July, 1020 



BETTER FRUIT 



Observations On the Codling Moth in Walnuts 



By H. J. Quayle, of the Citrus Experiment Station, Riverside, California 

 (A partial report of investigations in 1919) 



THE codling moth (laspeyresia pomo- 

 nella) has been known to attack the 

 English or Persian walnut in Califor- 

 nia since 1909. In that year Mr. S. W. 

 Foster of the United States Department 

 of Agriculture observed it in the vicin- 

 ity of Concord and published a bulletin 

 on the subject. Five years later the 

 writer received the first specimens from 

 Santa Barbara County, and during the 

 same year also from Orange County. 

 While these seem to be the first actual 

 records, no doubt the insect occurred 

 in walnuts previous to that time. 



In 1914 the infestation was very 

 slight, only a fraction of a per cent in 

 a few groves, but since that date there 

 has been a marked increase in the 

 amount of infestation, until in 1918 it 

 suddenly reached the status of a serious 

 pest. The Citrus Experiment Station 

 at once decided to undertake studies 

 looking toward the control of the pest. 

 In the meantime the California Walnut 

 Growers Association, through its mana- 

 ger, Mr. Carlyle Thorpe, realizing the 

 importance of the problem, sponsored 

 a bill which was passed by the Califor- 

 nia legislature, and which carried a 

 sum of money for the investigation of 

 the problem. This money was appro- 

 priated to the State Commission of Hor- 

 ticulture, now the State Department of 

 Agriculture, and through the director, 

 Mr. G. H. Hecke, one-half of the appro- 

 priation was generously turned over to 

 the university for investigational work, 

 and one-half retained by Mr. Hecke's 

 office for work in connection with the 

 prevention of spread of the pest. 

 Codling Moth in Walnuts Elsewhere 

 The codling moth attacks the walnut 

 in South Africa, where it seems to have 

 taken to the walnut at about the same 

 time that the insect began to attack 

 the walnut in California. Mr. C. W. 

 Mally, entomologist at Cape Town, re- 

 ports that in certain districts in 1915 

 as high as from 50 to 60 per cent of the 

 crop was attacked. The codling moth 

 also occurs in walnuts in France, where 

 it has been known to attack the nuts 

 as far back as 1859. It was first de- 

 scribed as a distinct species having the 

 scientific name of carpocapsa putamina, 

 but later it was considered as a variety 

 of the species pomonella, which attacks 

 the apple. In correspondence with Mr. 

 Carl Heinrich, of the Bureau of Entom- 

 ology at Washington, Mr. Heinrich 

 states that it is his opinion that the in- 

 sect attacking the walnut in Europe is 

 not a variety, but the same species that 

 occurs in the apple in the United States. 

 Identity of the Species 

 A number of experiments were car- 

 ried out for the purpose of determining 

 how the insect would thrive when 

 transferred from the apple to the wal- 

 nut, and vice versa. Eggs, small larvae, 

 half-grown larva?, and nearly matured 

 larvae which were secured from the 

 apple were transferred to the walnut, 

 and in all cases the insect went through 

 its development in due course. Like- 



wise, different stages of the larvae were 

 taken from the walnut and transferred 

 to the apple with similar results. In 

 cheesecloth cages the insect from the 

 apple deposited eggs equally freely on 

 the apple and walnut which were sus- 

 pended in the same cage. Similar re- 

 sults were secured where the insects 

 were taken from the walnut. A wal- 

 nut tree was covered with cheesecloth 

 and cocoons of the codling moth from 

 the apple placed within the cheesecloth 

 covering. Apples were suspended in 

 the walnut tree, some of which were 

 practically in contact with the nuts on 

 the same tree. The moth deposited eggs 

 on the walnuts under these conditions 

 and the insect came to maturity. 



From our experiments of the first 

 season, then, the insect may be trans- 

 formed from one food plant to another 

 without affecting its development. 



Under field conditions, however, the 

 insect exercises more discrimination. 

 Where walnut and apple foliage are 

 interwoven, 90 per cent of the apples 

 may be infested with not more than 

 one per cent of the walnuts infested. 

 This would be the situation in the area 

 where the codling moth is known to 

 infest walnuts. Outside of this area, 

 apple and walnut foliage may be in con- 

 tact without any record of the insect 

 attacking the walnut. 



Distribution 



At the present time the areas where 

 the codling moth infests walnuts, and 

 where it is an economic problem, is in 

 the vicinity of Santa Ana and Tustin, 

 in the vicinity of Capistrano and Car- 

 pinteria. Occasional records of the in- 



Pa-ge 10 



sect in walnuts have been secured in 

 several other localities. Mr. D. B. 

 Mackie, who is in charge of the pre- 

 vention of spread of the moth, has rec- 

 ords from several localities where it 

 has not yet reached the status of a pest. 



Life History 



The life history of the codling moth 

 in walnuts is essentially the same as 

 the life history of the same insect in 

 the apple in the same locality. Until 

 the present season it was supposed that 

 the later broods only attacked the wal- 

 nut. 



In 1919 the first eggs were observed 

 on the walnut in Santa Ana on May 8. 

 These were located on the stem of the 

 new wood, a short distance back of the 

 nut, and also on the leaves. Like the 

 apple, the walnut in the early stages 

 has a fuzzy surface, which is not suit- 

 able for egg laying. The first larvae ap- 

 peared during the s*cond week in May 

 and continued to appear until the 

 middle of July. The first brood of 

 moths began to emerge on June 28 and 

 continued until the last of August. The 

 second brood of eggs was first observed 

 July 7 and continued to appear until 

 the first of September. Larvae of the 

 second brood began to appear about 

 the middle of July, the maximum num- 

 bers occurring the last of July and the 

 first of August. A third brood appeared 

 later and larvae were observed to enter 

 the nuts up to the first of October. 



The data as given are for the Santa 

 Ana district. At Carpenteria, the life 

 history is very different since the in- 

 sect is three or four weeks later in 

 making its appearance. The maximum 

 number of larvae entered nuts in that 

 section last year about the middle of 

 July, and these were larvae of the first 

 brood instead of the second brood, as 

 at Santa Ana. The difference in temper- 



acco 



ii 



<V£T> 



"Are You Getting Real 



says the Good Judge 



There's more good, last- 

 ing taste in a little of the 

 Real Tobacco Chew than 

 you get out of the ordi- 

 nary kind. 



You don't need a fresh 

 chew nearly so often — 

 that's why it costs you 

 less to chew this class cf 

 tobacco. 



Any man who uses the 

 Real Tobacco Chew will 

 tell you that. 



Put up in two styles 



RIGHT CUT is a short-cut tobacco 



W-B CUT is a long fine-cut tobacco 



Weyman-Bruton Company, 110/ Broadway, New York City 



