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AgronomyTopics
Trevor will be updating this page on a regular basis with relevant, topical information pertaining to agronomy issues. If you believe there is an agronomy issue that needs discussion then please contact info@pacseeds.com.au
Tilt approved for use on sunflowers A chemical control for powdery mildew on sunflowers has now been approved for use. According to Pacific Seeds Summer Grains Agronomist, Trevor Philp this will give sunflower growers in affected areas another management technique for the problem. Powdery mildew has been increasing in severity and occurrence on the later planted sunflower crops. “Over this summer the QDPI, Syngenta and Pacific Seeds will be conducting trials to determine efficacy of timing,” Mr Philp said. To see a copy of the permit which will outline more information on the conditions of use, click here. Recent papers presented to GRDC conference Recently, Trevor was asked to present papers on some of his experimental work to a GRDC conference, Below are brief outlines and links to the extended versions of these papers. Grain Sorghum: Starting soil water, variety choice, row configuration, plant population, yield expectationTake home message; Making more profit from Irrigated Grain Sorghum Take Home Message. Screening in Sorghum - can we avoid it? Take Home Message.
Summer crop pest warning
Early planted crops which are flowering at the moment may be carrying high numbers of heliothis grubs. Early inspections indicate grub numbers of only 1-2 grubs per head, however, emergence of moths from chickpea crops and early planted maize are expected in the next few weeks. Checking should begin early as the first few heads start to emerge, often these early heads attract high pressure from midge and heliothis. Early spraying is recommended.
From left to right are the stages of sorghum, from when pests are laying eggs on the left, to the start of flowering, mid flowering, end of flowering and the beginning of grain fill.
Crop checking should occur at the start of flowering for midge which, whilst grub checking should begin around 50% yellow (mid flowering), grubs at this stage will be very small (2.5mm) to small (5mm). Sorghum heads that have 100% average flower will have small (5mm) to small medium grubs (13mm). Virus sprays are only effective on grubs less than 13mm long, so crops that have already flowered and have begun grain fill may have large grubs that need a different chemical for effective control. For more information see your local consultant agronomist.
Early Pest of Sorghum and Maize.
As we all know planting time is single most important operation that we will do for the season, and unfortunately we get precious few opportunities to plant these day’s. For these reasons it very important to make sure our emerging seedling are protected from seedling pests such as insects and mice. By their very nature; attack from these types of pest is sporadic from season to season and field to field. Due to this it is very difficult to anticipate their occurrence and numbers, so regular inspection of emerging crops is essential. Maize in particular is sensitive to plant spacing variation, growers in recent times have recognized the importance and yield benefits of even seed spacing and are going to considerable effort to ensure the best possible result. All this effort could be for naught if we ignore the risks of early pests. The effect of uneven plant spacing in maize is estimated to cost growers on average 400-500 kg/ha, this before insect and mice have had there share; for more information on the effects of seed spacing variation follow the link to research from Purdue University http://www.agry.purdue.edu/ext/corn/pubs/agry9101.htm. The most likely seedling pest we encounter are ground dwelling insects such as false wire worm and cut worm, above ground predators such as Northern army worm and mice, and sap sucker such as thrips and aphids. The best defense against a lot of ground dwelling insects is an integrated attack which includes; good weed control, well controlled planting depth and evenness, sowing into good moisture, warm soil, quality seed treated with an insecticide. Even with best practice the desired result is not guaranteed, early planted crops usually come under the most pressure, false wire worm in particular are generally in abundance in the early part of the season, so planting without seed treatment is definitely not recommended. Cutworms appear in a number of paddocks each year and unfortunately are not controlled by Cruiser® and Gaucho®, in furrow applications of chlorpyrophous may be successful if the cutworms are present, chlorpyrophous has very short residual control, so if eggs laid after the planting operation limited control can be expected. Cutworm are very difficult to find in dark, moist clay soils as they are the same colour, in row crops planted with a twin disc they are often found at the base of the seedling in the seed trench. Damage to seedling is often the first sign of their presence, typically cutworm lop off the seedling at ground level at night and pull the green material into the ground for safe consumption. Fields close to pasture, weedy road sides or fields with heavy weed pressure are usually at risk, some species of cutworm like to lay their eggs under the leaves of weeds such as wild turnip and milk thistle. Chemical control typically revolves around surface sprays of chlorpyrophos applied late in the afternoon or at night. Control is usually adequate but under high pressure a second application is often needed and replanting with in furrow sprays has occurred. Please consult you consultant before application of any chemical. Common Armyworm can cause severe damage to winter cereals and emerging summer crops, generally the moths lay in barley crops in September and October. The larvae prefer lush crops that provide good cover and protection. If larvae are not finished their development as the barley is haying of they can migrate to near by fields of summer crops. Bare patches on the edges of fields adjoining barley is a good indicator that armyworm may be present, low numbers in barley can cause high levels of damage in young summer crops. In dry years Armyworm damage can be mistaken for dry patches in the field. Mice seem to be increasing in their importance as a pest