Predators Of Bollworm Eggs

Item Type Article

Authors Butler Jr., G. D.

Publisher College of Agriculture, University of Arizona (Tucson, AZ)

Journal Progressive Agriculture in Arizona

Rights Copyright © Arizona Board of Regents. The University of Arizona.

Download date 02/10/2021 19:26:15

Link to Item http://hdl.handle.net/10150/299672 as the insectsincreased in age.An 9fraect P'iedale'ss example of this difference in consump- tion with age is shown in Table 2 for the damsel bug ( Nabis f erus) and a liate4ine99d. big -eyed bug ( Geocoris punctipes) . Another factor important in assess- ing the relative effectiveness of vari- ous predators in the field isthe num- By G. D. Butler, Jr. bers that are present.One way to measure insect populations in cotton is with a vacuum insect net. On July 9, 1965, samples from 1000 feet of cot- The role of predaceous insectston row were collected from each of in the reduction of populationsfive commercial cotton fields in the of pest insectsisdifficulttoTucson area, and the number of the various insect predators determined. evaluate. Laboratory studiesThe number of the more abundant in- were carried out last summer to evaluate the potential effective- ness of some of the common predators in destruction of boll- worm eggs. One measurement of the relative effectiveness of predators against boll- TOP PHOTO shows a big -eyed bug feed- worms is the number of bollworm eggs ing on a bollworm egg which has been that an individual predator can con- glued to a green bean. Note how eggs are placed along the bean.Second photo is sume in 24 hours.Some 30,500 boll - an extreme enlargement -close up, show- bollworm eggs were fed to 19 species ing the big -eyed bug actually piercing the of insect predators, with 1050 daily bollworm egg, preparatory to feeding. feeding records made. The eggs were glued on pieces of fresh green beans with egg albumen in groups of 10, CLOSEUP OF a black flea- hopper, above, sect predators collected in each field feeding on a bollworm egg.This insect is 25,50, and 100 eggs.Individualvery desirable for biological control uses is given in Table 3.Populations of beans with eggs were placed in petri in Peru.In the bottom photo a lacewing the different species varied from field dishes and a single predator intro-larva has discovered the choice bollworm to field, as Field B had the most duced.After 24 hours, the numberegg dinner placed on the "dining roomNotoxus, Nabis, and Orius, field D of missing and injured eggs was de-table" of green bean. had the most Collops and Field A termined. A summary of the relative (Continued on Next Page) effectiveness of the adults of several species of predators is given in Table 1. Table 2. Average Number of Boll- worm Eggs Consumed by Older Eat More Two Individual Predators Studies were also made with sev- in 24 Hours, by Different eralpredatorspeciesatdifferent Stages of Age of Preda- stagesoftheirdevelopment.We tor. learned that the number of eggs con- sumed in 24 hours generally increased No. Mean No. Predator I ndi- Eggs Dr. Butler is an associate professor in the and vid- Con- Department of Entomology. Stage uals sumed Big -eyed bug Table 1.Average Number of Bollworm Eggs Consumed Per Individual Geocoris punctipes Beneficial Insect in 24 Hours. 1st instar 16 3.0 2nd instar 6 2.7 Number of Mean No. 3rd instar 15 2.9 Predator Species Individuals Eggs 4th instar 12 7.5 Consumed adult 45 36.2 Damsel bug Lacewing larva, 3rd stageChrysopa carnea 104 44.1 Nabis f Brus A big -eyed bug Geocoris punctipes 45 36.2 1st instar 43 4.4 Damsel bug Nabis ferus 46 29.0 2nd instar 20 5.5 Collops Collops vittattus 26 26.8 3rd instar 29 10.8 A big -eyed bug Geocoris pallen 4 26.0 4th instar 18 14.1 Convergent lady beetle Hippodamia convergeas 21 17.9 5th instar 13 12.0 Minute pirate bug Onus tr1.Sticl)loi' 50 8.5 adult 46 29.0 Black fleahopper Spanogonicus albo f asciatus 72 8.2 Notoxus beetle Notoxus calcaratus 33 6.0 July -August Page 26 (Continued from Previous Page) Thurber Bull Tops Gain -Test Sale had the most Geocoris. Eggs X Bugs Equals ? ?? A type of mathematical exercise based on information just given is to multiply the number of eggs eaten in 24 hours by the number of predators present.This theoretical number of eggs consumed in24 hours by the different predators isalso given in Table 3. With these calculations, a big -eyed bug ( G. pallens) appears to be the most important predator.Notoxus , which have never been re- ported to be predaceous, appear to be potentially very important.Sim- ilarly, the black fleahopper appears to be potentially as important as the well -known predator, minute pirate bug. With these calculations, one field has potentially four times as much predation as two other fields. Many additional studies are needed. Bollworm eggs are not laid in masses but are scattered singly over the tops of the plants, so an evaluation of the searching capacity of the predators is important.Also, studies are needed on the relative effectiveness of various species against the larval stages of e bollworm, and their preference for bollworms in thepresence of other prey.Also important is timing.Are the predators presentinsufficient numbers when needed? These evaluations need to be made for other potential predators, suchas crab spiders whichwere more numer- ous than any other predator in three out of the five fields studied.

Table 3.Number of Predator Insects Collected in 1000 Feet of Cotton At the close of gain -test trials of young Row With a Vacuum Insect Net, July 9, 1965, Tucson, Arizona,herd sires at the U of A River Road Farm and Theoretical Number of Bollworm Eggs They Might Con-near Tucson, many of the were sume in 24 Hours. offered for sale. Walter Fathauer of Tuc- son (right), owner of IV Bar Ranch at Theoretical Bisbee, paid the top price of $1,800 for this Average No. Eggs young Hereford, sold by Thurber Hereford Consumed by Ranch at Sonoita. At the left is Dr. Bruce FieldFieldField Field Field Each Predator Taylor, head of the UA Science Predator A B C D E For All Fields Department and supervisor of the garn- test project and the sale. Geocoris pallens 390 142 137 26 33 18928 Collops vittattus 2 24 49 69 39 4904 Geocoris punctipes 40 9 19 14 5 3149 CONVIENE dar antibióticos a los becer- Notoxus calcaratus ros por tres razones :1) Su crecimiento au- 38 330 29 12 64 2838 menta. 2)Losantibióticosmejoransu Nabis ferus 2 40 7 12 21 2378 apetito Adquieren un aspecto de animales Spanogonicus más fuertes y resistentes.3) Tienen mayor albo f asciatus 48 55 26 15 36 1476 aumento de peso por kilo de alimento.Los Orius tristicolor animales de 3 and 4 meses responden mejor 0 84 6 13 34 1164 al tratamiento sise siguen administrando Theoretical Total losantibióticos,losresultadossonclara- No. Eggs Consumed mente benéficos hasta la edad de 6 meses. in 24 Hrs. by the 12321 8966 604 3685 3113 34837 Después la reacción es menos notablea 7 Predatorsin Each medida que crecen los animales. Field Page 27 Progressive Agriculture