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Early instar A. ipsilon larvae can create 'shotholes' while feeding on tender leaves of seedling plants. Third to seventh instars become negatively phototaxic and feed mostly at night. Damage from these instars is usually observed as a cutting of young seedlings, often causing death of the cut seedlings. Sometimes wilting is observed because of partial cutting. Larvae are destructive out of proportion to the actual plant material they consume because several plants may be cut by a single larva. A larva will often cut one plant, quickly move on to other plants and continue cutting. Relatively small populations of cutworms are capable of destroying entire stands of some crops, such as cotton or maize. When seedlings are too large to be cut, foliar feeding may reduce plant vigour and subsequent yield.
Difficulty in assessing A. ipsilon injury is due to their habit of tunnelling under the soil in the daytime and feeding at night. This characteristic makes determination of damaging larval populations difficult, and a great deal of damage can occur in a relatively short period before an infestation is suspected. As plants become larger, older instars will occasionally tunnel into the growing stalk, disrupting the xylem and phloem. Climbing behaviour in A. ipsilon is not well developed, but when plants become too large to cut or too difficult to tunnel into, larvae will cut off leaves. However, this leaf cutting does not usually cause economic damage to the plant. Fruit piercing may occur in plums, peaches and pears.
Cutworms are among the insects that continue to challenge the best efforts at pest management. The following practices may prove advantageous to some growers:
General Management Tactics
- If possible, avoid planting crops in fields with a known history of cutworm problems.
- Avoid planting crops (especially maize) following longstanding pastures, meadows, lucerne or red clover.
- Plough in the autumn and use shallow tillage to keep down late autumn and early spring vegetation (where conservation practices allow).
- Monitor larvae with larval cutworm bait traps (Story and Keaster, 1982, 1983; Munson et al., 1986).
- Monitor adults to predict attacks (Hachler and Brunetti, 2002).
- Monitor weather to predict attacks (Bhagat and Praveen Sharma, 2000; Zhou and Chen, 2004).
- Low mow grass to remove eggs, disposing of cuttings at a distance (Williamson and Potter, 1997).
- Topdressing with sand does not kill larvae but deters them from travelling (Williamson and Potter, 1997).
- Encourage predators by encouraging their other prey species nearby, e.g. by having conservation strips between fields or golf fairways (Frank and Shrewsbury, 2004).
Three genes have been transferred from their original species to crop plants in order to make them resistant to A. ipsilon. One is the cowpea trypsin inhibitor (CpTi). Another is the barley trysin inhibitor (Bti-cme). Another is the Bacillus thuringiensis cry1Ac gene (Bt). These genes each code for the production of a different insecticidal toxin. The resultant crops are termed 'transgenic'. More than one of these genes can be transferred to give increased resistance.
Grass resistant to A. ipsilon was created by Agrobacterium-mediated transformation of Bermudagrass (Cynodon dactylon) with the Bacillus thuringiensis cry1Ac gene (Salehi et al., 2005).
Transgenic Bt+CpTI cotton was resistant to higher instars of A. ipsilon but could not control the pest effectively (Cui et al., 2002).
Transgenic (Bt) maize was found to be no more resistant to A. ipsilon than regular maize (Pilcher at al., 1997).
Transgenic Bt+CpTi tobacco gave 48% mortality to first-instar A. ipsilon larvae (Luo et al., 1999).
Transgenic wheat and tobacco with the barley trypsin inhibitor gene (Bti-cme) were resistant to A. ipsilon (Carbonero et al., 1998).
Studies of predators feeding on A. ipsilon larvae which were feeding on transgenic crops have been ambiguous. The predator Orius albidipennis was found to be both negatively (Hafez et al., 1997) and positively affected. However, daily feeding of four other predatory species with A. ipsilon larvae fed on transgenic cotton displayed a normal feeding function in agreement with a Holling type II functional response (Cui and Xia, 1997).
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
A. ipsilon has a very wide host range. Many of the plants attacked are not of economic importance, but damage to seedling maize, many vegetables, cotton, tobacco, turf grasses, and other crops can be economically significant. It is known to damage crops in North, Central and South America, Europe, Asia, Australasia, Oceanania, Africa and the Middle East.
A. ipsilon is a pest on many crops in tropical and subtropical regions all around the world, causing significant losses, in Chile (Carrillo et al., 2001), Brazil (Secchi, 2001), Egypt (Amin and Abdin, 1997), India (Verma and Verma, 2002), Myanmar (Morris and Waterhouse, 2001), Poland (Walczak, 2002), Spain (Amate et al., 1998) and USA (Amin and Abdin, 1997).