FRUIT NOTES 

 February 19Sh 



■ J^THOIYCHLO.. \/:liSUS DIELDRIM 



This year iQanjr '.lassachusetts fruit :^'roTifers must decide vtiethor to use methox- 

 ychlor or dieldrin to control plum curculio on their a;:)plt;s and poaches. They have 

 heard that both insecticides give excellent control of ti"iis important pest. However, 

 thoy do not v/ant to turn their orchard into an experiment station nor do they -vdsh 

 to be the last of their fruit grov/inc neishbors to take on "a good thin^". The fol- 

 loidng analysis of the availal:le iixCornation and a fe\r sug^^estions nay help them dec- 

 ide. 



For the control of pluin curculio in .assachusetts both imterials have been 

 very effective. In the i.iiddle West and South dieldrin has uiade a better record than 

 methoxychlor \ihich has not "stood up" under the higher temperatures in those areas, 

 Dieldrin also has a better record in preventing damage by plant bugs and from that 

 standpoint may be preferred on peaches and pears. 



On the other hand dieldrin is a complete loss for the control of caterpillars 

 and vnorms. 8uch as the red banled leaf roller, gypsy moth, codling ;ioth and Oriental 

 fruit moth. In applications that are nade while any of these pests are active, DDT, 

 TDE, parathion or lead arsenate must be added to dieldrin for adequate protection, 

 thus taking considerable of the "glamour" from this na«r .material. 



Both materials are exceptionally compatible lith other pesticides used on 

 fruit trees. The only caution refers to an undesirable combination vdth alkalir^ 

 chemicals such as liine sulfur and perhaps "Jordeaux llixture. Even then they may form 

 a less effective cOiUbination rather than one vhich is harmful to fruit and foliage. 



Of the many chemicals used for insect control, methoxychlor is one of the 

 safest to use arjd its residue is one of the least poisonous to operator and consumer, 

 Dieldrin, on the other hand, is poisonous and has a long lasting residue. Its use 

 is forbidden after the 2nd cover spr^ and it cannot be used for control of apple 

 ma;jgot even though it is c^te effective against that pest. 



One of the niost amazing features of dieldrin is its inild toxicity to benefi- 

 cial lady beetles including the several species vrhich live on aphids, and the red 

 mite destroyer, Stethorus punctum , -which is now quite aburiiant in several local or- 

 chards. In experiments at the riaLtham Field Station, methoxychlor has regularly 

 kilied lOO/j of the lady beetles ivhile 86;' survived sprays of dieldrin. In another 

 test, tvace as many Stethorus beetles were observed in a block sprayed with dieldrin 

 as in an adjacent block sprayed vfith lead arsenate. Therefore less trouble from 

 aphids and mites may be expected where dieldrin insteadof methoxychlor is applied. 



Obviously, the most debatable factor is the cost, liCthoxychlor costs 6^ 

 cents a pound. Using 3 pounds, the cost per 100 gallons is ;l,95^ or vrith lead ar- 

 senate in a 2^2-100 mixture about vLS^, In our schedule iiethoxychlor in the Galyx, 

 1st and 2rjd Cover Sprays has given satisfactory control of the major insect pests but 

 a heavier mite and aphid infestation is likely to result, Dieldrin 50,^ vrettable 

 povjder costs about $2,05 a pound. Using l/2 pound in 100 gallons, the cost is .,.1,03, 

 In most orchards it will be desirable or necessary to add 2 pounds of TDE ^C',] in 

 either the Calyx or 1st Cover Spray, bringing the cost to \,lt9S, and to add 2 pounds 

 of 50:.: DDT in the 2nd Cover Spray making .,a,65 per 100, TDE v.dll increase the kill 

 of lady beetles only slightly "out DDT is just as destructive to the beneficial in- 



