INSECT CONTROL TRIALS 2000: EVALUATION OF 'SOFTER' PROGRAMS AGAINST KEY PESTS

Michael Reding & Diane Alston

Utah State University, Department of Biology, 5305 Old Main Hill, Logan, UT 84322-5305

Objectives. Evaluate the efficacy of new insecticides against three key pests of tree fruits compared to an industry standard program under large-block conditions. In addition, to evaluate the influence of these insecticides on non-target arthropods such as spider mites, apple aphids, and their natural enemies. Also to evaluate the efficacy of mating disruption against peachtree borer (crown borer) in peach.

Background on new insecticides tested. Calypso (thiacloprid) and Provado (imidacloprid) are neonicotinoids and act at the same sites on the insect's nervous system as nicotine. Intrepid (methoxyfenozide) mimics the action of the insect's molting hormone, which causes premature molting and is generally selective for moths. Success (spinosad) is a mixture of 2 spinosyns (A & D), produced by the bacterium Saccharopolyspora spinosa. Success targets the insect's nervous system. Provado is registered on pome fruits, but not on stone fruits. Success is registered on pome and stone fruits. Calypso and Intrepid are not yet registered. Calypso and Intrepid were tested against codling moth on apple; Success was tested against peach twig borer on peach; and Calypso, Provado, and Success were tested against western cherry fruit fly on sour cherry.

GENERAL METHODS: All Spray Trials

Insecticide trial blocks were 1-2.1 acres (0.4-0.85 ha). Experimental design was randomized complete block with 3 or 4 replications. Replications were 3 rows wide by 5 (peach) or 7 (apple & cherry) trees long. All test insecticides were applied in 70-80 gallons of water/acre (ca. 655-748 liters/hectare) by an airblast sprayer. No other insecticides/miticides were applied after the trials began (delayed-dormant treatments: oil + insecticide were applied in the apple and peach blocks).

APPLE TRIAL

This trial was conducted in a 10-year-old block with a mixture of apple cultivars (Dixiered, Gala, Idared, Jonathan, Mutzu, Prime Gold, Supreme, Ultrastripe) at the Utah State University research farm in Kaysville, UT. This trial had four treatments with four replications.

Treatments: 1st cover was applied 250DD after biofix. 3rd cover (4th cover Calypso) was applied 1260 DD after biofix.

1). Calypso 4F (thiacloprid) @ 4 fl oz/acre, 6 cover sprays (ca. 14-d interval)

2). Guthion-Intrepid rotation: Guthion 50W (azinphosmethyl) @ 2 lb/acre (1st & 3rd cover sprays), Intrepid (methoxyfenozide) @ 1.1 lb/acre (2nd & 4th cover sprays)

3). Guthion 50W (azinphosmethyl) @ 2 lb/acre (standard program, 4 cover sprays)

4). Untreated

Populations of spider mites, predaceous mites, green apple aphids, and aphid natural enemies were surveyed. Fruit were evaluated at harvest maturity (ca. 100 fruit per cultivar/replication).

RESULTS

All three insecticide treatments had significantly less codling moth damage than the untreated check (Table 1). Overall, percentage of fruit damaged was high in the untreated trees (22%, all cultivars combined), and damage levels differed among cultivars. There were no differences in performance of insecticides among cultivars.

Populations of twospotted spider mite (T. urticae) were significantly higher in the Calypso treatment than in other treatments (Table 2), but predaceous mite (Typhs & Zetzellia) populations were not different (Table 2). Populations of Aphis pomi (green apple aphid) were similar among treatments. The Calypso and Guthion treatments significantly reduced populations of Campylomma verbasci and total aphid natural enemies versus Guthion/Intrepid rotation and Untreated.

 

PEACH TRIAL

This trial was conducted in a 10-year-old block of peaches ('Suncrest') at the Utah State University research farm in Kaysville, UT. A delayed-dormant (calyx-green to first pink) treatment of Superior oil + Thiodan 3EC at 0.67 qt/acre was applied to the entire orchard on 6 April 2000 for control of early season peach twig borer larvae. This trial had three treatments with four replications. Each replication was 3 rows wide and 5 trees long.

Treatments: 1st cover applied 400DD after biofix, 2nd cover applied 1460DD after biofix.

