FRUIT NOTES 

 September 19^5 



-X- a -if- ^/<r a -K- it ■»■ -Si- * ii- -;;- ^ PREHA.RVEST DROP CONTROL OV APPLES ■«• ^ * * ^- -k- ■«• ^f- ■«• ■»■ ^ •«■ * 



The materials available for preharvest drop control of apples seem to have stabir- 

 lieod, at least temporarily, follo\Ting several nev/ introductions during the past feu 

 years. Hence, most commercial grarers in Massachusetts have had some experience 

 or introduction to all the materials which are to be discussed, ' 



Gro\Ters may now choose among the three available materials, naphthaleneacetic 

 acid (NAA), 2,[|,5-trichlorophenoxypropionic acid (2,U,5-TP) and 2,h,^trichlorophen- 

 oxyacetic acid (2,U,5-TA), The selection of a given material should be related to 

 the variety, how long it v/ill take to pick a block or orchard following treatment, and 

 \7hether hastened ripening is desired or not. For example, we believe 2,l4,5-TA repre- 

 sents the best of the three materials listed for Mcintosh when drop control of more 

 than 2 vreeks is desired vdth a minimum of hastened ripening. However, NAA is still a 

 good material for the grower v^o can harvest his liclntosh crop in 7 to 12 days, 



NAA 



1, Apply when drop of many-seeded, blemish-free fruit commences, 



2, It may be applied as a spray, dust, or by airplane. Spray applications may 

 be concentrated, 



3, Vifhen used at single (10 ppm) or double (20 ppm)strength (U to 8 oz, of most 

 commercial formulations per 100 gallons) it will reduce the rate of drop of 

 Mcintosh for 7 to 12 days. If a single strength application is made somewhat 

 longer drop control may be obtained by the use of a repeat application about 

 7 days after the first treatment) 



kt NAA generally causes less direct ripening to fruit than 2,U,^-TP and slightly 

 less than 2,I|,5-TA but the higher the concentration of NAA \ised and the great- 

 er the number of applications the greater the ripening effect, 



5, It is satisfactory for drop control of Mcintosh providing the block can be 

 picked 7d.thin 7 to 12 days after treatment, 



6, For most late varieties 2,i|,5-TP is probably a more satisfactory material, 

 (See discussion under 2,It,5-TP,) 



2,U,5-TA - For Mcintosh Only 



1, Apply when drop coimmences (Same timing as NA.A), 



2, Use at 20 ppm (read label) as a spray. Dust formulations are not generally 

 available. It can be applied by airplane, 



3, 2,U,5-TA will often control drop for 3 to ii weeks but not quite as effectively 

 as 2,It,5-TP for the first 3 weeks, 



h» 2,U,§-TA does not hasten ripening as much as 2,U,5-TP and not much more than 

 NAA, Remember that the longer apples hang the softer they become even if no 

 stop-drop material is used. Don't let the fruit remain unharvested too long" 

 if a good apple for long storage is desired , 



$» This material is not suggested for varieties other than Mcintosh because of 

 lack of experience or failure to control drop (2,U,5-TA was ineffective in 

 controlling drop of Baldwin), 



6, 2,U,5-TA is a brush-killer at high concentrations so do not use it at concen- 

 trations above those suggested and do not make repeat applications. 



