Mirids (Creontiades dilutus, C. pacificus) in summer pulses – mungbean, navy bean, adzuki bean, peanut and soybean
Download the management table as a printable pdf
||Podfill and Podripening/Harvest
|Find insects and damage
Adult female green mirid
|Mirids migrations from inland areas are associated with weather fronts.Mirids can also move in from surrounding crops and weed hosts early in the summer.
- Low numbers (one or less per m2) often present in vegetative crops.
- These do not damage vegetative terminals or reduce yield.
- Mirids are very mobile and in-crop populations can increase rapidly as the crop reaches the budding stage.
|Mungbeans, navy beans and adzukis are highly susceptible. Peanuts and soybeans are far more tolerant.Budding, flowering and early-podding crops are at greatest risk. Populations typically increase rapidly due to in-crop breedingDamage:
- When feeding, mirids release a chemical that destroys cells in the feeding zone causing black spots
- Flower and bud abortion
- Soybeans/peanuts are not at risk.
- Mungbeans, navy beans and adzukis remain at risk- mirids attack late buds/flowers
||Populations are influenced by climatic conditions. Numbers may be lower after heavy rains or storms, though storm fronts may also bring influxes of adults. Influxes of mirid adults often follow northwest winds in spring. Consider these factors when sampling.
- Population increases – cloudy days with temperature around 30°C.
- Population decreases – temperatures above 35° C for 3 or more days.
- twice weekly using a beatsheet from budding to early podding.
- Sample 5 one-metre lengths of row (non consecutive) within a 20 m radius, from at least six sites throughout a crop.
- Avoid sampling in very windy weather as mirids are easily blown off the sheet.
- Record the numbers of mirid nymphs and adults, and number and types of beneficial insects.
||Predatory bugs (damsel bugs, big-eyed bugs, predatory shield bugs) as well as ants and lynx, night stalker and jumping spiders feed on mirid adults, nymphs and eggs.
- Control weeds (mirids move into crops as alternative hosts dry off).
- Hosts include wild turnips, wild beans, wild sunflower, marshmallow, noogoora burr, verbena and thistles.
- Mirids can migrate between crops. Cultivated mirid hosts include cotton, safflower ,sunflower, and lucerne
- Shorten the crop flowering period by planting on full moisture profile and water crops just before budding.
- Intercropping – mirids have a preference for lucerne – strip cropping with lucerne may prevent movement of mirids into pulse crops. Lucerne may also promote natural enemies
- Thresholds vary from 0.3-0.6/m2, depending on application costs and commodity prices.
- Note that the mirid thresholds are based on continuous mirid activity at the above levels over a 28-day period.
- Find economic thresholds for mirids in the ready reckoner for mirids in mungbeans
Peanuts and Soybeans:
- Only spray if populations exceed 5/m2. Populations up to this level have not reduced yield in field trials.
- Trials have shown that the addition of salt (0.5% NaCl) as an adjuvant can improve chemical control of mirids at lower chemical rates.
- Salt mixtures allow a reduction in chemical rate of 50-60%, which significantly reduces impact on beneficials and the risk of flaring helicoverpa.
- Refer to the beneficial impact table for impact of insecticides on beneficials
- Insecticide resistance has not been detected in mirids. The continual influx of mirids into cropping areas from inland regions reduces selection pressure for resistance.
- To reduce the risk of flaring helicoverpa, delay spraying by up to 1 week (i.e. not spraying mirids at first sight, unless mirid populations are at least 1.5x threshold).
- Consider mirid sprays with dimethoate at lower than the full registered rate of 500 mL/ha to reduce the risk of flaring helicoverpa.
- If using a lower rate, always include a 0.5% salt adjuvant.
|Communicate and discuss management of mirids
||Growers and consultants can discuss:
- Weed control
- Crop selection – avoiding other mirid hosts in close poximity
- Monitoring techniques and frequencies
- Chemical control options and the use of salt adjuvant to reduce chemical rates/cost
- The possibility of trialling some alternative strategies e.g. strip cropping with lucerne
- Spray management plans with neighbours and consultants – Area wide management
- Industry publications can provide up to date information about regional pest issues