~ m, ,_,.»»<~ ». Z TA245.7 oo 3 5 Al‘ O N TDOC 3 7 8 B [Blank Page m ongsm mum; % *1‘: A Method for Predicting Egg Diapause Initiation and Its Use in Control of Dark Ricefield Mosquitoes D. R. Delorme, R. W. Meola, and J. K. Olson* )% Introduction Psorophora columbiae (Dyar and Knab), the dark ricefield mos- quito is widely distributed throughout the United States and is a serious pest because it readily feeds on both humans and live- stock. In an effort to develop more cost-effective measures for the control of this mosquito the mech- anism allowing overwintering sur- vival was investigated. Results of this study showed that adult mos- quitoes develop diapausing eggs in the fall in response to photo- period (length of alternating periods of lightness and darkness) and temperature conditions per- ceived by the larvae, pupae, and adults. The eggs must undergo a latency period which prevents hatching during the winter months when environmental con- ditions are unfavorable for development. From this research, a control program was developed to reduce the number of mosquitoes by pre- venting the deposition of overwin- tering eggs. Since diapausing eggs cannot be controlled after they are laid, this control strategy involves suppressing populations of adult mosquitoes that produce diapaus- ing eggs during the autumn months. Elimination of this egg source coupled with natural mor- tality of diapausing eggs reduces the overwintering population of mosquitoes to levels which may *Respectively, Principal Entomologist, Associate Professor, and Professor, Texas Agricultural Experiment Station (Department of Entomology), College Station, Texas. substantially delay the build-up of pest populations during spring and summer of the following year. Model Description The model presented here is designed to predict the incidence of mosquitoes laying diapausing eggs in rice growing regions of Texas and Louisiana. The model determines the percentage of dark ricefield mosquitoes capable of producing eggs in response to photoperiod and temperature conditions which prevail during the larval and pupal stages and the initial three days after adult emer- gence. Three conditions were taken into consideration when the model was developed: (1) the in- teraction between photoperiod and temperature, (2) the length of the photoperiod-sensitive devel- opment stages of the mosquito, and (3) the response of individual females to diapause-inducing photoperiod and temperature conditions (Delorme 1984). The model requires only a few simple calculations to determine when diapause egg-producing mosquitoes will emerge in the fall. The decision to start the appropri- ate control procedure depends upon whether an adequate num- ber of mosquitoes are present to warrant control efforts. As shown in Figure 1, the inci- dence of diapause induction on any given date may vary greatly (A) OBTAIN DAILY MAXIMUM AND MINIMUM TEMPERATURES 1 (B) CALCULATE AVERAGE DAILY TEMPERATURES 1 (c) DETERMINE DAILY DIAPAUSE VALUES FROM TABLE 1 1 l (D) CALCULATE THE AVERAGE DAILY DIAPAUSE VALUE FOR THE 9 DAY PERIOD ll (E) DETERMINE THE PERCENT DIAPAUSE FROM TABLE 2 AS A FUNCTION OF THE CALCULATED AVERAGE DAILY