of agricultural crops, damage caused by mice to agriculture is estimated at between 10-30 million. Recent surveys by the Qld NRW has identified some areas where mice numbers are on the increase and look like they will need controlling. Areas on the Eastern & Central Darling Downs are already incurring damage in winter crops and some baiting has already started. The western downs is at moderate risk and numbers around Mungindi are reported as high. Mice like to over winter in zero till sorghum paddocks and in table drains, as food supply diminishes in these areas they migrate to winter crops. If left uncontrolled they can cause high levels of damage in the winter crop and can move on to the summer crops. In my opinion they cause their worst damage in dry years were water and food are short, in these years they will attack developing heads in the stem or at the milky dough stage, causing much more damage if they just attack the hard grain for food. Aphid numbers have been high in the barley and canary crops these are predominately oat aphid which can be found at the base of the plant where they are well protected, oat aphid do not usually infest sorghum and maize in Australia but have been a pest of maize in the US. Corn aphids are present in the upper leaves and the whorl of the barley and have started to migrate to early planted maize crops. Control of aphids is not on either of the seed treatment label, however both Cruiser® and Gaucho® give good suppression for two to three weeks. Corn aphid very rarely requires controlling these days as the number of disruptive sprays has been drastically reduced in the farming system. Aphid numbers can get very high in moisture stressed crops, it is very hard not to want to spray in these situations, however if left alone beneficial insect usually control these sticky pest. Spraying disruptive chemicals in the vegetative stage can cause bigger problems later with aphid and heliothis infesting the sorghum heads in particular. The economic cost of midge and heliothis damage In recent seasons, particularly last summer, midge were again a problem and according to Pacific Seeds Summer Grains Agronomist, Trevor Philp are set to remain so. “Despite the advent of midge tolerant varieties significantly reducing the threat of midge damage and helping with integrated pest management in grain sorghum, midge and heliothis still pose a significant threat to late planted grain sorghum crops,” he said. Mr Philp said there is a high degree of confusion surrounding midge tested ratings, what they mean and at what threshold spraying for midge or heliothis is financially advantageous. He has written the article below to help clarify the issue. A variety with a six midge rating has six times the resistance to midge compared to a variety with a rating of one. At today’s high sorghum prices, damage from midge could be very costly, example; a crop with five flowering heads/meter squared has 10 midge/head, the potential dollars lost for a variety with a midge rating of six would be $121/ha versus $364/ha for a variety with a two rating. The spread of planting in Central Queensland and the soft humid conditions has provided an ideal breeding ground for midge, and significant damage has already been reported. Growers and consultants need to rigorously check crops from start of flowering through to the end of flowering, this usually last around five to seven days but uneven crops can flower for several weeks. Table 1: Visual sorghum midge damage and subsequent yield loss in sprayed and unsprayed crops in midge susceptible and resistant hybrids
* means in columns (columns and rows for midge damage and yield) not followed by the same letter differ from each other at p<0.05. SOURCE; QLD DPI&F, DAVID MURRY & ADAM HARDY Generally sorghum midge is sprayed with a synthetic pyreithroid; these chemicals are very effective and are cheap to use. However they are highly disruptive to the survival of beneficial insects. The use of disruptive chemistry to control midge increase the risk of flaring other pest such as Heliothis and Aphids. Heliothis generally lay their eggs just prior to flowering and develop at a very rapid rate especially when temperatures are high. New research by Dr Bernie Franzman from the QDPI & F has identified that damage from Heliothis larvae is 60% higher than previously thought; new data suggest that larvae eat a total of 2.4g of sorghum not 1.5g. Checking for Heliothis should start at early flowering, I like to start checking when the anthers have started to turn orange 50mm from the top. Larvae are still very small at this stage and can be hard to see. The easiest way to sample is to beat a number of flowering heads into a bucket, and then count the larvae. The most cost effective control for Heliothis is nucleopolyhedrovirus (NPV); trade names are Vivus Gold and Gemstar. This product has no impact on beneficial insects and very safe for the operator to use. This product takes around five days to kill larvae, so it needs to be applied to larvae when they are small. Significant damage occurred in crops last year when NPV was applied late on large larvae in high numbers. Overall control on these crops was good but high levels of damage occurred before the larvae died. Recommended size for the control of Larvae with NPV is 5mm and up to 13mm.
The fight against Mycotoxins Pacific Seeds is doing its bit to try and overcome the increasingly complex issue of mycotoxins in corn grain. This is often more commonly recognised as “dead grain” resulting from fungi growing in the grain. Aspergillus, Fusarium and Penicillium species are the most important mycotoxin producers. According to the company’s corn breeder, Paul Newell (pictured below) there is no doubt the incidence of mycotoxins in all grains and particularly corn is commonly associated with stress during grain fill to maturity. “In our harsher environment this induced stress could be attributed to a singular form of stress or often a combination of readily available soil moisture, excessive heat, insect or bird damage,” he said. “By having an active local corn breeding program here in Australia, with our objective to develop corn hybrids that are specifically bred and selected for adaptation to the Australian environment and market specifications, we are able to eliminate a lot of hybrids before getting to the market place.”
