Eggplant Integrated Pest Management AN ECOLOGICAL GUIDE

_____________________________________________________________________Ecology of insect pests and natural enemiesYellow sticky traps: these are yellow colored plates, covered with glue or grease. They can also bemade from empty yellow engine oil jars and many lubricants are suitable as grease. The yellow colorattracts some insect species like moths, aphids, flea beetles and whitefly. The trap is especially suitableto monitor the adult population density. To a lesser degree, it can be used as a control measure, to catchadult pest insects. However, not only pest insects are attracted to the yellow sticky traps but alsonumbers of beneficial natural enemies. Thus, care should be taken when considering using sticky trapsand it would be advisable to place just one as a trial and monitor in detail whichinsects are caught. If large numbers of natural enemies stick to the glue it mightbe better to remove the traps.Light traps: Light traps are usually made of a light (can be electronic, on abattery or on oil-products) switched on during the night, and either a sticky plateor a jar filled with water or other liquids. Insects (mainly night-active moths) areattracted to the light, and are caught on the sticky plate or fall into the waterand die. Various types of traps are used, and they normally serve only assupplementary measures to other control methods. When adult moths arefound in the trap, look for egg masses and young larvae in the field. However,natural enemies may also be attracted to light traps. When large numbers ofnatural enemies are caught it may be better to remove the traps.Related exercises from CABI Bioscience/FAO Vegetable IPM Exercise Manual:4.2. Sampling for arthropods with light trap4.3. Sampling for arthropods with sticky board4.4. Sampling for arthropods with water pan trap4.6. Soil-dwelling predatorsA light trap4.11.3 Use of threshold levelsThe decision to take control action against an insect population requires an understanding of the level ofdamage or insect infestation that a crop can tolerate without affecting the yield. Very often the termaction threshold level, economic threshold level (ETL), or tolerance level is mentioned. These terms areoften explained as “the level of infestation or damage at which some action must be taken to prevent aneconomic loss”. Traditionally, you had to look for the population of a certain insect in the field and whenthe population was higher than the value given for ETL, you were advised to spray.There are many formula to calculate economic thresholds. One of them is the following:cost of control (price/ha)ETL = ——————————————————————————————————-commodity value at harvest (price/kg) x damage coefficient (kg/ha/#pest/ha)The formula basically says that economic damage (=financial loss) begins at the point where costs ofdamage (yield loss due to insect/disease damage) are equal to the cost of control (costs of pesticides forexample). However, to actually calculate the threshold level for your own field situation is very difficult asmost of the values that should be included in the equation are not known today, or can just be roughlyestimated. That results in a very theoretical value!The thresholds vary with stage of crop growth, with costs of pesticides or labor, with environmentalconditions, with market prices, etc., etc. and can therefore be very different for a region, for a season, fora field!Nonetheless, in practice, most economic threshold levels are based on fixed infestation values. Thesesingle values do not consider the natural enemy population, the ability of the crop to compensate fordamage from insects, and many other factors such as weather conditions, market prices and personalhealth that are part of IPM agro-ecosystem analysis (AESA).The next list gives examples of a number of factors involved in decision making for ETL and for AESA.60Eggplant Ecological Guide