Friday, May 11, 2012

Reducing Heat Stress and Insect Pressure in Crops Using Kaolin Clay (Surround WP) - Part 2

Case study - MELON: Melon field studies and years of commercial use in melons show Surround WP applied close to harvest can dramatically reduce sunburn, thereby boosting marketable yields. If applied throughout the season, Surround has been shown to increase melon size and brix, and cause more uniform ripening. For reducing sunburn damage to melons, Surround should be applied at 50 lbs/per acre prior to the occurance of sunburn-causing conditions. Make one to two applications seven days apart to provide thorough coverage of the plant and fruit. Surround can suppress cucumber beetle and grasshoppers on melons. To be effective, Surround must be used in a preventive program and should be sprayed on plants before insects appear.

Case study - CUCUMBER and EGGPLANT: In 2010, research aimed at investigating the effectiveness of kaolin clay at reducing flea beetle numbers and damage to young eggplants and cucumber beetles numbers in young cucumber plants was conducted by Dr. Jaime PiƱero at Lincoln University Carver Farm. Four varieties of eggplants were used for the first study. For each variety, half of the plants (8 inches tall) were treated with Surround WP formulated at 4% and the other half was left untreated. Damage by flea beetles was recorded every day for a 3-day period. Substantial decreases in the numbers of flea beetles were recorded in plants treated with Surround WP compared with untreated plants, although some differences were noted amonst eggplant cultivars. In cucumber, one application of Surround WP resulted in significant reductions in the numbers of striped and spotted cucumber beetles for up to a 10 day period in the absence of rain. The four graphs below show the numbers of spotted and striped cucumber beetles in Surround-treated and untreated cucumber plants for a 96-hour (4 days) interval. Insects were counted daily at 06:00 AM, when cool temperatures allowed insects to be counted.

Case study - TOMATO: Excessive heat can stress the entire tomato plant, causing irreversible damage to plant function or development. Temperatures higher than 90 to 95°F can interfere with pollination and fertilization, contributing to poor fruit set. Higher temperatures may result in blossom and fruit drop or oddly shaped fruit. Heat also affects fruit color, as lycopenes and carotenes are not synthesized above 86°F. High daytime temperatures can increase evaporation – resulting in high transpiration rates and poor water uptake – resulting in reduced plant vigor. This can lead to early canopy collapse, ultimately exposing the fruit to more heat and solar radiation – and increasing the potential for damage. In trials where temperatures regularly exceeded 90 to 95°F, Surround WP reduced the temperature of treated tomato leaves by 9°F. The engineered particles in Surround do not inhibit carbon dioxide uptake in leaves. Therefore by reducing plant temperatures Surround increases net photosynthesis. Trials where Surround was used season-long produced significantly decreased the proportion of tomatoes that had sunburn and increased tomato weights and yields.

Case study - APPLE: In experiments conducted in two apple orchards in Missouri, researchers evaluated the effectiveness of Surround WP against important insect pests of apple such as plum curculio and red-banded leafroller. Surround WP was successful at suppressing plum curculio damage to fruits, red-banded leafroller damage to leaves (but not consistently to fruits), and flyspeck and sooty blotch diseases on fruits, but was not consistently effective against cedar apple rust. Overall grade of apple was improved with applications of Surround WP. Generally, higher rates and more frequent applications resulted in better pest suppression. The particle film coating also reduced plant stress during extreme temperature conditions. Altogether, these results suggest that kaolin-based particle films have potential applications in integrated management of apple pests, while providing some physiological benefits to the plants. Organic farmers have reported good results in apple.

Case study - STRAWBERRY: Researchers in Florida reported that the application of Surround WP on the strawberry foliage the following morning after either 6 or 8 days of sprinkler irrigation had the same plant establishment, plant canopy diameter, and early fruit weight as the 10-day irrigated control. Application of Surround WP resulted in a 40% reduction of establishment irrigation volumes, which might represent major water savings for strawberry production in West Central Florida. The white film of kaolin clay dissipated within three to five weeks, and it did not show reduction in plant growth, flowering, and yields.

Some considerations for applications of Surround WP: According to the manufacturer, fruits and vegetables that are to be marketed fresh but have a white film of Surround remaining at harvest may be washed to remove the film. Though Surround is designed to have moderate adhesion to fruit surfaces the film is normally removed with common washing techniques found in packinghouses. Field-packed fruit that will not be washed may be applied with Surround early in the season for heat stress. The sprays should be discontinued when the fruit are still small. The remaining film coating will eventually weather off the fruit from rain and wind attrition. This attrition will be more pronounced in rainy climates. Note however, that when Surround applications are discontinued and the crop begins to lose its protective coating, sunburn protection will be lost.

Post-harvest techniques for washing Surround-treated fruits and vegetables are available at  and

(by Jaime Pinero, State IPM Specialist, Lincoln University)

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