Milo Information

Sorghum:

As with feed, milo (or sorghum) does not have many  herbicides specifically labeled for it.

Commonly, milo is treated with a pre-plant or pre-emergence application to  control weeds early in the season.  This can be effective if precipitation occurs soon after application to incorporate the herbicide. With sprinkler irrigation, this can be a reliable technique.

In many cases, a post emergence herbicide application is used. These post-emerge applications can also work well. The important thing is to treat the milo early, usually when it is about two inches tall. At this stage, the weeds are smaller, and the potential crop damage is minimized. Herbicide applications for milo can be quite economical, as a relatively small amount of herbicide is required. 

A variety of insects can cause problems in milo. Below ground insects such as wireworms are normally addressed with seed treatments.

In our area, the most common insects are greenbugs, corn leaf aphids, spider mites, grasshoppers, cutworms, and fall armyworms.

Greenbugs are the most likely to do damage to your milo.  These sucking insects are small, lime-green in color, and appear in colonies on the undersides of leaves. They have a dark green line down the middle of the back and antennae that are as long or longer than
their body.

In warm weather, females may produce several off-
spring per day for up to two weeks, so populations can explode. Greenbugs inject saliva that is very toxic to sorghum, destroying chlorophyll in the leaves and turning them a red or rusty brown. Well developed infestations begin to develop winged forms that are capable of riding the wind for long distances. Symptoms include leaf discoloration and distinctive weeping which can leave the ground damp underneath the plant.

Injury may occur at any time during the growing season, from seedling through soft dough stages. Resistant milo varieties can accommodate higher populations of greenbugs before treatment is required, but greenbug biotypes change rapidly, negating some of the protection afforded by varieties resistant to a specific biotype.

Greenbug treatment thresholds vary from as few as 25 per plant on very small milo to as many as 700 per plant in the late whorl stage. Predator insects, such as the lace wing fly and ladybug can rapidly reduce greenbug populations. Treatment is normally quite effective but no residual control is afforded, so reinfestation is possible, requiring a second treatment.

Corn leaf aphids are similar in appearance to greenbugs, but slightly larger and darker in appearance. They are easily differentiated, however, by their location on the plant: they congregate in the whorl instead of on the bottoms of the leaves. Unless corn leaf aphids have very large numbers and persist into the heading stage, they are normally not treated, since their presence can host insects which may reduce greenbug populations.

Spider mites are not a common pest in milo, but in hot dry conditions they can reach economically treatable levels. Treatment is recommended when a majority of the plants have expanding colonies on the lower regions and some mites are appearing in the plant's midsection.  Treatment should not be delayed, as damage can accelerate rapidly.  

Grasshoppers normally congregate along the borders of fields, and early treatment can arrest their progress. If border levels reach 15-20 nymphs per square yard, treatment is justified. Inside the field, treat when nymphs populations reach 5 to 8 per square yard. Grasshoppers hatch from untilled soil, such as pasture and road ditches, so scout those field edges first. 

Cutworms normally reduce plant populations in the two weeks after planting, and are more likely if adjoining corn fields have had cutworm infestations. Treatment is required when damage is causing unacceptable stand damage. KSU says that 1/2 inch long larvae might kill 4 to 6 plants before they reach maturity.

Fall armyworms arrive in mid-summer when moths lay eggs on plant leaves. Late planted milo is more susceptible to damage, which appears as ragged perforations in the foliage.  This damage becomes more evident as leaves unfold. Leaf damage causes little yield loss, so KSU does not recommend treatment until 75 percent of plants show damage and one to two larvae per head are evident. Larvae deeply burrowed in the whorl can be difficult to control. It is possible for corn earworms to coexist with fall armyworm, and treatment guidelines are the same for both insects.

Insects which cause damage south and east of our area include chinch bugs, midge beetles, sugarcane rootstock beetle, and sorghum webworm.  Any of these insects could conceivably migrate toward our area in future years. 

For a complete analysis of all the insects that can damage milo, including those which are not covered here, we recommend the KSU Sorghum Insect Management Guide. You can download it by clicking here.  (PDF, 335 Kb)