72 



The records are those obtained from eggs laid by confined moths. Eggs collected 

 in the field showed a high percentage of parasitism, which is discussed in another 

 section of this paper, and were quite unsatisfactory for rearing. 



When emerging from the egg, the j'oung larva chews a ragged hole in one end 

 and crawls forth upon the surface of the squash plant. Its subsequent action shows 

 considerable variation in habit. In many cases it burrows directly into the host 

 tissue. In other instances newly-hatched larvae have been seen to crawl to distances 

 of eight to ten inches from the egg-shell, feeding here and there on the leaf or stalk 

 before finally tunneling out of sight. Those which invade the leaf-stalks and main 

 leaf veins gradually work their way toward the main stem. Since the average 

 squash plant has not put forth runners when the majority of the eggs have been 

 laid, the result of this movement is a concentration of injur}' in the main stem near 

 the base. 



The burrow made by the squash vine borer larva is a twisting one, and is fre- 

 quently obstructed by a webbing of silk mixed \\dth j^ellowish grains of excrement, 

 called "frass". The greater part of the frass is pushed out through holes in the 

 stem, where it clings in moist masses, serving to indicate the position of the borer 

 within. The popular opinion seems to be that borers penetrate directly to the 

 central cavity of the main stem along which thej^ work, feeding at the walls of this 

 cavity. This is not strictly the case. The larvae usually work in the tissue sur- 

 rounding the central cavity of the stem, and often do not break through into this 

 cavity until they are about half grown. 



One borer can usually find food for its complete development at the base of the 

 stem. When more borers are present, however, the mining is extended along the 

 main stem and runners, into the bases of the leaf-stalks and, in rare instances, even 

 into the fruit itself. Upon the death of one plant, the larvae are able to transfer 

 their activities to one nearby. 



Growth is completed in a month to six weeks, at the end of which time the full- 

 grown caterpillar deserts its burrow in the squash plant and enters the soil nearby. 

 After penetrating to a depth of from one to six inches it hollows out a cell, spins 

 its cocoon of tough black silk and, gradually shrinking within its last larval skin, 

 settles down to pass the winter. 



There is but one generation of the squash vine borer each year in New England. 

 It is partially double-brooded, however, in the latitude of New Jersej^ and Southern 

 Ohio, and two full generations occur in Georgia and further south. 



Nature of Injury. 



In late July in IVIassachusetts, squash growers begin to notice plants with wilted, 

 drooping leaves. This condition may be a result of excessive feeding in the root 

 by larvae of the striped cucumber beetle. It is also a symptom of the disease known 

 as bacterial wilt. The chief cause of this wilting, however, is found in the gradual 

 destruction of the main stem of the squash plant near its base by the tunneUng of 

 squash vine borer larvae, which ma}'- be detected by the yellowish masses of frass 

 which the}^ push from their burrows. 



The base of the main stem frequently fails to support all the borers present, and 

 becomes a filthy, rotting mass, invaded by various sap-feeding beetles and filth- 

 loving insects. See Plate II, figure 4. It is finally reduced to a few dried shreds, 

 separated from the root by a light pull. See Plate II, figure 5. 



The effect of squash vine borer infestation varies from a slight check in the growth 

 and productiveness of the infested vine, to its death outright, and the loss of its 

 partly-formed fruit. In the same field one may see a well-grown, thrifty vine which 

 shows some borer injury, and nearby a dried, withered remnant of a vine, the 

 shredded and distorted base and hardened masses of frass testifying to the cause 

 of its death. A combination of factors is involved in this difference in the effect 

 of infestation. First, a thrifty vine can often support one or two borers, while a 

 less vigorous plant will be completely girdled. Second, plants which have been 

 girdled do not always die. If the runners have developed far enough to "strike" 

 numerous secondary roots from the nodes, and if these roots can find sufficient 

 moisture and food, the vine may yet produce a fair crop. The crop is materially 



