the larvae of which devoured the celery leaves in large numbers, Two other 

 types ox moth larvae, namely the celery loopor ( Autographa falsi f era ) and 

 the cutworm (Phalaenidao) also caused considerable damage. The damage is 

 most severe during mild winters when the temperature averages a little above 

 normal throughout the growing season, which extends from December to the 

 of March. Th3 harvest continues until late in April, ard occasionally a 

 late crop is harvested in June. 



2. D. Sail, who conducted a detailed study of the celery insect pests 

 for the Florida State Plant Board, reported that during warm weather three 

 insect parasites helped to keep the celery leaf-tier in chock. By far the 

 most important Of these is a tiny black wasp (Trich o gramma mi nut urn ) , which 

 lays its eggs in the eggs of the leaf-tier. During a normal winter, how- 

 ever, this wasp becomes inactive for several months, and since most of the 

 celery growth takes place during that period, an influx of migrant birds 

 serves as the principal natural control on the insect pests. 



Four, species of birds were found to be of primary importance in the 

 control of the celery leaf-tier. These were the palm warbler ( Dendroica 

 palmarum ) , tree swallow (I ridoprocne bicolor ) , red-winged blackbird 

 ( Agelaius phoeniceus ) , and, near the end. of the harvesting season, the 

 bobolink ( Dolichon yx orvzivoru s) . 



The palm warbler was more widely distributed in large numbers through- 

 out the celery area during the entire growing season than any other bird. 

 The western race (D. p_. palmarum ) outnumbered its eastern relative, the 

 yellow palm warbler ( D, p_. hypochrysea ) , by about 25 to 1. These birds 

 were occasionally found in the woods, but typically they are lovers of 

 open fields with brushy borders or scattered trees. 



The palm warblers showed little fear of man and were active in the 

 celery fields throughout the day, feeding even during the midday heat, 

 when most other birds remained quiet. Twenty-three of these warblers were 

 collected for stomach examination, and 22 of them were found to contain 

 celery leaf-tiers in all stages of metamorphosis. This ineect pest made up 

 75.14 percent of the total volume of food eaten by the palm warblers, and 

 other lepidopterous pests (chiefly cutworms) composed an additional 5.09 

 percent. Some of the stomachs contained as many as 54 leaf-tiers; the 

 average for the series was 15. The birds worked far down among the stems 

 of the celery plants and removed the insects with surprising thoroughness. 



True swallows also rendered great service in reducing the number of in- 

 sect pests. The celery crop was commonlj dusted with pyrethrum in an ef- 

 fort to drive out the adult leaf-tiers, Whon tl Lust wars applied to the 

 celery the moths could dart into the air in short flights and then dr 

 back into the field. This procedure was continued until the insects finally 

 escaped from tho dusted area. The beginning of iustij rations in any 

 field served as a signal for vail tho tree swallows in the vicinity to con- 

 centrate over the infested area. Hundreds would swarm around the luster 

 and hover near it as it traversed the fields. Dr. Ball Btatod 

 effectiveness of pyrethrum in controlling tho adult leaf-tiers was >r- 

 tionate to the assistance given by swallows. In one series of obs_ - 

 made whilo lying prone between the celery rows he found that only 2 c 

 first lO'O moths that arose during dusting operations esc I tho remarkable 



