Gangavalli, R. R. and M. T. AliNiazee
Department of Entomology, Oregon State University, Corvallis, Oregon 97331
1985
Environ. Entomol. 14: 17-19.

Abstract
Developmental thresholds and thermal-unit requirements for egg hatching, larval and pupal development, and the period before oviposition were determined for the obliquebanded leafroller, Choristoneura rosaceana (Harris). An average of 111.9 degree-days (thermal units) above 10.0oC was required from oviposition to hatching. Development of the total larval stage required 435.6 degree-days. The developmental thresholds for different larval instars were variable, and significantly different from each other. The fourth larval instar had the lowest developmental threshold, 7.1oC. Other thresholds were: first instar, 11.0oC; second and third instars, 9.9oC; fifth instar, 8.8oC; and sixth instar, 11.3oC. Diapausing third-instar threshold was 11.1oC. Pupae required 117.4 thermal units (above 9.5oC) for adult eclosion. Females required a period before oviposition of 35.2 degree-days above 11.9oC. Egg, larva, pupa, and preoviposition period represented, respectively, 16, 62, 17, and 5% of the total thermal development period from egg to egg.

Bailey, Clyde G.
Research Station, Agriculture Canada, Winnipeg, Manitoba
1976
Can. Ent. 108: 1339-1344.

Abstract
Differential survival and development rates were obtained for the bertha armyworm, Mamestra configurata Wlk., reared at nine constant temperatures. Eggs and larvae had high survival rates at temperatures ranging from 8C to 32C and pupae showed good survival between 8C and 28C. Eggs and larvae did not complete development at 6 and 36 C; and 32 C was lethal for pupae. Duration of the egg, larval, and pupal stages decreased as the temperature increased from 8C to 28C. When duration and developmental rates were plotted against temperatures, the observed points did not differ significantly from curves formulated from the logistic equation 1/y = K(1-e^a-bx). With a developmental threshold of 7C, 82, 356, and 352 accumulated day-degrees above the threshold were required for development of eggs, larvae, and pupae, respectively.

J. F. Brunner and S. C. Hoyt
WSU Cooperative Extension Bulletin 1072

Excerpts
The Codling moth is a key pest of apples and pears in Washington. Left to only natural controls, the codling moth can infest 80-90 percent of an apple crop. The primary means of crontrolling the codling moth is one to four annual insecticidal cover sprays. Correct timing of cover sprays is a critical factor in obtaining adequate control of the codling moth with minimum insecticide usage. A field model for predicting the development of codling moths was produced in 1976 at Michigan State University. The Michigan model was tested in Washington from 1979-81. Use of the model was found to give very accurate predictions of codling moth activity.

In order to use the program properly, several elements must be considered:
-accurate knowledge of daily temperatures
-calculation of degree-days
-proper use of pheromone traps
-proper timing of coversprays based on information from the previous three elements.

Pheromone Traps
It is important to monitor the initial activity of codling moth adults in the spring. The codling moth pheromone trap provides a sensitive tool for monitoring initial adult activity. It is recommended that pheromone traps be placed in the orchard after an accumulatino of 150 degree-days. Traps should then be checked regularly (every other day) until the accumulation of 180 degree-days, after which traps should be examined daily.

The first consistent or large (3-4 in a single trap) catch of adults in the pheromone trap is called the codling moth model BIOFIX. This is the biological cue used to initiate the model every growing season. When the BIOFIX is observed the degree-day total is automatically set at 200 [reset to 0]. The accumulation of degree-days for the remainder of the growing season proceeds from the 200 [0] degree-day base. Growers may continue to monitor subsequent adult codling moth activity, butr is not necessary for implementing the codling moth model. If monitoring is continued, examination of traps once or twice per week is sufficient.

Timing of Cover sprays
The following recommendation for timing of cover sprays are based on the assumptions that little or no codling moth problem exits internally in the orchard, and that nearby external sources of codling moths are not severely infested. The timing for the first cover spray is recommended after an accumulation of 450 degree-days (or 250 degree-days following BIOFIX). The second cover spray is recommended at 21 days following first cover spray. These two cover sprays will control first generation codling moths. In the unique situation where no internal codling moth problem exists and external sources of codling moth infestation are nil, only a single cover spray may be required to control first generation. Under these conditions it is recommended that the first cover timing be delayed to 560 degree-days.

