OBSCURE SCALE ON THE PECAN AND ITS CONTROL 9 



in two Shreveport orchards. Less complete data from other orchards 

 indicate that the above percentages give a fair idea of the numbers 

 of parasites usually present. Naturally, these numbers vary some- 

 what from orchard to orchard and from year to year. 



PREDATORS 



Predators exert their greatest influence during the period of egg and 

 crawler development. The coccinellids, or lady beetles, which are 

 important predators of other scale insects, are unimportant in con- 

 nection with the obscure scale so far as has been observed. 



Mites, several species of which are present in considerable numbers 

 at most seasons of the year, are largely scavengers, destroying old 

 dead scales, but four species of mites have been observed to attack 

 live individuals of the obscure scale. Specimens of Cheletia sp., Atomus 

 sp., and Allothrombium sp. 5 have been observed in a few rare instances 

 to attack crawlers after they have emerged from beneath the parent 

 scale cover but before they have settled. They are relatively unim- 

 portant predators. A fourth mite, Hemisarcoptes sp. 5 , is an important 

 predator as well as a scavenger. Examinations over a 3-year period 

 of 600 females of the obscure scale shortly after they completed repro- 

 duction showed them to contain an average of 15.93 unextruded eggs 

 and to have an average of 20.03 unhatched extruded eggs plus dead 

 unsettled crawlers remaining beneath their scale covers. The last- 

 mentioned mite is responsible for a portion of these remaining eggs 

 and dead crawlers, as it attacks reproducing females, causing their 

 premature death and consequent failure to finish the extrusion of their 

 eggs. It also attacks the extruded unhatched eggs and newly hatched 

 crawlers before they emerge from beneath the parent scale's cover. 

 This mite has not been found in any numbers until after the egg- 

 extrusion, crawler-emergence period is well advanced. Examinations 

 of scale-infested material late in the season have shown nearly 100 

 percent of the producing females on some samples to be attacked by 

 this species. Although this mite arrives too late to prevent a large 

 portion of the crawlers from settling, it does arrive in time to destroy 

 a portion of them and to cut short the reproduction. 



DISEASES 



Diseases, like parasites, are an important natural means of control 

 of this scale insect. Two diseases have been found attacking the 

 obscure scale, namely, Myriangium duriaei Mont, and Berk, and 

 Sphaerostilbe aurantii-cola (B. and Br.) Petch. 6 Because these dis- 

 eases occur over such a long portion of the year, it is not possible to 

 make an accurate estimate of their work, but some idea of their value 

 may be ascertained when it is considered that, with the help of para- 

 sites, they are apparently holding this scale in check in some southern 

 Louisiana pecan orchards in which artificial control measures are not 

 being practiced. Although diseases may attack newly settled speci- 

 mens as early as August and older specimens as late as June of the 

 following year, their greatest development takes place during the 

 winter and early spring. The examination of 29,714 specimens from 

 three Shreveport orchards in January and early February 1931 



5 Determined by H. E. Ewing of the Bureau of Entomology. 



6 Determined by Vera K. Charles, of the Bureau of Plant Industry. 



4485°— 33 2 



