Surround® WP Crop Protectant in Ontario Apples - Report on 2002 Field Trials

Kaolin clay is a naturally occurring mineral widely used in the food industry as an anti-caking agent, in the pharmaceutical industry and in the manufacture of paper and paper products. Its most recent application has been in crop protection of numerous horticultural crops, including pome fruit, stone fruit, vegetables, berries, tree nuts, and grapes. Surround WP Crop Protectant ® (Englehard Corp), a product formulated using kaolin clay, was registered for use in the US in 1999; it is not yet available for commercial use in Canada.

How does it work?

Surround is non-toxic to both pests and beneficial insects and mites. Kaolin clay works to repel insects by creating an inhospitable environment, forming a barrier between the crop and the pests. Tiny mineral particles adhere to insects and mites, causing irritation leading to repellency, disorientation, and/or reduced feeding and egg laying. Because repeated application creates a highly reflective white film, the ability of insect pests to recognize the plant as a potential host may also be reduced. As a result, kaolin clay may be considered a behaviour-modifying agent with broad-spectrum activity against arthropod pests.

Surround was evaluated in several Ontario apple orchards in 2001 and 2002 for its effectiveness as a tool in pest management programs, for sunburn control and fruit finish, and for suppression of Blister Spot. The results of the 2002 efficacy trials are provided herein.

Seven commercial apple blocks were selected for evaluation of Surround in IPM programs. Three sites followed an advanced IPM program that included monitoring and the use of soft, pest-specific pesticides; four others followed an organic program. At each site, blocks following these programs were compared to those using only Surround for control of various direct insect pests; one organic grower combined Surround with mating disruption (MD) for oriental fruit moth (OFM) and codling moth (CM). Surround was applied at approximately 1-2 week intervals as required by pest pressure and product weathering. Varieties included in the trials included Red Delicious, McIntosh, Royal Gala and Golden Delicious.

Organic growers began applications in late April or early May and continued the program into late August/September for season-long control, while IPM growers applied the product following petal fall through mid-August. IPM growers applied insecticides following fruit assessments (late August) for control of late-season internal caterpillars due to the unacceptable levels of damage caused by the OFM/CM pest complex.

Harvest assessments of fruit were conducted in late August and early to mid September, approximately 2 weeks after the last application of Surround. At two of the organic sites, a mid-season assessment was also conducted following the protocol listed above; these two sites were chosen due to their historically high incidences of early-season ovipositional damage by plum curculio. Limited surveys of predators (limb taps, mite counts) and parasitoids were conducted during the growing season. Levels of parasitism in spotted tentiform leafminers (STLM) were determined at harvest.

Was Surround effective?

For the direct pests evaluated - plum curculio (PC), tarnished plant bug (TPB), spring feeding caterpillars (SFC), obliquebanded leafroller (OBLR), internal caterpillars (OFM, CM, other), and apple maggot AM) - Surround performed as well as, or better than, the grower standard (see Figure 1 for average performance across all treatments).

At the two organic sites with a history of damage by PC, Surround provided excellent control of early oviposition (egg-laying) damage (PC scar). Damage levels at harvest were 0% and 0.9% in the Surround blocks versus 4.2% and 15% in the standard blocks. Damage levels for PC in Surround treated and IPM programs were comparable.

Overall damage levels due to internal caterpillars (for all programs: conventional, organic and Surround WP programs) were unacceptable at several sites. These numbers may be indicative of a developing problem with insecticide resistance in CM, a lack of available pest control products for OFM, and/or poor timing of spray applications. Surround does not adequately control this pest complex under high insect pressure, although it does appear to suppress damage when combined with other pest control products. If the product is registered for use, growers following a season-long program with Surround as their primary pest management tool should consider the use of additional strategies for control of internal caterpillars.

What about predators and parasitoids?

The number of STLM mines per leaf were higher in the Surround blocks than in the grower standard at two of the sites; however, rates (percentages) of parasitism by Pholetesor ornigis and chalcid wasps, two common parasitoids of STLM, did not vary by treatment. The numbers of STLM mines per leaf never exceeded the established threshold of 4 (healthy trees) in any program.

The effect of Surround on predatory and phytophagous mites was inconsistent. Numbers of predatory mites were often reduced in Surround blocks, but this difference did not translate to higher numbers of phytophagous mites. Other studies have indicated Surround has a negative impact on the number of predatory mites, and, therefore, a thorough study on beneficial mites may be warranted. Though not formally evaluated in this trial, foliage at harvest appeared healthier (no bronzing and leaf retention versus extensive bronzing and premature leaf-drop) in Surround blocks as compared to standard blocks despite heavy in-season European red mite populations (2 sites). These differences may be attributable to improved tree health in Surround treated trees under the severe dry weather conditions experienced in 2002.

Large predators (ladybird beetles, lacewings, syrphid fly larvae, flower bugs, spider mite destroyers, spiders), where assessed, were present in similar numbers for all treatments.

Residues at harvest

Residues were observed in the calyx and stem area of some fruit, despite washing through a standard packing line (2001). The addition of an approved cleaning agent did improve the look of the fruit, and waxing removes all traces of the product. Consumer acceptance of kaolin residues has not been determined in Ontario, but several "pick-your-own" grower participants indicated the alternative program using Surround attracted repeat customers specifically looking for fruit treated with this product. Encouraging trials with fruit finish and yield in Mutsu (Cripsin) have also been conducted in Ontario but are not reported here.

This project was conducted in collaboration with Bernt Solymar, EarthTramper Consulting Inc. and Ken Wilson, Horticulturalist, Thornbury. The author gratefully acknowledges all grower co-operators.