In those orchards with a history of codling moth problems, two additional cover sprays are recommended to control second generation. Full cover sprays are recommended if the codling moth problem is internal. Border or spot spraying combinations may suffice if problems result from an external source, such as unsprayed orchards or wild unsprayed trees. Apply a third cover spray during second generation, the timing of the third cover spray is recommended at 1660 degree-days.

In small orchards spraying should be completed on the day the above-degree-day totals are reachied. In large orchards where several days may be required to spray the entire orchard, a grower should begin spraying in advance of the listed totals so that spraying can be completed at or slightly after the accumulated degree-days for the particular spray.

The codling moth model program is a new tool available to the orchardist to better time codling moth control sprays. Good spray coverage is required, as well as accurate sprayer calibration and application of the proper insecticide dosage. The codling moth model program does not reduce the need for orchard examination. For further information about the codling moth model program and recommendations on implementing it under commercial grower conditions consult the article by Jay F. Brunner and S. C. Hoyt in the Goodfruit Grower, December 1981, Volume 32 No. 21.

R. P. Regan, J. D. DeAngelis, and G. Gredler

Environ. Entomol. 20(5): 1403-1406 (1991)

Abstract
A linear regression model for predicting pheromone trap catch of male European pine shoot moth, Rhyacionia buoliana (Denis & Schiffermuller), based on accumulated heat units is presented. The model was developed from 3 yr of maximum-minimum air temperature and pheromone trap data collected in western Oregon during 1986-1988. Data collected the following years, 1989-1990, were used to evaluate the model. A lower threshold (base) temperature of -2.2oC [28oF] was used in calculating daily degree-days since 1 January. The model successfully predicted accumulated male moth catch to within 1-3 d during 1989. Predicted degree-day requirements (above -2.2oC [28oF]) are 1712 for 10% catch, 1,958 for 50% catch, and 2,205 for 90% catch.

M.T. AliNiazee

Proc. Nut Growers Soc. of Oreg. Wash and Brit. Columbia. Vol. 68:37-39

The filbertworm, Melissopus latiferreanus Walsingham is certainly the most important pest of commercial filberts in Oregon. The pest causes extensive damage and requires 2-3 sprays per season. The sprays are applied on a calendar date basis without regard to the exact time of moth emergence and the total number of moths present. In an attempt to improve the filbertworm monitoring program, AliNiazee (1983) suggested the use of sex pheromone traps. A simple degree-day accumulation model which accurately predicts the onset of certain biological events such as emergence, will be highly useful in management of the filbertworm.

The degree day concept which has been employed by both horiculturists and entomologists in predicting the developemnt of plants and insects is based on the assumption that a certain number of heat units are required for a certin amount of development, and that these developmental events occur only above a certain base threshold or development-zero threshold. Conversely, it is assumed that the development staops above a certain high temperature threshold. Beginnning of accumulation of degree days is started from certain arbitrary dates or from onset of a specific biological event such as the 1st adult moth captures in pheromone traps. The degree days are calculated using a simple formula given below:

     Daily Max .Temp. Plus Daily Min. Temp.
     --------------------------------------  - Developmental Threshold
                      2

The filbertworm emergence can be accurately predicted by using a degree-day model. Based on a 10 year study just completed, the first emergence of the filbertworm adults seems to occur at accumulation of approximately 610 degree-days above a base threshold of 51oF. The peak emergence occurs at about 1188 degree-days starting April 1. The range (with 95% confidence limits) for first emergence was 580 to 637 degree-days and peak emergence was 1158 to 1217. Although the date of first emergence might vary depending upon the elevation, slope, ground cover, and population levels, degree-day models can still serve a useful purpose in predicting general levels of emergence. Most filbert growers can use a degree-day model as described here by employing a maximum-minimum thermometer to record daily maximum and minimum temperatures and estimating the degree-days using Table 1. For example, if on a given day a maximum temperature of 88oF and a minimum temperature of 50oF was reached, then the degree-days (dd) for that particular day would be 18. Accumulation of these degree-days starting April 1 should provide an adequate indication of filbertworm adult emergence. Like any other predictive method, the degree-day method is not without its limiations, but it is a substantial improvement over what is currently available and is much more effective thatn the calendar date approch.

References Cited

AliNiazee, M. T. 1983. Monitoring the filbertworm, Milissopus latiffereanus with sex attractant traps: Effect of trap design and placement on moth catches. Environ. Entomol. 12:141-146.