DIAPAUSE VALUE Figure 1. Flow chart of the procedural steps followed to calculate the predicted incidence of diapause induction. from one year to the next. Since photoperiodic changes are con- stant from year to year, variabil- ity in percent diapause is due to temperature fluctuations, (i.e., lower temperatures cause earlier development of diapause egg- producing female mosquitoes). Therefore, temperature changes must be monitored during August and September to predict when diapause eggs will be produced. Procedure To use the model, average daily temperatures need to be cal- culated and converted to diapause induction values (Table 1). For most regions, average daily tem- peratures can be calculated from maximum and minimum daily temperatures obtained from the nearest national weather service station. 2 The sequence of steps for pre- dicting the incidence of diapause illustrated in Figure1 is outlined as follows: A. Daily maximum and minimum temperatures are obtained from the nearest weather sta- tion. The average daily temper- ature is calculated from these values as follows: (MAX TEMP + MIN TEMP) + 2. Occasion- ally, maximum and minimum temperatures may not be avail- able because of instrument malfunction. To compensate for missing temperatures, es- timated temperatures may be used in the model based on temperatures from the previ- ous day. Although this may cause a slight error, it is doubt- ful whether this procedure will change the predicted per- cent diapause by more than a few percentage points. B. Using the average daily teme/ perature, daily diapause in- duction values are determined from Table 1 for the date on which the temperature oc- curred. The higher the value, the lower the percentage of diapause predicted. C. The daily diapause induction values are summed for 9 con- secutive days (day1 + day2 + day 3, etc.) and the average daily diapause induction value is calculated. The 9-day period corresponds to the 6 days re- quired for larval and pupal de- velopment and the first 3 days after adult emergence. D. From Table 2, the percent diapause is then determined as a function of the average daily diapause value. E. As indicated in Figure 2, the difference in the incidence of diapause induction responses between mosquitoes hatching on consecutive days can vary by as much as 30 percent. Therefore, percent diapause should be calculated on a daily basis to detect rapid changes in the predicted incidence of diapause, especially during periods of declining average temperatures. Sample Problem To illustrate the procedural steps used to predict the inci- dence of diapause, Figure 3 shows a sample of 13 daily temperatures and the results of computations based on these temperature read- ings. To become familiar with the steps involved, the user should attempt to verify the compiled and computed values. In the sample provided, the model was started on September 8. Daily diapause values were compiled from Table 1 as a func- tion of the average daily tempera- tures for the days on which the temperatures occurred. The pre dicted incidences of diapaus were determined from Table 2. (Continued on page 12.) Tab/e 1. Daily diapause induction values