Early season pests - Elders Rural Services
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Early season pests

Pests come in all shapes and sizes. Two-legged or four, flying or crawling. In this article broadacre cropping specialist Peter Eliott-Lockhart takes a look at some of the smaller pests who can do big damage.

At this time of year you’re busy seeding and praying for just enough rain to help germination. But you should also take time to monitor what could be lurking in your emerging crops. Young crops are particularly susceptible to damage from pests during the first three to five weeks following emergence. Broad leaf crops are generally more at risk to early pests, while cereal crops can generally recover with early detection.

Grubs

Grubs include but are not limited to cut worm, web worm, budworm.

Cutworm
There are several different species of cutworm. All are plump and smooth. The most common is white/grey in colour with a pink to green underside. They generally feed at night and can chew off entire stems of canola and lupins. Look for tops lying on the surface of the furrow.  In cereals they may take leaves off, so look for burrows near stems during the day.

Weed web moth
The larvae of the weed web moth (Achyra affinitalis) have a black head and get up to about 15mm in length.  These grubs hide in silk cocoons in and among the damage they’ve created. They tend to cut leaves off and can pull the leaves down into the burrows.

Budworm
The native budworm (Helicoverpa punctigera), sometimes known as Heliothis, is not generally an early season pest but has been found in low levels in cereal crops in the Northern Ag Region (NAR).

They and the lesser budworm damage the emerging plants by chewing on leaves. Thresholds have not been developed and whilst crops can tolerate some level of grazing, if damage starts to get extensive then control measures should be used.

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Native budworm larvae showing prominent hairs (left) and buff coloured adult (right) (Source: cesar, via PIRSA)

Controlling grubs

Generally speaking, most grubs are relatively cheap and easy to control. You should talk to your local agronomist who can tailor a solution to suit your situation.

Mites and weevils

Mites and weevils survive over summer in a number of ways and this affects where to detect them. Three of the most common are the vegetable weevil, the red-legged earth mite and the lucerne flea.

Vegetable weevil
The vegetable weevil (Listroderes difficilis) is found widely across Australia and normally a pest of canola and pastures. Adults have a weevil snout and are 10 to 12 mm long. They tend to hibernate in summer under bark and debris in tree lines so damage is generally on the margins of these areas. Look for sections of leaf being removed from plants. Barrier sprays can be effective if damage is detected.

Redlegged earth mite (RLEM)
The redlegged earth mite (Halotydeus destructor) are common and widespread pest of most crops and pastures and can be found on may soil types. Distinctive red legs on a black body give this pest its name but bryobia mite can look similar.

Redlegged earth mites are often found on the leaf surface in feeding clusters of up to 30 individuals. Feeding damage from RLEM causes silver/white looking leaves as they graze on the chlorophyll on the surface of the leaf. In high levels they can cause plant death.

Females generally keep over-summering eggs within their bodies, therefore high levels the previous spring can lead to high hatchings in autumn. This has led to the development of the time right system – spraying before these eggs form to reduce numbers. RLEM have developed resistance to SP insecticides so if employing this system mixing and rotating chemical groups in and between seasons is very important. Targeted seed dressings and spraying when only necessary will help slow resistance levels.

Lucerne flea
The lucerne flea (Sminthurus viridis), also known as Clover springtail is an introduced pest commonly found in broadleaf crops and pastures. They are generally found on heavier soil types as the eggs are protected by clay particles. The adults are about 3mm long and have a furcula underneath their abdomen that acts like a spring, enabling them to ‘jump off’ vegetation when disturbed.

They graze windows out of the leaves, sometimes leading to the description of a shotgun damage to the leaf, but in high numbers the area can look bleached from a distance. Lucerne fleas are often concentrated in localised patches so it is important to monitor the entire paddock.

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Adult lucerne flea (Source: cesar via PIRSA)

 

Controlling mites and weevils

There are a range of biological and chemical management options for mites and weevils. It is best to consult with your local agronomist who can assist in identification of these, and other pests such as Russian wheat aphid, Green peach aphids, locusts and grasshoppers.

 

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