Stark, S. B. and M. T. AliNiazee. 1983. Evaluation of modification to a basic thermal summation model for predicting the time of emergence of the adult western cherry fruit fly, Rhagoletis indifferens. Z. Ang. Entomol. 94: 401-407.

AN ABSTRACT OF THE THESIS OF
Joseph Francis Cacka
for the degree of Master of Science in Entomology
presented on February 1 1982,
Oregon State University

This study of the strawberry root weevil, Otiorhynchus ovatus (L.), on peppermint, Mentha piperita (L.), in central Oregon provided biological information to assess economic importance and to develop a sequential sampling plan.

Teneral adult weevils emerged from the soil from late May until late July. Oviposition of new generation adults commenced in early July. A minimum 12 day egg incubation period was observed. Larvae were present in peppermint fields all year and were the dominant life stage from late August until midMay the following year. Pupation commenced during early to midMay and was completed by late June. Over wintered adults were found in spring samples at densities not greater than 11.6% of the sampled population.

Developed ova were observed in the overwintered adults in late May. A carabid beetle, Pterostichus vulgar is (L.). was predaceous on larval, pupal and adult strawberry root weevils, no other predators or parasites were observed.

Fall plowing of peppermint fields increased the depth at which weevils were found the following spring. When fields are sample in midMay, a minimum depth of 15 cm is suggested for fall plowed fields and ten cm for unplowed fields.

Strawberry root weevil adults, pupae, larvae and the total of all these life stages have a clumped distribution that fit the negative binomial distribution when sufficient data were available to determine frequency distributions.

Statistically significant negative relationships were found between pupae, larvae and the total strawberry root weevil population and peppermint oil yields.

A modified sequential sampling plan was developed for the total strawberry root weevil population using a common K value (0.411) and a tentative estimate of the economic injury level (ca. 8.19 weevils/1000 cm²) .

L. B. Coop, B. A. Croft, and R. J. Drapek

J. Econ. Entomol. 86(3): 906-916 (1993)

Abstract
Phenology models of development of corn earworm, Helicoverpa zea (Boddie), and processing sweet corn, Zea mays L. ('Jubilee') were combined to predict pest infestation and economic loss in western Oregon. Cohorts of corn earworm larvae feeding on newly silking corn and artificial diet were monitored in the field. Degree-days for larval development (threshold = 12.5oC) were 185 +/- 54 (SD) and were represented in the model by varying degree-day totals for six larval subpopulations. Oviposition of moths closely followed corn silking and was normally distributed for degree-days. Harvest-time distributions of larvae combined with ear damage tunnel lengths for each instar were used to estimate cullage and economic loss. The model was validated by comparing predictions with damage and economic loss in three randomly selected fields from each of 4 yr. The predicted versus actual damage distributions matched more closely than did larval distributions at harvest; predicted and actual economic losses differed by an average of $0.88/ha in economic loss caused by varying harvest date using one planting from 1990 that had earworm-induced losses of $22.16. Harvest 7 days early decreased loss to $18.79 (-19%). Harvest 7 days late increased loss to $25.39 (+10%), indicating that a delay in harvest has less effect on loss than an early harvest.

Simulations were run to assess economic loss potential of an infestation level of 41% using 21 yr of temperature data and four silking dates. Analysis showed decreased averages and increased variation in loss for later silking dates. Late-season plantings generally had less economic loss than early-season plantings because of declining average temperatures, but year-to-year late-season temperature variations increased the uncertainty of losses.

Methods - Sweet Corn Development
During 1986, 1987, and 1988, development stages of corn (1-11 leaves, average tassel length, percentage of ears with apparent silks [at least 5 cm of silks emerged], percentage of silks at least 50% brown, mature for fresh market or late milk, and mature for processing or early dough) were recorded twice weekly in 26 fields. Growing degree-day requirements were determined for certain corn development stages. Computation ofa growing degree-day is achieved by subtracting a low development threshold (10oC) from the average of the daily maximum and minimum temperature, but the 10oC threshold is substituted for the minimum if it is greater thatn the minimum, and a high threshold (30oC) is substituted for the maximum if it is less than the maximum (Gilmore & Rogers 1958, Scott et al. 1984). Average days and growing degree-days were determined for the following stages: tassel langth 12 cm, 5% ears with silks emerged, 50% ears with silks emerged, 95% ears with silks emerged, 50% ears with silks at least 50% brown, mature for fresh market, and mature for processing.

