Euschistus spp.

Scientific Name Euschistus spp.
Common Names English: Stinkbugs; Spanish: Chinche; French: Pentatomide (all are referring to the entire family Pentatomidae)
Description In all species of the genus Euschistus, the adults have the broad, shield-shaped bodies and scutellum characteristic of „true bugs“. They are about 10-15 mm (0.39 - 0.58 inch) in length, mostly brownish in color, although some have a yellowish-green underside. When disturbed, they can secrete tiny drops of a foul-smelling liquid.

Biology

Damage

Stink bugs have piercing-sucking mouthparts, which both larvae and adults use to puncture plant tissues, injecting
saliva that contains digestive enzymes and sucking-in the mixture of sap and dissolving cells. Several species also feed on other insects, many of which are serious pests themselves. Most of the injury to plants is caused by the toxic saliva, and to a lesser extent by the physical damage.
On older plant organs, feeding by Euschistus spp. leads to local lesions; however, on younger tissues, growth distortions can occur. This is aggravated by the fact that the insects prefer soft, young tissues, e.g. growing points: if the latter are affected, development may be stopped completely.
In cereal crops, young seedlings may die off or remain stunted; older corn plants sometimes show excessive tillering and produce little grain. Stink bugs very often feed on immature seeds, e.g. in sunflower, resulting in a heavily-reduced number of healthy, mature kernels. Attack at the early development stages of fruits will generally cause a proportion to be dropped prematurely, with the rest being at least partly damaged. Peaches and other pome fruits may show „catfacing“, i.e. severe distortion and gnarling. Nuts may stay empty, or the kernels may be shrunken and bitter-tasting („black pit“ in Pecan, „kernel spot“). Cotton bolls may open only partially or not at all, or the lint may be stained. Feeding on vegetable crops causes blemishes (e.g. „cloudy spot“ in tomatoes), reducing their marketability.

Lifecycle

Adult stink bugs overwinter in diapause under leaf litter, tree bark, on crops sown in autumn, in tall grass, in harvest residues or in similar, sheltered places. If the winter is mild, however, they may stay active. In the spring, they start to feed on weeds or crops again. After 2-4 weeks, the first eggs are laid in batches: the larvae hatch 1-2 weeks later. Like other Hemiptera, stink bugs show incomplete metamorphosis. This means that there is no pupation. The larvae (called nymphs), are smaller than the adults and have undeveloped wings, but they gradually become more and more similar to them with each of the (in this case five) moltings. The generation cycle lasts about 6-8 weeks, so several per season are possible.
Adult stink bugs are good fliers, and they will move between emerging, maturing or removed host plants, according to their changing attractivity. The insects can thus migrate from one crop to the other, e.g. from wheat through corn or soybean to cotton. Sudden invasions are common when the original food source nearby has been eliminated, e.g. by ploughing or herbicide treatment of cover crops etc. The number of bugs found in orchards will increase when host plants become less abundant in the field in the autumn.

Occurrence

Additional Crop Information

Euschistus spp. feed on a wide variety of crops, including corn and small grains, peach, pecan and other nuts, peanut, soybean, sunflower, tomato and cotton.

Agricultural Importance

While Euschistus spp. normally cause only moderate damage, losses can be spectacular under certain circumstances. Changes in cultivation methods and in the prevalence of some crops can lead to an increase in the importance of this pest. In vegetables, the economic significance of the damage largely depends on the intended use of the produce, either for industrial processing or for direct consumption.

Control

Integrated Crop Management

Low numbers of stinkbugs are considered harmless, and several species can even be beneficial in some crops. However, their population development is rather unpredictable due to their mobility. Preventive treatment is ineffective: careful monitoring is absolutely essential to decide whether economic thresholds have been reached. Corn is mainly at risk when sown as a no-tillage crop into existing plant cover (weeds, harvest residues). Conventionally-grown fields are much less endangered.

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