-9- 
Delta beets prior to April 6. -On that date a population of 12 hoppers 
per 100 feet of row was found on Union Island, _ The same number were ° . 
found in one field on Bishop Islend on April 10, but popula tions were 
lowtr in other fields’: On this date a few hoppers could be found even 
in the most northern arcéase The collections inditate that another 
migration occurred about: April 18, although populations in the beets 
were not materially increased. | Between April 20 and 24, there was a 
movement from the. southern section, resulting in a noticeable increase 
in population near Modesto. At the present time there are, no high 
leaf hopper populations in, the beets north of Stocktone" 
Derris. as stomach poison fails to kill larvae of variegated cut 
worme--Ge E. washburn, of the Alhambra, Calif., laboratory, reports as 
follows: “Larvae of the variegated cutworm (Lycophotia margaritosa 
saucia Hone) in the last instar were used in a small series of tests to 
determine the effect of derris- purely as-a stomach: poison. Kale leaves 
were dusted and made into sandwiches, so that there would be no contact 
between the dust and ‘the bodies of the larvae. Thirty larvae were fed 
‘sandwiches of 10 ‘percent ground derris dust (6 percent. rotenone) in 
diatomaceous earth, with tio ill] effects whatever; 40 larvae were fed 
pure ground derris dust (6 péereent SePROAG) Mitt h no ili effects; 40. 
larvae of the fourth instar were fed derris dust (6 percent rotenone) 
with no ill effects; 20 larvae of the same age were put on leaves fresh- 
ly dusted with pure derris dust and showed no hk effects. The only ef- 
fect noted was that the derris seemed to be somewhat repellent, as the 
larvae did not eat as freely of the treated material as they did of the 
untreated." ! 

‘Derris dust not toxic to celery 1 leaftier, tests” indicate.--According 
to a report from the Sanford, Fla., la laboratory, the results of a single 
test, presented in the table below, indicate very clearly that the use > 
or Peterone products will be very limited, if not entirely impractical 
against Phiyc ctaenia rubigalis Guene 
~- 
Larvae killed in 6 days 
Percentage of roten- 
one-in dust _ ; One fourth grown : “Half grown ; _ Mature Bs. 
: Percent : Percent : Percent 
O.1--~---+------: : Twa all 9) 3 () 
05 ee | ae the ead : . Def ° 0 ° * 
1,0------------- : 16.6 ; 1.8 : 0 
4 ean naa ane ewe : 414 : Tee : 0 


No noticeable effects resulted from. the use of any of the dilutions 
against the larger larvae, and even the 4 percent dust gave unsatisfactory 
tesults against the small lervae. In all of the derris tests with the 
celéry leaftier it was noted that the repellent effect of the dust was much 
less than with the southern armyworm (Prodenia eridania Cram.) and several 
species of cabbage worms. The amount of feeding ot the armyworm and 
cabbage worms decreased as the dust concentration was increased, but there 
was some feeding in all cageSe 
