ipi8 



BETTER FRUIT 



Page 7 



The Strawberry Root Weevil ( Otiorhynchus Ovatus) 



By A. L. Melander. Entomologist, Washington Agricultural Experiment Station. Read at Thirteenth Annual Meeting 

 Washington State Horticultural Association, North Yakima, Washington 



IT was in May, 1904, that the experi- 

 ment station first received intima- 

 tion that the dreaded strawberry 

 root weevil, Otiorlujnchus ovatus, had 

 reached Washington. A bundle of dead 

 plants was sent in from the extensive 

 berry fields on the shores of Lake Wash- 

 ington near Seattle, and in the midst of 

 the package were two or three weevils. 

 A couple of years later Fruit Inspector 

 Pendleton of Seattle informed us that 

 the insect had destroyed several hun- 

 dred acres of berry plants from this 

 infestation. Since that time we have 

 received specimens from several places 

 near Spokane, from Walla Walla to the 

 Milton-Freewater district, from Kenne- 

 wick, North Yakima, Everett, Anacortes, 

 Puyallup and Olympia. There are also 

 two closely related sister species, 0. sul- 

 catus and 0. rugifrons, which occur in 

 Washington, sometimes living with the 

 small root weevil and sometimes work- 

 ing in new territory. We have seen 

 these larger weevils from Pullman, 

 White Salmon, Everett, Anacortes, Port 

 Townsend, Puyallup, Kelso and Wash- 

 ougal. The strawberry root weevils 

 have thus already invaded the principal 

 berry regions of the state. 



The small root weevil of the straw- 

 berry is a European emigrant which 

 first reached the Atlantic shore about 

 fifty years ago. The writer collected it 

 in Illinois and Indiana twenty years 

 ago, which was at that time about its 

 most western distribution. In the mean- 

 time the insect has spread by jumps, 

 probably through the sending of in- 

 fected nursery stock, until now it occurs 

 in the northern states all the way across 

 the continent. The experiment stations 

 of Maine, Connecticut, Michigan, Min- 

 nesota, Montana, Oregon and British 

 Columbia have experimented with the 

 insect and published accounts of its 

 behavior, but none has had any very 

 practical suggestions to offer toward a 

 solution of its control. Weevils of all 

 sorts are notoriously resistant and 

 hardy insects. They do not readily 

 succumb to poisons or contact sprays, 

 and the fact that this weevil lives under- 

 ground for practically the whole year 

 makes the problem especially difficult, 

 flie Kennewick-Piichland district has 

 400 acres in strawberries whose crop is 

 worth $100,000 a year. The advent of 

 the insidious root weevil was a just 

 cause for alarm, for although the insect 

 has only just obtained a foothold in a 

 few fields, its past reputation was 

 known' and its present work already 

 resulted in the utter ruin of the infested 

 spots. One field thai had produced 205 

 crates to the acre was being plowed up; 

 another that had sold 300 crates had its 

 output drop to 20 crates to the acre; 

 still other fields were entirely gone and 

 were lying idle. Such is the work of the 

 weevil that a field which this year 

 showed only the slightest signs of infes- 

 tation might have the plants dead and 

 worse than worthless the next year. 

 Through the generosity of the Commis- 



sioners of Benton County $500 was 

 made available this spring to the ex- 

 periment station for an investigation of 

 the pest. In undertaking the study, of 

 course, we held out no hope of discov- 

 ering a solution. 



Our first experience was with a 

 farmer whose berry field had been de- 

 stroyed by the weevil. "No, you can't 

 experiment here," said he. "There is 

 too much bedcvilment of the farmers 

 by you state-paid men. Leave us alone 

 and we will work out our own prob- 

 lems." When asked what solution he 

 had found for the weevil he explained 

 that he was going to plow out his field 

 and grow alfalfa. Now, plowing out a 

 ruined field is the best possible means 

 of sending the weevils out over the 

 country. The insects cannot be killed 

 by the plowing and when there are no 

 longer berry plants they will move on 

 to new fields where they can find their 

 desired food. It would be comparable 

 to a system of fighting smallpox by 

 turning all the patients out of the pest- 

 house and letting them go where they 

 will. It is a safe bet to say that this 

 respected citizen of Kennewick, with 

 all his notions for state economy, scat- 

 tered weevils enough to cost his neigh- 

 bors future losses that will be measured 

 by many, many thousands of dollars. 



