24 



Insects. 



San Jose Scale^ Aspidiotus perniciofms. — The most serious insect pest of the 

 plum tree is undoubtedly the San Jose. It is to be found in most of the com- 

 mercial plum districts. Here it needs no description, but unless kept well under 

 control the damage will be similar to that on peaches and apples. The trees wilJ 

 become weakened and the fruit will be unsaleable. 



Control: Spray thoroughly with lime-sulphur just before growth starts. If 

 scale is quite plentiful use the spray as strong as the 1.032 specific gravity hydro- 

 meter test. The work must be done thoroughly. 



Plum -CuRCULio, conotrachelus nenuphnr, is the most serious pest on the fruit. 

 It is a rough looking grayish snout-beetle about one-fifth inch in length, the 

 female of which lays eggs in the green plums. The eggs hatch and the larvae 

 develop in the fruit. The adult beetles also sometimes do damage by eating the 

 leaves, though this is not serious. The larvae in the plum destroys it and causes 

 it to drop prematurely. 



Control : All old brush piles, weeds, rail-fences, etc., that are the hiding 

 places of the insects should first be cleaned up or burned. Jarring the trees, 

 causing the insects to fall in nets held below, was once practised, but has now given 

 way to spraying methods. The regular sprays as outlined under spraying will keep 

 this pest under control. In case the regular sprays are not applied three pounds 

 of lead arsenate in forty gallons of water applied as soon as the blossoms fall 

 and again ten days later, will keep them under control. It is much better to use 

 the summer strength lime sulphur than the water as it tends to control Brown-Rot 

 as well. 



Shot-Hole Borers of various species attack the trunks and main limbs of 

 plums. Their work can be recognized by small gum exudations which, if removed, 

 expose an opening in the bark about the size of a small shot. If a few trees 

 are more attacked than others it is almost a sure sign that those trees are weak 

 or unhealthy. 



Control: Control measures are not very effective. Eemove any brush piles 

 or piles of wood that may be near and clean up all waste. This destroys the 

 breeding grounds. Increase the health and vigor of the tree by heavy applications 

 of barnyard manure. The insects cannot thrive where there is a good sap flow. 



Aphids, attack the twigs and foliage of plums very seriously at times. They 

 might be recognized in the spring as tiny green or black ^^ugs" on the buds just 

 before they burst. In the summer and fall, if plentiful, they give the tree a dark, 

 dirty appearance. They do damage by sucking sap from the leaves and twigs. 



Control: When once they get established they are very difficult to control, 

 as they live on the under side of the leaf which appears to curl around and 

 protect them. Examine the buds just when they are beginning to burst and 

 if present in quite large numbers spray at once with Kerosene emulsion or whale 

 oil soap. At this time they have not the means of protection that is afforded them 

 later. 



Other insects attacking the plum are Tent Caterpillars, Tussock Moth, Spring 

 and Fall Canker Worms, and Green Fruit Worm. These sometimes become serious, 

 but not generally, and all should be controlled by the regular spray application. 

 It is always best to spray while the larvae is small and it can not be too strongly 

 urged to apply the regular applications thoroughly rather than make any special 

 applications later. There are, I believe, about thirty other species of insects listed 

 as attacking the plum or becoming occasional parasites, but the most serious one^, 

 with the treatment for each, is civen above. 