for various temperatures and dates during August and ¢;;Q_ September Temp. °F Date 8/1 8/2 8/5 8/4 8/5 8/6 8/7 60.00 0.8387 0.8387 0.8358 0.8545 0.8314 0.8300 0.8286 61.00 0.8509 0.8509 0.8480 0.8466 0.8457 0.8422 0.8408 62.00 0.8631 0.8631 0.8603 0.8588 0.8559 0.8545 0.8551 63.00 0.8754 0.8754 0.8725 0.8711 0.8682 0.8667 0.8653 64.00 0.8876 0.8876 0.8847 0.8833 0.8804 0.8790 0.8776 65.00 0.8998 0.8998 0.8970 0.8955 0.8927 0.8915 0.8898 66.00 0.9121 0.9121 0.9092 0.9078 0.9049 0.9055 0.9021 67.00 0.9243 0.9243 0.9215 0.9200 0.9172 0.9158 0.9145 68.00 0.9366 0.9366 0.9557 0.9323 0.9294 0.9280 0.9266 69.00 0.9488 0.9488 0.9459 0.9445 0.9417 0.9403 0.9388 70.00 0.9610 0.9610 0.9582 0.9568 0.9559 0.9525 0.9511 71.00 0.9755 0.9755 0.9704 0.9690 0.9662 0.9648 0.9655 72.00 0.9855 0.9855 0.9827 0.9815 0.9784 0.9770 0.9756 75 .00 0.9977 0. 9977 0 .9949 0.9955 0.9907 0. 9895 0.9878 74.00 1.0100 1.0100 1.0071 1.0057 1.0029 1.0015 1.0001 75.00 1.0222 1.0222 1.0194 1.0180 1.0152 1.0138 1.0123 76.00 1.0544 1.0544 1.0516 1.0302 1.0274 1.0260 1.0246 77.00 1.0467 1.0467 1.0459 1.0425 1.0597 1.0383 1.0569 78.00 1.0589 1.0589 1.0561 1.0547 1.0519 1.0505 1.0491 79.00 1.0711 1.0711 1.0684 1.0670 1.0642 1.0628 1.0614 80.00 1.0834 1.0834 1.0806 1.0792 1.0764 1.0750 1.0756 81.00 1.0956 1.0956 1.0928 1.0914 1.0887 1.0873 1.0859 82.00 1.1079 1.1079 1.1051 1.1037 1.1009 1.0995 1.0981 83.00 1.1201 1.1201 1.1173 1.1159 1.1132 1.1118 1.1104 84.00 1.1323 1.1323 1.1296 1.1282 1.1254 1.1240 1.1226 85.00 1.1446 1.1446 1.1418 1.1404 1.1376 1.1363 1.1349 86.00 1.1568 1.1568 1.1540 1.1527 1.1499 1.1485 1.1471 87.00 1.1690 1.1690 1.1663 1.1649 1.1621 1.1608 1.1594 88.00 1.1813 1.1813 1.1785 1.1771 1.1744 1.1730 1.1716 89.00 1.1955 1.1935 1.9076 1.1894 1.1866 1.1853 1.1839 90.00 1.2057 1.2057 1.2050 1.2016 1.1989 1.1975 1.1961 8/8 8/9 8/10 8/11 8/12 8/13 8/14 60.00 0.8257 0.8242 0.8213 0.8184 0.8170 0.8141 0.8127 61.00 0.8579 0.8365 0.8336 0.8307 0.8295 0.8265 0.8249 62.00 0.8502 0.8487 0.8459 0.8430 0.8415 0.8387 0.8572 63.00 0.8624 0.8610 0.8581 0.8552 0.8538 0.8509 0.8495 64.00 0.8747 0.8755 0.8704 0.8675 0.8661 0.8632 0.8618 65.00 0.8870 0.8855 0.8827 0.8798 3.8784 0.8755 0.8741 66.00 0.8992 0.8978 0.8949 0.8921 0.8906 0.8878 0.8865 67.00 0.9115 0.9100 0.9072 0.9043 0.9029 0.9001 0.8986 68.00 0.9257 0.9223 0.9195 0.9166 0.9152 0.9123 0.9109 69.00 0.9360 0.9546 0.9517 0.9289 0.9275 0.9246 0.9252 fl'70.00 0.9482 0.9468 0.9440 0.9411 0.9597 0.9569 0.9555 /1.00 0.9605 0.9591 0 . 9565 0.9554 0.9520 0.9492 0.9477 72.00 0.9728 0.9713 0.9685 0.9657 0.9643 0.9614 0.9600 Table 1. Continued Temp. °F Dal ___,, 8/8 8/9 8/10 8/11 8/12 8/13 8/14 73.00 0.9850 0.9836 0.9808 0.9780 0.9766 0.9737 0.9723 74-00 0.9973 0.9959 0.9930 0.9902 0.9888 0.9860 0.9046 75.00 1.0095 1.0081 1.0053 1.0025 1.0011 0.9983 0.9969 76.00 1.0218 1.0204 1.0176 1.0148 1.0134 1.0106 1.0091 77.00 1.0341 1.0327 1.0298 1.0270 1.0256 1.0228 1.0214 78.00 1.0463 1.0449 1.0421 1.0393 1.0379 1.0351 1.0337 79.00 1.0586 1.0572 1.0544 1.0516 1.0502 1.0474 1.0460 80.00 1.0708 1.0694 1.0666 1.0639 1.0625 1.0597 1.0583 81.00 1.0831 1.0817 1.0789 1.0761 1.0747 1.0719 1.0706 82.00 1.0953 1.0940 1.0912 1.0884 1.0870 1.0842 1.0828 83.00 