1). Success (spinosad; 22.8% ai; Dow AgroSci.) @ 6 fl oz/acre - applied on 12 June and 27 July

2). Thiodan 50 WP (endosulfan; 50% ai; FMC) @ 4 lb/acre – applied on 12 June and Guthion 50WP (azinphosmethyl; 50% ai; Bayer) @ 2 lb/acre – applied on 27 July

3). Untreated Check

Upon maturity, 40 fruit were sampled from 2 center trees per plot (320 fruit/treatment). Each fruit was cut open to determine if a larva was present.

RESULTS

Both the Success and Thiodan-Guthion treatments provided excellent control of peach twig borer and had significantly lower levels of damage than the untreated trees (Table 3).

SOUR CHERRY TRIAL

This trial was conducted in a ‘Montmorency’ tart cherry orchard at the Utah State University research farm in Kaysville, UT. The only pesticides applied to trees besides the insecticides evaluated were Rally (myclobutanil) for powdery mildew on 13 June and Omite (propargite) for spider mites on 21 July 2000 after the conclusion of the western cherry fruit fly trial. This trial had six treatments with three replications (18 plots) and replications were 3 rows wide and 7 trees long (12 ft. x 20 ft. row spacing). One yellow AM sticky trap plus bait was placed in each of the 18 plots to follow seasonal adult densities. Traps were checked and flies counted at approximately weekly intervals (8, 15, 21 and 29 June, and 10 July). Mean cumulative fly capture for the season was compared among treatments with analysis of variance (GLM; SAS).

Treatments: First cover applied 9 days after first fly capture.

1). Calypso 4 F (thiacloprid; 40.4% ai; Bayer) @ 4 fl oz/acre every ca. 14 d (applied 3 times: 1, 16, and 29 June)

2). Provado 1.6F (imidacloprid; 17.4% ai; Bayer) @ 8 fl oz/acre every ca. 14 d (applied 3 times: 1, 16, and 29 June)

3). Success (spinosad; 22.8% ai; Dow AgroSci.) @ 6 fl oz/acre every ca. 14 d (applied 3 times: 1, 16, and 29 June)

4). Success (spinosad; 22.8% ai; Dow AgroSci.) @ 6 fl oz/acre every ca. 7 d (applied 5 times: 1, 10, 16, 22, and 29 June)

5). Guthion 50 WP (azinphosmethyl; 50% ai; Bayer) @ 1.5 lb/acre every ca. 14 d (applied 2 times: 1 and 16 June) and Sevin XLR Plus (carbaryl; 44.1% ai; Rhone- Poulenc) @ 2 qt/acre (applied 1 time: 29 June)

6). Untreated Check

Effects of the insecticide treatments on secondary pests and non-target natural enemies were evaluated for spider mites and predaceous mites. No other arthropod pests were noted in any abundance.

RESULTS

No infested fruits were found in any treatment in the mid-way fruit injury sample on 21 June. So few infested fruits were found in untreated plots in harvest samples on 10 July (0.11%) and 17 July (0.33%) that fruit from the insecticide treatments was not dissected. Despite a lack of fruit injury, cumulative adult fly captures from 1 June through 10 July were low to moderate in the six treatments. Significantly more adult flies were caught in untreated plots than in all others, except Success reapplied at 14 d intervals (p=0.006).

The lack of fruit injury in untreated plots was surprising and disappointing. Evidently, plot size was too small so that drift of insecticide treatments overran untreated plots or reduced the effective adult fly population to such an extent that fruit injury was minimal even in untreated plots. The latter reasoning seems more likely, although fly capture data presented below provides evidence of fly activity in the orchard. Good coverage of fruits with insecticides is generally required to control fruit fly injury. Insecticides need to act as adult deterrents for oviposition, as once eggs are laid inside fruits, insecticides have much less effect on hatch and development of larvae within. We have had success with a similar plot size in previous western cherry fruit fly trials. However, there was greater untreated area in those trials due to fewer treatments and greater plot replication.

Twospotted spider mite densities greatly exceeded an economic threshold of 10 mites per leaf in most treatments. There were >25 twospotted spider mites per leaf in all treatments except untreated and Guthion-Sevin. There were significantly more twospotted spider mites in Calypso-treated plots than in Guthion-Sevin and untreated plots (p=0.031) (Table 4). There was also a block effect on twospotted spider mite densities, with significantly more mites in Block 3 than in 1 and 2 (p=0.011). Block 3 was a border replication on the eastern edge of the orchard. We observed more mite injury to trees in this area than in other areas of the orchard during and after the trial. European red mite densities were generally low in all treatments except Success reapplied at 7 d intervals (Table 4). High populations in this treatment were primarily from high densities in Block 3, although there was no overall block effect.