To make a long story short, we may 

 outline enough of the life history of the 

 root weevil to make intelligible why we 

 undertook certain experiments. At 

 Kennewick the insect hibernates in the 

 white grub or larval condition, among 

 the roots of the plants on which it had 

 been feeding, from two to four inches 

 down in the soil. A very few of the 

 grubs live in the crowns of the plants, 

 which then become riddled by their 

 hurrowing. In the spring, preceding 

 the blossoming period, the larvse change 

 to the soft pupa state in cells or cham- 

 bers in the soil. With the maturing of 

 the crop of berries the adult weevils 

 transform from the pupae. By the time 

 the crop is picked the weevils are de- 

 positing eggs for the next generation of 

 larvre. The work of these summer and 

 fall larva? kills the roots, so that in the 

 spring infested plants appear sick or 

 dead and can be readily dislodged and 

 pulled up, but the weevils remain be- 

 hind. The adults have the habit of 

 playing 'possum and feign death for 

 many minutes when disturbed, drawing 

 in their legs and feelers so as to be 

 quite difficult to discern among the 

 plants and in the soil. Boot weevils are 

 wingless and so spread only slowly 

 through a field. The customary system 

 of mowing and harrowing the plants in 

 midsummer undoubtedly serves to scat- 

 ter the weevils broadcast, as il is clone 

 at the height of the normal migration 

 season. As the insects are known to he 

 able to subsist on many dozens of com- 

 mon plants they cannot be starved out 

 of a field by plowing out the plants 

 We have found them living in the 

 ground in a clean cultivated apple 



orchard several blocks removed from 

 the nearest berry field. As the insects 

 at the time of the experimentation last 

 May were all beneath the soil the prob- 

 lem of their control was limited to sub- 

 terranean treatments. It will be of in- 

 terest to not what was tried, even 

 though without success, for the hardi- 

 ness of the weevil can then be better 

 appreciated. 



First — Crushing the insects in the 

 ground. Since the weevils in all their 

 stages are scarcely ever more than four 

 inches down it has been thought that 

 disking, hoeing, harrowing, plowing, 

 rolling or tamping the soil should kill 

 them. Accordingly, to make a test we 

 secured a ten-pound sledge hammer and 

 dropped it ten inches, twenty inches 

 and thirty inches; in each case having 

 little effect on the insects beneath the 

 ground. So the writer buried his hand 

 under three inches of Kennewick soil 

 and permitted the sledge to be dropped 

 as before. He was surprised to find 

 that the cushioning effect of the soil 

 made the impact of the weight scarcely 

 felt. A quantity of weevils was then 

 put in the ground and the sledge swung 

 overhead with all possible force time 

 and again on them. The ground was 

 pulverized, the berry plants were torn 

 to shreds, but actually half of the wee- 

 vils were unharmed and were still alive 

 in the cages far weeks afterwards. It 

 was concluded that mashing the straw- 

 berry root weevil in the soil was im- 

 practicable. 



Second — Drowning the weevils. It is 

 often possible to flood a strawberry 

 field, so to make a test of its value 

 against the root weevil, some of the 

 beetles were held under water for sev- 

 eral hours. When they were permitted 

 to dry they revived unharmed from the 

 bath. As a matter of fact, we have 

 found weevils abundant in the wet soil 

 about the intakes for irrigation water, 

 where they are periodically submerged 

 for days at a time. It was concluded 

 that the strawberry root weevil could 

 not be killed in a practical way by 

 drowning. 



Third — Killing in the soil by contact 

 insecticides. It ought to be perfectly 

 possible to pour over the worst infested 

 spots some materials which would soak 

 in and kill the weevils; but it isn't. We 

 soaked the ground with strong soap- 

 suds, oil emulsions and solutions of 

 borax and of copperas, hut with no 

 apparent discomfort to the weevils or 

 their larvae, although in most cases the 

 plants were completely killed. Such 

 treatment was accordingly judged im- 

 practical. 



Fourth — Killing by poisonous fumes 

 and gases. We placed in holes different 

 measured quantities of standard insect 

 killers, such as carbolineum, cenol, 

 kreso, carco and crude petroleum oil; 

 we used gasoline, kerosene, turpentine, 

 chloroform and carbon disulphid; we 

 generated the poison gases chlorine, 

 sulphur dioxide, acetylene and cyano- 



