THE PLUM CURCULIO IN APPLES 51 



creases steadily to a maximum between June 21 and 30. Oviposition ceases 

 about August 1. Feeding bj^ overwintering beetles begins and reaches the 

 maximum about the same time as oviposition, but it continues in decreasing 

 amounts until cold weather. Larvae leave the fruit first about June 30, in 

 greatest number between July 10 and 20, and cease before September 1. 

 Beetles emerge from the soil from late July to early October, reaching a 

 maximum between August 6 and 20. 



Sixty to seventy-five per cent of the plum curculio beetles die during the 

 winter in Masachusetts. 



Larvae and pupae may be killed by exposure to hot saui and by baking 

 and packing of the soil sun-ounding the pupal cells. 



A few birds and predatory insects eat the plum cuicuHo, and one species 

 of hymenopterous parasite has been reared from it, but none of these 

 natural enemies decreases the abundance of this pest to a noticeable extent. 



Many beetles may be killed by burning the leaves, binish, and woods in 

 which thoy are spending the winter. 



Picking up dropped apples between June 20 and July 20 and killing 

 the larvae in them is the most effective cultural operation for combating the 

 plum curculio in apples. The apples should be picked up not later than 

 ten days after they fall and either buried with quicklime, boiled, burned, 

 or fed to livestock. Sheep or hogs in the orchard help to control the pest 

 by eating the infested apple "drops." 



Cross cultivation close to the tree trunks with an extension disc haiTow 

 may kill many pupae if done between July 20 and August 1. 



A Yz per cent solution of carbon disulfide emulsion applied to the soil 

 at the rate of 3 pints per square foot killed 99.5 per cent of the plum 

 curculio larvae and pupae in laboratoiy experiments. 



With a normal crop of fruit, thorough spraying will give commercial control 

 of the plum curculio when the number of insects averages less than 25 

 per tree. Thoroughness of application with adequate machinery in good 

 repair is the most important factor in the spraying operation. 



The caljrx spray, the 7-day spray, and the 3-weeks spray are the most 

 important for combating the plum curculio in apples. Of these, the 7-day 

 or first curculio application is the most effective. 



Powdered lead arsenate, 2 pounds in each 50 gallons of spray, is recom- 

 mended in a spray schedule to combat the plum ciu-culio. There is little 

 danger of excessive arsenical residue following the recommended spray 

 schedule. 



The addition of stickers to the poison has consistently reduced the number 

 of days necessary to kill the beetles as well as the number of pvmctures made 

 in sprayed fruit. Fish oil at the rate of 4 liquid ounces to each pound of 

 poison, regardless of the quantity of diluted spray, and molasses at the rate 

 of 1 gallon in each 100 gallons of spray, have proved the most satisfactory 

 stickers. 



Lime-sulfur solution combined with lead arsenate slightly but not seriously 

 decreases the effectiveness of the poison. 



Dusting although not thoroughly compared, does not appear to be as 

 effective as spraying for combating this insect. 



