recorded included cleaning (using legs to cleanse or wipe antennae, appendages, or abdomen), feeding (proboscis inserted in the leaf tissue), jumping (leaping from one point to another on the leaf), resting (not moving, mouthparts not in contact with leaf), off leaf (exiting or abandoning the leaf surface), and walking (walking on leaf surface) (Liu & Trumble 2004).

All data were analyzed with an analysis of variance (ANOVA) (P<0.05). A Fisherís protected least significant difference (LSD) test was used to compare means at the P<0.05 level.

Results:

No significant differences were seen for any of the observed behaviors between the different pepper varieties that were tested. Results are shown in figures 6-11. Due to the similarities of plant characteristics in the varieties we tested, we werenít able to identify a particular plant variety that showed some resistance to the psyllids. Development of different pepper plant lines by back crossing current varieties with wild type varieties that exhibit psyllid resistance, may provide better results for future studies.

Figure 6.



Figure 7.



Figure 8.



Figure 9.



Figure 10.



Figure 11.



Psyllid Developmental Study

Experimental Design:

We evaluated the same 5 commercially-available pepper varieties (ëMercadoí, ëDouble Upí, ëBaroní, ëSweet Pepper Orange Belleí and ëValiantí). The pepper varieties used in all tests were grown in 15-cm diameter pots with UC mix (Matkin and Chandler 1957) and fertilized weekly with the label rate of Miracle-Gro nutrient solution (Scotts Company, Ohio, USA). All plants used were between 1.5 and two months of age. Plant leaves used as substrates for all tests will be standardized by selecting the uppermost fully expanded leaf. Newly emerged adults were held on fresh leaves in a Petri dish for 3 d (the pre-ovoposition period), after which 10 adults were caged on each treatment (plant line) and allowed to oviposit for 4 to 8 hours. Ten eggs will be allowed to remain on each plant. Each treatment was replicated 5 times. All tests were conducted at 26oC and a photoperiod of LD: 16-8. Data collected included developmental rate and survival on each accession.

Results:

The developmental study did not yield any significant results due to the inconsistent survival rates of the psyllids on the different pepper plant accessions. Several attempts were made to try and establish enough psyllid nymphs on each plant replicate in order to measure development and survival of the psyllids. For some reason the pepper plant accessions were not a suitable hosts for our laboratory colony. These same pepper plant accessions have shown that they can be suitable hosts in a field setting. Further tests need to be done to determine why these plants were not suitable hosts for our psyllid colony and if laboratory colonies of psyllids can become preconditioned for certain host plants.

Leafminer Developmental Study

Experimental Design:

We evaluated the same 5 commercially-available pepper varieties (ëMercadoí, ëDouble Upí, ëBaroní, ëSweet Pepper Orange Belleí and ëValiantí). The pepper varieties used in all tests were grown in 15-cm diameter pots with UC mix (Matkin and Chandler 1957) and fertilized weekly with the label rate of Miracle-Gro nutrient solution (Scotts Company, Ohio, USA). All plants used were between 1.5 and two months of age. Seven replicates of each accession were tested. A single plant was placed into a leafminer (Lyriomyza trifolii) emergence chamber containing approximately 50 male and 50 female flies for a timed exposure of 20 minutes. The number of mines and pupae were recorded for each replicate. Data were analyzed using an ANOVA.

Results:

No significant differences were seen between any of the plant lines as shown in figure 12. Backcrossing plant lines with wild type varieties that show leafminer resistance may produce some pepper plants that are more resistant to leafminers.

Figure 12. Pepper varieties and L. trifolii



Results

Objective 1. Adult and larval tests with L. trifolii

Experimental Design:

Adults

Adult tests were performed by treating scintillation vials with rynaxypyr and cyazypyr. L. trifolii females were standardized by collecting adult female flies that emerged within a 12 hour period, and caging them for 24 hours with a plant (lima bean, Phaseolus vulgaris) and food (honey). From this group we tested six replicates of 10 females each (60 total). We then recorded mortality at 3 hours and again at 6 hours.

Larvae

One day old newly emerged adults were allowed to oviposit on lima bean plants. Ten first instar larvae were identified on each plant and any remaining larvae were killed to simplify tracking and recording of survivorship. The leaves of each plant were sprayed until runoff to achieve maximum coverage of the leaves. Larval mortality was recorded daily until 100% kill or pupation was achieved.

Results:

Rynaxypyr and cyazypyr has shown good efficacy against the adult flies and we are developing an LD50 for the materials (Figure 13&14). Larval tests using rynaxypyr have only shown a 20% reduction in survival when compared to the control (Figure 15). Using a penetrant may improve the results of rynaxypyr, and we hope to investigate this possibility.

Figure 13. Rynaxypyr Adult L. trifolii trials



Figure 14. Cyazypyr Adult L. trifolii trials



Figure 15. Rynaxypyr Larval Test


5. Additional Funding Support

Funding from the Pepper Commission has been leveraged by acquiring additional financial support for our pepper research. We have received monetary awards from the "UC Hansen Trust", and the "UC ANR Core Grant" agencies to study and develop pepper IPM program strategies.

Design and hosting provided by Spinhead Web Design