1.1076 1.1062 1.1034 1.1007 1.0993 1.0965 1.0951 84.00 1.1199 1.1185 1.1157 1.1129 1.1115 1.1088 1.1074 85.00 1.1321 1.1307 1.1280 1.1252 1.1238 1.1211 1.1197 86.00 1.1444 1.1430 1.1402 1.1375 1.1361 1.1333 1.1320 87.00 1.1566 1.1553 1.1525 1.1497 1.1484 1.1456 1.1442 88.00 1.1689 1.1675 1.1648 1.1620 1.1606 1.1579 1.1565 89.00 1.1812 1.1798 1.1770 1.1743 1.1729 1.1702 1.1688 90.00 1.1934 1.1920 1.1893 1.1866 1.1852 1.1824 1.1811 8/15 8/16 8/17 8/18 8/19 8/20 8/21 60.00 0.8098 0.8098 0.8069 0.8040 0.8011 0.7982 0.7968 61.00 0.8221 0.8221 0.8192 0.8163 0.8134 0.8105 0.8091 62.00 0.8343 0.8343 0.8315 0.8286 0.8257 0.8228 0.8214 63.00 0.8466 0.8466 0.8438 0.8409 0.8380 0.8351 0.8337 64.00 0.8589 0.8589 0.8460 0.8532 0.8503 0.8474 0.8460 65.00 0.8712 0.8712 0.8683 0.8655 0.8626 0.8597 0.8583 66.00 0.8835 0.8835 0.8806 0.8778 0.8749 0.8720 0.8706 67.00 0.8958 0.8958 0.8929 0.8901 0.8872 0.8843 0.8829 68.00 0.9081 0.9081 0.9052 0.9024 0.8995 0.8967 0.8952 69.00 0.9203 0.9203 0.9175 0.9146 0.9118 0.9090 0.9075 70.00 0.9326 0.9326 0.9297 0.9269 0.9241 0.9213 0.9198 71.00 0.9449 0.9449 0.9421 0.9392 0.9364 0.9336 0.9322 72.00 0.9572 0.9572 0.9544 0.9515 0.9487 0.9459 0.9445 73.00 0.9695 0.9695 0.9667 0.9638 0.9610 0.9582 0.9568 74.00 0.9818 0.9818 0.9789 0.9761 0.9733 0.9705 0.9691 75.00 0.9941 0.9941 0.9912 0.9884 0.9856 0.9828 0.9814 76.00 1.0063 1.0063 1.0035 1.0007 0.9979 0.9951 0.9937 77.00 1.0186 1.0186 1.0158 1.0130 1.0102 1.0074 1.0060 78.00 1.0309 1.0309 1.0281 1.0253 1.0225 1.0197 1.0183 79.00 1.0432 1.0432 1.0404 1.0376 1.0348 1.0320 1.0306 80.00 1.0555 1.0555 1.0527 1.0499 1.0471 1.0443 1.0429 81.00 1.0678 1.0678 1.0650 1.0622 1.0594 1.0566 1.0552 82.00 1.0801 1.0801 1.0773 1.0745 1.0717 1.0689 1.0675 83.00 1.0923 1.0923 1.0896 1.0868 1.0840 1.0812 1.0798 84.00 1.1046 1.1046 1.1019 1.0991 1.0963 1.0935 1.0922 85.00 1.1169 1.1169 1.1141 1.1114 1.1086 1.1058 1.104’ , 86.00 1.1292 1.1292 1.1264 1.1237 1.1209 1.1182 1.116._4 87.00 1.1415 1.1415 1.1387 1.1360 1.1332 1.1305 1.1291 Table 1. Continued f‘ .emp. °F Date 8/15 8/16 8/17 8/18 8/19 8/20 8/21 88.00 1.1558 1.1558 1.1510 1.1485 1.1455 1.1428 1.1414 89.00 1.1661 1.6601 1.1655 1.1606 1.1578 1.1551 1.1557 90.00 1.1785 1.1785 1.1756 1.1729 1.1701 1.1674 1.1660 8/22 8/25 8/24 8/25 8/26 8/27 8/28 60.00 0.7959 0.7924 0.7895 0.7866 0.7852 0.7825 0.7809 61.00 0.8062 0.8047 0.8019 0.7990 0.7975 0.7946 0.7952 62.00 0.8185 0.8171 0.8142 0.8115 0.8999 0.8070 0.8055 65.00 0.8508 0.8294 0.8265 0.8256 0.8222 0.8195 0.8179 64.00 0.8451 0.8417 0.8588 0.8560 0.8545 0.8516 0.8502 65.00 0.8554 0.8540 0.8511 0.8485 0.8468 0.8440 0.8425 66.00 0.8678 0.8665 0.8655 0.8606 0.8592 0.8565 0.8549 .\ 67.00 0.8801 0.8786 0.8758 0.8729 0.8715 0.8686 0.8672 68.00 0.8924 0.8910 0.8881 0.8855 0.8858 0.8810 0.8796 69.00 0.9047 0.9055 0.9004 0.8976 0.8962 0.8955 0.8919 70.00 0.9170 0.9156 0.9127 0.9099 0.9085 0.9056 0.9042 71.00 0.9295 0.9279 0.9251 0.9222 0.9208 0.9180 0.9166 72.00 0.9416 0.9402 0.9574 0.9546 0.9551 0.9505 0.9289 75.00 0.9559 0.9525 0.9497 0.9469 0.9455 0.9526 0.9512 74.00 0.9665 0.9648 0.9620 0.9592 0.9578 0.9550 0.9556 75.00 0.9786 0.9772 0.9743 0.9715 0.9701 0.9673 0.9659 76.00 0.9909 0.9894 0.9867 0.9859 