“As well as a wide-scale testing program, there are two breeding nursery locations with breeding material screened each year on a late plant under high disease pressure." “In more recent years this is one of the main reasons why Pacific Seeds hybrids have been much cleaner of cob and grain disease’s compared to hybrids lifted straight out of the corn belt in the USA or hybrids that have been selected in the softer environments of southern Australia.” Even this current season’s crop in the major corn growing area of Australia (MIA based around Griffith), Pacific Seeds' hybrids are showing far lower levels of fungi contamination than other hybrids being grown. "If cob diseases continue to be a real issue we may see in the future slightly lower yielding hybrids but with much better resistance to stress and therefore cob rots. The emphasis on local breeding definitely has a significant advantage in overcoming local environmental stresses,” Mr Newell said. Choose forage over oats in hot soil conditions Good rain in the south east may be prompting many cattle producers to plant grazing oats in anticipation of good winter feed. However, Pacific Seeds’ Forage Crop Business Manager Ken Reimers is calling for producers to consider a sweet forage sorghum instead due to higher soil temperatures in February. “Although some oats varieties, such as Taipan and Drover will germinate and establish in soil temperatures up to 29°C, February soil temperatures can be much higher and precious oat seed should be planted when it has a much greater chance of optimum crop establishment,” he said. Regardless of warnings about poor seedling germination and emergence under high soil temperatures, Mr Reimers said it has become regular practice over recent years to plant oats on the first decent rainfall in February. ”Even if establishment is affected to some extent growers reason that when follow up rain falls, the early oats are far ahead of crops planted on the second rain.” “This is OK in years when oat seed is plentiful and resultant establishment failures can be readily replanted, but the record dry winter throughout eastern Australia last year has seen oat seed in very limited supply, so failures this season will be all but impossible to replant.” This is the key reason Pacific Seeds is urging sweet forage sorghum over oats on the February plant. “A much safer option should rain fall in early to mid February is to plant a sweet forage sorghum such as Sugargraze,” Mr Reimers said. “It loves the hot weather and in such conditions will produce first feed faster than oats. If left run to head it also provides high energy winter standover feed or quality silage due to the high soluble sugar levels in the stems.” “I am not suggesting you plant Sugargraze instead of oats, but on a very early plant, into hot soils, forage sorghum is a much safer option.”
Caution urged when feeding out drought affected sorghum crops Prussic acid in sorghum can kill cattle if not managed properly. That’s the message market leaders in forage and grain sorghum seed, Pacific Seeds want to get out there. The reason behind this announcement is an increase in requests for information the company has received about prussic acid poisoning and management, due in part to growers baling failed grain sorghum crops for hay.
“Prussic acid is found in all sorghum varieties and grain sorghum generally has considerably higher levels than forage sorghums.” “Levels of Prussic Acid at or below 600 parts per million are safe for cattle, however in feed tests that have been conducted on some drought affected grain sorghum hay, levels of 3000 ppm have been detected which in anyone’s book will cause problems.” According to Mr Philp, the younger a sorghum, the higher the prussic acid levels. “This problem can be compounded if the sorghum is stressed in the growing phase.” “As a general rule of thumb, if the parent crop is too risky to feed, the hay made from that crop will also be too risky to feed.” As part of a management plan, if it’s not feasible to do a feed test farmers should introduce stock to the sorghum slowly and observe them for signs of prussic acid poisoning in the first 24 hours. Additionally it is important to provide stock with sulphur licks as this helps break down the toxin. However if hungry cattle gorge on fodder that is high in prussic acid, toxic levels of this compound are formed at too rapid a rate to be detoxified and deaths will occur. “I guess message for growers to note is that while baled sorghum can be a very handy feed option in tight times, such as we’re now experiencing, it’s important to know what to look for as far as prussic acid is concerned and how to manage it,” Mr Philp said. Symptoms of poisoning include muscle trembling, staggers, deep and rapid breathing, frothing at the mouth and gasping. “To borrow a phrase from the government; be alert, not alarmed.” Caption: Trevor is pictured in a heat stressed sorghum crop.
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Pacific Seeds' summer grains agronomist Trevor Philp carries out a number of innovative trials each summer, aiming to bring further value to farmers enterprises. Some of that trial work and his wealth of knowledge of summer cropping is presented here.
With such an extensive research trialing program being conducted from the bottom of Victoria to north Queensland each year, with 13 trials being planted, Mr Newell said it gives the company good coverage of all growing environments in Australia. 
The company’s recently appointed Summer Grains Agronomist, Trevor Philp said that while failed sorghum can offer a valuable part of the feed ration for cattle producers in these dry times, any feed from this source should be tested for prussic acid levels.