g62-encyclopaedia-of-pests-and-natural-enemies-in-field-crops

Minor and/or emerging pestsMinor and/or emerging pestsOther flea beetlesCrops affectedCereals✔ Oilseeds✔ Vegetable brassicasPotatoesCarrotsAlliumsPeasField beans✔ Sugar beetLettuce© Frank PorchTurnip flea beetle© Rothamsted Research LtdFlea beetle damage tosugar beetA number of flea beetles, including Wessex, stripedand turnip flea beetles, cause occasional cropdamage. Phyllotreta species can be very damagingpests of seedling crucifers, for example, swede androcket.The Wessex flea beetle is of increasing importance insouthern England and is most likely to damage earliersownoilseed rape crops, especially if they are slow togrow away in September. Crops can be severelychecked.The striped and turnip flea beetles are principally pestsof spring brassicas, of which later-sown crops aremost susceptible; however, any crop may be at risk ifgrowth is checked by sunny, dry weather.Adult beet or mangold flea beetles can cause seriousdamage to the upper or lower surface of cotyledons,leaves and petioles of sugar beet. They overwinter insheltered spots (field margins or hedges) and emergein spring. Eggs are laid in late spring and larvae feedon roots before pupating but the damage is caused byadult feeding in the spring. They are most damagingwhen they are present in large numbers, in cold, dry,sunny weather, and when soil temperatures are lowand plant growth is slow.Linseed is also particularly susceptible to flea beetles.All of these beetles are smaller than the cabbagestem flea beetle (page 21).Pygmy beetle (Atomaria linearis)Crops affectedCerealsOilseedsVegetable brassicasPotatoesCarrotsAlliumsPeasField beans✔ Sugar beetLettuce© Rothamsted Research LtdPygmy beetleCrops affected✔ CerealsOilseedsVegetable brassicasPotatoesCarrotsAlliumsPeasField beansSugar beetLettuceA small, elongate beetle of 2 mm in length, the pygmybeetle can damage sugar beet seedlings. Damage afterthe six true leaf stage is rarely of economic significance.Beetle bites on the root and hypocotyl cause small blackpits, which may allow invasion by parasitic fungi. Severedamage can destroy the vascular tissue, causing theseedling to collapse. Cotyledons and leaves may also beeaten, leaving irregular-shaped holes.The adults overwinter in the soil and survive on beetcrowns left after harvest. In spring, they move to the soilsurface and fly on warm, still days from May onwards tocolonise new beet fields. In dry weather, the beetlesmove deep into the soil. In humid weather, they move tothe soil surface and feed on the hypocotyl and leaves.Eggs are laid in late spring and summer and the larvaefeed on roots of well grown plants, causing little damage.Seedlings are most sensitive to damage from adults infields where beet is grown in close rotation or wherecrops are infested early from adjacent fields with beetthe previous year. Rotation is usually the most effectivecontrol.Wheat shoot beetle (Helophorus nubilus)The wheat shoot beetleis an occasional pest ofwinter cereals following agrass rotation.The larvae feed at thebase of the shoot,causing the plant orcentral leaves to yellowand die.© Dr Christoph Benisch – kerbtier.deDamage is usually seen Wheat shoot beetlefrom January to Marchbut can be avoided by leaving a sufficient intervalbetween ploughing grass and drilling the crop – amonth should be sufficient under most conditions.39Pests: BeetlesPests: Beetles40