0.9825 0.9796 0.9782 77.00 1.0052 1.0018 0.9990 0.9962 0.9948 0.9920 0.9906 78.00 1.0155 1.0141 1.0115 1.0085 1.0071 1.0045 1.0029 79.00 1.0278 1.0264 1.0256 1.0208 1.0194 1.0166 1.0152 80.00 1.0401 1.0587 1.0560 1.0552 1.0518 1.0290 1.0276 81.00 1.0524 1.0511 1.0485 1.0455 1.0441 1.0415 1.0599 82.00 1.0648 1.0654 1.0606 1.0578 1.0564 1.0556 1.0525 85.00 1.0771 1.0757 1.0729 1.0701 1.0687 1.0660 1.0646 84.00 1.0894 1.0880 1.0852 1.0825 1.0811 1.0785 1.0769 85.00 1.1017 1.1005 1.0976 1.0948 1.0954 1.0906 1.0895 86.00 1.1140 1.1126 1.1099 1.1071 1.1057 1.1050 1.1016 87.00 1.1265 1.1249 1.1222 1.1194 1.1181 1.1155 1.1159 88.00 1.1586 1.1575 1.1545 1.1518 1.1504 1.1276 1.1265 89.00 1.1510 1.1496 1.1468 1.1441 1.1427 1.400 1.1586 90.00 1.1655 1.1619 1.1592 1.1564 1.1550 1.1525 1.1509 8/29 8/50 8/51 9/1 9/2 9/5 9/4 60.00 0.7780 0.7751 0.7722 0.7708 0.7679 0.7664 0.7655 61.00 0.7905 0.7874 0.7846 0.7851 0.7802 0.7788 0.7759 62.00 0.8027 0.7998 0.7969 0.7955 0.7926 0.7911 0.7885 65.00 0.8150 0.8121 0.8095 0.8078 0.8049 0.8055 0.8006 64.00 0.8275 0.8245 0.8216 0.8202 0.8175 0.8159 0.8150 "‘<5.00 0.8597 0.8568 0.8540 0.8525 0.8597 0.8282 0.8254 56.00 0.8520 0.8492 0.8465 0.8449 0.8420 0.8406 0.8577 Table 1. Continued Temp. °F Datw 8/29 8/50 8/51 9/15 9/2 9/5 9/4 67.00 0.8644 0.8615 0.8587 0.8572 0.8544 0.8529 0.8501 68.00 0.8767 0.8759 0.8710 0.8696 0.8667 0.8655 0.8625 69.00 0.8890 0.8862 0.8854 0.8819 0.8791 0.8777 0.8748 70.00 0.9014 0.8985 0.8957 0.8945 0.8914 0.8900 0.8872 71.00 0.9157 0.9109 0.9081 0.9066 0.9058 0.9024 0.8995 72.00 0.9261 0.9252 0.9204 0.9190 0.9162 0.9147 0.9119 75.00 0.9584 0.9556 0.9528 0.9515 0.9285 0.9271 0.9245 74.00 0.9507 0.9479 0.9451 0.9457 0.9409 0.9595 0.9566 75.00 0.9651 0.9605 0.9575 0.9560 0.9552 0.9518 0.9490 76.00 0.9754 0.9726 0.9698 0.9684 0.9656 0.9642 0.9614 77.00 0.9878 0.9850 0.9022 0.9808 0.9780 0.9765 0.9757 78.00 1.0001 0.9975 0.9945 0.9951 0.9905 0-9889 0-9861 79.00 1.0124 1.0097 1.0069 1.0055 1.0027 1.0015 0.9985 80.00 1.0248 1.0220 1.0192 1.0178 1.0150 1.0156 1.0108 81.00 1.0571 1.054 1.0516 1.0502 1.0274 1.0260 1.0252 82.00 1.0495 1.0467 1.0459 1.0425 1.0597 1.0584 1.0556 85.00 1.0618 1.0590 1.0565 1.0549 1.0521 1.0507 1.0479 84.00 1.0742 1.0714 1.0686 1.0672 1.0645 1.0651 1.0605 85.00 1.0865 1.0857 1.0810 1.0796 1.0768 1.0754 1.0727 86.00 1.0988 1.0961 1.0955 1.0919 1.0892 1.0878 1.0850 87.00 1.1112 1.1084 1.1057 1.1045 1.1015 1.1002 1.0974 88.00 1.1255 1.1208 1.1180 1.1166 1.1159 1.1125 1.1098 89.00 1.1559 1.1551 1.1504 1.1290 1.1262 1.1249 1.1221 90.00 1.1482 1.1455 1.1427 1.1415 1.1586 1.1572 1.1545 9/5 9/6 9/7 9/8 9/9 9/10 9/11 60.00 0.7592 9.7578 0.7549 0.7554 0-7491 0.7476 0.7447 61.00 0.7716 0.7701 0.7672 0.7658 0.7615 0.7600 0.7571 62.00 0.7859 0.7825 0.7796 0.7782 0.7759 0.7724 0-7695 65.00 0.7965 0.7949 0.7920 0.7906 0.7865 0.7848 0.7819 64.00 0.8087 0.8075 0.8044 0.8029 0.7986 0.7972 0.7945 65.00 0.8211 0.8196 0.8168 0.8155 0.8110 0.8096 0.8067 66.00 0.8554 0.8520 0.8291 0.8277 0.8254 0.8220 0.8191 67.00 0.8458 0.8444 0.8415 0.8401 0.8558 0.8544 0.8515 68.00 0.8582 0.8568 0.8559 0.8425 0.8482 0.8468 0.8459 69.00 0.8706 0.8691 0.8665 0.8649 0.8606 0.8592 0.8565 70.00 0.8829 0.8815 0.8787 