Monitoring Consperse Stink Bug with Pheromone Traps

Eileen Cullen and Frank Zalom, Entomology Dept., UC Davis

Introduction
Several stink bug species are associated with tomatoes in the San Joaquin Valley. The most important are:

• the consperse stink bug which has a gray to brown coloration,

• the Say's or Uhler's stink bugs which are green in coloration and have both a yellow margin on the sides of the abdomen and 3 spots spaced horizontally on it's ventral side,
  

• and the red-shouldered stink bug which is smaller than the other species and is typically green with a horizontal red line across the 'points' of it's pronotum.

Stink bug populations build up during the spring on roadside, riparian and other wild host vegetation, moving into nearby cultivated crops in summer as wild hosts become unpalatable. Affected vegetable crops include, but are not limited to, fresh market and processing tomato fruit, snap beans, cowpea seeds, peppers, pumpkins melons, asparagus stems, okra pods, and corn.

All stink bug species share the same life cycle (egg – 5 nymphal stages – adult) and cause feeding damage by injecting salivary fluid with piercing sucking mouthparts. In addition, bacteria and yeast can be carried on bug mouthparts, causing rapid vegetable and fruit decay in the field.

Stink bug sampling
Canopy shake sampling is the most effective way to assess stink bug densities in low growing vegetable crops. Research in tomatoes has indicated that about half of all stink bugs present will be found beneath the plant on the soil, rather than on the foliage. Therefore, following each shake sample, scan the soil around the beating tray for additional bugs and include these in the sample count.

Consperse stink bug pheromone trap
A pheromone trap attractive to consperse stink bug male and female adults is commercially available from several sources to simplify the labor-intensive shake sampling protocol. Pheromones are not commercially available for other stink bug species, but research is currently underway to identify these pheromones and to determine synthesis approaches.

Early season trap catch is used to detect consperse stink bug migration into the crop and identify areas within the field where canopy shake samples should be concentrated later in the season, during fruit development. Traps are placed on the center of the bed, between two plants, and marked with flags tall enough to indicate trap position later in the season as the canopy develops.

Stink bugs typically migrate into crops from habitat adjacent to field edges and remain aggregated in patchy distributions, rather than spreading uniformly throughout the field. Consperse stink bug pheromone traps should be located within the field along sides and corners at a distance of 20-160 feet from the edge.

Degree-day accumulation from trap “biofix”
Insect development is temperature-dependent with each species requiring a specific measure of heat accumulation (degree-days = DD) between lower and upper developmental thresholds to complete its life cycle from egg to adult emergence. DD accumulation begins from a “biofix”, typically the first catch of adults or peak of adults in a set of traps. DD can be used to forecast subsequent developmental events such as egg hatch, nymphal development and adult emergence.

Consperse stink bug pheromone traps attract reproductively active adults, both females containing mature eggs and males. Consperse stink bug requires between 756 and 993 DD (Fahrenheit) to go from egg to adult. On average, egg incubation through 1st, 2nd and 3rd instar development are complete at 558 DD. From the early season trap peak observed in your area, begin accumulating DD until approximately 558 have been accumulated. It is at this time that intensive shake sampling should begin to confirm nymphal hatch in the field and determine if sufficient numbers are present to warrant treatment.

Pheromone-based pest forecasting
Stink bug shake sampling is time consuming under commercial conditions, often resulting in a trade-off between time spent sampling and accuracy of the resulting population estimate. Employing pheromone trap catch as an indicator of consperse stink bug migration and field distribution, using DD to forecast population development in the field, and limiting intensive shake sampling efforts to the period of nymphal hatch are likely to reduce total field monitoring time. When treatment is necessary, good coverage deep into the plant canopy is essential to achieve acceptable control. A nymphal management focus should increase treatment efficacy, as nymphs are more susceptible to insecticides than are adults.

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