376 NEW YORK STATE MUSEUM 



II beetles from a sprayed vine and 12 from a similar one in the 

 unsprayed area, and at that time there appeared to be just as 

 many beetles on the sprayed as on the tmsprayed area. 



A study of the egg clusters taken on vines in both the sprayed 

 and unsprayed areas, is interesting and considerable variation in 

 the numbers will be observ^ed. Comparisons of the numbers of 

 egg clusters taken from vines in the middle of the treated and 

 untreated areas (rows 3-7 and 14-18), show that in the sprayed 

 section July 25 there was an average of . 7 of a cluster per vine; 

 on the 29th an average of 3, and Aug. 5 an average of 4.8 clusters 

 per vine, whereas in the imsprayed area there was, July 25, an 

 average of 5 egg clusters per vine; on the 29th an average of 12 J- 

 clusters per vine, and Aug. 5 an average of 10.5 egg clusters per 

 vine. Averaging each of these we find that during the entire 

 period there was an average of 2.82 egg clusters per vine on the 

 sprayed area and of 9.16 on the unsprayed area\ This appears 

 like a very substantial reduction in eggs, and were it borne out 

 later by an examination for grubs around the roots, we would be 

 inclined to accept it at its face value. Unforttmately such is not 

 the case, and for some reason or other, if the above figures are 

 correct, there had been a greater mortality among the eggs deposited 

 on the imsprayed than among those deposited on the sprayed 

 ^^ines, as examinations in October, extending across the entire 

 .area, show that on the southern portion of the vineyard we had 

 • an average of 4.75 grubs per vine on the sprayed area and of 7.4 

 ; grubs on the imsprayed area, indicating a reduction of less than 

 50% on the worse infested section. A comparison of vines on the 

 ■.northern portion of the experimental plots, where the beetles were 

 :not present in such large numbers, shows that there was an average 

 of 2 . 2 grubs -under the sprayed vines, and of 5 . 5 grubs under 

 •Ainsprayed vines, indicating a decrease of a little over 50%. Con- 

 sidering the entire data, we find an average of 3.47 grubs under 

 the vines on the sprayed area, and one of 6.45 grubs under the 

 unsprayed vines. It will be seen that in the case of both beetles 

 and eggs, the relative proportion of each on the sprayed area in- 

 creases with the advance of the season, and that consequently it 

 is almost impossible by a single examination to correctly estimate 

 the value of the spraying. Reliable data apparently can be 

 obtained only by digging about the vines in order to estimate 



'The percentage reduction, 86 ^ does not differ widely from that obtained about the same 

 -time by Mes.srs Slingerland and .Johnson, namely 93-95 %, The significant feature is that 

 these percentages are true for only a limited period and the real protection from spraying is 

 •considerably less. [See C. U. Exp. Sta. Bui. 224. p. 67] 