0.8772 0.8750 0.8716 0.8687 71.00 0.8955 0.8959 0.8910 0.8896 0.8854 0.8840 0.8811 72.00 0.9077 0.9065 0.9054 0.9020 0.8978 0.8964 0.8955 75.00 0.9200 0.9186 0.9158 0.9144 0.9102 0.9087 0.9059 74.00 0.9525 0.9510 0.9882 0.9268 0.9225 0.9211 0.9185 75.00 0.9448 9.9454 0.9406 0.9592 0.9549 0.9555 0.9507 76.00 0.9572 0.9558 0.9529 0.9515 0.9475 0.9459 0-9451 77.00 0.9695 0.9681 0.9655 0.9659 0.9597 0.9585 0.9555 78.00 0.9819 0.9805 0.9777 0.9765 0.9721 0.9707 0.9679 79.00 0.9945 0.9929 0.9901 0.9887 0.9845 0.9851 0.9805 4 80.00 1.0067 1.0055 1.0025 1.0011 0.9969 0.9955 0.9927~#' 81.00 1.0190 1.0176 1.0148 1.0155 1.0095 1.0079 1.0051 Table 1. Continued Temp. °F Date 9/5 9/6 9/7 9/8 9/9 9/10 9/11 82.00 1.0514 1.0500 1.0272 1.0258 1.0217 1.0205 1.0175 85.00 1.0458 1.0424 1.0596 1.0582 1.0541 1.0527 1.0299 84.00 1.0561 1.0548 1.0520 1.0506 1.0465 1.0451 1.0425 85.00 1.0685 1.0671 1.0644 1.0650 1.0588 1.0575 1.0547 86.00 1.0809 1.0795 1.0768 1.0754 1.0712 1.0699 1.0671 87.00 1.0955 1.0919 1.0891 1.0878 1.0856 1.0822 1.0795 88.00 1.1056 1.1045 1.1015 1.1001 1.0960 1.0946 1.0919 89.00 1.1180 1.1166 1.1159 1.1125 1.1084 1.1070 1.1045 90.00 1.1504 1.1290 1.1265 1.1249 1.1208 1.1194 1.1167 9/12 9/15 9/14 9/15 9/16 9/17 9/18 60.00 0.7455 0.7404 0.7575 0.7546 0.7552 0.7505 0.7274 61.00 0.7557 0.7528 0.7499 0.7470 0.7456 0.7427 0.7598 62.00 0.7681 0.7652 0.7625 0.7595 0.7580 0.7551 0.7525 65.00 0.7805 0.7776 0.7748 0.7719 0.7704 0.7676 0.7647 64.00 0.7929 0.7900 0.7872 0.7845 0.7829 0.7800 0.7771 65.00 0.8055 0.8024 0.7996 0.7967 0.7955 0.7924 0.7895 66.00 0.8177 0.8148 0.8120 0.8091 0.8077 0.8048 0.8020 67.00 0.8501 0.8272 0.8244 0.8215 0.8201 0.8175 0.8144 68.00 0.8425 0.8597 0.8568 0.8540 0.8525 0.8297 0.8268 69.00 0.8549 0.8521 0.8492 0.8464 0.8449 0.8421 0.8595 70.00 0.8675 0.8645 0.8616 0.8588 0.8574 0.8545 0.8517 71.00 0.8797 0.8769 0.8740 0.8712 0.8697 0.8669 0.8641 72.00 0.8921 0.8895 0.8864 0.8856 0.8822 0.8794 0.8765 75.00 0.9045 0.9017 0.8989 0.8960 0.8946 0.8918 0.8890 74.00 0.9169 0.9141 0.9115 0.9084 0.9070 0.9042 0.9014 75.00 0.9295 0.9265 0.9257 0.9209 0.9195 0.9166 0.9158 76.00 0.9417 0.9589 0.9561 0.9555 0.9519 0.9291 0.9265 77.00 0.9541 0.9515 0.9485 0.9457 0.9445 0.9415 0.9587 78.00 0.9665 0.9657 0.9609 0.9581 0.9567 0.9559 0.9511 79.00 0.9789 0.9761 0.9755 0.9705 0.9691 0.9665 0.9655 80.00 0.9915 0.9885 0.9857 0.9829 0.9815 0.9788 0.9760 81.00 1.0057 1.0009 0.9981 0.9954 0.9940 0-9912 0.9884 82.00 1.0161 1.0155 1.0105 1.0078 1.0064 1.0056 1.0008 85.00 1.0285 1.0257 1.0250 1.0202 1.0188 1.0160 1.0152 84.00 1.0409 1.0581 1.0554 1.0526 1.0512 1.0284 1.0257 85.00 1.0555 1.0505 1.0478 1.0450 1.0456 1.0409 1.0581 86.00 1.0657 1.0650 1.0602 1.0574 1.0560 1.0555 1.0505 87.00 1.0781 1.0754 1.0726 1.0698 1.0685 1.0657 1.0650 88.00 1.0905 1.0878 1.0850 1.0825 1.0809 1.0781 1.0754 89.00 1.1029 1.1002 1.0974 1.0947 1.0955 1.0906 1.0878 90.00 1.1155 1.1126 1.1098 1.1071 1.1057 1.1050 1.1002 9/19 9/20 9/21 9/22 9/25 9/24 9/25 .60.00 0.7245 0.7216 0.7202 0.7158 0.7144 0.7115 0.7101 Table 1. Continued Temp. °F Date 9/ 1 9 9/ 20 9/ 21 9/22 9/25 9/24 9/ 25 61.00 0.7369 0.7341 0.7326 0.7283 0.7269 0.7240 0.7225 62. 