Insect pest management in peanuts

Peanut crop at Bundaberg. Photo: H Brier
© Queensland Government

Peanuts can tolerate higher insect thresholds than other more-determinate crops. However, crops grown in cotton and lucerne growing areas often have more above-ground pests than crops in other regions.

In traditional peanut growing areas (e.g. the South Burnett), soil pests can cause major economic damage. Foliar pests rarely cause economic damage. The worst soil-insect damage usually occurs where there is a long history of peanut growing with few non-legume crops in the rotation.

In drought years, etiella is a major problem in dryland crops. Etiella larvae are able to reach the pods in dry soil and damaged pods are at greatly increased risk of aflatoxin contamination. Most other pest problems only occur occasionally.

As peanuts expand into newer areas some pests, such as helicoverpa, mites and mirids, are a more constant problem. Soil pests are likely to become important in newer areas as more peanuts are grown, and new species may be encountered that are specific to the soil type in question. Pest damage to peanuts can start as soon as the crop is planted and continues until maturity. Under intensive production a number of pests will warrant control.

Major pests of peanuts

Minor pests of peanuts

Pre-emergent and seedling pests

Pre-emergent and seedling damage is often caused by larvae from the whitefringed weevil. False wireworms and mole crickets also cause occasional damage.

Vegetative pests

During the vegetative stage, damage to peanuts is mainly to foliage and caused by leaf-chewing or sap-sucking insects. Insects that suck sap can occur any time after crop emergence and include leafhoppers (jassids), peanut mites and cowpea aphids. Cowpea aphids (Aphis craccivora) are not considered a pest in peanuts. However, they are vectors of the peanut mottle virus. While this virus is not usually a problem in peanuts, it is a major concern in navy beans if these are grown nearby.

Leaf-chewing pests include helicoverpa, cluster caterpillar and on some occasions, red-shouldered leaf beetles.

Flowering, pegging and podfill pests

Leaf-feeding and sap-feeding insects remain present into this growth stage. Helicoverpa larvae attack flowers and pegs, as do cluster caterpillars. Mirids can also affect this growth stage by feeding on buds and flowers, causing them to abort. Heavy silverleaf whitefly (SLW) infestations at flowering and podding reduce plant vigour and yield but peanuts are not a favoured host for SLW and populations are rarely damaging.

Western flower thrips (WFT) are a potential threat to peanuts, mainly because they transmit tobacco spotted wilt virus (TSWV). However, an increased incidence of TSWV has not yet been observed in response to WFT in Australian peanuts. Etiella are a major pest in drought years, and etiella-damaged pods have much higher aflatoxin levels than undamaged pods.

Other pests capable of inflicting severe pod damage include whitegrubs, false wireworms, wireworms and earwigs. Mites can be a problem in late crops in some regions, particularly where there is widespread use of non-selective pesticides.