Predaceous mite, Typhlodromus (=Galandromus) and Zetzellia, densities were low to moderate and did not differ among treatments or blocks. Spider mite densities increased rapidly in early to mid July, but predaceous mite densities did not build at the same rate. Prey-to-predator ratios were significantly higher in Provado plots than in all others (p=0.015) (Table 4), however ratios were "high" in relation to pest management practice in all treatments except the untreated and Success-14 d plots. In spider mite sampling protocols used by pest managers, prey-to-predator ratios of <5 are considered "very good". When prey-to-predator ratios are in the range of 5-10 and spider mite densities are <10 per leaf, pest managers are advised to sample again within a week to determine if predaceous mite numbers are building and may provide adequate biological control. Because spider mite densities were so high in some treatments (27-65 twospotted and European red mites per leaf) and prey-to-predator ratios were so high for most treatments, a miticide treatment (Omite) was applied two days after the mite sampling. Therefore, we did not take a subsequent mite sample to determine if insecticide treatments had an influence on increase in predaceous mite numbers in response to abundant prey.

CONCLUSIONS: All spray trials

Apple. In general, the new insecticides performed as well as the standard treatments on each fruit. However, in the apple trial damage levels were above 1% in the Calypso treatment. Furthermore, because Calypso required 6 treatments versus 4 for other insecticides it is not likely to be as easily accepted by growers unless registration of materials such as Guthion is lost. The fact that Calypso significantly reduced Campylomma populations suggests it may be useful as a control against this pest. Spider mite populations were elevated in the Calypso treatments in both the apple and cherry trials with no reduction in predaceous mite numbers. This interesting occurrence needs further investigation. The Guthion-Intrepid rotation program was as effective as Guthion alone, which indicates this program should be a good fit in IPM programs and would help reduce organophosphate (OP) usage.

Peach. Success was as effective against peach twig borer (A. lineatella) as a standard program, thus should provide an excellent alternative to more broad-spectrum insecticides.

Sour cherry. Because very few infested fruit were detected in the cherry trial it is difficult to draw conclusions. However, all insecticide treatments, except Success 14-day, reduced captures of western cherry fruit fly in traps versus the untreated plots. This is an unreliable indicator of efficacy, but encouraging enough to warrant further testing of these insecticides.

 

EFFICACY OF MATING DISRUPTION AGAINST PEACHTREE BORER (SYNANTHEDON EXITIOSA)

Michael Reding and Diane Alston

Utah State University, 5305 Old Main Hill, Logan, UT 84322-5305

The peachtree borer (PTB) is an important pest of peach, apricot, nectarine, and sweet cherry. Damage is caused by the larvae, which burrow beneath the bark of the trunk near to or just below the soil surface. Larvae feed on the cambium beneath the bark and can girdle trees, thus, killing them. The standard treatment to prevent damage by this pest in commercial orchards is application of an insecticide to the trunk of susceptible trees during early July. A potential non-chemical alternative to insecticide treatments is pheromone-based mating disruption. The objective of this trial was to test the efficacy of mating disruption against peachtree borer (PTB) in Utah.

METHODS:

Isomate-PÒ (rope-style) dispensers from Biocontrol Limited (formerly Pacific Biocontrol) Vancouver, WA 98660, 1-800-999-8805, were applied in two small (about 1 acre ea., 5-6 rows wide) peach blocks at the Utah State University research farm in Kaysville, UT. The dispensers were applied at a rate of one per tree, which resulted in 155 and 175 dispensers per acre for the two blocks. The recommended rate is 100-250 dispensers per acre. The Isomate-P dispensers were applied 21 June; the day after the first capture of PTB in Kaysville. A third peach block at the Kaysville farm, also about one acre, was treated with a single application of Lorsban (chlorpyrifos) in early July, and was used as a treated comparison. A sticky trap baited with PTB pheromone was placed in each block to monitor PTB. An assessment of PTB injury was conducted 20 September. Every tree in the three blocks were examined for PTB injury. Another assessment of injury will be conducted in April 2001.

RESULTS:

No PTB were captured in the mating disruption blocks after the Isomate-P dispensers were applied. In contrast, PTB were captured in the Lorsban-treated comparison block from late June through 8 August. No PTB injury was detected in either of the mating disruption blocks or the insecticide treated block on 20 September 2000.