00 0.7494 0.7465 0.7451 0.7407 0.7595 0.7564 0-7450 63.00 0.7618 0.7589 0.7575 0.7532 0.7518 0.7489 0.7474 64.00 0.7742 0.7714 0.7699 0.7656 0.7642 0.7613 0.7599 65.00 0.7867 0.7838 0.7824 0.7781 0.7767 0.7738 0.7724 66.00 0.7991 0.7963 0.7948 0.7905 0.7891 0.7862 0.7848 67.00 0.8115 0.8087 0.8073 0.8030 0.8016 0.7987 0.7973 68.00 0.8240 0.8211 0.8197 0.8154 0.8140 0.8112 0.8097 69.00 0.8364 0.8336 0.8321 0.8279 0.8265 0.8236 0.8222 70.00 0.8488 0.8460 0.8446 0.8403 0.8389 0.8361 0.8346 71.00 0.8613 0.8584 0.8570 0.8528 0.8514 0.8485 0.8471 72.00 0.8737 0.8709 0.8695 0.8652 0.8638 0.8610 0.8596 73.00 0.8861 0.8833 0.8819 0.8777 0.8763 0.8734 0.8720 74.00 0.8986 0.8957 0.8943 0.8901 0.8887 0.8859 0.8845 75.00 0.9110 0.9082 0.9068 0.9026 0.9012 0.8983 0.8969 76.00 0.9234 0.9206 0.9192 0.9150 0.9136 0.9108 0.9094 77.00 0.9359 0.9331 0.9317 0.9275 0.9261 0.9233 0.9219 78 . 00 0 . 9485 0 - 9455 0 - 9441 0 . 9599 0 - 9585 0 - 9557 0 . 9545 79.00 0.9607 0.9579 0.9565 0.9524 0.9510 0.9482 0.9468 80.00 0.9732 0.9704 0.9690 0.9648 0.9634 0.9606 0.9592 81.00 0.9856 0.9828 0.9814 0.9772 0.9759 0.9731 0.9717 82.00 0.9980 0.9953 0.9939 0.9897 0.9883 0.9855 0.9841 83.00 1.0105 1.0077 1.0063 1.0021 1.0008 0.9980 0.9966 84.00 1.0229 1.0201 1.0187 1.0146 1.0132 1.0104 1.0091 85.00 1.0353 1.0326 1.0312 1.0270 1.0257 1.0229 1.0215 86.00 1.0478 1.0450 1.0436 1.0395 1.0381 1.0353 1.0340 87.00 1.0602 1.0574 1.0561 1.0519 1.0506 1.0478 1.0464 88.00 1.0726 1.0699 1.0685 1.0644 1.0630 1.0603 1.0589 89.00 1.0851 1.0823 1.0809 1.0768 1.0755 1.0727 1.0713 90.00 1.0975 1.0948 1.0934 1.0893 1.0879 1.0852 1.0838 9/26 9/27 9/28 9/29 9/30 60.00 0.7057 0.7043 0.7014 0.7000 0.6971 61.00 0.7182 0.7168 0.7139 0.7124 0.7095 62.00 0.7307 0.7292 0.7263 0.7249 0.7220 63.00 0.7431 0.7417 0.7388 0.7374 0.7345 64.00 0.7556 0.7542 0.7513 0.7499 0.7470 65.00 0.7681 0.7666 0.7638 0.7623 0.7595 66.00 0.7805 0.7791 0.7762 0.7748 0.7719 67.00 0.7950 0.7916 0.7887 0.7875 0.7844 68.00 0.8055 0.8040 0.8012 0.7998 0.7969 69.00 0.8179 0.8165 0.8137 0.8122 0.8094 70.00 0.8304 0.8290 0.8261 0.8247 0.8219 71.00 0.8429 0.8414 0.8386 0.8372 0.8343 72.00 0.8553 0.8539 0.8511 0.8497 0.8468 73.00 0.8678 0.8664 0.8635 0.8621 0.8593 74.00 0.8802 0.8788 0.8760 0.8746 0.8718 75.00 0.8927 0.8913 0.8885 0.8871 0.8843 Table 1. Continued XX / Temp. °F Date 9/ 26 9/ 27 9/ 28 9/ 29 9/50 76.00 0.9052 0.905s 0.9010 0.8996 0.8967 77.00 0.9176 0.9162 0.9154 4.9120 0.9092 70.00 0.9501 0.9297 0.9259 0.9245 0.9217 79.00 0.9426 0.9412 0 .9584 0. 9570 9 .9542 80.00 0.9550 0.9556 0.9509 0.9495 0.9467 81.00 0.9675 0.9661 0.9655 0.9619 0.9591 82. 00 0.9800 0. 9786 0.9758 0.9744 0. 9716 85.00 0.9924 0.9911 0.9885 0.9869 0.9841 84.00 1.0049 1.0055 1.0007 0.9994 0.9966 85.00 1.0174 1.0160 1.0152 1.0118 1.0091 86.00 1.0298 1.0284 1.0257 1.0245 1.0215 87.00 1.0425 1.0409 1.0582 1.0568 1.0540 88.00 1.0548 1.0554 1.0506 1.0495 1.0465 89.00 1.0672 1.0659 1.0651 1.0617 1.0590 \ 90.00 1.0797 1.0785 1.0756 1.0742 1.0715 Table 2. Predicted incidence of diapuse in relation to the average daily diapause value Avenl)aHy Percent Avenlafly Percent Diapause Value Diapause Diapause Value Diapause 1.075 0.0 1,000 50.0 1.070 0.5 0.995 55.0 1.065 1.0 0.990 60.0 1.060 2.0 0.985 65.0 