Evaluation of Kaolin Clay (Surround^'^) 

 for Control of Plum Curoulio 



Ronald Prokopy and Tracy Leskey 



Department of Entomology, University of Massachusetts 



Developing an effective trap for monitoring plum 

 curculio (PC) in orchards would provide a means for 

 determining the need and time to apply an insecticide 

 treatment for controlling this pest. The question then 

 arises of what insecticide to use. For the past 30 or 

 more years, azinphosmethyl and phosmet have been 

 the recommended materials against PC. Conceivably, 

 new regulations under the Food Quality Protection Act 

 may seriously compromise future use of these and other 

 insecticides in orchards. 



Therefore, in 1 999 we decided to evaluate a new 

 material, called Surround^'^, as a candidate for con- 

 trolling PC. It consists entirely of particles of white 

 kaolin clay, the same clay in fact that is used in porce- 

 lain pottery. Research to date by Michael Glenn and 

 Gary Puterka of USDA's Appalachian Fruit research 

 Laboratory in Keameysville, West Virginia suggests 

 that insects contacting foliage or fruit sprayed with an 

 aqueous solution of Surround are not killed but instead 

 are repelled. Apparently, the clay particles are very 

 annoying to insects walking on treated surfaces and 

 cause them to seek food and egglaying sites elsewhere. 



Our 1999 tests of Surround against PC consisted 

 of a small-scale trial conducted in a commercial or- 

 chard and preliminary trials conducted in the 

 laboratory. 



100 gallons water. A single perimeter tree in another 

 row did not receive any insecticide against PC and 

 served as an untreated control. No PC injury was ob- 

 served in samples of fruit taken prior to insecticide 

 application. On June 17 (just before June drop), ten 

 fruit were sampled for curculio injury on each treated 

 or untreated tree. Only 1/6 inch of rain fell between 

 May 31 and June 17. 



The laboratory trials involved caging PC adults 

 singly with either (a) one untreated apple or one apple 

 sprayed with Surround and adjuvant at above rate 

 (termed a no-choice test), or (b) one untreated apple 

 together with one Surround-treated apple (termed a 

 choice test). These trials were conducted in August 

 using adults that emerged from pupae about 2 weeks 

 before testing and were starved for 1 day before test- 

 ing. Apples were examined 24, 48, and 120 hours af- 

 ter initial exposure for feeding punctures made by 

 adults (young adults, as used here, are unable to lay 

 eggs). 



Results 



Results of the orchard trial showed that averages 



Materials & Methods 



The orchard trial was carried out at the 

 Prokopy Orchard in Conway using six rows 

 of Liberty trees, each with five trees per row. 

 Every other row was sprayed twice with 

 Surround: once on May 31 (one week after 

 petal fall) and again on June 8. Surround 

 was applied at the recommended rate: 50 

 pounds per 100 gallons water, along with a 

 manufacturer-provided adjuvant at 1 pound 

 per 100 gallons water. Remaining rows were 

 sprayed once (May 31) with phosmet at the 

 recommended rate: 1 pound of 70WP per 



Table 1. Percent apples injured by plum curculio 

 adults in commercial orchard trees receiving two 

 applications of Surround, one application of phosmet, 

 or no treatment. 



Treatment 



Number of trees 



Injured apples 

 per tree (%) 



Surround 

 Phosmet 

 Untreated 



15 

 15 



1 



6.0 



3.3 



30.0 



Fruit Notes, Volume 64 (Number 3), Summer, 1999 



11 



