Orchard IPM - Insect Monitoring

Monitoring insect pests continues to be one of the pillars of integrated pest management in Pennsylvania orchards.
Orchard IPM - Insect Monitoring - Articles


Large Plastic Delta trap with sticky liner baited with Oriental fruit moth sex pheromone lure

With pests developing resistance to insecticides and removal of older broad-spectrum products, the old ways to manage insects had to change. The introduction of effective but highly specific new products with narrow spectrum activity, as well as the introduction and wide adoption of insect mating disruption practices, pushed fruit growers to much more scrupulous attention directed toward pests and beneficial insect populations coexisting in their orchards.

The monitoring of insects in orchards is an activity not only easily paying for itself, but also a practice that is able to save a lot of money throughout the entire season. It is much easier to detect a presence (or absence) of pests by checking traps placed in orchards than to attempt to find them resting on the foliage or feeding on fruit. A timely detection of adult moths, beetles, bugs, or flies can help to prevent injuries caused by them and/or their offspring. Additionally, establishing biofix and then seasonal follow-up observations of activity patterns will help in deciding what management practices are necessary.

The biofix, which is defined as the beginning of sustained moth activity, is usually established based on capture of adult male moths in sex pheromone traps. A correctly established biofix should be very helpful in determining actual development of pest insects in the field. In order to establish biofix and precisely monitor pests, the pheromone traps should be placed in the orchard before each monitored species becomes active. To establish the biofix for the Oriental fruit moth the pheromone traps should be placed in the orchard in early April; for codling moth and tufted apple bud moth traps should be placed in the orchard at the beginning of the bloom of apple trees. The obliquebanded leafroller does not need to be monitored with pheromone traps until about two weeks after the blooming of apples.

The established insect developmental models are based on specific lower and upper temperature developmental thresholds, which are used to calculate the accumulation of heat units (degree-days, DD). Based on various field and laboratory observations, we can accurately correlate the accumulation of degree-days with consecutive phases in insect development for most fruit pests. Paid service by SkyBit (Zedex, Inc. Bellefonte, PA) incorporates insect developmental models and daily updated weather information to provide a site specific forecast of insect development based on exact orchard location and biofixes of various pests. The 2012 season experience served as a great reminder of the importance of monitoring insects at the orchard level. With early biofixes for most insect species and unusual temperature patterns, the traditional/historical timings for the control of insect pests would not work and deliver expected results. With the common usage of stage specific pest management products, applying even the best products at the incorrect timing frequently resulted in failure. The early start for the 2012 spring allowed pests such as codling moth and Oriental fruit moth to complete an additional generation per season and if not accounted for, it could have led to a much higher than normal presence of live larvae in harvested fruit.

The sex pheromone sticky traps, such as the Large Plastic Delta trap, are commonly used in monitoring programs designed to survey or monitor the presence of lepidopteran pests in the orchards (see photo). Although sex pheromone traps collect only male moths, they can be utilized as a way to better understand the dynamics of pest populations. By utilizing the pest information provided by pheromone traps, the control effort (and expense) can be directed against the species that really needs a grower's attention. Traps themselves will not control insects or prevent fruit injuries, but if maintained properly, they should provide valuable information for a better use of available pest control tools and tactics.

Collection of various insect traps presented during Penn State FREC Grower Field day.

A single pheromone trap should be used to monitor only a single insect species. In a fully monitored orchard at least two traps per species should be used per block. In larger, over 20 acre blocks, at least one trap per every 10 acres should be employed. It is important that traps within each block be placed in locations where they will provide accurate readings of moth pressure. Placing traps far away (or too close) from possible moth sources such as large bin piles, abandoned or neglected orchards may provide an inaccurate assessment of actual pest pressure. In orchards where only the absolute minimum trapping program is to be implemented and traps will be used only to provide information about the best timing for insecticide applications, at least two traps per species have to be used per operation.

In some situations a single trap collects more than one species of insect, but under normal conditions, a single trap is baited with a single species sex pheromone lure attracting only the monitored pest. The capture of other species can often be attributed to random moths flying into the trap, or in rare instances, some impurity of the pheromone blend. The pheromone loaded lures attract moths only for a set period of time, usually from 4 to 10 weeks. In order to maintain reliable pest monitoring, the lure needs to be replaced before a lure's attractiveness starts to deteriorate.

Detailed recommendations for insect pest monitoring, names and contact information for trap and pheromone suppliers are listed in the Pennsylvania Tree Fruit Production Guide.