1.055 4.5 0.980 70.0 1.050 7.0 0.975 74.5 1.045 9.5 0.970 79.0 1.040 15.0 0.965 85.0 1.055 17.0 0.960 87.0 1.050 21.0 0.955 90.5 1.025 25.5 0.950 95.5 1.020 50.0 0.945 96.0 1.015 55.0 0.940 98.0 1.010 40.0 0.955 99.0 1.005 45.0 0.950 100.0 Figure 2. Predicted incidences of diapause induction for Psorophora columbiae populations in Chambers County, Texas. Temperature °F 78 8O 82 84 190 I I I I I I I P 1983—-'>/ 80 1971-1982 ,’ " 1982 f 1 r- I I 3 60 I- D cu c1 _ FE D g 4O *' 2O - '- //\\\ //\\/ Q 4 l l 11f ,4 1O 2O 3O 1O 2O 3O August September 1O o , /\_ Figure 3. Calculation of percent diapause—a sample worksheet Date Aver. Daily Daily Diapause Induction Values % Diapause Temp. °F From Table 1 9-Day Average From Table 2 9/8 87 1 .0878 9/9 86 1.0712 9/10 85 1.0575 9/11 86 1.0671 9/12 84 1 . 0409 9/15 83 1.0257 9/14 84 1.0554 9/15 85 1.0202 9/16 80 0.9815 1.0450 9.5 9/17 80 0.9788 1.0509 21.0 9/18 79 0.9655 1.0189 50.0 9/19 78 0.9485 1.0068 45.0 9/ 2O 75 0 . 9082 0 . 9891 60 . 0 Computations 9/8 9/9 9/ 10 9/11 9/12 1.0878 1.0712 1.0575 1.0671 1.0409 2.1590 2.1287 2.1246 2.1080 2.0666 5.2165 5-1958 5.1655 5.1557 5.1020 4.2856 4.2567 4.1912 4.1691 4.1222 5 . 5245 5 . 2624 5 . 2266 5 .1895 5 .1057 6.5502 6.2978 6.2468 6.1708 6.0825 7.5856 7.5180 7.2285 7.1496 7.0460 8.4058 $2995 8.2071 8.1151 7.9945 9-5875 9.2785 9.1706 9.0614 8.9025 '7 Average = 1 .0450 1 . 0509 1 .0190 1 . 0068 0.9892 11 Conclusions The incidence of diapause egg production by field populations of dark ricefield mosquitoes varies from year to year. A diapause con- trol program initiated without prior knowledge of the existing level of diapause in field popula- tions can result in a waste of man- power and insecticide in control- ling nondiapausing mosquitoes. If control operations are applied late in the season, many diapausing eggs may have already been pro- duced. By utilizing the diapause induction model described in this 12 bulletin, control operations can be timed to coincide with the de- velopment of diapause egg- producing mosquitoes in the field. Once diapause has been predicted with the model, control personnel can locate those areas harboring mosquitoes and imple- ment the appropriate control operations. Literature Cited Delorme, D. R. 1984. Egg diapause in Psorophora columbiae (Dyar and Knab): Development of a predictive diapause induction model. Unpub- lished dissertation. Texas A&M University. Acknowledgement This study was conducted in cooperation with the U.S. Depart- ment of Agriculture, Agricultural Research Service as part of the CSRS Southern Regional Project S 122 Riceland Mosquito Manage- ment Program, and was funded in part by special grants from the Environmental Protection Agency (Grant No. CR 806771) and the USDA (Grant No. 82 CRSR 2-1010). ‘w [Blank Page in 01mm Bulletin] ' #574 ‘n aw W? :2 h: f . 11 T. a ‘m? A A. ,. 1 v, n “M 2w , Mmw. 3 away pww , , . v . ,M%‘w~ , x . Q wad/w“: Mwwwwuvw/ WMMQ,<@M.\<.»\, . . ___ Y». . ..uw_ae\wawzwfi , , . éapwww. w? z Y w w , .. , . , . . V: v \ : H qwv. , , I I W , v . . , @ ‘ . , . . 1 W , . » , ‘£62m . 3% C , MY» » saw“ Mmffiyv Mwwwwwvwfi~9 w w » y. Nw x w. qx H; uwiwmwxx; 1? “LY k » \\ . y» (nwfl 9w \ )4‘\3 < \1 n