Results and Discussion - Sweet Corn Development
For 'Jubilee', the mean +/- SD days between planting and later stages were as follows: tassel langth 12 cm, 58.0 +/- 4.1; 5% silks emerged, 66.3 +/- 4.4; 50% silks emerged, 69.7 +/- 4.5; 95% silks emerged, 74.4 +/- 4.9; 50% ears with silks at least 50% brown, 83.2 +/- 4.3; mature for fresh market, 97.0 +/- 6.9; and mature for processing, 104.4 +/- 4.4. The number of growing degree-days between planting and later stages were as follows: tassel length 12 cm, 491 +/- 27; 5% silks emerged, 558 +/- 24; 50% silks emerged, 590 +/- 24; 95% silks emerged, 636 +/- 30; 50% ears with silks at least 50% brown, 716 +/- 28; mature for fresh market, 855 +/- 27; and mature for processing, 887 +/- 29. Within the model, mean growing degree-days of these intervals were used to represent sweet corn development. Date of harvest was used as the time to convert corn earworm larval distrubution to damage.

AN ABSTRACT OF THE THESIS OF
Leonard B. Coop
for the degree of Doctor of Philosophy in Entomology
presented on April 16 1987,
Oregon State University

A pest management program for variegated cutworm (VC), Peridroma saucia (Hübner), in Oregon peppermint was developed based on studies of pheromone trapping, sampling methods, and economic thresholds.

Pheromone traps effectively trapped VC males and were used to reflect development and oviposition trends. Trap height was linearly correlated to moth catch (P = 0.001); the largest catch occurred at a height of 80 cm.

Male moths caught from midMay through June, the number of egg masses collected on pheromone traps, and estimates of peppermint canopy height were used to estimate third and fourth instar larval densities by regression analysis (r² = 0.64). A discriminant analysis based on similar independent variables correctly placed 16 out of 18 fields into two threshold density classes by a validation procedure.

Parasitism rates of variegated cutworm and peppermint leaf consumption rates of parasitized and unparasitized larvae were measured. Instars 4 to 6 consumed an average of 184 cm², equivalent to 888 mg (dry weight) of peppermint foliage. Leaf consumption by VC larvae parasitized by Meteorus communis (Cresson) was reduced by 93%. Parasitism rates averaged 35.1% for instars 2 to 4 and 5.4% for instar 5.

Addition of peppermint mainstem and lateral leaves, rates of leaf senescence, leaf specific oil yields, VC larval development, feeding behavior, feeding injury, and parasitism rates were all simulated by a computer model to determine economic threshold values. Significant injury occurred when fifth and sixth instar larvae were present in early August just prior to harvest. Fields harvested later in August had higher thresholds because of increased time for regrowth following cutworm injury. Economic threshold values calculated from this study ranged from 1.7 to 3.0 times higher than the previously used threshold of 0.9 larvae per 1000 cm². Larval damage units (LDUs) were used to express individual instar damage potential (kg/ha oil per cutworm) at various times in the growing season.

Sweepnet samples (n = 10, 180° sweeps) were most efficient for sampling VC instars 2 to 4. Ground search (GS) samples (1000 cm² for 10 minutes) were more efficient for instars 5 and 6. Sweepnet sample means were regressed against GS sample means for each VC instar. Efficiency of GS sampling for each instar was determined by vacuuming and searching the soil surface sampled. Slope values from sampling method regressions were used with GS recovery efficiency percentages to derive approximate economic threshold (ET) estimates for instars 2 to 4 using the sweepnet method. Sample size requirements and sequential sampling plans for each sampling method also were developed.

M. T. AliNiazee

Can. Ent. 111: 1101-1109 (1979)

Abstract
A phenology model based on a time-temperature relationship has been developed for the western cherry fruit fly, Rhagoletis indifferens Curran. The model predicts the occurrence of various biological events such as emergence levels, mating, ovipostiion,larval appearance, parasite activity, and pupation. These events are predicted as a function of summation of thermal units (TU) starting 1 March. For example, emergence begins at 462, oviposition at 541, hatch at 594, and pupation at 795 TU. The model was validated by actual field observations for a period of 3 years (1976-1978). Extended validation of first emergence was obtained from an entirely different cherry growing area, the Hood River Valley. The model could be a useful tool in integrated pest management program on cherries.